Site selection by Microphallus pygmaeus Levinsen, 1881 (Trematoda: Microphallidae) in the laboratory mouse.

When Microphallus pygmaeus Levinsen, 1881 was inoculated orally to laboratory mice, most specimens, failed to attach to the intestinal wall and passed out rapidly with the faeces. Those which did settle were distributed more or less evenly throughout the small intestine by 4 h after inoculation. By day 1 after inoculation the worms had developed to oviposition and most were found in the ileum. By 2 days after inoculation all worms were established, and they remained in this region where they grew and continued egg production with very little further mortality until day 6 after inoculation. Thereafter, gravid worms progressively detached and passed rapidly through the caecum, colon, and rectum with the faeces. All parasites had been voided by about day 12 inoculation. In spite of high mortality, distribution in the small intestine is also affected by the site of implantation.