Bilharziasis (Schistosomiasis)

Bilharziasis (Schistosomiasis)

• Also known as Schistosomiasis
• It's granuloma Definition: specific type of chronic inflammation
• It's granuloma characterized by nodular collections of macrophages with a variable mixture of epithelioid cells, giant cells, and lymphocytes

Granuloma Types

• Infective granulomas include those caused by bacteria (e.g., TB), parasites (e.g., Bilharziasis), and fungi (e.g., Histoplasmosis)
• Non-infective granulomas include foreign body granulomas and those of unknown etiology, such as Crohn's disease

Definition and Etiology

• A chronic granulomatous disease caused by Schistosoma infection
• Endemic in Egypt and caused by two species
• Schistosoma hematobium infects the urogenital system
• Schistosoma mansoni infects the digestive system

Life Cycle

• Cercariae penetrate the skin and enter small venules
• They then travel through the systemic veins to the right side of the heart, then to the lungs, and finally to the left side of the heart
• From there, they enter systemic circulation, where Schistosoma hematobium reaches the vesical, prostatic, and utero-vaginal venous plexus
• Schistosoma mansoni reaches the mesenteric veins
• Worm maturation occurs, and ova are deposited in these sites
• Ova of S. hematobium are passed in urine, while those of S. mansoni are passed in stool
• The eggs hatch into miracidia which infect snails, in which the cercaria develop

General Pathological Features

• Bilharzial lesions represent hypersensitivity reactions (type I and IV) against antigens produced by cercariae, adult worms, and ova

Lesions Produced by Cercariae

• Acute allergic dermatitis, also known as swimmer's itch, occurs at sites of skin penetration

Lesions Produced by Adult Worms

• Dead worms release antigens, leading to thrombophlebitis, with severe venous wall necrosis and inflammation
• Living worms feed on red blood cells and produce a dark brown pigment, being phagocytosed by reticuloendothelial system cells
• Worms can also produce ova

Lesions Produced by Ova

• Recurrent bleeding and anemia occur due to injury by the spines of the ova
• There is also bleeding in the form of hematuria or blood passing with stool

Bilharzial Granuloma

• Some ova become trapped in the wall of the bladder or intestine
• Miracidia from trapped ova produce egg antigens, leading to the sensitization of T-lymphocytes
• This causes the secretion of lymphokines, which attract macrophages, eosinophils, and plasma cells, resulting in granuloma formation

Types of Bilharzial Granulomas:

• Cellular granuloma: Ova surrounded by macrophages, lymphocytes, giant cells, and eosinophils
• Fibrocellular granuloma: A cellular granuloma surrounded by fibroblasts and capillaries
• Fibrous granuloma: Small-sized, dense fibrous tissue

Lesions Produced by Bilharzial Antigens

• Bilharzial antigens from worms or eggs cause hyperplasia of lymphoid and reticuloendothelial cells

Bilharziasis of the Urinary Bladder (Bilharzial Cystitis)

• Caused by Schistosoma hematobium
• Lesions mostly occur in the most vascular areas of the submucosa of the posterior wall (trigone)
• Hyperemia and petechial hemorrhage in the bladder mucosa are mild and early lesions

Pathological Lesions of Bilharzial Cystitis

• Sandy patches: Very common; Trapping of large numbers of ova followed by dystrophic calcification, which results in irregular grayish, gritty, granular patches and causes pressure and ischemic mucosal atrophy
• Bilharzial polyps: Less common; Trapping of small numbers of ova leads to a granulomatous reaction and repeated processes will cause a polyp to form; Generally 2-20 mm in diameter
• Common Ulcers

Features of Bilharzial Ulcers

• Can be caused by ova penetrating the mucosa, shedding of atrophic mucosa, or detached polyps
• Single or multiple
• Small or large
• Superficial or deep

Other features of Bilharzial Cystitis (Pathological Lesions)

• Dense fibrosis will occur in long-standing lesions
• Epethelial changes can occur in Bilharzial Cystitis
• A common occurrence is Hyperplasia
• Brunn's nests: Focal dipping of hyperplastic mucosa (Solid buds of Urothelial epithelium in the submucosa )
• Cystitis cystica: Central degenerative changes of Brunn's nests that are pale mucosal vesicles that have cells lined by transitional epithelium

Types Epithelial Lesions

• Cystitis glandularis: Cysts lined by mucin-secreting columnar cells are precancerous
• Squamous metaplasia: This is a very common occurance and is cancerous
• Dysplasia: It is highly precancerous

Complications of Bilharzial Cystitis

• Recurrent hematuria causes anemia
• Secondary bacterial infections can cause calcium phosphate stone formations
• The spread of bilharziasis can affect the lungs
• Bladder neck obstruction can cause bilateral hydronephrosis, hydroureter and chronic renal failure
• Can cause bladder carcinoma

Bilharziasis of the Large Intestine (Bilharzial Colitis)

• Caused by Schistosoma mansoni
• Lesions occur mostly in the submucosa of the colon, particularly the rectum
• Hyperemia and petechial hemorrhage in the colonic mucosa are mild and early lesions

Pathological Lesions of Bilharzial Colitis

• The most common is Bilharzial Polyps
• Sandy patches and Bilharzial Ulcers
• Then Bilharzial fibrosis, and there will be no epethelial changes

Complications of Bilharzial Colitis

• Recurring intestinal hemorrhaging can cause anemia
• Can cause intestinal obstruction
• Then secondary bacterial infection bilharzial dysentry
• The disease spreads to the liver
• It will NOT lead to carcinoma

Bilharziasis of the Liver (Bilharzial Hepatic Fibrosis)

• Ova are carried as emboli through portal veins, leading to a potral tract, granuloma, and fibrosis
• This results in the compression of the portal vein causes portal hypertension, ascites, esophageal varices (hematemesis), Caput medusae, Piles (Bleeding per rectum ) and splenomegally
• Hematemesis a major cause of death

Bilharzial Splenomegally

• Normal spleen weight is 150 gm
• Early enlargement leads to 300 gm
• This causes lymphoid and reticulo-endothelial hyperplasia
• Late enlargement expands between 1 – 3 kgs
• Liver fibrosis will cause portal hypertension, along with chronic venous congestion of the spleen
• Can cause a lot of complications

Complications from Bilharzial Splenomegally

• Compression of adjacent structures, like the stomach
• Then Hypersplenism, which is the pancytopenia (anemia, leucopenia and thrombocytopenia)

Bilharziasis of the Lung

• Ova trapped in the interstitial of lung lead to granuloma, which leads to fibrosis
• The fibrosis will cause compression in the pulmonary artery, which results in pulmonary hypertension

Complications of Pulmonary Hypertension:

• Aneurysm of the main pulmonary arteries.
• Atherosclerosis
• Right-sided heart failure.