Diagnosis of human opisthorchiasis

Abstract

Opisthorchiasis viverrini is a liver fluke infection causing a serious public health problem in Thailand, Laos, Cambodia, and South Vietnam because it acts as a strong promoter of cholangiocarcinoma. The diagnosis of human opisthorchiasis is based on four approaches due to clinical manifestations, parasitological, molecular biological and serological methods, which still have problems. Clinical manifestations of the patients are practically indistinguishable from those of other liver diseases. The features of the O. viverrini eggs using a light microscope as a parasitological method are difficult to differentiate from the minute intestinal flukes' eggs. Molecuar biological methods, polymerase chain reaction (PCR) techniques are very complicated, expensive and time-consuming, although they are highly sensitive and specific. PCR can detect a single egg an experimental animal faces and a test has been practice. At present, their applications for the detection of human specimens have never been reported. Actually, serological tests are a choice of these approaches; the techniques can possibly be developed for routine work and field or epidemiological studies. Of these tests, enzyme-linked immunosorbent assay (ELISA) and immunoelectrotransfer blot assay are the most published serological tests in the detection of O. viverrini-specific antigens (coproantigens) and antibodies (IgM, IgG, IgA, or IgE antibodies). The monoclonal antibodies are prepared to detect coproantigens in stool specimens while the crude somatic and excretory-secretory antigens from the adult worms, metacercariae, eggs, and snail intermediate hosts are prepared to detect antibodies in sera. The appropriate amount, type and efficacy of antigen and antibody preparations are considered to prevent the cross-reactions between parasites. Advantages and disadvantages of the four diagnostic methods are discussed.