Differentials
Crohn's disease
SIGNS / SYMPTOMS
Lack of exposure history to endemic areas for schistosomiasis.
Crohn's disease (CD)-specific manifestations, including mouth ulcers and fistula formation, are not commonly found with schistosomiasis. Additionally, extra-intestinal manifestations such as arthritis, erythema nodosum, uveitis, and pyoderma gangrenosum are not found with chronic schistosomiasis.
INVESTIGATIONS
Colonoscopy is the preferred test to differentiate schistosomiasis from CD. CD is defined by deep geographic and serpiginous ulcers. In contrast, chronic schistosomiasis colonoscopy may demonstrate normal-appearing colonic mucosa, necessitating tissue biopsy for diagnosis. On tissue biopsy, granulomas may be present with both diseases. However, in CD these granulomas do not contain any eggs. Typically the inflammation in CD is transmural, whereas that associated with schistosomiasis is localised around the egg-containing granulomas.
Additionally, upper gastrointestinal series with small-bowel follow-through can be used to examine the small intestines for CD-related inflammation and narrowing of the lumen. A barium enema can be used to demonstrate ulcer depth and any fistulae. CT scan and MRI can also be used for examining the intestines, especially for CD complications such as abscesses, obstruction, or fistulae.
Ulcerative colitis
SIGNS / SYMPTOMS
Lack of exposure history to endemic areas for schistosomiasis.
Ulcerative colitis (UC) patients can exhibit extraintestinal manifestations such as aphthous ulcers, uveitis, arthritis, ankylosing spondylitis, erythema nodosum, or clubbing, which are not found with chronic schistosomiasis.
INVESTIGATIONS
Colonoscopy is the preferred test to differentiate chronic schistosomiasis from UC. UC is defined by continuous shallow ulcers often with pseudopolyps limited to the colon and rectum. Biopsy demonstrates shallow mucosal ulcerations without eggs.
Colon cancer
SIGNS / SYMPTOMS
Lack of exposure history to endemic areas for schistosomiasis.
A family history of colon cancer, adenomatous polyposis, smoking, or long-standing ulcerative colitis or Crohn's disease increases the suspicion for colon cancer.
INVESTIGATIONS
Colonoscopy is the preferred test to differentiate chronic schistosomiasis from colon cancer. On endoscopy of patients with colon cancer, colonic mucosa often contains polyps that on histological investigation demonstrate neoplastic cells and the absence of Schistosoma eggs.
Malaria
SIGNS / SYMPTOMS
Travel to malaria endemic area.
Malaria characteristically has a more abrupt onset of high fever of approximately 40˚C (104˚F) with profound malaise, headache, and fatigue.
INVESTIGATIONS
Giemsa-stained thick and thin blood smears showing parasitised erythrocytes.
Positive result for malaria antigen detection assay.
Salmonella infection
SIGNS / SYMPTOMS
Salmonellosis can be confused with acute or chronic schistosomiasis. With Salmonella infection, 'rose spots' frequently occur 7 to 10 days into the febrile course of untreated S typhi infection, but are less common with enteric fever caused by other Salmonella species. A reactive arthritis can also develop that is not associated with acute or chronic schistosomiasis.
Persistent or recurrent Salmonella bacteraemia has been associated with chronic schistosomiasis in endemic areas.[58]
Concurrent Salmonella and schistosomiasis infections may also occur in advanced HIV infections as an AIDS-defining illness.[58][59][66]
INVESTIGATIONS
Positive blood cultures and serological testing for Salmonella.
Salmonella may be cultured from stool.
Visceral larva migrans (toxocariasis)
SIGNS / SYMPTOMS
Lack of exposure history to endemic areas for schistosomiasis. Toxocariasis occurs around the world and is typically a disease of children. Risk factors include exposure to contaminated soil, presence of unwormed puppies in the home, unhygienic conditions, and geophagia (pica) in children.
Pruritus associated with toxocariasis is often more pronounced than that associated with acute schistosomiasis. Ocular larvae migrans can occur and affect visual acuity or cause unilateral blindness, which is rarely seen with schistosomiasis.
INVESTIGATIONS
Positive serological test specific for anti-Toxocara species antibodies.[67]
Visceral leishmaniasis
SIGNS / SYMPTOMS
Lack of exposure history to endemic areas for schistosomiasis; 90% of the world's cases of visceral leishmaniasis are in India, Bangladesh, Nepal, Sudan, and Brazil.
History of chronic nodular or ulcerating skin lesions and isolated splenomegaly.
INVESTIGATIONS
Splenic or bone marrow aspirates demonstrating amastigotes.
Positive serological/PCR test specific for leishmaniasis.
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