Heartworm is a parasitic roundworm that is spread from host to host through the bites of mosquitoes. The heartworm is a type of filaria, a small thread-like worm that causes filariasis. The definitive host is the dog, but it can also infect cats, wolves, coyotes, foxes and other animals, such as ferrets, sea lions and even, under very rare circumstances, humans. The parasite is commonly called "heartworm"; however, adults often reside in the pulmonary arterial system as well as the heart, and a major effect on the health of the animal is a manifestation of damage to the lung vessels and tissues. Occasionally, adult heartworms migrate to the right heart and even the great veins in heavy infections. Heartworm infection may result in serious disease for the host, with death typically as the result of congestive heart failure.
Many dogs will show little or no sign of infection even after the worms become adults. These animals usually have only a light infection and live a fairly sedentary lifestyle. However, active dogs and those with heavier infections may show the classic signs of heartworm disease. Early signs include a cough, especially on exercise and early exhaustion upon exercise. In the most advanced cases where many adult worms have built up in the heart without treatment, signs progress to severe weight loss, fainting, coughing up blood and, finally, congestive heart failure.
If an animal is diagnosed with heartworms, treatment may be indicated. Before the worms can be treated, however, the dog must be evaluated for heart, liver, and kidney function to evaluate the risks of treatment. Usually, the adult worms are killed with an arsenic-based compound. The currently approved drug in the US, melarsomine dihydrochloride, is marketed under the brand name Immiticide. It has a greater efficiency and fewer side effects than previously used drug which makes it a safer alternative for dogs with late-stage infections.
After treatment, the dog must