Application of Urine and Copro Antigen Assays after Primary Infection and Drug Treatment in an Experimental Opisthorchiasis Animal Model

Infection by Opisthorchis viverrini causes significant health problems, including cholangiocarcinoma (CCA); thus control and elimination of this trematode is an important strategy for the reduction of CCA. Currently, urine and copro antigen detection is more sensitive than parasitological examination of the feces for the diagnosis of opisthorchiasis. Given limitations in human studies, we used an animal model to quantify the parasite antigen profiles in urine and feces in O. viverrine-infected hamsters, and postdrug treatment. The positive detections of O. viverrini antigen began from week 1 in urine and week 2 in feces after infection until week 28 of the study. The recoveries of O. viverrini worms were detected starting from week 1 and eggs of O. viverrini were detected in feces from week 3 after infection and remained detectable throughout the study period. There was a significant positive correlation of urine and copro antigen levels with the number of fecal egg counts (P < 0.01) and worm recovery (P < 0.01). In the drug-treatment experiment, treatment of infected hamsters with praziquantel (PZQ) significantly reduced worm burden, fecal egg output, and antigen in urine and feces compared with the untreated controls (P < 0.001). At 4 weeks posttreatment, the egg and worm reduction rates were 100% and 95.5%, respectively. The positive antigen detections in urine and feces corresponded with partial worm clearance from praziquantel treatment. This study demonstrated a direct link of urine and copro antigen tests with worms infecting the liver thereby reaffirming the reliability of urine and copro antigen assay in opisthorchiasis diagnosis.