Disaccharidase activity in the small intestine of susceptible and resistant mice after primary and challenge infections with Giardia muris.

The activities of four disaccharidases were examined in resistant (C57Bl/6) and susceptible (C3H/HeN) mice during the primary infection with Giardia muris and after challenge with either trophozoite extract or cysts. Significant decreases in lactase, sucrase, trehalase, and maltase activities in C57Bl/6 mice and lactase and sucrase activities in C3H/HeN mice in the anterior 25% of the small intestine were observed on day 10 after infection. The activities of maltase, sucrase, trehalase, and lactase in the jejunum of C3H/HeN mice were significantly reduced after challenge with trophozoite extract, when compared with the uninfected or infected, but not challenged animals. Decreases in enzyme activities of C3H/HeN mice were evident as early as 12 hours after challenge with the extract. The resistant C57Bl/6 mice showed little change in disaccharidase activity after challenge with trophozoite extract. On the other hand, challenge with cysts resulted in a few decreases in disaccharidase activities in both strains of mice: C57Bl/6 mice showed decreases in the duodenum, while disaccharidases of C3H/HeN mice had lower activity more posteriorly. Thus, challenge with parasite antigen results in a more severe disaccharidase deficiency in susceptible hosts when compared with resistant ones.