Question of the Day

The blood smear reveals a Dirofilaria immitis microfilaria, which indicates that heartworm disease (HWD) is the cause of the dog’s respiratory signs and acute collapse.

It is uncommon to visualize D. immitis microfilariae on a blood smear, however, HWD is a common infection, particularly in the southeastern U.S. Typical testing includes a HW antigen test, which can be performed in-clinic with a SNAP test, and a Knott’s test performed at reference laboratories. The Knott’s test is a more sensitive method of detecting circulating microfilariae.

Patent infection (i.e., when microfilariae are first detected) occurs six to seven months after initial exposure. HW are transmitted by mosquitoes during feeding.

HWD is easily preventable with monthly oral or topical preventative. Recommend year-round treatment in regions where ambient temperature does not drop below 65ºF (18.3ºC).

Image courtesy of Seth Chapman, DVM, MS, DACVP.