Where would you expect to find Dirofilaria immitis during the necropsy of a dog?

• A. In the heart
• B. In the liver
• C. In the small intestine
• D. In the feces

Answer: (A)

Dirofilaria immitis is the canine heartworm that lives in the heart and pulmonary arteries. At necropsy you would expect to find adult worms in the right side of the heart—primarily the right atrium and right ventricle—and in the nearby proximal pulmonary arteries. The liver, small intestine, or feces are not typical locations for heartworms, since these worms reside in the cardiovascular system rather than in those organs or in waste products. Microfilariae circulate in the blood, so you would more likely detect them on a blood smear rather than in feces. During necropsy, focusing on the heart and lungs will reveal the worms and reveal any related vascular changes.