Development of Dirofilaria immitis third stage larvae (Nematoda: Filarioidea) in micropore chambers implanted into...

Groups of 100 third stage larvae of Dirofilaria immitis recovered from Aedes aegypti were loaded into 250 microliters capacity micropore chambers (0.3 micron pore size) and implanted into the peritoneal cavity of mice, jirds, cotton rats and ferrets. In all hosts 74-87% of larvae moulted by 74 hours, with less than 5% mortality. The fourth stage worms recovered at 74 hours were cultured in vitro in L-15 (Leibovitz) medium plus 20% foetal bovine serum with a dog sarcoma feeder cell line. After 96 hours cultivation, the larvae were comparable in size to those recovered from the dog 7 days post-infection (Orihel 1961). Chambers were also recovered from mice at intervals up to day 8. Larval survival at the longer times was approximately 90% and growth was similar to that reported for larvae in the dog. Incubation of third and fourth stage larvae in chambers with Trypan blue demonstrated that the gut is non-functional until the completion of the third moult.