Heartworm disease

Subject: Heartworm disease Fri 04 Jul 2008, 8:43 pm

http://www.essortment.com/all/heartwormdogsc_rgli.htm

Heartworm, or Dirofilaria immitis, is a potentially dangerous parasitic worm spread by mosquitoes. Dogs are the most common hosts for heartworm, although it is also found in cats and other animals, including humans. It commonly lives in the right side of the heart as well as the lungs and the pulmonary arteries. In cats, heartworm is usually only found in the lungs. Cats are initially more resistant to heartworm than dogs. Outdoor male pets are much more likely to be infected than indoor pets.
The life cycle of a heartworm in a dog is six to seven months; in a cat it is eight months. Larvae from an infected female mosquito are deposited in the skin usually where the coat is thinnest. They burrow into the animal and change in form, moving into the veins and eventually the heart. In three to four months adult worms emerge. They can survive for about five years in a dog's heart and reach lengths of twelve inches. In cats, worms are smaller and live for only two or three years. Male and female worms mate and produce millions of offspring called microfilaria that live in the small blood vessels of up to 90% of infected dogs for as long as seven years, causing lung and liver problems from blocked blood flow. Single-sex heartworm infections are more common in cats; microfilaria are seen in less than 20%, and they are only present for about a month. The microfilaria are then swallowed by biting mosquitoes, and develop into infective larvae in the mosquito in ten to forty-eight days, depending on the climate. The larvae move into the mouth parts of the mosquito, where they can infect a new host--a cat or dog--when the mosquito bites the animal.

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The disease may be advanced by the time an animal shows signs of infection. It is diagnosed mostly in three-year-old to eight-year-old dogs; but in some regions, dogs as young as one-year-old can be infected. Cats can harbor a heartworm infection at any age from nine months to seventeen years. Some cats seem to be able to get rid of the infection spontaneously. Dogs have been found to have as many as 40 to 250 heartworms; cats rarely have more than ten, and usually only one or two. The severity of the disease depends on the number of worms, their location, the duration of infection, and the dog's immune response. If there are only a few worms present, there may be no signs of heartworm disease. In cats, just a few worms can produce fatal illness, and sometimes infected cats die suddenly with no time for diagnosis or treatment. There may be no symptoms at all, or they may exhibit many of the same signs of infection as dogs. These include shortness of breath, fainting after exercise, tiring easily, </FONT></FONT></FONT>and loss of appetite, and listlessness and nervousness. There may be anemia, jaundice, poor coat condition, swelling of the abdomen, and bloody sputum and stool. Labored breathing at rest, prominent ribs, and chest bulging are signs of progressive disease. In advanced stages, heart failure and pulmonary clotting can cause collapse and death. Cats may also suffer from convulsions, diarrhea and vomiting, rapid heartbeat, and even blindness.

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