Heartworm in WA?

***Note our recommendations changed as of April 2021…https://fairhavenvet.com/heartworm-in-wa-update-testing-now-recommended/***

What is heartworm? Are pets at risk for heartworm disease in western Washington? How do I protect my pet from contracting this serious parasitic infection? These are important questions asked by clients new to the area or those travelling with their pets on vacation.

What is heartworm? According to the FDA website on animal diseases, “Heartworm is a serious disease that results in severe lung disease, heart failure, other organ damage, and death in pets, mainly dogs, cats, and ferrets. It is caused by a parasitic worm called Dirofilaria immitis. The worms are spread through the bite of a mosquito. The dog is the definitive host, meaning that the worms mature into adults, mate, and produce offspring while living inside a dog. The mosquito is the intermediate host, meaning that the worms live inside a mosquito for a short transition period in order to become infective (able to cause heartworm disease). The worms are called “heartworms” because the adults live in the heart, lungs, and associated blood vessels of an infected animal.

Is there heartworm risk in WA? The good news is we live in an area that does not support the sustained development of this serious parasite. Thanks to our relatively cold climate, western WA is not an area of concern for heartworm. According to the American Heartworm Society, laboratory studies indicate that development and maturation of heartworm microfilariae in mosquito populations require a steady 24 hour daily temperature in excess of 64 degrees for at least 1 month. This is definitely unlikely in our current climate and relatively infrequent for much of the rest of WA state.

How do I protect my dog or cat from heartworm infection? If your pet has lived its entire life in western WA you do not need to do anything to protect your pet from this parasite. If your pet has relocated to western WA from a potential risk area (i.e. east of the cascades or south of Portland) your pet should not need continued use of heartworm prevention medication. If you are travelling with your pet to or through heartworm risk areas for less than a month it is recommended that your pet receive 3 consecutive monthly doses of heartworm prevention immediately upon return. If you are travelling for longer periods of time in heartworm areas you should place your pet on once monthly prevention medication. For all dogs that have relocated to the western Washington area from heartworm endemic regions, or traveled outside western WA at anytime during their life, testing is required prior to heartworm prevention administration. Administering heartworm prevention medication to a dog that may already have heartworm exposure can result in serious consequences for limited patients. Cats do not need testing prior to heartworm prevention administration.

The veterinary staff at Fairhaven Veterinary Hospital recommend the use of Interceptor Plus in dogs and Revolution Plus in cats as a heartworm preventative. Interceptor Plus is a monthly chewable tablet for dogs that treats and controls hookworms, whipworms and roundworms, tapeworms and prevents heartworm disease. It is often paired with a once-monthly product, Credelio, for the prevention of flea and tick infestations. Revolution Plus is a once monthly topical for cats that kills fleas and prevents flea infestations, treats and controls roundworms, hookworms and ear mites, and prevents heartworm disease.


Useful Links:

American Heartworm Society

Heartworm Infection

Feline Heartworm Infection