INSEMINATION AND EGG PRODUCTION OF MOUSE-ADAPTED NIPPOSTRONGYLUS BRASILIENSIS (NEMATODA)

Average egg output per individual female Nippostrongylus was increased as the helminth density approached 148 worms per host. After this number, the individual production by females decreased, but was compensated for by the increased helminth density. Egg release, based on fecal recovery, began at 5 days postinfection. The period of maximum egg production occurred earlier with increased numbers of intestinal adults during the preimmune period in the host. A male ratio of 9.1% yielded fecal egg values that were equivalent to the normal levels with 31–44% males in a natural laboratory infection. Immunosuppression of the mouse host revealed cyclic peaks in fecal egg production. The peak intervals were dependent on helminth density, based on worm recovery at 29 days postinfection.

At 105 h after subcutaneous inoculation, 17% of the female N. brasiliensis were inseminated while 81% were mated by 110 h. Intestinal temperature showed no significant effect on female insemination. Examination of intestinal sections also revealed no distinct influence on the time that was required for a 50% insemination level. Observation of egg production by females in vitro showed that 2.2 eggs were released in a ½-h period.