Heartworms, Dirofilaria immitis, live in the lungs, hearts, and associated blood vessels of various pets (dogs, cats*, and ferrets). Other animals, such as coyotes, wolves, and foxes, can also get heartworm disease. D. immitis are spread through the bite of a mosquito (Aedes, Culex, Anopholes, Mansonia).Adult female heartworms living within a dog release offspring, called microfilariae, into the animal's bloodstream. When a hungry female mosquito comes along and gets blood meal, she ingests the microfilariae and becomes infected. Under the right environmental conditions, the next 10-14 days can cause the microfilariae to become infective larvae. At this point, when the infected female mosquito bites another dog (or cat, ferret, etc.) the larvae are transferred to the animal through the bite wound. When a dog is newly infected, it takes 6-7 months for the infective larvae to mature to adulthood. Once the adult heartworms mate, the cycle can begin anew.
Heartworms can live within a dog for 5-7 years. Males reach 4-6 inches long while females can be 10-12 inches long. The average number of worms in dogs is 15, but can number from 1- 250. Symptoms depends upon worm burden (how many worms are within the dog). Dogs with low worm burdens can be asymptomatic, while those with heavy burdens can have exercise intolerance, hypertension, and possible failure of the right side of the heart.
*Both indoor and outdoor cats can get heartworm disease. Cats are not as susceptible as dogs and heartworms do not thrive within cats.
The best treatment for heartworms is PREVENTION! Check with your veterinarian about the best preventative method for your dogs and cats. Remember, we have mosquitoes year round here in Texas, so your heartworm preventative also needs to be all year.
