What is Heartworm?
Heartworm is a mosquito-borne disease that affects many animals, including all breeds of dogs and cats.
Heartworm disease is present in every region of the world except Antarctica. It is found in every state of the United States, with southeastern states and states along the lower half of the Mississippi River having the highest number of cases.
This serious and potentially fatal condition is caused by parasitic worms living in the arteries of the lungs and occasionally in the right side of the heart of dogs, cats and other species of mammals, including wolves, foxes, ferrets, sea lions and in rare cases, humans. As one of the many species of filarids, more commonly known as roundworms, heartworms are classified as nematodes. Filarids rely on insect species to transport them from one animal to the next. Dirofilaria immitis is the specific filarid that causes heartworm in dogs and cats.
Mosquitoes become infected with the filarid while taking a blood meal from an infected animal. Within the mosquito, the filarid mature into an infective larval stage. When the disease-carrying mosquito bites another dog, cat or other animal, the larvae are deposited on the skin and actively transfer into the new host. It takes about two months for the larvae to travel through the connective tissue under the skin and pass into the animal's blood stream. Once there, the larvae are quickly transported to the arteries in the lungs. The larvae mature into adult worms and begin producing offspring in about six months. Adult heartworms can survive and thrive for five to seven years in an animal host.
Is Heartworm Fatal in Dogs and Cats?
Heartworm can be fatal in dogs. The severity of disease is determined by the number of adult heartworms present, the age of the infection and how active the dog is. There are more severe lung and heart disease changes with dogs with higher numbers of worms. The best form of protection from heartworms in dogs is to avoid being bitten by a mosquito in the first place.
Cats can fare better than dogs, since they are resistant hosts of heartworms. When they do become infected, cats typically have fewer and smaller worms than dogs. The life span of worms is shorter, approximately two to three years in cats as compared to five to seven years in dogs. However, heartworms can still cause significant pulmonary damage in cats, especially since there are no products in the United States approved for the treatment of feline heartworm infection.
Does My Dog Have Heartworm?
Dogs with this disease most often display small signs of a chronic infection as well as show a combination of physiologic changes. Although, dogs that are not active may never show signs of the disease at all. Heartworms may cause dysfunction of the lungs, heart, liver and kidneys. Some clinical signs associated with heartworm include cough, listlessness, abnormal lung sounds, enlargement of liver, loss of consciousness and abnormal heart sounds.
Does My Cat Have Heartworm?
Heartworms in cats can be hard to diagnose, since the symptoms often mimic many other feline diseases. Some generic signs of the illness include vomiting, lethargy, lack of appetite, weight loss, coughing, difficulty breathing and gagging. The signs of the disease cats have are often related to the organs where the adult heartworms are thriving. Infected cats can die quickly because there is not sufficient time to make a diagnosis or offer appropriate treatment. The best way to protect cats is with preventive heartworm measures.
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