Print Article
Five Myths & Misunderstandings

What if the heartworm larvae never develop into adult worms?

Cats do not need an adult heartworm to exhibit clinical signs; in fact, larvae are a main cause of the problems. Studies show 50 percent of cats infected with heartworm larvae have significant disease of the small arteries supplying blood to the lungs.

Effect of Heartworm on Arterioles


A: An arteriole (small artery) in the lungs of a cat receiving heartworm preventive medication.


B: An arteriole from a cat infected with heartworm larvae, showing thickened walls which can cause complete obstruction.

Images courtesy of Dr. Ray Dillon and Dr. Byron L. Blagburn, Auburn University College of Veterinary Medicine.

download pdf

Email Article to Friend