 Parasitic disease caused by several species of flatworm  Affects many in developing countries  a disease caused by parasitic worms. The organisms (a type of fluke) inhabit tropical lakes and rivers, completing part of their life cycle in snails. They leave the snails as cercariae, which can infect humans by burrowing through the skin as they bathe. The flukes attach themselves in the veins of the intestine and bladder, and release eggs into these organs. The eggs are then expelled with urine and faeces, and pass back into the water. Chronic infections can damage many organs, including the lungs (as here), brain and liver. Drugs can treat the disease.

Distribution Map

 In liver, m & f pair up  female inserts herself into the gynecophoral canal of male  they are now ‘paired’.  Migrate to favoured sites: S. mansoni – mesenteric venules of large bowel & rectum S. japonicum – mesenteric veins of the small intestine S. haematobium – perivesical venous plexus surrounding the bladder Paired male & female

Cercaria: Cause acute dermatitis Adult worms: o Living worms: ingest blood and excrete brown bilharzial pigment o Dead worms: cause severe allergic inflammation with necrosis and eosinophilic infiltrate

 Ova: Produce granulomatous reaction formed of:  Macrophages  Lymphocytes  Plasma cells  Eosinophils  Few giant cells  Fresh or calcified bilharzial ova

 Ova: Produce granulomatous reaction formed of:  Macrophages  Lymphocytes  Plasma cells  Eosinophils  Few giant cells  Fresh or calcified bilharzial ova

Bilharzial large intestine

Section in large intestine. Bilharzial ova deposited mainly in the submucosa and to a lesser extent in the mucosa and muscle layers. Fresh ova show granular meracidium and surrounded by refractile shell. Degenerated ova are pink, while calcified ova are blue. The ova are surrounded by macrophages, plasma cells, eosinophils, lymphocytes and foreign body giant cells. Old lesion shows fibrosis. Diagnosis: Bilharziasis large intestine

section in the secum shows multiple polyps ranging in size from 1x1 up to 2x2 some of them have stalk multiple bilharzial polyps

Bilharzial polyp

Bilharzial bladder

Section in a polyp shows: Central core of connective tissue showing fresh, degenerated and calcified ova surrounded by bilharzial reaction (described). The covering mucosa shows hyperplastic glands surrounded by inflammatory infiltrate and bilharzial ova. Diagnosis: Bilharzial polyp, colon.

Section in a bladder wall showing bilharzial ova deposited in the submucosa and surrounded by bilharzial reaction (described). Old lesions show fibrosis. The mucosa shows areas of hyperplasia, atrophy, ulceration or squamous metaplasia.The hyperplastic epithelium dips down in the submucosa to form Brun’s nests. The centers of the nest show degeneration to form cystitis cystica. Dignosis: Bilharziasis, urinary bladder.

Bilharzia. Gross specimen of a lung showing damage (grey, right) caused by bilharzia (schistosomiasis),

Fresh and Dead ovum infect the lung tissue

Granulomatous bilharsial reaction in lung tissue

Adult worms infect the lung tissue