Shipment of infective-stage filarial larvae (L(3)s) usually has been accomplished by transporting living infected vectors or L(3)s cryopreserved in liquid nitrogen. Our objective was to find culture conditions for transporting L(3)s that would promote survival of Brugia malayi larvae without altering their capacity to infect susceptible animals. In preliminary studies we observed that Ham's nutrient mixture F-12, with antibiotics and 1% fetal calf serum, could support L(3)s without apparent development for at least 10 days. In order to evaluate the effect of culture temperatures on infectivity, fresh L(3)s were divided into groups that were either immediately injected into jirds (infectivity control) or incubated for 24, 48, or 120 hr in tightly sealed tubes maintained horizontally at either 0 C, 20 C, or 37 C, before they were injected into jirds. Necropsies were performed on the jirds 120-130 days after injection to recover and count adult worms. Levels of microfilaremia were also determined. We found that L(3)s held overnight at 0 C, although apparently viable, were unable to survive in jirds. However, larvae kept at 20 C and 37 C produced patent infections with adult worms in normal locations even after 120 hr of in vitro cultivation. There was no statistical difference in mean worm recovery or size of worms from jirds infected with freshly harvested L(3)s and jirds injected with larvae that were maintained overnight at 20 C or 37 C. When cultured L(3)s were shipped from Michigan to Connecticut by overnight air courier, along with infected living mosquitos, the L(3)s appeared to be 99% viable upon arrival. L(3)s shipped in F-12 produced patent infections in C.B.-17 scid/scid mice with worm recoveries comparable to those observed in mice injected with L(3)s freshly obtained from shipped mosquitos.
