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Heartworm (Dirofilaria immitis) can cause mild symptoms, such as coughing, but with time, more severe symptoms such as congestive heart failure, weight loss, fluid build up in the abdomen, fainting spells, anemia, collapse, and death usually occur. We recommend regular heartworm testing. If a dog has undetected heartworms and it is given a dose of preventative medicine, the dog could have a detrimental or deadly reaction. Treatment for adult heartworms in dogs is expensive and potentially harmful to the dog. This is why prevention is so important.
Luckily we have several excellent medications which can prevent heartworm if given as directed. There are oral medications which need to be given monthly, and which also help protect against some intestinal parasites. There are topical medications which is also applied monthly.
Heartworm is very common: it has been diagnosed in dogs in all 50 states and Canada, and has a virtual 100% prevalence rate in unprotected dogs living in highly endemic areas. It is transmitted by mosquitoes. The mosquito injects a microscopic larvae which grows into an adult worm six to eighteen inches long inside the heart of the affected dog.
Heartworms were once thought to be rare in cats. Now we know the incidence is anywhere from 10% to 50% of the canine rate. Heartworm disease in cats is different than in dogs. Cats usually test negative on the routine blood test done in the hospital, the worms are smaller and usually do not produce microfilaria which are like baby heartworms that circulate in the bloodstream. Veterinarians have to do different tests to diagnose heartworms in cats; these are available at the Clinique Vétérinaire du Vieux Village.
Heartworm symptoms are different in cats. Cats usually have asthma signs or cough, even vomit. Cats can die acutely. Currently, no treatment exists for adult heartworms in cats. Depending on the incidence of canine heartworm in a given area, many veterinarians are now recommending monthly heartworms preventative in cats also.