When a mosquito carrying infective heartworm larvae bites a dog or cat it transmits the infection. The larvae grow and migrate in the body over a several month period to become mature, male/female worms which reside in the pulmonary artery system heart and associated blood vessels of the infected animal. As the worms in the body make the females release their offspring (microfilaria) into the bloodstream. Females grow to a length of up to 12 inches, males to about 6 inches and their lifespan inside the infected animal is up to 7 years.
The severity of the disease is a reflection of the numbers of heartworms present and the age of the infection.
Dogs and cats may show an absence of symptoms during the first several months following infection but eventually heartworm will cause a variety of medical problems affecting the functioning of the lungs, heart, liver, and kidneys. Symptoms may be very mild at first but can easily advance to critical stages. A cough is often an early indicator of infection but the disease will progress to an intolerance for exercise, abnormal lung sounds, and fluid accumulation in the abdominal cavity.
The Viaguard antigen test has been used with much success to detect heartworm infection. The presence of antigens is often available long before clinical symptoms and it is important for as early a diagnosis as possible.
Veterinaries have a wider range of preventative and treatment options to deal with heartworm and obviously a positive test would indicate consultation with a veterinarian.
TEST METHODOLOGY AND INTERPRETATION
Harvey Tenenbaum, PhD
Director of Operations