Survival and infectivity of Brugia malayi microfilariae after cryopreservation.

Methods were studied for the cryopreservation of microfilariae of periodic Brugia malayi. RPMI-1640 tissue culture medium containing 6% dimethyl sulfoxide (DMSO) and 15% newborn calf serum was used as cryoprotectant. Samples were frozen slowly in the vapor phase of liquid nitrogen prior to emersion in liquid nitrogen (-196 degrees C). The freezing rate was -0.5 to -1.0 degrees C per minute, microfilariae remained viable for as long as, 212 and 375 days, survival rates were 94 to 98% and they were infective to Aedes togoi mosquitos. The infective larvae (L3) were obtained for 10-11 days after feeding at 28 degrees C room-temperature and the infection rate of L3 in test mosquitos was 22.4-30.6%. All DMSO should be removed from the freezing medium to restore microfilariae activity after freezing.

Blood meals of mosquito vectors of filariasis in Guizhou Province, China.

The blood meals of mosquito vectors of W. bancrofti and B. malayi were determined by performing CIEP of the eluant of crushed mosquitoes in filter paper against rabbit anti-human, cow and pig sera. The mosquitoes were collected from houses, cowsheds and pigpens in two counties in Guizhou Province. It was shown that all three species fed on blood from humans, cows and pigs with different preference. While An sinensis fed more on cows, Cx. fatigans and An. lesteri fed on the hosts that were nearby, i.e., Cx. fatigans caught from households fed more on humans, and those collected from cowsheds or pigpens fed more on cows and pigs, respectively.

Cryopreservation of infective-stage larvae of Brugia malayi.

Third-stage larvae of Brugia malayi (Guizhou, China strain), in RPMI-1640, 6% DMSO and 15% calf serum, frozen slowly in the vapor phase of liquid nitrogen prior to emersion in liquid nitrogen, remained viable for as long as as 321 days and were infective to Mongolian jirds. All DMSO should be removed from the freezing medium to restore larval activity after freezing.