Schistosoma mansoni in Colon and Liver

Abstract

Schistosoma mansoni is the species of the superfamily Schistosomatoidea that is pathogenic to humans. It is found in many countries in Africa and the Arabian Peninsula, as well as in the Western Hemisphere, including the islands of the West Indies and parts of Brazil. Its life cycle alternates between asexual multiplication in aquatic snails and sexual reproduction in humans. The life cycle of the major Schistosoma species has been described previously. 1 Cercariae infect humans through skin penetration in snail-infected waters. The parasites then migrate to the lungs and liver as schistosomula. They mature (female size, 1.6 cm) and mate in approximately 6 weeks. The adult worms are free of host reaction. Their habitat is portal venous, primarily of the large intestine, and egg deposition is hepatic and colonic. The eggs are elongated, with a prominent lateral spine near the more rounded posterior end, and measure up to 180 3 70 mm. They have a propensity to invade the venous walls and to penetrate the adjacent stroma. The eggs elicit the host reaction, which consists of suppurative inflammation and all stages of granulomas. Some eggs are excreted and are capable of hatching in water and infecting the snail intermediate host. Other eggs are trapped in the host tissue, where they die and disintegrate. Dead eggs usually are surrounded by resolving or scarred foci. Schistosoma mansoni eggs do not calcify. Inflammatory reaction can cause symptoms related to impairment of any organ in which the eggs are deposited, producing significant scarring. Therefore, an early diagnosis and prompt treatment are important. The diagnosis is based on the presence of eggs in feces (possibly using concentration methods to detect them) and in colonic biopsy specimens. 2 The images of eggs surrounded by inflammatory reaction in the colonic mucosa and the liver illustrate our case and correlate with clinical symptoms. A 25-year-old woman presented with a multiyear history of diarrhea. On examination, anemia, elevated liver enzymes, and gastrointestinal bleeding were found. She underwent elective colonoscopy, which revealed friable, erosive, and granular mucosa of the distal colon. Microscopic examination showed colonic mucosa with generally preserved crypt architecture, moderate inflammatory infiltrate of mucosal stroma, and multiple viable and nonviable parasitic eggs scattered in the mucosal stroma. Some areas with distorted crypt architecture and intraluminal leukocytes were noted, usually next to disintegrating eggs; however, no significant increase of intraepithelial leukocytes was seen