EXPERIMENTAL BLASTOCYSTIS-HOMINIS INFECTION IN LABORATORY MICE

Young (less than 8 weeks old) immunocompetent BALB/c mice became infec ted with Blastocystis hominis after inoculation of fecal cysts orally and of in vitro axenic-culture forms intracecally. This study confirme d that the fecal cyst was the form responsible for external transmissi on and that the mode of transmission was by the fecal-oral route. The infection was self-limiting and the infected BALB/c mice appeared norm al except that some of them showed weight loss and lethargy. Both vacu olar and granular forms were found in the cecum, but only cyst forms w ere observed in the colon. Histological examination of the cecum and c olon showed intense inflammatory-cell infiltration, edematous lamina p ropria, and mucosal sloughing. It is apparent that although B. hominis is not invasive, it is capable of causing pathogenesis in BALB/c mice .