Effects of larval tapeworm (Taenia taeniaeformis) infection on reproductive functions in male and female host rats.

Abstract This report examined the effects of larval tapeworm infection on the reproductive functions in both male and female host rats. Female rats were matched by age, then randomly assigned to control and treatment groups (infected with larval tapeworms). Estrous cycles were determined by vaginal smear with 95% of the control group exhibiting 4-day normal cyclicity and only 55% of the treated group exhibiting normal cycles. Female fertility was then evaluated for the normally cycling rats based on the percentage of successful matings on the evening of proestrus, number of implantation sites on Day 8 of pregnancy, and number of pups born at term. The normally cycling rats exhibited 96% successful mating, 12.95 ± 1.80 implantation sites, and 11.20 ± 1.80 pups born. Five months after larval tapeworm infection, the fertility parameters were decreased to 79%, 9.10 ± 1.20, and 7.50 ± 1.50, respectively. The control females were then used in a study of male fertility after larval tapeworm infection employing the same parameters used to test female fertility. At the onset of the study, control groups exhibited 95% successful mating, 12.50 ± 1.50 implantation sites, and 11.60 ± 1.60 pups born at full term. After the 5-month infection period, the parameters were substantially reduced to 29%, 6.20 ± 0.80 implantation sites, and 5.10 ± 0.80 pups, respectively. Average testosterone concentrations in serum and testis from control male rats were 8.80 ± 0.95 ng/ml and 3.88 ± 0.25 ng/mg protein, respectively. After the 5-month infection period, these levels were reduced to 2.47 ± 0.31 ng/ml and 1.28 ± 0.12 ng/mg protein, respectively. These results indicate an adverse effect on the fertility of both male and female host rats. The mechanism by which this occurs is yet to be elucidated.