Disaccharidase activity in male and female C57BL/6 mice infected with Giardia muris.

To elucidate the contribution of host and parasite factors in induction of small-intestinal disaccharidase deficiency in giardiasis, we determined the activity of four enzymes in male and female C57BL/6 mice infected with Giardia muris. Both male and female mice exhibited significant disaccharidase deficiency as shown by decreases in the activities of lactase, sucrase, trehalase and maltase on day 10 after infection. However, by 20 days after infection the females had normal enzyme activities, whereas those in males remained significantly reduced. Prolonged disaccharidase deficiency in the males was related to the course of the primary infection where males had higher parasite loads in the small intestine than did females on day 20 after infection. By day 40 after the primary infection the enzyme activities had returned to normal levels and were similar in male and female mice. Secondary exposure of mice to either the infective cysts or a crude extract of the trophozoites caused disaccharidase deficiency. The females had lower activities of sucrase and trehalase as compared with males after the challenge. Thus, during the primary infection, disaccharidase deficiency was strongly associated with parasite number, whereas after challenge infections the more resistant females had lower enzyme activities in the small intestine than did males.