Is there a good alternative to Immiticide treatment?

Eric writes:

Thank you for all the information regarding heartworm prevention and treatment. There is a lot of misunderstanding. We are an animal welfare group who took in a dog which tested positive for heartworms. The dog has received ivermectin weekly + doxycyline daily for two weeks, paused a week, and will receive another week of doxycycline.

A few studies conclude doxycyline + ivermectin kill adult heartworm: "Results indicate that the combination of these two drugs causes adult worm death." http://www.ncbi.nlm.nih.gov/pubmed/18433753 There is also internet talk of a "slow kill" method.

Do you have any advice for animal welfare groups or others with a budget that would not involve Immiticide? There are also such frequent shortages of Immiticide, it appears to be an annual event. Thank you.

For some reason, my reply is not posting to the original blog thread, so I am publishing it here.

Hello, Eric,

The American Heartworm Society has withdrawn its endorsement of so-called "slow kill" or "soft kill".

First, while some of the worms may die with long-term (like two years)administration of ivermectin and doxycycline, you cannot be certain of clearing the dog.

Second, the dog's problems with treatment arise from dealing with the death and movement of the worms within the pulmonary arteries.  We want to keep the dog's activity restricted until the dead worms have been dissolved by the body's defenders.

It takes at least five weeks for the dead worms to be cleared from the circulation.  With the Immiticide, we know when the worms will be dying (within a week), and can watch the dog accordingly. 

If you are treating long term with other medications, you would have to keep the dog's activity restricted for years, as you have no idea when (or if) the worms will be dying and moving.

The frustration with Immiticide shortage and expense is something I feel pretty personally.  While I have an adequate supply at present, I had none for several months.

My experience with humane organizations has been that resources are limited and must be allocated where they can do the most good.

When there was no indication that Immiticide would be available, the American Heartworm Society recommended monthly ivermecin (Heartgard, Iverhart, etc.) and 10 mg/kg of doxycycline twice daily for one month.  The doxy inhibits the Wohlbachia (beneficial symbiote of the heartworm)for an additional two months after giving it for one month.  Thus, they recommended repeating this at 3-month intervals.

If I were in a shelter environment, I would follow that protocol.  This is what one would do in the month prior to starting Immiticide treatment anyway.

The adopting owner just has to realize that he/she is taking on a bigger commitment when adopting a pet with heartworms.  There isn't a quick fix.

Thanks for reading and writing.

Comments

[Susan]

This is a very informative article. This shortage is unbelievable but at least they’re working on more alternatives (Trying to be positive)*. I have heard that now there is a product that both kills and prevents heart worms called HWF (Heart Worm Free)- this seems to be doing the best as a substitute for right now.

[Doc]

This product has no proven effectiveness.

I have spoken with veterinarians who are well-known experts on holistic and alternative medicines, as well as those interested in Chinese traditional herbal medicines.

The product is considered to be what used to be known as "snake oil", i.e. bogus.

[Eric]

Thank you Dr. Mobley.

This dog is also not neutered and the veterinarian does not want to neuter until the dog is free of heartworms.

We have been treating for doxycycline + ivermectin for 3 weeks so time to make a decision. I am going to the vet on Saturday and will discuss it.

I thought this study stated ivermectin + doxycycline killed 78.3% of adult heartworms after 36 weeks, but it states "reduction of adult heartworms" so perhaps they are referring to physical size reduction, not reduction in actual number.

http://www.ncbi.nlm.nih.gov/pubmed/18930598

Thank you for a good discussion of an important issue.

[Doc]

Hello again, Eric,

I am not a heartworm researcher, but do try to relay correct and current information from experts I respect.

We pre-treat dogs with this regimen, as I said before, and they still have the heartworms. It is a good thing to do, but I certainly would not depend on it clearing the dog of adult heartworms (without the Immiticide).

Thanks for reading and writing.

[Erich]

We ultimately treated with Immiticide and the dog has now tested free of heartworms.

At least, free based on the SNAP 4 DX.

It was a long and hard ordeal for the dog and with all the confusing information about heartworm and prevention and treatment it seems impossible to know the best choice. The person who was fostering him is a nurse and she told me more than once she thought he was going do die during recovery.

[Doc]

Glad you've had a good outcome. Thanks for writing.