Heartworm Disease in Canines
What causes heartworm disease?
Heartworm disease is caused by a worm called "Dirofilaria immitis." Heartworms are most commonly found in dogs. However, they can infect a wide variety of mammals including cats, ferrets, sea lions, bears, foxes, wolves, coyotes, and even people. Adult heartworms generally live in the heart and major arteries of the lungs, although they may be found in other areas of the body.
How are heartworms transmitted?
Heartworms can only be transmitted from one animal to another by mosquitoes. Adult worms produce microfilariae (small, immature heartworms) which may be found in the blood of infected dogs. The mosquito ingests heartworm microfilariae when biting an infected host (usually a dog). The microfilariae develop in the mosquito into "infective larvae" and are deposited with saliva on the dog's skin as the mosquito is feeding. The infective larvae pass through the skin and migrate through the body tissues.
Are all dogs at risk?
Dogs are considered the preferred host of the heartworm. While the highest prevalence of heartworm infection is in areas with heavy mosquito populations, heartworm-infected animals can be found in all environments making heartworm disease a health consideration regardless of where you live. Ask your veterinarian for recommendations regarding testing and preventing this disease in your pet.
What are the signs of heartworm disease in dogs?
Many dogs infected with heartworms may not show any evidence of infection in the early stages of the disease. Signs may appear eventually and may worsen over time. Early detection is important in managing your pet’s health.
Initially, dogs tend to develop a cough and experience difficulty breathing. They may exhibit decreased tolerance to exercise, develop fainting episodes or suffer severe weight loss. Since the heart and lungs are affected, many of the clinical signs seen are typical of heart failure, pneumonia or other debilitating disease. The severity and onset of clinical signs relate to three things: the number of heartworms present, the duration of the infection and the dog's response.
My dog rarely goes outside. Can it be infected with heartworms?
Heartworm infections have been reported in dogs that rarely go outside. If a mosquito carrying heartworm infective larvae enters the house, it can bite your dog and the larvae may infect your dog. In addition, most dogs make frequent short trips outside, during which mosquito bites may occur.
When do veterinarians recommend testing for heartworm infection?
Veterinarians recommend testing for heartworm infection before beginning heartworm preventive medication, at regular intervals after the dog is on a preventive medication and when dogs have clinical signs suggestive of heartworm disease. In heartworm endemic areas, testing may be recommended as part of the annual physical examination.
Can canine heartworm disease be prevented?
Fortunately, heartworm disease can be prevented, if preventive medications are started early and are consistently given throughout the dog's life. However, these medications will not eliminate existing infection. Knowing the heartworm infection status of your dog is an important part of keeping your dog healthy and fit.
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