Clinical Features:
Most infections are asymptomatic.  In mild cases, manifestations include dyspepsia, abdominal pain, diarrhea or constipation.  With infections of longer duration, the symptoms can be more severe, and hepatomegaly and malnutrition may be present.  In rare cases, cholangitis, cholecystitis, and chlolangiocarcinoma may develop.  In addition, infections due to O. felineus may present an acute phase resembling Katayama fever (schistosomiasis), with fever, facial edema, lymphadenopathy, arthralgias, rash, and eosinophilia.  Chronic forms of O. felineus infections present the same manifestations as O. viverrini, with in addition involvement of the pancreatic ducts.

Laboratory Diagnosis:
Diagnosis is based on microscopic identification of eggs in stool specimens.  However, the eggs of Opisthorchis are practically undistinguishable from those of Clonorchis.

Treatment:
Praziquantel is the drug of choice to treat Opisthorchiasis.  See recommendations in The Medical Letter for complete information.