Heartworm Medication Part 2: Options to Fear-Based Recommendations

Written by Jan on June 16, 2009 – 12:01 am

If you haven’t read Part 1 of this article, “Heartworm Medication: Truths, Omissions and Profits,” please read it now unless you completely understand how and when heartworms are transmitted. Click the link at that article’s end to return here. 


A Heartworm Society news release states:  “By giving heartworm prevention every month, forgetful pet owners will have their pets protected when they need it most.”  But doesn’t that also mean they get it when they need it least? Or need it not at all? Are you a “forgetful” owner?

In this part of my heartworm series, we’ll discusses informed decision-making, and suggests ways, if you want them, to limit or eliminate heartworm drugs. I am a researcher and holistic health advocate, not a vet.  Please learn the facts then discuss with your vet the appropriate course given your dog’s location, lifestyle, travel schedule, health, climate and the time of year.  Expect an open-mind and respect from your vet, or find another vet.  Just as with vaccination, “one size fits all” is outdated, profit-driven, lazy medicine.

Take a look at the map above, courtesy of the  Heartworm Society.  Part 1 of this article demonstrated that transmission is heat and mosquito dependent.   As expected, dark areas of the map, which show the most heartworm cases per clinic, are found in the hot, humid Southeastern US, especially the Atlantic and Gulf coasts and Mississippi Delta.

Don’t let the map scare you. If published seasonally, map colors would pale significantly during cool months. Also remember that you’re seeing generalities, not specifics.  A clinic near a rural pond will likely have many cases while an urban clinic 15 miles away may have a much lower incidence.  Maps are general.  Determine your own microclimate. Ask your vet how many cases of heartworm infection he/she treated in the past year.  Also ask if he/she treats all positive cases, or just those with advanced infestation. If the vet doesn’t keep detailed records, that should tell you something.

Conservative start/stop maps from heartworm researchers Drs. David Knight and James Lok (in “Seasonality of Heartworm Infections and Implications for Chemoprophylaxis”) show only two areas requiring year round heartworm meds: the southernmost areas of Florida and Texas.  Houston, New Orleans and similar areas are shown requiring meds for 9 months.  Other states range from 3-7 months. The Drs. wrote:  “For nearly 80% of the states, the potential for heartworm transmission is limited to 6 months or less.” Here are start/stop maps for the US and California. Again, they are very conservative and very general. Do your own research and be specific.

The Heartworm Society warns that heartworm infectations are getting worse.  DVM Magazine, a magazine for vets, reports that recent results do show a rise in the number of positive cases per clinic in 31 states. DMV reports: “The reasons likely are multifactorial, including increased heartworm testing, increased client base per clinic or even climate trends.”

Does Year Round Medicating Bring Extra Protection?

Applying suncreen at night is useless. So is taking heartworm medication when climate conditions prevent transmission.  Only a small percentage of climes permit year-round transmission. Everyone else is unnecessarily subsidizing drug companies and “preventatives” sellers and, more importantly, exposing their dog to unnecessary risks.

Two exceptions: 1) “Forgetful” and irresponsible pet parents who won’t begin the medication on time or build their dog’s natural immunity might want to medicate year round, although that means they have to remember to give meds every month.  2) If your dog contracts heartworms within a few years of beginning medication … and you can show you gave meds year round … and your dog had the required blood tests (2 or 3),  you may benefit a little financially because drug companies will pay for dog’s treatment. (Read the guarantee terms published by an on-line seller.)

Are Heartworm Preventatives Safe?

You’ve seen those scary photos of worm-strangled hearts, right? Shouldn’t you give meds year round just in case? Isn’t safe better than sorry?

But is that harmless little pill or yummie medical “brownie” really safe?  No drug is completely free of risk and  adverse reactions. I can find no long-term studies regarding cancer risks and organ damage for dogs receiving heartworm insecticides year round (or even for a few months). Such a study would be difficult to conduct and very expensive.  Who would fund such a study — or publish any negative findings?

One clue to the possibility of adverse reactions should be label warnings: call your doctor immediately if ingested; keep away from children; wash your hands immediately after use…. How can medication be good for dogs but so dangerous for you?

Another question: is your dog healthy enough for these medications? The “Heartworm Prevention” page of the American Animal Hospital Association states: “Healthy kidneys and normal liver functions are essential in metabolizing most medications.”  Many dogs, including my Jiggy, do not have healthy organ function. I wonder how many unhealthy animals are nevertheless on meds?

Adverse Reactions to Heartworm Medications

With any drug, study FDA and manufacturer information before medicating.

These adverse reactions have been reported to the FDA by manufacturers.  (Click the links for more information; write or call manufacturers with any questions). Terms you might not understand include ataxia (gross lack of coordination of muscle movements), pruritus (itchy dermatologic condition), urticaria (hives), mydriasis (excessive pupil dilation), and erythema (skin redness). Other terms should be self-explanatory.

HEARTGARD and TriHeartPlus (ivermectin): Depression/lethargy, vomiting, anorexia, diarrhea, mydriasis, ataxia staggering, convulsions and hypersalivation. INTERCEPTOR (milbemycin oxime) reports the above reactions plus weakness.  Sentinel (milbemycin oxime) reports vomiting, depression/lethargy, pruritus, urticaria, diarrhea, anorexia, skin congestion, ataxia, convulsions, hypersalivation and weakness.

REVOLUTION® (selamectin), Topical Parasiticide For Dogs and Cats: pre-approval reactions of vomiting, loose stool or diarrhea with or without blood, anorexia, lethargy, salivation, tachypnea, and muscle tremors. Post-approval experience included the above plus pruritis, urticaria, erythema, ataxia, fever, and rare reports of death and seizures in dogs.

Proheart 6 :  severe allergic reactions (anaphylaxis): facial swelling, itching, difficulty breathing, collapse;  lethargy (sluggishness); not eating or losing interest in food; any change in activity level; seizures; vomiting and/or diarrhea (with and without blood); weight loss; pale gums, increased thirst or urination, weakness, bleeding, bruising; rare instances of death. This product was voluntarily withdrawn from the market in 2004 because of deaths but has been reintroduced. Read my post Heartworm Protection: Do We Need ProHeart 6?

For any other brand, research the product or its active ingredient before even thinking of administering it.

Also, never give any meds without first learning if any vitamins, minerals, herbal products or drugs interact negatively with the medication. Note age restrictions. Most importantly,  learn what symptoms alert you to a reaction. Important note: Collies, Australian Shepards and related breeds have a sensitivity to ivermectin (Heartgard and others).

Beware any website or person professing the absolute safety of any medication.  I’d like adverse reactions for pet medications to be included in all TV ads, as they are for meds for humans — but I don’t expect it.

Reporting Adverse Events: Call your veterinarian immediately if you suspect a reaction to this or any other drug.  Discuss alternatives and treatment and make sure the reaction is recorded in your dog’s file. The AVMA says : “… notify the US Food and Drug Administration (FDA) by contacting the manufacturer. The FDA requires that manufacturers of FDA-approved drugs forward adverse event reports to the agency.”   Is the fox is guarding the hen house? Ask your vet to report the reaction, then follow up and make sure your vet did it. Under-reporting is common. (An estimated 99% of adverse reactions go unreported according to the FDA.) Click here for FDA reporting instructions.

Tests for Heartworm Infection

Heartworms can, and should, be detected by a simple blood test before administering medication.  The antigen test detects an adult female worms at least 5-8 months old. The Merck Veterinary Manual says: “The antigen detection test is the preferred diagnostic method for asymptomatic dogs or when seeking verification of a suspected HW infection.”

Microfilariae (babies) in the blood are detected by a different blood test.  These show exposure, but do not detect  female adults (potential breeders).  Antibody tests (as opposed to antigen tests) are not preferred because they indicate only that the dog has been exposed to heartworms at some time in his or her life, even if the worms subsequently died.

If you plan to give “preventatives,” test before beginning medication, preferably within a month of when daily temperatures consistently climb above 57˚ F.  Read more at the Heartworm Society Serology section.

If you’re not going to use meds, homeopathic veterinarian Jeff Feinman wrote me that he advises semi-annual testing when not using preventatives.  My own vet, Tamara Hebbler, agrees.  Testing twice yearly helps you catch disease early when it’s easier to treat. Dr. Martin Goldstein in The Nature Of Animal Healing says: “Only a small percentage of dogs who get heartworm die of it, especially if they’re routinely tested twice yearly for early detection. Even in untreated dogs, after a period of uncomfortable symptoms, the adult worms die….”

Did you know that the latest canine movie star “Benji” was found in a shelter, infected with heartworms? Benji was treated successfully and went onto canine fame and a healthy life.

Heartworms, like other parasites, don’t become life threatening quickly or inevitably. It takes at least 5 months, and more often 7-8 months, for a baby to grow to a reproducing adult — presuming the dog’s immune system doesn’t intervene.  Also, adult males and females must both survive to breed.

Important Note If your dog’s antigen test comes back positive, holistic vet Tamara Hebbler suggests that before you rush into treatment with harsh, poisonous drugs, you should get a cardiac ultrasound to determine the extent of the infestation. Heartworms, like other parasites, often live with their hosts without ever causing a dangerous problem.  It’s quite common for animals in the wild to live entire lives with heartworms. (If worms always killed dogs, they’d soon run out of hosts.)  Unless heartworms are re-introduced by another infected mosquito, the adults and their babies will eventually die off.

When Should You Start Administering Meds — If You’re Going To?

Remember, you kill heartworm babies after the fact. You can only “prevent” them by avoiding mosquitoes.  (You can also kill them with a healthy immune system.) This means starting meds 30-45 after the weather warms and mosquitoes appear. Also, Washington State University warns, “If your pet travels to heartworm areas, prevention needs to be administered within 30 days of exposure to infected mosquitoes. Adult dogs (older than 6 mos.) need to be tested before starting preventative.”

Dr. Margo Roman, an integrative vet from in Massachusetts, documentary film maker and Founder of the first-ever Integrative Health Pet Expo in Massachusetts this fall, tells me she begins medication six weeks after sees mosquitoes. This allows 2 weeks for the microfilariae (baby heartworms) to mature  inside a mosquito to the infective stage and be transferred to a dog, plus 30 days additional days covered by the medication working backwards to kill those babies.

When Should You Stop Heartworm “Preventatives”?

Dr. Roman recommends stopping meds after the first frost for people living in an area with cold winters.  In other areas, vets recommend stopping 30-45 days after weather is consistently below 57 F degrees and you see no mosquitoes. See Part 1 of this article, and the start/stop maps, for more details.

What Brand Should You Use?

Consumers often think that “preventing” as many parasites as possible with one product is a bargain — and ultimately safer for the dog.  But why expose your dog to additional, unnecessary toxins?  Most holistic vets will tell you to protect against only those pests (and diseases) your dog is likely to encounter.  To see which products do what, see the “preventatives” comparison chart at Veterinary Partner.

***Low Dose “Safeheart” Medication Approved by the FDA

More than a decade ago — on June 4, 1998 — the FDA approved a 1/5 dose version of Interceptor heartworm medication, a product called Safeheart. This expensive field trial was conducted and the dosage approved  — but inexplicably the product was never marketed in the U.S.

To duplicate the Safeheart heartworm “prevention” method — which you can’t buy — you have split the Interceptor dose into quarters. Check with Interceptor first, and ask your pharmacist or vet how to do this accurately.  The recommended once-a-month dosage is 0.1 mg of milbemycin oxime per kg of body weight (0.05 mg/lb). (Interceptor’s regular dose of dosage is 0.5 mg milbemycin oxime per kg of body weight.) Print the FDA’s Safeheart report and take it to your vet for your prescription and additional instructions.

Note: At this dose, only heartworms will be treated with the Safeheart method, not other worms or fleas.

How Often Should You Give Meds?

In his important book Homeopathic Care For Cats and Dogs, veterinarian Don Hamilton says of heartworm:  “In dogs the “monthly” preventives are effective if given at six week intervals, and possibly even at seven- or eight week intervals….”  Author/veterinarians Richard Pitcairn and Allen Schoen told us essentially the same thing when we were researching our book Scared Poopless.  If you opt for this “less is more” treatment with “preventatives,” mark dosing dates on your calendar and don’t miss them.

The vets at Holistic Vet Center say:  “… monthly heartworm preventatives are actually 100% effective if given every 45 days and 99% effective if given every 60 days.”

I presume that the monthly schedule was designed for the ease of remembering when to give meds.  However … giving meds monthly rather than every 45 days requires more doses  — and offers more opportunities for adverse reactions.  For someone medicating year-round, that’s 4 fewer doses per year.

Are There Natural Heartworm Preventatives?

Mosquito control is the ultimate natural preventative.  No mosquitoes, no heartworms.  Control mosquitoes by eliminating standing water and staying indoors at dusk and dawn. Use bug spray (marked safe and non-toxic for animals and children). Buy bug zappers. (All these are good ideas for human protection from mosquito-borne diseases as well.)

Is mosquito control 100% effective? No, but  Mosquito.org has some great tips. (Note: one study showed that a full moon increased mosquito activity by 500%.)  Find more information on controlling mosquitoes in this University of California report.

What do I do? Well, for me, the choice was easy. I live in So. California. I rarely see mosquitoes. My dogs spend most of their time indoors. Nights are invariably cool.

With the advice of two local vets, I decided to protect my own dogs (both of whom have health challenges) against the toxicity of heartworm “preventatives” rather than protect against an unlikely infection. I use non-toxic alternatives like mosquito control, an excellent diet and no drugs unless they’re absolutely unavoidable. I increase safety by testing blood twice yearly. I haven’t used “preventatives” for five or six years and my dogs remain heartworm free. This is my personal decision.  I am not a vet.

If I lived in a mosquito-heavy area, however, I might do much the same. I would determine local risks and would consult a local holistic vet to get help preventing heartworms naturally. I would control mosquitoes and test blood twice or more yearly. Someone who had “outside dogs,” and who was the nervous about heartworms, might also use heartworm meds or the Safeheart method during the peak heartworm months of July and August, but only if their dogs had healthy kidneys and livers. They should make any decision with a knowledgeable vet.

Dr. Will Falconer, a holistic vet certified in acupuncture and homeopathy, has written an e-book called “Drug-Free Heartworm Prevention.”  This 50+ page, well-written e-book is delivered electronically.  I do not profit from sales of this book although I was given a complementary review copy.  Drs. Richard Pitcairn and Martin Goldstein have also written about heartworms in their books.

Please leave us a comment and let us know how you liked this article. Tell us about your concerns and decisions.  If we have made any errors, please let us know so we can rectify them. And, please, tell your friends the facts behind heartworm transmission.

Most importantly, do not make decisions out of fear. Don’t let anyone, even your vet, intimidate or ridicule you. Be an educated consumer and a rabid advocate for your dog’s health.

Disclaimer: The information provided here is for educational purposes only. Do not rely on this information without doing your own research including consultation with your own veterinarian.  Do not buy or fail a product for treating heartworm without evaluating it carefully.

Sign up for notification of  future articles and our free dog care e-newsletter (delivered quarterly). Follow K9Author at Twitter.

There are reports of medication-resistant  heartworm in the deep South region of the US.  Read the article at http://www.clarionledger.com/article/20100424/NEWS/4240342/1001/Pet-owners-concerned-with-resistant-heartworms

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95 Comments to “Heartworm Medication Part 2: Options to Fear-Based Recommendations”

  1. Major Heartworm Med Rant!!!! - Page 3 - YorkieTalk.com Forums - Yorkshire Terrier Community Says:

    […] is an article by Jan Rasmusen, the author of Scared Poopless on heartwrom medication. Heartworm Preventatives: Safety and Alternatives | Truth4Dogs I consider Scared Poopless to be a must have for any pet owner. Not only is it full of important […]

  2. Jan Says:

    I’m excited to see the important subject of heartworm prevention discussed in the Yorkie Talk forum. My hope is that people will read Part 1 (the facts behind heartworm transmission)and Part 2 (options for prevention) and make informed decisions. My only desire is to bring information to light that is often buried in veterinary journals. There is so much fear in this subject (some justified, some not), so much money in selling products, so much hype in advertising with very few people offering options and facts. I hope you’ll post comments on my Truth4Dogs.com blog so others can share in your concerns and knowledge. My regards, Jan Rasmusen, author, Scared Poopless: The Straight Scoop on Dog Care.

  3. Janet J Says:

    This is the most informative article I have found on the subject. We have recently moved from an area where heartworm prevention was not indicated to one which was (according to our veterinarians) “problematic.” Now learing the actual climatic indications to cause infection probability, I realize that this area does NOT indicate prophylactic measures.

  4. Jan Says:

    Janet, I’m delighted my articles on heartworm were helpful. (You did see both of them I hope.) I just posted an article on the dog flu vaccine just approved. I hope you’ll read it before you think of giving it. — Jan

  5. jane Says:

    Thanks so much for an informative article. I’ve been “researching” casually now for a few hours (and of course in the past too). It’s frustrating to see how much covering up of the truth goes on with this topic. I live in Springfield/Eugene, Oregon area. Although I’m sure we have the occasional mosquito here, I’ve never been bit or even seen one (I live on a high hill where it’s rather dry/fire hazard in summer). And believe me, I’m quite familiar with what they look like and feel like, as they’d eat me (or anything with blood) alive where I’m from — by the water in Michigan. I found the incident map too. It’s interesting that there are incidences here, although rare, because for as long as I’ve lived here (4 years), I’ve NEVER seen it go above 60 at night. Explain that one! Even in summer, it’s always in the 40/50s at night religiously. And there aren’t many bodies of water inland. I am not close to any rivers either. I would think a rapid flow of water would decrease the mosquito habitat too – we have rapids, not standing water as in a marsh (which are also so common in Michigan). Anyway, interesting stuff. After 3 years of heartworm plus, I plan to take my Old English Sheepdog off the meds and stick with the testing once or twice a year. I never thought about the side effects and possible toxicity of these meds. I also have to say that my vet doesn’t push the meds either. If I ask her about incidence, I have to say she is incredibly honest in saying, “no, or yes, it’s that important to take it”….they leave it up the client and provide information. Bush Animal Hospital is a good vet office, for whatever that’s worth, if you’re in my area. I stick with the female vets too. Not biased, but my experience there has been that the females vets there are less pushy. Well, thanks again for enlightening me. Jane

  6. Jan Says:

    Jane, I’m glad the heartworm articles were useful. Please tell your friends. I hate to see dogs getting heartworm meds in areas where infection is all but impossible.

    I hope you’ll take a look at our vaccination articles, too. Lots of coverup of the truth there!

  7. Carol Says:

    Thank you, thank you. I have not had time to do what you are doing…tell the truth about veterinary medicine.

    I have three tiny Maltese, all of whom were bred and delivered at home as family members. One of them pretty much has a seizure with a few days each time I give the heartworm preventative. Vets here in Austin Texas use the guilt/shame approach to influence pet owners to poison their pets. So even the vets trying to stop the seizures, encourage me to continue to poison her.

    After she started having seizures, the vets started doping her up with other strong (very expensive) pharmaceuticals. My beautiful 6 lb,spirited lively little dog is now a bloated, lethargic little girl who is on five-six drugs a day. I am afraid she will end up like Michael Jackson if I can’t find a vet capable of helping me withdraw her from the drugs. I have switched to all raw food, have a mosquito zapper, and don’t let her outside very often. I think confinement indoors is safer at this point.

    I will write later about a horror story which was allowed by the Texas Board of Veterinary Examiners. I don’t know about other state, but in Texas the Vet Board is all about promoting profits for vets at the expense of pet safety and pet owner consumer rights.

  8. Julie Says:

    Here you are again taking about the unnecessary de-worming that is forced on pet owners. If you reviewed the drugs that are in monthly preventatives you would know that they are also used to kill deadly zoonotic parasites, not just heartworms.

  9. Jan Says:

    Heartworm medication and seizures. Carol, I’m so sorry for your dog’s problems. Click this link to find a holistic vet who can help you with your dog’s problems.

    Why would a vet continue to give the same medication that caused seizures? For one thing, different preventatives use different insecticides.

    I wonder, have you reported the problem to the manufacturer and asked them to pay for your dog’s treatment and recommend what you should do. I bet the first thing they tell you to do is to stop the medication. I’m sure a holistic vet will help you wean your dog off the meds and will suggest safer ways to prevent heartworm infection.

    I wish you the best of luck.

  10. Ted Says:

    I live in Portland OR. I have a black lab. Like most labs, he eats everything he finds on the ground that looks interesting, even right haver he’s been fed. pine cones, cat and dog turds, tree bark, you name it, he eats it. I’m constantly pulling his head out of some disgusting thing or other, one of his favorites is the toilet, expecially if there’s paper in there and someone has used it and forgot to flush. He’s never been sick from any of this. I give him the monthly heatworm preventative. He’s never been sick from that, either. Not every dog is delicate. Just thought I’d give some balance, here. By the way, I buy the preventatives online. They are a lot chepaer than a yearly blood test.

  11. Jan Says:

    Hi Ted. I understand what you’re thinking, but all the items you mentioned as favorites of your dog to gobble down — pine cones, bark and poop — are organic. Your dog’s high level of hydrochloric stomach acid protects him from pathogens and hard-to-digest items. Heartworm preventatives and other meds are synthetic chemicals. The hydrochloric acid doesn’t help. That your dog has shown no symptoms doesn’t mean anything. If your dog ultimately dies of cancer or organ failure, you may go looking for a cause. Toxic chemicals cause cancer in humans. Do you think they don’t cause them in dogs?

  12. Day Marie Says:

    Jan, Thank you for the most informative articles Part 1 & 2 about heartworms. My beloved Sport, a Lhasa mix of 14.5 years took ill just one week after taking heartgard & advantix (one day apart) and within one month died from liver cancer that triggered so many other organs to breakdown. I was so devastated because I had just moved to San Antonio, TX from Colorado and the fleas & ear mites had become a problem for him. Even the holistic vet told me it would be okay to give both although she knew his prior history of liver disease. I had doubts about giving both of these chemicals but instead trusted the vet too much…
    I made the mistake of believing the holistic vet knew what she was talking about. Since his death 5 months ago, I have researched books & the internet & learned how toxic these chemicals really are and the alternatives available. I have had to deal with huge amounts of regret & despair by not listening to my own gut feelings. I did report to the EPA about the toxicity of Heartgard & Advantix. Now that I have a new companion, I will not give either of these meds to her but instead will be more proactive in natural remedies and have her tested twice yearly for heartworms, continue cooking homemade meals, etc to keep her immune system strong & healthy. I have found a new vet who practices regular vet care with Chinese herbs & acupuncture for my Australian Shepherd but she still encourages Heartgard & using antibiotics but I won’t agree to these any longer especially since I’ve learned Aussies are sensitive to Ivermectin. Thank you Jan. Keep up the good work. I learned of your book from Val Heart, animal communicator here in San Antonio.

  13. Jan Says:

    Hi Day Marie. I’m so sorry about your dog. The “holistic” vet who told you to take Heartgard and Advantix is unlike any holistic vet I know. These days, lots of vets are calling themselves “holistic” for marketing purposes, but they clearly aren’t.

    You should report your dog’s death to the EPA. Here’s a link to report the reaction to Advantix. http://pesticides.custhelp.com/cgi-bin/pesticides.cfg/php/enduser/std_adp.php?p_faqid=5482&p_created=1224683751&p_sid=-wtG7MJj&p_accessibility=0&p_redirect=&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9MTQsMTQmcF9wcm9kcz00NzQmcF9jYXRzPSZwX3B2PTEuNDc0JnBfY3Y9JnBfcGFnZT0x&p_li=&p_topview=1

    You can also report a problem with pesticides, drugs or foods at a new AVMA reporting page. Also fill out the form at Beyond Pesticides. You can find links to these sites, and an article about the dangers of pesticides and pets. http://www.dogs4dogs.com/blog/2009/01/08/pesticides-poisoning-pets/

    Thank you for your kind words about my articles. (Tell Val thanks!) I hope you’ve read the ones on vaccinating as well. Shots are yet another can of worms.

    Best of luck. — Jan

  14. Nancy Says:

    Thank you for the great article, I’m a holistic supporter myself and am always looking for a better way for my pet. My vet always uses the scare tactic and tells me that Heartgard protects against other worms and parasites as well as heartworm. She says that these other parasites can be transmitted to my kids. I question if this is really true, and if so, is this just a problem in warm months. I live in Colorado Springs, which according to the start and stop months, I only need to do the meds from July to November. We have an incredible dog park nearby and my Miniature Schnauzer goes every day of the week.

  15. Mary Ellen Says:

    As an owner of a rescue dog, who during her first exam, tested positive for heartworm I will continue giving her year round preventative. She is 4 years old, and while she is classified as a Class I/II (leaning toward Class I, she already had changes to her pulmonary and heart vessels. Is it better to risk getting the heartworm and then having to treat it with an arsenic based product? If she had cancer, I would also opt for chemo therapy. Holistic is nice, but let’s use some common sense in treating and/or preventing serious diseases, whether we are talking about canine, feline or human!

  16. Debbie Smith Says:

    I would like to comment to Mary Ellen – if you read the article, testing is suggested twice a year in very warm climates. If you are testing twice a year and they find any heartworms, you can probably kill them with the regular heart meds instead of the arsenic treatment. This is because it takes 180-183 days for the larva to develop into adult worms. I don’t know if the number of days was in part I of the author’s article, or if I have read it elsewhere. If a dog has a large number of adults, they don’t want a quick die-off of a large number of worms because of damage to the heart that could cause death, but I’m thinking that with testing every 6 months you would – IF your dog actually had heartworms – be able to give a “regular” so-called preventative.

    Also, remember that rescued dogs are often in a poor state from things like neglect, poor nutrition, stress from outdoor life in extreme temperatures, etc. This can make them more susceptible to heartworm compared to healthier dogs that may be infected but are able to get rid of the problem before it becomes one! I certainly know of many rescues that come in with heartworm, yet not all owners give heartworm meds and their well-kept, well-nourished, unstressed dogs don’t get heartworm.

  17. Karen R Rickers Says:

    These two articles were incredibly informative. Thank you so much for putting so much energy into keeping dogs everywhere healthy! I’m going to be reading a lot more on your website.

  18. Cindy Says:


    I live in Portland too. What vet do you use? Mine won’t approve a prescription getting filled by PetCareRx, because they want to charge me $14 MORE dollars for my Interceptor. Their practice is all about the revenue – not necessarily what is best for my dog.

  19. Kathy Webster Says:

    Jan, Thanks!!! I was very thankful to find the info about vaccinations on your site. I am not a fan of vaccinating dogs unless as you say it is necessary. I took my puppy to be spayed on Friday and they also gave her a rabies shot. Then I read about NOT vaccinating before spaying or neutering. I was horrified!!!!

    My puppy was given too much anesthesia when the clinic did her surgery and it made her sick. She is much better now, but she still smells like it.

    I have read several articles about Diatomaceous earth and its wonders. I wanted to know if any of the holistic vets you have spoken of recommend using it to kill the bugs and worms. I am not sure, but I am truly hoping that this stuff will also kill mosquitoes.

    I will probably spray just to be safe. We have had lots of rain in our area, as well as the 12 inches of snow that we have had this month and last, here in TEXAS, of all places.

    I appreciate the Heartworm info. I am now concerned about giving the stuff I bought (during the visit I mentioned above) to my puppy dog.

    Last, but certainly not least I wanted to share some info with you. The clinic gives every dog (and cat, too, I think) a tattoo to show they have been fixed! I was very impressed. Evidently, tattooing fixed animals is not a requirement as it should be.

    From what I was told countless animals (both male and female) are brought in to clinics and vets offices to have a 2nd surgery to get them fixed. The lady at the clinic said that many times “they open one up to find that they have already been fixed.”

    Their policy is to tattoo every pet that they fix. Of course, they give you a choice to go elsewhere, if you don’t want your pet tattooed.


  20. Jan Says:

    Hi Kathy. I love the idea of tattoos for neutered pets, especially females. Tell me where you live in Texas and I will try to recommend vets.

  21. Kim Says:

    I too really enjoyed your article related to heartworm medications. I live in Ontario, Canada and it is the time of the year where we begin to receive notifications from our local vet clinic to have our dog tested for heartworm. Invariably, when they get you in there, they sell you the product to be given monthly. I too consult with a wonderful holistic vet in Vermont (usually only by phone when I need advice and I use a traditional vet here in Canada for visits when required) and he advised when I first got my pup that if I were to use heartworm medications instead of alternatives that I should use on a 6 week schedule. I do that usually between the months of June (although vets here recommend May) through to September – so my dog gets about 2-3 doses yearly. One thing I have also done is cut down on the amount of liquid I apply to the back of her neck. On the package that I receive, it says the application is for dogs from 60 to 120lbs. Now my dog is only 70 pounds, so I do not see why she should have the full application so I usually put half the amount on her. I just cannot see the value of putting the whole amount on my dog. It is like the vaccination question – why should a 30lb dog get the same dosage as a 90lb dog? Perhaps my rationale is wrong here, but I feel that I am taking a responsible and hopefully proactive approach to providing heartworm protection for my dog.
    Again thanks for all your informed research and publishing these eye-opening truths that can be hard to find in most publisehd articles online. I applaud your dedication to providing pet owners with sage advice geared towards healthy living.

  22. lin Says:

    Hi, thanks so much for this article. I live in the Dallas, TX area and have been pressured to put my tiny toy poodle on heartworm preventative. I’m concerned about the long-term effects and am wary of giving him anything toxic, so I’ve been trying to get to the truth of the matter. He’s a year and a half old and doesn’t even weigh four pounds.

    I’m taking him tomorrow to get tested for heartworms, and before I read this article I was going to also buy the medicine. But now I’m considering not. Would it be okay to just test twice yearly…. or should I consider giving the meds for the prime summer months? I’ve read so many horror stories with these tiny toy breeds.
    Any recommendations for vets in the Dallas area or south of Dallas would be soo appreciated. Thanks so much for all the info you give.

  23. Jan Says:

    Lin, I have no idea if this vet is anywhere near you, but if she is, you might want to check her out. I learned about her because she made a big donation to the Rabies Challenge Fund. Click here: http://www.vitalitypetcare.com/pages/home.htm Shawn Messonier is a holistic vet and author in the area. Find referral lists at http://www.dogs4dogs.com/vet

    Re heartworm meds, you’ll have to make the decision for yourself. If it were my dog, I’d probably test twice yearly and give the meds if there is indication of heartworm. You would want to test religiously. A lot depends on your dog’s lifestyle. If he’s outdoors in summer, especially when mosquitoes are biting, that’s very different than being a dog that lives in air conditioning. I’d use the Safeheart method on my own dog if I decided to use use meds for the summer months, and give it every 6 weeks. But that’s me. You and your vet will have to decide.

  24. Lin Says:

    Thank you for your reply. He tested negative for heartworms. I went ahead and got Interceptor as it seemed the best option for us here in TX, and with how much my dog loves to play outside. However, I do want to give it every 60 days rather than 30.
    If I were to cut the pill per the Safeheart method, could I still give it every 60 days? Or should I give it monthly? I asked the vet about cutting the pill and I could not get a straight answer out of him. Would cutting it in half work, and if so, how often should I give this reduced amount?
    One last thing: Since my dog was just tested negative, what good would giving the medicine now do, since it works backward? Wouldn’t it essentially be pointless? Would it make sense to wait a bit, or am I wrong on this?
    Thank you so much for the help- it’s soo hard to get any straight answers about these things, almost impossible!

  25. Lin Says:

    edit– sorry, i just realized wht you said about giving the safeheart method every six weeks- so should it be cut in half?

  26. tara Says:

    There is alot of fuzzy math going on to compare Interceptor and Safeheart. The are the same meds and both actually overdose dogs at certain weights.
    Take for instance a 10 lb dog.
    It would take:
    Interceptor… (2-10 lb.) tablet…which is 2.3mg milbemycin oxime.
    Safeheart……..(2-50 lb.) tablet…which is 2.3mg milbemycin oxime.

    You state above ” FDA approved a 1/5 dose version of Interceptor heartworm medication, a product called Safeheart”. It is not a 1/5 dose version. It just appears to be same product delivered in different dosing.
    What is important in the info from Safeheart is that they say “once a month, at the recommended minimum dosage of 0.1 mg milbemycin oxime per kg of body weight (0.05 mg/lb).”
    Using that same dog of 10lbs you would still need to quarter the tablet.
    The difference appears to be that Novartis (maker of both Interceptor and Safeheart) waivers on what they feel the minimum dosage should be. Interceptor’s papers say 0.23, whereas Safehearts say 0.1 mg per pound of body weight.
    There is potential for overdosing with both. Isn’t Novartis (modern pharmecutical world ) wonderful ?
    Equally interesting ~~MORE dogs had reactions to Safeheart than Interceptor.
    Observations Safeheartä (n = 75) Interceptorâ (n = 75)
    Anorexia 4 0
    Vomiting 3 3
    Diarrhea 3 1
    Lethargy 2 1
    Could be another case of fuzzy math. There were only 75 dogs tested in each case, no mention of stats of dogs.

  27. tara Says:

    Continued…So who are you going to believe Novatis or Novartis?

    It appears the Safeheart dose of 0.1 mg per pound of body weight (effective for heartworm) VS the Interceptor 0.23mg per pound (heartworm plus other worming). May indeed be effective dosage for heartworm medication.
    What puzzles me is why more dogs had rxns. to Safeheart?

    The original FDA approval for Interceptor states, “Complete (100%) protection was achieved in dogs treated at 30 days post infection, with 95% protection at 60 and 90 days.” Safeheart was tested only at a 30 day dosing interval. i understand the larvae cycle, but then why 100% at 30 days and %5 less at longer interval. Maybe they went too long…well past the 45 day range?

    Having human relatives who are drug reps i know that it is about the money (imagine my surprise).
    But, why make it so convoluted to get at the truth? You probably will not get your vet to okay the cutting of tablets as it would be against standard of practice to do so and open them to liability if your dog got infected.
    There are vets in my area which will not even write scripts for heartworm medication if you cannot prove your dog has been on it monthly. Patients were asked to produce receipts showing they had purchased it before a new script was written.
    tara….mother of 10 lb. Japanese chin (who gets rxns taking Interceptor at the 2.3mg dosage).

  28. Jan Says:

    Tara, thanks for your comments. Re: “There are vets in my area which will not even write scripts for heartworm medication if you cannot prove your dog has been on it monthly” I have to presume that they will also accept a blood test showing no infection. Giving heartworm meds to a dog with heavy mature infestation is very dangerous.

    Refusing to prescribe meds (if you want them) otherwise would potentially be causing harm to your animal and the vet could be resprimanded or even sued.

  29. Diane Says:

    So…the scales were broken at the vets when I took my dog in yesterday to be tested for heartworm (as she has never had any heartworm meds.) She was 49 pounds at her visit in Dec….turned one sometime in Feb. I don’t think she has grown much, and since she is probably hovering around 50 pounds, is it ok to give her the 25-50lb dose, rather than almost double dosing her with the 50-100lb dose?
    I live just north of you in Mission Viejo….cold spring…watching the temps….great article!
    One more question. If I give her meds based on temps., do I need to have her tested every spring? Or can I assume she is fine and just start up the meds again?

  30. Jan Says:

    Diane, sorry for the delay. My blog software had a virus. It took a while to fix it.

    With medications, they make doses big enough for the upper limit and then some. A bigger question is why would you use heartworm meds at all in Mission Viejo? Your climate is similar to mine in San Diego and there’s virtually no heartworm here except from dogs coming from across the border. What I do with my own dogs is test once or twice a year. If there’s a problem, you start on the meds then. Remember, you medicate after infection, not before. The medication is an insecticide, not a preventative.

    This is what my vet friends recommend. It’s the cool evenings and dry weather that protect us. And remember, absent a big mosquito population and lots of exposure, heartworm is fairly difficult to contract.

  31. Susan Says:

    Hi Jan, I’m a fan of Scared Poopless and was so happy to see you partnering with Dr. Dodds and others this month for a seminar to benefit the Rabies Challenge Fund. I couldn’t go, but I’ll be purchasing the media when it becomes available.

    I’ve received conflicting information about heartworms – while being trained as a vet tech I was told that it’s basically unheard of in my area and so preventative isn’t necessary, yet most vets sell it to everyone they can talk into buying it while flourishing the map you included at the start of this article. This is mostly just ignorance on the part of the vets, who rely on the sales reps for their information – it adds revenue, after all. Of course, these are the same vets that still push annual vaccines. Not all vets were “A” students. 😉

    So, I wanted to point something out about the incidence maps that may not have occurred to some owners. They reflect where the dog was diagnosed, NOT necessarily where the heartworms were contracted. For example, a dog we saw at school a few years back had a horrible, raging heartworm infestation, but he didn’t contract it in our area – he contracted it while vacationing with his owner in South America. All of the cases of heartworm I’ve seen in my area of So. Cal. (which are limited since I’m new to the field) have been in dogs that were traveling to other parts of the country, or moved from heartworm-prevalent areas. The incidence increased after Katrina due to the influx of dogs from affected areas, as I know it did in many areas that took these dogs into rescue; native dogs weren’t the problem. I have yet to see a heartworm positive dog that contracted them locally. Also, the statistics are given as average reported cases per clinic, meaning that the number of clinics in a given area will affect the prevalence rate as it’s shown here. Food for thought when your vet is giving his/her well-rehearsed speech and pointing to a pretty red map.

  32. Diana Says:

    I’ve been web researching the subject of the necessity for heartworm meds in dogs for several months. I’ve had dogs aand cats as companions my entire life and they all lived happy and long lives WITHOUT HEARTWORM MEDS…..UNTIL the last three who were australian shepherds. Living in Eastern New Mexico and Lubbock in West Texas, I was convinced by vets that my dogs needed heartworm meds. These three lovely companions died early from brain tumor, diabetes, and the last from sudden unknown etiology organ failure! Odd, that the only three who died in such a terrible way were the only ones who I’ve ever given heartworm meds. These were inside dogs, only went out quickly with supervision for potty time and short walks. I have felt for over a year since my last sweet girl died suddenly, that I contributed to their deaths by giving them heartworm meds.
    I now have a new little guy, a 9 lb chihuahua who is healthy and full of energy. I live full time in Lubbock Texas now and I’m really afraid to give him heartworm meds, he is so tiny and the thought of toxic chemical coursing through that little body makes me feel ill. He is a good eater, loves fresh vegetables and goes for a daily walk. I don’t mind having him tested twice a year, however, I would prefer to use a natural repellant. Do you think this decision is wise? He is an inside kind of guy who prefers sleeping and playing indoors than hanging outside, but does love his daily trot. I don’t want to put him at risk due to my guilt over the previous three loving companions now gone as described earlier. This is a difficult decision for me and even after reading everything I can find, still wonder what is best for my year and a half old boy. He was given heartworm meds at the shelter where I adopted him, and our vet says not to worry yet, as we aren’t in heavy mosquito season, but we may want to revisit giving him the meds. I want him toxic free, eating his veggies, and doing yoga stretches with me for many years to come. Sorry to go on so long but truly, it seems most of us are in the same boat, rowing in circles over what is really best for the very special companions in our lives. I appreciated your articles so much, but am still conflicted.
    HELP! Thanks from Di and Peppy.

  33. Jan Says:

    Diana, if you test blood twice yearly, I’m told you catch any infestation quickly enough to treat it. It’s what I do, but I don’t live in a heartworm areas. An alternative is using the Safe Heart method, or giving a dose every six weeks just during hot weather. It’s a difficult decision only you can make.

  34. LIsa Says:


    Thank you for the article. We live in Michigan and have 2 dogs, a 85 lb weimaraner and 55 lb labradoddle. We just went to the vet today and they were negative with their heart worm test. We bought a 3 month supply of heartgard for now but they would like us to give it to them every 30 days year round. Is that necessary here in Michigan? Can we do just May through Sept. and every 45 days? They are indoor dogs and we live in the city area.

    Thank you in advance for your advice


  35. Jan Says:

    Lisa, I’m sorry, I don’t know your climate or how bad mosquitos are in your area.
    Also, I’m not a vet so I really can’t give you advice. I can say that all my holistic vet friends advise using it every 6 weeks rather than monthy, but the choice is up to you. You have to be diligent when giving it every 6 weeks so you don’t forget.

  36. Dan Says:

    The drugs approved for heartworm prevention in the US are ivermectin (sold under the brand name Heartgard and several other generic versions), milbemycin (Interceptor Flavor Tabs and Sentinel Flavor Tabs) and moxidectin (ProHeart) administered as pills or chewable tablets.

    You can buy a 50 ml bottle of 1% Ivermectin solution for cattle and swine for about $30 at a farm supply store (except in in CA and maybe elsewhere – I live in Missouri where you can).

    The dosage of Ivermectin in Heartgard for a 100 lb dog is about 275 micrograms (272mcg/lb of dog). If I did the math right that means there are about 1,800 (one thousand eight hundred) monthly doses in that $30 bottle or less than 2 cents per dose. How much do they charge for a dose of Heartgard? Don’t kid yourself – it’s ALL ABOUT THE MONEY.

    Now there is also 227 milligrams (mg) of pyrantel (as pamoate salt), a de-worming agent in the treatment of hookworms and roundworms, in that Heartgard pill. It must be very expensive.

    I have a Good Ol’ Boy country Vet who treated a puppy of mine for demodectic mange. He told me he could give me some expensive prescription or I could stop by the Orschelin Farm & Home store to buy a bottle of ivermectin and treat the dog myself. While he was at it he mentioned it was the active ingredient in a common heartworm medication. I did the rest of the research above myself and will use the half a bottle of Ivermectin I had left over to treat my dogs for heartworm the rest of my life. He went on to explain that ivermectin has many other veterinary uses but the FDA approval process keeps it from being widely used. It’s like Aspirin in that regard.

    Ivermectin is also not very toxic. The dosage on the label of the bottle recommends 1 ml per 100 lbs for cattle. One ml of 1% solution comes out to 10 mg or 10,000 mcg per 100 lbs of animal. I administered half that dosage to my puppy every day for three weeks to clear up the mange with no ill effects. This daily dose was almost 40 times more than the monthly dose in Heartgard.

    NOTE: Some breeds (especially the Rough Collie, the Smooth Collie and the Australian Shepherd) are affected by a genetic defect and should never ever be given Ivermectin.

    I am in no way suggesting that anyone administer Ivermectin without the advice of a veterinarian. But, I do think everyone should know just how big a scam the heartworm fear mongering is and that it’s ALL ABOUT THE MONEY.

    FACT: You are twice as likely to be murdered than your dog is of dying from heartworm.

    FACT: Heartworm is not fatal (but the treatment and arising complications can be).

  37. Drew Says:

    HI there, I used to live in Michigan and my vet urged me to give my lab/pitbull mix HW every month…so I did. Then I moved to Seattle and continued to give it to her until the meds ran out. I then called a vet and she told me it was highly unlikely that my dog would get it here so I stopped. I am visiting Michigan for about a week, driving across the country with my dog, should I give her HW when I get back or not?

  38. Jan Says:

    Drew, Dr. Dodds says to give it within 45 days of returning.

  39. Tony Stark Says:

    This is such a terrifying disease. Luckily that we got the right medication for them. Wish that your dog will recover soon.

  40. Phyllis O'Reilly Says:

    I live in Hawai’i. My dog tested postive for heartworm and the vet suggested monthly heartguard treatment. That was one year ago. What should I use for a preventative measure as heartworm here in the jungle, is pretty prevalent.

  41. Jan Says:

    Phyllis, your vet can recommend a product suitable for your area. Protect against as few parasites as seem likely. That is, if there are no ticks in your area, get a product that does not protect against ticks. Dr. Jean Dodds, world-renowned expert, talks about heartworm at length in our soon to be released DVD of a seminar I put on in March. Learn more about it at http://www.dogs4dogs.com/saferpet

    All my other suggestions are in my article on Heartworm Prevention: Options to Fear-Based Recommendations. I think you already read it.

  42. Jessica Draheim Says:


    I have just found your article and it is exactly what I have been looking for. I recently graduated with a degree in biology and an emphasis in nutrition. I have always had a facination with nutrition and completely believe in the advantages of organic and natural. Our bodies are not designed to be exposed to all of the chemicals which we are exposed to. Even tho our life expectancy has been improving over the last decades, there is a reason cancer is becoming so prevalent, even if we cannot prove what that reason is, it seems to me to be implied.

    I have recently also became the owner of a Maltese. Right now, he is 7 months old. I have spent the last 3 months stressing about the issue of heart worm, knowing that he needs to be protected, but not knowing the best way how. The trouble is, right now I am traveling for work. I spent the last few months in Texas, I am currently in OKC, and will eventually be back in Phoenix which is home. After lots of research, I found a herbal supplement called Only Natural Pet HW. I was set on giving him this, and when I went to the store to buy this, the person helping me out made me feel like I was not taking care of my pet right, I was completely making the wrong decision, and I was going to kill him without it. I finally gave in and took him to the vet to get him heartworm.

    This vet visit was also very unsettling. They weighed him and he is 8.2 pounds. They ended up giving him intercept, and they gave him the prescription for an 11-25 pound dog. I questioned this. I asked him why they were giving him a higher dose. This product should be tested and assigned to a specific weight for a specific reason. He told me that in 6 months he could grow to be more than 10 pounds. I felt uncomfortable giving him this, so I decided to call the number on the box and ask them. I asked if I could administer half the does to him instead. They had told me that I could not do this because it because they are unable to know where the specific medication is in the pill. I proceded to tell them that if i completely smashed up the pill, mixed it, and weight out half of the amount, law of averages said that this should be acceptable. They still advised against it.

    I felt very used and taken advantage of after this phone call. I felt like the drug company just wanted my money, and I felt like the vet was very outdated on this thinking and close minded to new ideas. That is when I stumbled across your blog. I feel much better after finding and reading this. I plan on just trying to keep him away from mesquitoes, getting him checked regularly, and if any, only giving him a small fraction of the pill when it is appropriate in my area.

    Do you know what would be the best approach when we are settled in Arizona? I also can’t wait to find a steady vet that agrees with my views instead of telling me I’m crazy and wrong. Also, where is the best site to begin making my dogs food on my own? I have been very concerned about making sure it has appropriate and necessary balance of protein, minerals, vitamins and fat.

    Thank you for being an advocate, and I sincerely appreciate your blog!!

  43. Michelle Says:

    Thank You so much for all this information. I love my dogs, they are my children. As an owner of 5 Chinese Crested Hairless (all were rescues), I always research and get as much information possible especially before going to the veterinarian.Chinese Cresteds seem to be a little more sensitive to vaccines and medications. I have a great relationship with my vet and respect his knowledge and training, but I know my dogs and trust my instincts. I question everything!! These are MY babies, I am responsible for their health and well being, who else would look out for them? One of my dogs, adopted from the state of Indiana, was tested for heartworm before being released from that state. Heartworm is far more common in the warmer states, as you tell us. Guess what? the test was negative. I do not believe in using heartworm meds, I have my pets tested. So one year after adopting the little guy, I took him in for his annual exam, and tested for heartworm. POSITIVE!!! What I did not know was how long they can be infected before it shows up, that he probably had heartworm when I adopted him, but when he was tested the first time the worms were not mature. Now I test every 6 months. Thanks again for the awesome information!

  44. Jan Says:

    Hi Michelle. I’m curious as to how your vet is treating the heartworm. If it’s in early stages, some vets just give heartworm preventative. You might check around. The typical treatments are pretty harsh.

    I hope you’ve also read my articles on vaccination for your small dogs.

  45. Deborah Says:

    I have learned that brewer’s yeast and garlic was a natural repellant for mosquitos. I also read that this could act as a dewormers (in correct doses per lb).

    I will be staying in the carribean so this is a very big conern for me.

    Any thoughts?

  46. Jan Says:

    Deborah, there are many holistic vets who are wary about using garlic other than in the smallest amounts. I’m no expert in using yeast and garlic for heartworm prevention. If I were taking MY dog to the Caribbean, I’d use the Safeheart method explained in my heartworm article. And I’d dose six weeks after arrival and departure in the Caribbean. Within several months afterwards, I’d have my dog tested. You might want to consult a holistic for more info. http://www.dogs4dogs.com/vets

    I would also worry about what shots they want. I’m sure they’ll want rabies. Please read my article about preventing reactions. http://www.dogs4dogs.com/blog/2010/09/23/rabies-vaccination-12-ways-to-vaccinate-more-safely/ And don’t get rabies with any other shots. This is very important.

    Have a nice trip.

  47. Susan Says:

    Jan, I’m a bit confused after reading your articles and would like some clarification on the administration of heartworm meds when a dog has already tested POSITIVE for worms. This question is for anybody who knows or is in a similar boat.

    The tech told us to give the Heartgard Plus monthly, on the same day so I can remember. Can I give it at six weeks even though it’s not intended as a preventative in our case but rather is acting to kill the worms already present in our dog.

    My own thinking is that it’s still effective at six weeks in either case.

  48. Jan Says:

    Susan, I’m sorry, but I don’t know the answer to that. You’ll have to ask your vet. Wish I could help.

  49. Heartworm meds making fluff sick - Page 4 - Maltese Dogs Forum : Spoiled Maltese Forums Says:

    […] If I did heartworm prevention meds I would use the protocol found on Jan Rasmusen's website which is a low dose of Interceptor every 45 day but not during winter – seems the safest to me. Heartworm Preventatives: Safety and Alternatives | Truth4Dogs […]

  50. DMH PenDragon Says:

    Has anyone ever considered that the transmission of Heartworm may not be via mosquito bite but rather by the ingestion of the egg/larva from infrequently changed drinking water dishes or puddles/ponds. The reason I ask this question is because humans have a body temperature range similar to dogs and cats and other animals that become infected. The question is are humans in the same geographic areas diagnosed with HW at the same rate as animal and if not why not? Is it because we seldom drink out of water dishes left out over nite, seldom drink water from standing puddles or ponds. Just a thought that I think needs to be explored. If true this would change the risk assessment for our dogs and cats and change the whole issue of preventive medication.

  51. Jan Says:

    DMH, It’s an nteresting thought, but heartworm infestation has been thoroughly investigated by major university vet schools. Not only is it transmitted by mosquitoes, but it’s only by female mosquitoes. But it’s a good question. Thanks for posting.

  52. Debbie Says:

    Help!! My neighbor took her dog to the doctor for his yearly shots. The dog is a rat terrier who had never taken heartworm medication. The doctor asked my neighbor why she does not give the dog heartworm medication and my neighbor said, “you never told me to”. The docotr perscribed a chewable monthly pill by Virbrac, called Iverhart Plus. The next day the dog stopped eating and started vomiting, a few days later the dog started swelling and my neighbor took the dog back to the vet. The vet did xrays and found the heart swollen and surrounded by fluids. The vet wanted her to take the dog to a specialist. Can this be a cause of and adverse reaction to the medication. My neighbor seems to think so and will not take the dog to a specialist due to the high cost, she feels that as the medicine wears off, the swelling will go down. I cannot sleep at night thinking about this, please give me advise as to what I can do?

  53. Jan Says:

    Debbie, I have a few thoughts.

    First, why would the dog need heartworm meds in the winter? Heartworms can’t mature absent mosquitoes and hot weather. Did you read: http://www.dogs4dogs.com/blog/2009/05/13/heartworm-medication-safety/ Also, did the vet do a heartworm test first, to make sure the dog didn’t have heartworms?
    This is very important. It’s extremely dangerous to give heartworm meds without a test first. Your vet has to know this. Every medication stresses this.

    Second, why is the dog getting yearly shots? No veterinarians are supposed to give them anymore. Actually, they never were necessary for the most important vaccines. Please read this http://www.dogs4dogs.com/blog/2010/12/02/what-to-do-when-your-dog-has-a-vaccine-reaction/ and also this about why the dog probably didn’t need shots in the first place.

    Find out some details and get back to me. This condition sounds serious. Don’t ignore it, but also see a better vet. If the vet caused the problem, he/she is unlikely to fix it. And especially contact the heartworm meds manufacturer.

    Your friend needs to find out what shots were given and should contact the vaccine manufacturer. Also contact the heartworm manufacturer.

  54. karen Says:

    Lost here on HW treatments We will be in Ocala Fla from jna- march have a 6 month old golden and confused if he should have heartworm med while we are there He is not going to be outside much In the other months we live in NYS We do put flea and tick treatment on him Our vet does not really convince me and she is new to us HELP

  55. Jan Says:

    Hi Karen. Everything I know about heartworm meds is in the two articles I wrote at Truth4Dogs. The decision has to be yours.

    If it were my dog, I wouldn’t give them when the weather is cold. 6 weeks after you return from Florida, presuming the weather is below 57 degrees at some time during each day, I’d ask your vet to test for HW. If it’s warmer, test sooner. You test and give meds 6 weeks AFTER exposure, not before. You’ll have to decide what to do during the summer months. The Part 2 article should help you.

  56. Kira Says:

    I came here because I was interested in Safeheart, and had never heard of it before. I was always told though that we can’t cut heartworm pills because the medicine isn’t distributed evenly. Is that true?

  57. Valerie Immel Says:

    Thank you for this enlightening information. My German Shepherd, Morgan, has developed bad side effects to Heartgard and Interceptor. I have thought many times he was being over medicated. Now I’m sure of it!

    We live in Southern California in a cool, mountainous area and the bats eat the mosquitos if there are any flying about. This wonderful article has helped me decide to test first, (twice a year), and then decide if treatment is needed. Once again, thank you so much for confirming what I have long suspected!!

  58. Jan Says:

    Valerie, I’m glad my article was helpful. Tell your friend! And do make sure you test your dog regularly.

  59. Lori Says:

    My rescued Golden Retriever almost died from heartworm preventative medication. He first got bloody diarrhea. Then he got ‘wandering lameness’ which went from leg to leg, he had to be lifted up with a towel to get up and limped severely when he had to go to the bathroom. He went to the Critical Care Hospital, had 7 joint aspirations, all abnormal (not Lyme), then developed a massive kidney/bladder infection, suspected glomerulonephritis and possible diabetes implications (the latter two worries cleared up). He was on massive doses of prednisone, antibiotics, and pain medication. Thankfully, I was lucky to have him for 4 more years when he succumbed to malignant melanoma of the mouth and I wonder if the prevent./meds instigated this. His major diagnosis was immune mediated polyarthritis – never could have any type of vaccine again as his immune system was rendered ruined. I am very wary about heartworm prevention and the vets said his illness was definitely caused by the med. I felt so bad, thinking I was protecting him and instead he got very ill. I grieve for him and miss him terribly. I love him so much, he’ll always be in my thoughts.

  60. Sharon Fraxer Says:

    I enjoyed reading the article and it is very informative. I had my 2 dogs on a heartwarm preventive for the first 2 years of their lives. However, I took them off of it. The blood test every year alone , cost very much. I can not understand if I had them on a “prevenitive” medication, why were they required to go in every year for a blood test. If the medication prevents heart warms, I do not feel they should be tested every year. Maybe every 2-3 years, but not once a year. I live in So. Calif. so I do not feel there was a big need for the medication. But the Vets here really push it on you.

  61. Jan Says:

    Sharon, ask your vet how many cases of heartworm he has reported to the Heartworm Society in the past three years. And ask how long the dogs had lived in Calif and where they were before that.

    I live in So Cal and just test my dogs every year or so — on the recommendation of my vet. I haven’t given them hw meds in many years.

  62. AJ Says:

    That map is from 2007! I live in a “cold” area of the country, by the Great Lakes, and we have had WARMER AND WARMER winters every year since then. The lakes haven’t frozen, we’ve had warm weather beginning in March, etc. We have been infested with bugs formally seen only in Southern areas, and we have not seen the long freezes we used to, and even our cold and flu patterns have shifted because we do not have the cold weather we used to. This is not to suggest that anyone needs to make any particular decision regarding heart worm meds, but I would suggest that we need very updated info on mosquito populations because ours have changed markedly since that map was created.

  63. DEBORAH Says:

    Thank you do much for the information. It has helped me decide what is best for my dog rather than just blindly giving her medication.

  64. pet sitting Says:

    Hi there, You have performed a great job. I will certainly digg it and in my opinion suggest to my friends. I am sure they’ll be benefited from this site.

  65. JR Says:

    Thanks I have been concerned about refilling Jeb’s meds. Money is tight right now and that would help alot. I understand so much now…. and once again I see it comes down to “lining the pockets of the drug company” human or pet…. GOD help us all.

  66. Alexa Says:

    I have 2 dogs–one is just over 25 lbs and one is just under. Of course, the packaged doses are for 1-25 and 25-50. I hate having to buy 2 different packages. Any thoughts on the efficacy of underdosing–giving a 28 1b dog dosage for a 25 lb dog?

  67. Jan Says:

    Alexa, I’m told that most brands of heartworm meds can’t be cut into pieces. Winter is coming up. Did you read the article on heartworms not being able to mature in cold weather?

  68. Liver Disorders in Dogs/Heartworm Preventives too - Pitbulls : Go Pitbull Dog Forums Says:

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  69. Susie Says:

    These articles are very freeing and confirmation of a decision I made a long time ago with regard to my dogs (and myself). I will not allow “Big Pharma” and doctors/vets scare me into taking meds or giving my pets meds that “they say” have been proven “safe”. My pets have had terrible reactions to annual shots and there is no telling what damage I have already inflicted upon them by buying into the fear factor that they must have monthly doses of poison to “prevent”/”kill” these parasites. I know now that the toxic heartworm meds are a very lucrative business and not necessary. The conflict of interest is HUGE and the incentives to sell yet more medicine and get pet owners to come in yearly for exams and give drugs to their pets monthly far outweighs their incentive to go against “conventional wisdom” and recommend healthy (non-processed foods) for their pets in order to build their immune systems as the best preventative. We (and our pets) are not broken by design and do not need help from drug companies to be “healthy”. My own research with myself and my pets is proof of this. I wish more people (especially MDs and vets) would be brave enough and take the time to do the research and tell the truth to their clients about how they can take control of their own health by leading a healthy lifestyle rather than depending on a system that encourages dependency on drugs to take care of problems that we create ourselves by poor choices.

  70. Jan Says:

    Susie, you seem very enlightened. You didn’t mention vaccines. I hope you read this: http://truth4pets.org/question-before-vaccination/ It’s one my other blog, truth4pets.org It’s all about vaccination.

  71. Judi Says:

    My 3 collies that I had on Interceptor Spectrum year round just became very, very ill after their last dose. My other 3 dogs on Heartgard did not. The 3 that were ill had terrible explosive diarrhea, vomiting, and would not eat for several days. It took 3 weeks to get them back to normal. I am positive they’d built up toxic levels of Interceptor. No more year-round for me. I have a breeder friend who uses Dimmitrol and worms for other worms periodically. I am going to try this only during our warm-weather months b/c I am still too scared to go with nothing. I’m also stopping Advantix. Less is more.

  72. Jan Says:

    Judi, make sure you report the reaction to Spectrum to the manufacturer. This is very important. If reactions aren’t reported, they’re considered safe. http://truth4pets.org/reporting-reactions/

    Please investigate Dimmitrol. I don’t know much about it and just because someone is a breeder doesn’t mean they know what’s best. I know many breeders who are completely ignorant about meds, shots and food. Sad but true. Your breeder may be great but would probably agree that many aren’t.

  73. 6Tigers Says:

    I was so relieved to find this article! We have finally solved the mystery of why our dog was having seizures. Thank you. Putting this page on my favorites for all the helpful reader comments.

  74. Jan Says:

    6Tigers, another thought about the seizures is vaccination. Many vaccines are known to cause seizures. http://www.dogs4dogs.com/dog-seizures-and-vaccination Also, look into acupuncture and homeopathy for treatment. Check out the referral lists at http://www.truth4pets.org/vets

  75. Brittany Says:

    I have a question that deals with both heartworm meds and vaccines. My dog needs to get his rabies vaccine this week so I can take him to the groomers ( he’s a mini poodle) as well as take him camping in a few weeks. He’ll be getting a CBC\chem before hand to make sure everything is good with him.

    Is 2 weeks long enough to wait till I give him his heartworm?

    Also, since only Sentinal is available now, is that still a good brand to use the safeheart dose with? Is every 6 weeks enough for the safeheart dose or is every 4 weeks recommended?

    I haven’t given him any heartworm meds yet this season so I would like to get him tested and started as soon as possible but since he needs to get the rabies vaccine I know I need to wait for at least a couple weeks. So in the mean time I’m trying to find the safest means to do so.

    Are there any better brands out there besides Sentinal and without the flea meds that use Milbemycin Oxime?

    If not it looks like I’m going to have to stop giving him a topical flea & tick preventative which worries me because he’s already had 2 tick born diseases with the use of Frontline.

  76. Jan Says:

    Brittany, see if the groomer will accept titers. If your dog has had two vaccines, they should be strong. Titers give the groomer assurance that the vaccine “took” — just vaccination guarantees nothing. And it’s a lot safer for your dog. Also, consider a groomer who is not a stickler for vaccines.

    Also, remember that heartworm meds are given 6 weeks after exposure. Doing it before does no good according to experts.

    If you have to vaccinate, have a holistic vet do it if you can. That vet will know how to do it more safely. http://www.truth4pets.org/vets

    Two weeks is a good rule of thumb between meds, but there are no guarantees, especially for a mini. http://truth4pets.org/2012/06/vaccinating-small-pets/

    The brands some of my vet friends use are Advantage (not Advantix) and Comfortis. Neither are really all that safe. I wish there is something I could recommend wholeheartedly, but there is not. I’m getting ready to research it again before too long. In the meantime, you might check out archived issues of whole-dog-journal.com.

  77. fm stecker Says:

    I have read all these comments and would love to have a definitive answer as I want to do the best for my 6 month old lab pup. I have never used heartworm med on any of my dogs..but the weather in Wis has been very wet and then gets warm. I would not forgive myself if my new puppy would test positive for heartworm but I struggle with putting toxic stuff” into his young body. I do as much as I can that is good and natural so I am going back and forth with what to do.IF I would do HW I would only do it every45 days and once he is older I would not use meds,when his immune system is stronger. Please, would you take time to answer my concerns. Thank you in advance. FM Stecker

  78. Jan Says:

    FM, I’m afraid there is no “definitive answer.” If you read the article on heartworm, you know what experts say.

    I am not a vet, but if it were my puppy, I’d probably not use meds and test at the end of heartworm season or maybe halfway through. Then you could give the meds under vet supervision to kill the worms, if any. Or, I’d start 45 days into the season and give it every 45 days. And I’d keep my dog inside when mosquitos are biting. There are also more natural sprays to ward off mosquitos. As I recall, there is another good article on it in the archives at whole-dog-journal.com.

    Of course, you won’t want to give the meds within several weeks of vaccinating. Here’s my best article on vaccinating. http://truth4pets.org/question-before-vaccination/

  79. Heart worm area map :)and Trifexis Warning - Boxer Forum : Boxer Breed Dog Forums Says:

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  80. wendy Says:

    I wanted to thank you for this site it has been very helpful! I wanted to know about other dogs, can heart worms infest other animals while you treat the one animal or do you treat all even thou there are no sighns?

  81. Jan Says:

    Wendy, heartworm infestations are caused by an infected mosquito biting an animal with a compromised immune system. They are not transferred from one dog to another. If you have a dog with an infestation, you need advice from a vet who understands the treatment.

  82. Nicole Says:

    Thank you for this very informative article. I live in Orange County, California, and my vet has not personally treated a dog with heartworm. My terrier mix is very sensitive to topical flea treatments, so in terms of heartworm, I have opted to test her twice per year instead of medicating her. Now to deal with those pesky fleas safely…yikes…

  83. dave gray Says:

    Great article,have to admit, I see some vets just ignore some signs and still over vaccinate and prescribe their money maker poisons.
    case in hand, adopted large terrier APBT.Early years for her with original owner wasnt the best in taking care of her. I adopted her and 1st changed her old roy kibble to Blue Buf. WILDERNESS.Big improvement but found out slight elevations in all of her liver enzymes and other liver functions. Put her on a good quality SAMe supplement and also some silymarin. 2 years go by liver is so so but what does the vet do, full vaccinations and changed from Trifexis to H.G . With in 40 days my baby came down with IMHA, 4k$ and 4 days later GONE.

    you think the vet seeing the age of the dog, compromised liver ,he would have known or advised ,”Hey this is your choice we can skip all of the non required by law Vac’s and I would suggest you might not want to give her HW meds any more from this time on or maybe just the summer months.” He knew the dog spent 22 hrs a day inside and 2 hrs a day outside for 2 one hour exercise romps at mid morning and late afternoon (5pm) Nope!! poison the hell out of her and make my $$ to pay off my loan. No regard for the life of the pet. I now am more in tune and knowledgeable in what my new companion needs.

    She gets just the rabies 1x every 3 yrs and we use essential oils to ward off skeeters and fleas & ticks. We do also administer an herbal extraction for HW as well but more importantly we provide 5 good basic components in her life 1. species appropriate raw diet, 2. purified water ,not the plastic jug BPA garbage but a very good reverse osmosis and filtration for all chemicals (VOC’S,CHLORAMINES , FLUORIDE,ETC) 3. enzymes and probiotics,4. a good quality greens mix im currently using one with blue green algae concentrates,chlorella,spirulina,it has over 20 trace minerals and vitamins in its compound , 5. exercise and structure and LOVE LOVE LOVE . This is the basics of building a rock solid immune system. We also give her coconut oil in her food 2x a day and also a good mushroom complex which aids in her organ functions. She is as strong as a horse and looks amazing, teeth white as snow and sweet breath from which she kisses you a lot with.

    I figure i can spend it NOW on giving her the best i can, for me its better than spending it on measures to save her life form not taking care of them as if they were your child. Pay now and give them a great life or pay later trying to save them from the neglect that you implemented instead of the prevention you should have been doing all thru out their life. My baby isnt my car or a piece of property as the law defines them but are furry 4 legged children who need us to help them be the great living creatures they are!!

  84. Jan Says:

    Dave, what a great doggy dad you are. I wish more people would follow your example. I wish more VETS would!

  85. M69 » Heartworm Preventatives: Safety and Alternatives | Truth4Dogs Says:

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  86. Ashley lozano Says:

    I’m a first time pet owner. My dog teddy is about 4 years old. He was doing great! For his first check up the vet asked me if he was on prevention unfortunately he wasnt. He told me they had to run a test before I choose which prevention I want to use. He came back with a positive test. So he explained the treatment and cost. I was horrified. So we began with steroids. He still seemed perfectly fine. Then was the moment for his first treatment. He came back pretty much the same Teddy. But now it’s been a week…he is coughing and gagging. He wasnt interested in his favorite treats. He wasn’t rushing out the door for his walk. I don’t think he can handle two more treatments of this. Then I read this article and another called “heartworms:the billion dollar scam” I don’t know what to think. I just want my teddy back to normal…do I have to go though the last two treatments? Any advice?

  87. Jan Says:

    Ashley, my vet recommends doing a heart ultrasound before doing treatments. A dog can be positive but not in a big danger, and the treatment is harsh. Unfortunately, the ultrasound is expensive. My advice: find a holistic vet. They’re likely to treat your dog with fewer side effects. Of course, it will cost money, too. http://www.truth4pets.org/vets

    Let me know where you live. Maybe I know a vet in the area.

  88. Heartworm Research | Perfect Dog Says:

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  89. Lindsay Jackson Says:

    Hi, and thanks so much for this site! I have a 3yr old Bouvier des Flandres who’s never been treated for heart worm. She was born in So. Calif., lived in Spokane WA, now lives in No. Calif. And we are moving to Atlanta GA this summer!
    I never used flea meds in WA but do in spring and summer here. I hate doing it but otherwise she gets flea problems.
    I’m not wanting to do heart worm medication either because I know that ALL of this stuff will ruin her health eventually.So I like the idea of seasonal treatment. Are there any natural options or less toxic options? What about the medication that was never marketed? Surely someone knows why. Thanks, Lindsay

  90. Jan Says:

    Lindsay, you might read this from holistic vet Will Falconer: http://vitalanimal.com/heartworms/

    And remember that vets tell me you give the meds, if you use them, after exposure and every six weeks is fine. You need to be especially careful in Atlanta, as you know.

  91. Joel Says:

    Hi Jan – Thanks for all the info! Can you recommend a holistic vet in the Long Island, NY area? Our new addition to the family came from a local shelter (our first pet…) and although they screened her for heart worms, she tested positive a week later. Thanks, Joel

  92. Jan Says:

    Find referral lists for holistic vets at http://www.truth4pets.org/vets.

  93. Kathy Says:

    Thank you for your research, information and articles. It really
    helps to make informed decisions. I live in the Midwest with cold winters. Many vets advise to keep dogs on meds year round. I give them every 6 weeks only in the warm weather. I am a firm believer in knowing facts and thinking for myself. We are all exposed to enough chemicals and toxins.

  94. BRE Says:

    Thank you for these articles on heartworms. I honestly didn’t know much about heartworms and never had an issue with any dog until I recently moved to Houston (from Kansas). My two, 11-year old German Sheps both tested positive according to my vet, I’ve used heartworm treatments but I admit I’ve never done so regularly. They wanted to do x-rays and give them the shots and have me keep them in cages for 2 months. My doggies are senior dogs that have never been crated for more than a couple hours and would not handle being crated that long. There couldn’t promise that the shots would make them live longer and at this stage in their life I just want them to enjoy the time they have. I agreed to giving them Doxycycline tablets for a couple months and retest but they said it would be a miracle if it cleared them of HW. They made me feel so terrible for not doing the “fast-kill” approach. Perhaps if they were just a couple years old I would consider it but not this late in their lives. Reading your articles make me feel like I’m not the horrible pet owner the vet is making me feel I am for not attacking this so aggressively.

  95. Jan Says:

    Bre, try contacting a holistic vet. They will likely be able to recommend a more gentle treatment. There’s a list of holistic vets at http://www.truth4pets.org. My own vet has long suggested that you do an ultrasound to see if the investation is serious. A dog can test positive without being in dire straights. Good luck.

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