Recovery and viability of Dirofilaria immitis microfilariae.

The viability of Dirofilaria immitis microfilariae recovered from canine blood by different methods was determined. Microfilaria recovery techniques included saponin lysis, saponin lysis with a trypsin treatment, dextran sedimentation and phytohemagglutinin treatment. Criteria for evaluating viability were microfilarial motility in vitro at 37 degrees C, microfilarial development in mosquitoes and the ability of microfilariae to circulate in mice. Although each method produced motile microfilariae, differences among groups of microfilariae recovered by different techniques were apparent by each of the criteria for viability. Saponin lysis gave superior yields of viable microfilariae.