Studies on the Microfilariae of the Dog Heartworm Dirofilaria immitis: Separation of Parasites from Whole Blood

Abstract

A technique employing saponin and enzymes (streptolysin O, trypsin) for the lysis of dog blood cells is described which fulfills several objectives for the development of in vitro culture methods with the microfilariae of D. immitis. i.e., the isolation of large numbers of viable parasites in a relatively short period of time, and the obtainment of cell-free microfilarial suspensions. Pronase and collagenase were as effective as streptolysin for yielding cell-free inocula, and under all conditions 80 to 95% of the microfilariae were routinely recovered. The viability of isolated microfilariae was assessed by noting changes in motility, the formation of vacuoles, and differences in survival or growth to the "sausage-form" in culture.