[Application of micro-ELISA in serodiagnosis of fascioliasis in cattle]

Fascioliasis in cattle is one of the most common and very serious trematode diseases in Korea. In the present study, the enzyme linked immunosorbent assay (ELISA) was applied in the diagnosis of fascioliasis using antigen of Fasciola hepatica, peroxidase of conjugate anti-cattle IgG and orthophenylenediamine as a substrate by micro-method technique of Voller et al. (1976b) and MacLaren (1978) with a slight modification. Results obtained from the present study are as follows: In assay for optimal dilution of stock antigen, the antigen (protein contents; 0.8 mg/ml) was diluted from 1/50 to 1/600 with carbonate buffer (pH 9.6), and then absorbance values were measured with 1/100 diluted sera. The regression equations between the OD values of ELISA and dilution of antigen were log Y=-0.181-0.00127X in infected sera, and log Y= -0.578- 0.000879X in normal sera. The significantly higher (p<0.05) OD value was observed in the former. In assay for optimal dilution of sera, the sera were diluted from 1/25 to 1/400 with in PBS/ Tween 20(pH 7.4), and absorbance values were measured with 1/200 diluted antigen. The regression equation between the OD values of ELISA and dilution of sera were log Y=-0.1540-0.0007238X in infected sera and log Y=-0.4834-0.00116X in normal sera. The former was higher than the latter (p<0.05). In the 27 cases of negative intradermal test, OD values of the ELISA are 0.447 +/- 0.144, the 95 percent confidence interval (Mean + 2 x SD) of the values was 0.735, and there was no case over the values. Therefore, the sensitivity of the antigen to diagnose fascioliasis was 100 percent in the negative case. The OD value 0.7 which is designed as a criterion (detection level of positive one) is useful for the performance of the ELISA in fascioliasis. According to the OD value of criterion in the regression equations, the optimal dilutions of stock antigen and serum were 1/250 and 1/100, respectively. In the 58 cases of fascioliasis from which the adult could be found in the bile ducts, the OD value was 0.846 +/- 0.224). The 75 percent (44 cattle) among them had higher value with compared to the criterion, and the 60 percent (20 cattle) of the cases of proliferative cholangitis of 33 cattle which had been infected previousely with Fasciola sp. is higher than the criterion. Prevalence of fascioliasis was 43.4 percent in the application of the ELISA to 272 cattle which were reared in Jeonbug district.