Prevalence of Dirofilaria immitis infection in dogs from a humane shelter in Ohio.

Hearts of 500 dogs more than 1 year old from a humane shelter in Columbus, Oh, were examined for Dirofilaria immitis infection. Peripheral blood from dogs with worms in the heart was examined for microfilariae. Dirofilaria immitis adults were found in 24 (4.8%) hearts. The number of worms in infected hearts were: 19 (1 dog), 6 (2 dogs), 5 (1 dog), 4 (2 dogs), 3 (1 dog), 2 (9 dogs), and 1 (8 dogs). Of the 24 infected dogs, 4 had only male worms, 8 had only female worms, and 12 had worms of both sexes. Microfilariae were found in 12 dogs--11 dogs having D immitis microfilariae, and 1 having only Dipetalonema reconditum microfilariae. The dog with D reconditum microfilariae had only 1 male D immitis adult in its heart.