Organism(s): Schistosomiasis Japonicum

Schistosomiasis (aka bilharzias or “snail fever”), is a chronic parasitic illness that, although rare in the United States, affects between 200 to 300 million people across the world, with another 600 million people at risk of contracting the infection. This disease is endemic to 74 countries to include Central and South America, Egypt and other African nations, the Middle East, Asia (particularly rural areas in China), and India. The infection is brought to the United States by immigrants and travelers returning from endemic areas.

The main species of blood flukes or Schistosomes to infect humans are S. mansoni, S. japonicum, S. mekongi, and S. haematobium. The first three species characteristically affect the gastrointestinal tract (inhabiting the portal veins) and the latter typically affects the urinary tract (inhabit veins of bladder) and is the most common cause of bladder calcification in the world. The incidence in males is nine times greater than in females. Risk factors include but are not limited to extreme poverty, lack of public health facilities, and poor sanitary conditions. Infection most commonly occurs in adults who live in rural areas and/or who work in either the agricultural or freshwater fishing fields.

Route of Infection: Schistosomiasis is a chronic infection caused by parasitic trematode worms that currently affects 200 million people in subtropical and tropical environments and is not an insignificant threat to deployed military members. Schistosomiasis infection in humans begins with cercariae penetration of the skin or buccal mucosal from a contaminated water source. Schistosome ova are subsequently deposited within the liver, gastrointestinal tract, and genitourinary tract and a granulomatous and fibrotic reaction ensues, resulting in a multisystemic and often nonspecific clinical manifestations. Schistosomiasis is major cause of portal hypertension worldwide and can potentially result in permanent gastrointestinal and urinary system damage if not appropriately treated.

Clinical: Clinical manifestations can be separated into three different phases: acute, chronic, and severe. Also known as Katayama fever, the acute phase is usually found in children or young adults who have not had any prior exposure to Schistosomes. Believed to be the result of high antigen exposure, this early phase is more commonly associated with S. japonicum infections. Clinical manifestations of this early phase include: dermatitis, bronchospasm, fever, malaise, diarrhea, lymphadenopathy, and arthralgia; amongst other nonspecific complaints. The chronic phase, which is usually subclinical, is characterized clinically by diarrhea and fevers. There may be related growth rate depression, hepato- and/or splenomegaly, and complications of hepatic fibrosis (i.e. portal hypertension, hepatosplenomegaly, ascites, varices of the esophagus and related hemetemesis).

The most frequent cause of death in hepatosplenic schistosomiasis is gastrointestinal bleeding. Bladder fibrosis may contribute to ureteral obstruction, pyelonephritis, and hydronephrosis which can lead to renal failure. Bladder infection has been linked with the development of bladder carcinoma. The severe phase of disease, unlike the chronic phase, is typically symptomatic.

The Schistosome has a complex life cycle: humans are infected through contact with contaminated fresh water. The pathophysiology of gastrointestinal calcification is related to the Schistosome fluke eggs deposited in tissues and not caused by the flukes themselves. Following deposition of these Schistoma fluke eggs within the venules of the urinary tract (most commonly the bladder and distal ureters), and gastrointestinal tract lumen, there is development of a hypersensitivity or granulomatous reaction and fibrosis around the Schistosome eggs. The severity or degree of calcification correlates with the number of eggs deposited. Many of the eggs are swept back into the liver, where they become lodged within the parenchyma and result in hepatic calcification, fibrosis and associated portal hypertension.

Clinical manifestations can be separated into three different phases: acute, chronic, and severe. Also known as Katayama fever, the acute phase is usually found in children or young adults who have not had any prior exposure to Schistosomes. Believed to be the result of high antigen exposure, this early phase is more commonly associated with S. japonicum infections. Clinical manifestations of this early phase include: dermatitis, bronchospasm, fever, malaise, diarrhea, lymphadenopathy, and arthralgia; amongst other nonspecific complaints. The chronic phase, which is usually subclinical, is characterized clinically by diarrhea and fevers. There may be related growth rate depression, hepato- and/or splenomegaly, and complications of hepatic fibrosis (i.e. portal hypertension, hepatosplenomegaly, ascites, varices of the esophagus and related hemetemesis).

The most frequent cause of death in hepatosplenic schistosomiasis is gastrointestinal bleeding. Bladder fibrosis may contribute to ureteral obstruction, pyelonephritis, and hydronephrosis which can lead to renal failure. Bladder infection has been linked with the development of bladder carcinoma. The severe phase of disease, unlike the chronic phase, is typically symptomatic.

The diagnosis can be readily made through the identification of eggs in stool in S. japonicum and S. mansoni infection or by detecting eggs in urine in S. haematobium infection. Other more aggressive means of definitive diagnosis include liver, rectal, or bladder biopsy. Additonal nonaggressive yet relatively sensitive diagnostic tests include oval precipitaiton testing and an intradermal immunological skin test for the Schistosome antigen.

Imaging can play a role in demonstrating the extent of organ involvement and complications of Schistosomiasis infection. Conventional radiography may be the initial means of detecting calcification of the bladder or distal ureters (parallel linear radiodense appearance). Intravenous pyleogram (IVP) or cystography in particular are very good studies for demonstrating ureteritis cystica, ureteral stricture (or dilation), hydronephrosis, mucosal irregularity, urolithiasis, decreased bladder capacity, bladder tumor, and inflammatory pseudoployps. CT is useful and more sensitive than radiography for the detection and characterization of urolithiasis and pyelonephritis.

Nodular hepatic lesions have been demonstrated sonographically and by CT in acute Schistosomiasis. In the colon, extensive curvilinear or tram-track calcifications have been identified in patients with schistosomiasis japonica. Another study involving intravenous contrast-enhanced CT in Schistosomiasis japonica hepatic infection, showed septal, amorphous, and capsular contrast enhancement patterns. This study concluded that septal enhancement may suggest the diagnosis of hepatic schistosomiasis japonica, particularly when calcification is not identified on noncontrast CT study. The most reliable diagnostic techniques for detecting chronic bladder disease are cystoscopy, serology, CT and to a lesser extent urography. Urinalysis in chronic disease may result in missed detection of disease that would otherwise be identified during the early phase of disease.

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