As a holistic veterinarian I am often asked which natural preventative I recommend for heartworm prevention. This is always a tricky question because there are so many variables that come into play. While there are websites that warn against the use of any and all chemicals in or on our pets, I often question whether it is possible in all environments to have our pets be completely chemical-free. It is a great goal, but we must face the realities of the polluted world in which we live, creating daily health stressors that contribute to compromised immune function.

Factors to consider when deciding whether to give heartworm prevention might include:

• Environmental temperature: Heartworms are spread by mosquitoes. A female mosquito must bite an infected canine. The immature larvae are ingested and live in the salivary glands of the mosquito where they mature in about two weeks, as long as the environmental temperature remains above 57 degrees fahrenheit around the clock. There are some areas of the world where the temperatures do not remain warm enough for a long enough period of time to allow this process to occur.
• There must be a reservoir of infected canines for mosquitoes to feed on.
• Mosquitoes survive best in high humidity.
• Most cases of heartworm occur in the Mississippi River Valley and southeastern United States.

There are many natural ways to minimize mosquito populations:

• Bats and purple martins eat very few mosquitoes. Their main predators are fish and dragonflies.
• Eliminate standing water. Mosquitoes spend the first ten days of their life in water.
• Bacteria can be used to kill mosquito larvae.  Bacillus thuringiensis israelensis (Bti) is a commercially-produced bacteria, sold in pellet and powder form, that can be laced into water where larvae live. It produces proteins that turn into toxins after the larvae eat it.
• Dark clothing attracts mosquitoes, as will dark coats on animals. Light-weight white fly netting can be used to keep mosquitoes away (commonly used as horse blankets to keep flies away in summer).
• Mosquito traps with attractants can kill thousands of mosquitoes per night.

A healthy dog with a healthy immune system will have decreased risk of development of adult heartworms, a process that takes seven to nine months from the time the mosquito bites. A healthy immune system will recognize heartworm larvae as foreign invaders, mounting an attack that can successfully defeat the invasion. Unfortunately, very few dogs have a fully functioning healthy immune system due to over-vaccination, over-use of medications and chemicals, and poor quality nutrition found in many commercial diets.

If you are considering skipping heartworm prevention, make sure you know the facts about heartworm prevalence in your area. Heartworm preventatives do not need to be given year-round in many locations, based on environmental temperature. Don't blindly accept the recommendation to give chemicals year-round if you live in an area that has cold winters. In my clinic the only preventative we carry is Interceptor, which contains milbemycin. Some clients opt for Sentinel, which also contains lufeneron, which prevents flea eggs from hatching. I do NOT recommend using Interceptor PLUS or Sentinel SPECTRUM, which also contain a tapeworm dewormer, praziquantel. Unless your pet has chronic flea infestation, they will not have chronic tapeworm infestation. Beware of products containing Moxidectin, a particularly dangerous chemical dewormer. Long-acting injections may seem convenient, but once given, there is no antidote to reverse side effects which may include the following adverse reactions: anaphylaxis, vomiting, diarrhea (with and without blood), listlessness, weight loss, seizures, and death.

If you are interested in learning more about keeping your pet's immune system healthy to help ward off heartworms and other parasites naturally, check out this e-book.