Trypanosoma cruzi: the development of estrus cycle and parasitemia in female mice maintained with or without male pheromones.

Female BALB/c or C57B1/6 mice, kept in small groups of three or five animals with or without male odor, all had a similar progesterone and corticosterone level, mean number of estrus and duration of estrus cycle. However, if males were kept in the same room, the mean duration of the estrus cycle was longer for both strains; and C57B1/6 females had a significantly higher number of estrus than BALB/c mice and showed a tendency to synchronize the estrus cycle within a group. After infection of females of both mouse strains with vector-derived metacyclic trypomastigotes of Trypanosoma cruzi, anestrus with intense phlegm production occurred during the acute phase of infection and this was positively correlated with higher parasitemia. Within individual groups of BALB/c mice, the female with the relatively highest corticosterone and progesterone level had the lowest parasitemia. In groups kept separate from male pheromones, one or two females in each group developed high parasitemias.