Intestinal schistosomiasis

Usually caused by S. mansoni, S. japonicum, S. mekongi and S. intercalatum infections.

• S. mansoni occurs mainly in South America, the Caribbean, Africa and the Middle East; S. japonicum occurs in the Far East, principally, in China and the Philippines
• S. intercalatum is found within the rainforest belt of central Africa while S. mekongi is found in Laos and Cambodia (1)

All segment of the colon may be affected, however the main sites of infection in around 90% of the patients are the rectum, sigmoid and descending colon (associated with inferior mesenteric vein) (2)

Adult worms migrate from their initial site in the liver sinusoids to their final site in the mesenteric venules whereupon the female lays eggs continuously. Egg deposition in the gut wall sub mucosa leads to inflammation, hyperplasia, ulceration, micro-abscess formation, and polyposis. These may lead to following symptoms in an individual:

• colicky hypogastric pain or pain in the left iliac fossa
• diarrhoea (particularly in children) that may alternate with constipation,
• haematochezia (blood in the faeces) (1,2)

In addition to the above colonic or rectal stenosis may be seen in severe chronic intestinal disease while protein loosing enteropathy may occur in colonic polyposis (1).

Furthermore granulomatous inflammatory response induced by embolised eggs of S mansoni and S japonicum to the liver results in presinusoidal inflammation and extensive fibrosis (periportal or clay-pipe-stem fibrosis) (1,2).

• is usually associated with sustained heavy infection and can take many years to develop
• results in progressive obstruction of blood flow, portal hypertension, and ultimately varices, variceal bleeding, splenomegaly, and hypersplenism (1,2)
• patients may present with upper abdominal discomfort with palpable nodular and hard hepato megaly, often with splenomegaly (3)

Reference:

• (1) Gray DJ et al. Diagnosis and management of schistosomiasis. BMJ. 2011;342:d2651.
• (2) Barsoum RS, Esmat G, El-Baz T. Human schistosomiasis: clinical perspective: review. J Adv Res. 2013;4(5):433-44.
• (3) Colley DG et al. Human schistosomiasis. Lancet. 2014;383(9936):2253-64.