Effects of thyroxine and thiouracil on the retention, growth and egg production of microphallus pygmaeus in mice

Abstract

Effects of thyroxine and thiouracil on the retention, growth and egg production of Microphallus pygmaeus in mice. International Journal for Parasitology 16: 541–544. Preinfection intraperitoneal injection of 1.0 μg thyroxine daily for 21 days increases the initial primary worm burden of adult Microphallus pygmaeus in male and female Swiss albino mice. The difference persists for up to 8 days post-inoculation. The linear decline in the worm burden is not significantly different in treated and untreated mice but the projected duration of infection is 14.5 days in thyroxine treated as compared to 13 days in untreated mice. The parasite is usually significantly larger, but egg production is unaffected by thyroxine treatment. Preinfection intraperitoneal injection of 1.0 mg thiouracil for 21 days has no significant effect on duration of infection, worm burden, growth or egg production by M. pygmaeus in mice. The results may reflect a balanced response to two conflicting actions of thyroxine, namely a direct beneficial effect on the parasite and an indirect harmful effect via the hosts' immune systems.