Dog's Diseases

Heartworm

As its name implies Heartworm disease is a parasite which can be found in the hearts and pulmonary arteries of dogs and much less frequently of cats. Heartworm (Dirofilaria immitis) is transmitted by mosquito. The mosquito becomes infected by feeding upon an infected dog. It spreads the disease by then feeding upon other dogs and infecting them in the process. The parasite undergoes a number of life stages in the dog before the mature worm migrates to the pulmonary artery and sometimes into the right side of the heart where the females will lay eggs which grow into the infective stage which infects mosquitoes during feeding.

Heartworm is diagnosed based upon clinical signs of right-sided heart failure and a number of laboratory tests which either detect the worm directly (PCR) or detect the antibodies produced by the host. It is the later type of test which is the most popular and used frequently in veterinary clinics. When infestation is heavy the microfilaria may be seen visually under a microscope. The adult worms can be seen using ultrasound.

The treatment of heartworm is not without risk. Injections are available to kill the adults and larval stages but the host's immune response to the dead worms can result in a severe reaction. Several treatment protocols have been developed to minimize these complications.

Heartworm is easily prevented by either a once yearly injection of ProHeart or by monthly dosing with any number of heartworm prevention tablets such as Heartgard.

In Hong Kong feline heartworm disease is not as common as heartworm disease in dogs and is rarely seen.