Bilharziasis: Schistosomiasis

• Bilharziasis, also known as Schistosomiasis, is caused by granulomas from Schistosoma worms.
• The three types of worms that cause Bilharziasis are S. haematobium, S. mansoni, and S. japonicum.

Life Cycle and Infection

• Cercaria penetrates the skin, passing to all body parts.
• Adult worms mature in the liver's portal vein.
• S. mansoni goes to veins around the rectum.
• S. haematobium settles in the urinary bladder's veins and the female lays eggs.
• The eggs pass out, hatch in water, and release miracidium.
• Miracidium infects snails (intermediate host), turns into cercariae, exits the snail, swims, and infects humans.

Lesions

• Cercariae causes swimmer's itch, characterized by neutrophils, macrophages, and eosinophils that disappear in 2-7 days.
• Adult worms acquire a coating of host antigens and do not produce reactions in the vessel wall.
• Most ova escape to urine and stools from the bladder and rectum.
• Some ova are arrested in tissues or become parasitic emboli in the bloodstream.
• Ova that bypass the pulmonary capillary bed can reach effectively any tissue.
• Ova excite a granulomatous reaction which results in bilharzioma.

Bilharziasis of the Large Intestine

• Occurs in the rectum.
• Pathological features include congestion, sandy patches, bilharzial polyps, bilharzial ulcers, bilharzioma, and fibrosis that causes closed intestinal bilharziasis.
• There is no definite relation between bilharziasis and carcinoma of the large intestine.

Complications of Intestinal Bilharziasis

• Bleeding and anaemia occur.
• Bilharzial dysentery and pericolitis can occur.
• Disimpacted ova can pass to the liver causing bilharzial hepatic fibrosis.

Bilharziasis of the Liver (Bilharzial Hepatic Fibrosis)

Lesions due to Ovum

• Ova are deposited in portal tracts, exciting a granulomatous reaction, which results in fibrosis and portal hypertension.
• Fine periportal fibrosis shows few ova in fine tracts.
• In this case, the liver appears slightly enlarged with a smooth surface.
• Coarse periportal fibrosis has a large number of ova and dead worms in coarse tracts.
• In this case, the liver is smaller and has shallow depressions.
• The cut surface shows thickening of large tracts, which appear as "pipes", giving rise to the name "pipe-stem" fibrosis.

Lesions Due to Dead Worms

• Dead worms can also reach the liver as emboli, especially during antibilharzial treatment.
• Dead worms can cause acute inflammation in the veins with thrombosis, necrosis, and fibrosis around the affected veins.

Effects and Complications of Hepatic Fibrosis

• Portal hypertension with CVC of the splanchnic area presents.
• Thrombosis of the portal vein can occur secondary to stasis.

Effects of Portal Hypertension

• Chronic portal venous congestion leads to oesophageal varices, piles, and caput medusae.
• Bilharzial splenomegaly presents with Gandy-Gumma nodules, perisplenitis, and hypersplenism.
• Ascites is due to splanchnic congestion.

Bilharziasis of the Urinary Bladder

• Leads to terminal haematuria.
• Causes epithelial changes including congestion, sandy patches, bilharzial polyps, and bilharzial ulcers.
• Bilharzial contracted bladder (cystitis).
• Cystitis cystica, where Brunn's nests form and then cystitis glandularis.
• Squamous metaplasia & Leukoplakia can predispose individual to bladder cancer.

Complications of Urinary Bilharziasis

• Anaemia due to chronic haematuria.
• Stone formation due to ova, epithelial debris, and alkalinity of urine.
• Secondary bacterial infection can occur.
• Bladder fibrosis leads to hydroureter and hydronephrosis and can cause chronic renal failure.
• Carcinoma of the urinary bladder can be a very serious complication.