During the summer, mosquitoes can transmit to dogs and cats heartworm larvae. This disease, the cardiovascular heartworm, can have very serious consequences for the health of your pet.

Heartworm is caused by a parasite called Dirofilaria immitis. Unlike classical verse (intestinal worms), heartworms live in the heart and adjacent blood vessels. Their presence in the blood vessels causes cardiovascular weakness, decreased lung capacity and quite possibly, death. Heartworm disease mainly affects dogs and wild canids, but it can sometimes affect domestic cats, wild felines, ferrets and marine mammals.

Heartworms are transmitted from one animal to another by more than 70 species of mosquitoes.

Heartworms are transmitted from one animal to another by more than 70 species of mosquitoes.

Heartworms are transmitted from one animal to another by more than 70 species of mosquitoes. When a mosquito sucks the blood of an infested dog or a cat , it also sucks small worms called microfilariae that are present in the blood. Once inside the mosquito, the microfilariae develop into larvae. Later, when the mosquito bites another victim, he injects the larvae in the blood of the dog or cat, which in turn become infected.

Larvae take six and a half to seven months to mature and begin,themselves, to produce thousands of microfilariae in the circulatory system of its host. Adult worms eventually lodge in the right side of the heart and in its pulmonary arteries, while the microfilariae circulate through the bloodstream.

All these worms inside the blood vessels eventually increase the workload of the heart by restricting blood flow to the lungs, kidneys and liver, and can cause multiple organ failure. Initially, the affected animal has a chronic cough and reduced exercise tolerance; followed by sudden loss of consciousness and death.

Cats with this disease have similar signs to cats that are stricken with feline asthma.

Once infected, the animal can easily become a source of infection for his entire neighborhood. Sometimes a dog or cat may be infected without showing symptoms, and when symptoms finally occur, the disease is usually already well advanced.

The best way to deal with this disease is prevention. In dogs, after doing a blood test, your veterinarian will prescribe a preventative medicine for their needs, which will keep it safe from heartworm disease. In addition to protection against heartworm, several drugs also combine protection against fleas and major intestinal parasites. It is unfortunately very difficult to diagnose the disease in cats. It is therefore recommended to administer a monthly preventative medication.

The administration of preventive medication usually begins June 1st and ends November 1st. Variations are possible depending on the region of Canada where you live. Talk to your veterinarian.

Finally, a word about the public health component of the disease. According to the Companion animal parasite Council (CAPC) more than one hundred cases of human pulmonary dirofilariasis have been recorded over the span of 50 years in the United States. No such statistics were available for Canada. But, according to Dr. Alain Villeneuve, a parasitologist at the Centre hospitalier universitaire de Saint-Hyacinthe ,the actual numbers of human infection is more likely to be higher.

The human risk of being afflicted with this condition, however small it may be, is actually present. So how can we reduce this risk even more? Using mosquito repellents to avoid being stung is an excellent start point and for pet owners, making sure that his companion does not become an agent of human infection by giving it a monthly preventive medication.


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