Exogenous Testosterone Mediates the Susceptibility Differences of Male and Female Mus Musculus to the Different Life Stages of Schistosoma Japonicum

Abstract

To determine if testosterone mediates susceptibility differences between male and female mice infected with Schistosoma japonicum, testosterone was either removed or exogenously applied in groups of BALB/C mice that were infected with the same number of cercariae. The mice were then monitored for host survival, worm burden, organomegaly, and egg count. By eight weeks after infection, 80% of the members of the negative control group or the mice with no testosterone source (castrated males and untreated females) were dead, while only 45% of the members of the experimental group or the mice treated with exogenous testosterone (testosterone-treated castrates and testosterone-treated females) had died. On the other hand, the positive control group or the mice with endogenous testosterone source (normal males) exhibited the same proportion of dead mice (80%) as the negative control group. The mean number of worms recovered from the negative control group was significantly higher than those from the experimental and positive control groups. The number of eggs counted in the liver sections of the mice correlated strongly with the worm burden, significantly more eggs were present in the liver sections of the mice in the negative control group than those in the experimental and positive control groups. The hepatomegaly exhibited by the mice likewise correlated with worm burden, but the degree of splenomegaly did not differ significantly between groups. Thus, the sex-based susceptibility difference observed in male and female mice infected with the same number of cercariae appears to be associated to the presence of testosterone.