Heartworm is a disease caused by a parasite called Dirofilaria immitis, which lives in the right side of the heart and the adjacent blood vessels. Its presence in these blood vessels causes cardiovascular weakness, compromised lung incapacity, and eventual death. Heartworm occurs primarily in dogs but can also occur in cats and other animals on rare occasions.
Heartworm is transmitted to dogs, cats and other animals by mosquitoes. Over 70 species of mosquitoes have already been implicated. Transmission of the parasite occurs when a mosquito draws blood from a heartworm infected dog or cat. Once inside the mosquito, the microfilariae develop into larvae. Later, when the mosquito bites a new victim, the larvae are injected into the dog, thereby causing the infection. It generally takes about six to seven months for the larvae to mature and to start producing the microfilariae inside the dog or cat’s circulatory system. The adult worms end up occupying the right chamber of the heart and the pulmonary arteries, while the microscopic microfilariae circulate throughout the bloodstream. All these worms within the blood vessels produce an increased workload on the heart, along with restricted blood flow to the lungs, kidneys, and liver, eventually causing multiple organ failure. At first, pets may exhibit a chronic cough and/or reduced exercise tolerance, followed by sudden collapse and death.
Once infected, your pet can easily become a "carrier" or reservoir of the infection for an entire neighborhood. Sometimes a dog or cat may have heartworm disease but show no symptoms. It’s important to note that by the time the symptoms become apparent, heartworm is well advanced. While there are effective treatments available, veterinarians prefer to promote prevention of heartworm disease. Oral and topical medications that are administered monthly and have shown to be highly effective in preventing heartworm disease are available from your veterinarian.