Reproduction and Trypanosoma congolense in Nigerian West African Dwarf ewes: I. Effects on the estrous cycle

Abstract

Ten cycling Nigerian West African Dwarf (WAD) ewes were used to determine the effect of Trypanosoma congolense infection on the estrous cycle. The estrus of ewes were synchronized using intravaginal progesterone sponges and divided into 2 groups (A and B) of 5 ewes each after 54 days (3 cycles). The ewes in group A were inoculated with blood containing approximately 5×10⁵ trypanosomes per ml of blood while ewes in group B served as the uninfected control. All the ewes were monitored from infection till the end of the study (56 days). Ewes in the infected group had silent estrus with clinical trypanosomosis that was characterized by undulating parasitemia, intermittent pyrexia, anemia and weight loss. There was no statistical (p > 0.05) difference between the mean estrous cycle length of the infected and the control groups. Estrus behavior of seeking the male, tail wagging, bleating, restlessness, edema of the vulva and mucus discharge from the vulva were observed in both groups at estrus, the basal progesterone profile corresponded with a true estrus rate of 60 % and 90 % for the infected and control groups respectively. However, there were statistical (p < 0.05) differences in the duration and intensity of estrus between the infected and control groups. The study shows that T. congolense infection affects the estrous cycle of Nigerian WAD but not detrimental to cause serious infertility.