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The American Heartworm Society has withdrawn its endorsement of so-called "slow kill" or "soft kill".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