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case32 - Schistosoma

case32 - Schistosoma - Case 32 Lydyard Peter Cole Michael...

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1. What is the causative agent, how does it enter the body and how does it spread a) within the body and b) from person to person? Causative agent Human schistosomiasis, also known as bilharzia, is mainly caused by three species of Schistosoma . S. mansoni occurs in Africa, parts of the Arabian penin- sula, the Caribbean, and South America. S. haematobium occurs in Africa and parts of the Arabian peninsula. S. japonicum is now found in China, the Philippines, and Indonesia. S. intercalatum occurs in pockets in west and cen- tral African and S. mekongi is restricted to small pockets in Cambodia and Laos. Schistosomes are blood flukes, which are also known as trematodes. Adult worms are less than 2 cm long (Figure 2). Males have a longitudinal groove in which the female worm resides. They live in the veins around the blad- der in the case of S. haematobium or in the mesenteric veins of the intes- tine in the case of S. mansoni and S. japonicum . Entry and spread within the body The life cycle of schistosomiasis is shown in Figure 3. Humans are infected when they enter water containing Schistosoma cercariae (Figure 4). These Case 32 Schistosoma spp. A 25-year-old male was admitted to hospital vomiting blood. On examination of the abdomen both the liver and the spleen were enlarged. A full blood count revealed a reduced hemoglobin level of 9 g dl –1 and the white cell differential showed a raised eosinophil count of 1.1 ¥ 10 9 L –1 (normal range <0.45 ¥ 10 9 L –1 ). Endoscopic examination revealed dilated esophageal varices (Figure 1). Cirrhosis of the liver was suspected, but the patient denied any excessive drinking of alcohol and tests showed that he was negative for hepatitis B and C. A liver biopsy was performed and confirmed an abnormal liver, with extensive granulomatous change and fibrosis . On further questioning it transpired that he had spent much of his childhood living in a small village in Kenya. His parents had been working there on a farm. He would regularly paddle and swim in a nearby lake. He recalled no particular illness while living in Africa. Urine examination was negative but stool microscopy demonstrated the presence of Schistosoma mansoni eggs. A rectal biopsy obtained at sigmoidoscopy showed granulomas , containing Schistosoma eggs. Schistosomal serology was also positive. He was treated with praziquantel and his stool was monitored for the disappearance of Schistosoma eggs. He was referred to a hepatologist for further management of his esophageal varices. Serial ultrasounds were performed to monitor the liver fibrosis. Figure 1. Endoscopic view of large esophageal varices (arrowed). Figure 2. Adult schistosome worms. The female (on the left) is slender and fits into a groove on the ventral surface of the male.
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