Heartworm Disease in Cats What causes heartworm disease?
Heartworms are a blood-borne parasite called Dirofilaria immitis
that reside in the heart or adjacent large blood vessels of
infected animals. The female worm is 6 to 14 inches long (15 to
36 cm) and 1/8 inch wide (5 mm). The male is about half the size
of the female. Heartworm disease is much more common in dogs.
"...incidence of heartworms that is far greater than previously
thought." However, recent studies of cats with heart and
respiratory diseases have found an incidence of heartworms that
is far greater than previously thought. Cats are relatively
resistant to heartworm infection when compared to dogs, with the
infection rate in cats reported to be 5-20% of the rate in dogs
in the same location. Approximately 1/3 of infected cats live
indoors only. Typically, cats have fewer adult worms than dogs,
usually less than 6. How are heartworms transmitted to a cat?
The life cycle of the heartworm is complex and requires two host
animals in order to comp