Abstract
Since opisthorchiasis does not show pathognomonic signs or symptoms, physicians can have serious problems to make a differential diagnosis of this infection in non endemic areas, in particular when there is a simultaneous occurrence with other seasonal infections. Moreover, symptomatic infections due to O. felineus can last a few weeks and then the signs and symptoms disappear, but the worms survive in the bile ducts for years causing hepatobiliary diseases including hepatomegaly, cholangitis, fibrosis of the periportal system, cholecystitis, and gallstones. Consequently, an early diagnosis prevents chronicity and loss of working days. The detection of specific antibodies has been considered as a complementary tool to the fecal examination to establish the definitive diagnosis of this infection and for the follow up. Therefore the aim of this work was the development and validation of an enzyme-linked immunosorbent assay (ELISA) using excretory/secretory antigens (ESA) from O. felineus adult worms to detect anti-Opisthorchis IgG in human sera. A total of 370 human sera were tested: 144 sera from persons with a confirmed diagnosis of opisthorchiasis, 110 sera from healthy Italian people, and 116 sera from people with other parasitic or non-parasitic infections. Results were analyzed by receiver-operator characteristic (ROC) curve analysis. The accuracy of the test, calculated by the area under curve (AUC), yielded a 0.999 value, indicating the high performance of the test. The sensitivity was 100% (95% CI: 97.40% to 100%) and no false-negative sera were detected; the specificity was 99.09% (95% CI: 95.02% to 99.83%). The validated ELISA shows a good performance in terms of sensitivity, repeatability and reproducibility, and it is suitable to detect anti-Opisthorchis IgG in human sera for diagnostic purposes and for the follow up to assess the efficacy of drug treatment.
Highlights
Opisthorchiasis and clonorchiasis are zoonotic diseases caused by liver flukes of the family Opisthorchiidae (Ophisthorchis viverrini, O. felineus and Clonorchis sinensis) which are transmitted by the ingestion of raw or undercooked fish parasitized by the larval stage
No false-negative (FN) sera were found; 5 (4.5%) false positive (FP) sera were detected among TN sera and 17 (14.6%) FP sera were detected from persons with other parasitic infections, namely one with C. cellulose, three with E. granulosus, four with L. loa, one with Toxocara spp., and eight with Trichinella spp
It is necessary to keep in mind that serological methods cannot replace the direct microscopic examination of the stool and the identification of the O. felineus eggs
Summary
Opisthorchiasis and clonorchiasis are zoonotic diseases caused by liver flukes of the family Opisthorchiidae (Ophisthorchis viverrini, O. felineus and Clonorchis sinensis) which are transmitted by the ingestion of raw or undercooked fish parasitized by the larval stage (metacercaria). In Italy, this parasite was first described in cats and dogs in Tuscany and Piedmont Regions, yet for over 100 years the infection was not detected or reported in humans and no investigation on this pathogen was carried out [3,4]. A wide range of species of freshwater fish of the family Cyprinidae can be naturally infected by these trematodes Carnivore mammals such as cats, dogs, and foxes act as definitive hosts where the parasite develops into adults in the intra- and extra-hepatic bile ducts and in the gallbladder. Humans are an accidental host [2,9]
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