Comparação de kits ELISA® comerciais para anticorpos no soro e leite com um teste coproparasitológico em bovinos naturalmente infectados por Fasciola hepatica

Abstract

The fascioliasis is a disease caused by a trematode that affects the liver mainly of domestic ruminants and can also parasite man; its diagnosis is routinely done by coprological methods. The aim of this study was to compare commercial ELISA kits for antibodies in serum and milk with a coprological test in cattle naturally infected by Fasciola hepatica. We collected fecal, blood and milk samples from cattle in the municipality of Jerônimo Mon-teiro, southern Espírito Santo state. The fecal samples were processed by the fecal egg sedimentation for F. hepatica, which is used as a gold standard for analyzis. Blood (92) and milk (43) samples were processed according to the manufacturer instructions of the respective commercial ELISA kits tested. We used the McNemar chi-square for statistical comparison and calculated the sensitivity, specificity, predictive values, and kappa. The results showed that the frequency of positivity for the commercial serum ELISA kits (λ2=34.02) and milk (λ2=19.04) differed significantly (p<0.0001) compared with fecal egg sedimentation. The sensitivity of the kits was 100%, but possessed low specificity, 42.85 and 30% for serum and milk respectively. The coefficient kappa showed agreement for testing serum (0.33) and milk (0.21). The positive predictive value of the kits for serum and milk were respectively 44.61% and 38.23%, and negative predictive values were 100% for both tests. Despite the increased sensitivity of commercial ELISA kits and the difference in relation to the fecal egg sedimentation test for detection of F. hepatica positive animals, the choice of a diagnostic test should consider the effectiveness. When a herd is affected by parasitism, treatment is applied to all animals; so, the fecal egg sedimentation test for the diagnosis of disease in the field is most efficient, as the test is cheap and easy to perform.