Development of a copro-antigen capture ELISA for detecting Ostertagia ostertagi infections in cattle

The present study reports on the development of a copro-antigen capture ELI SA for detecting Ostertagia ostertagi infections in cattle. The ELISA was b ased on polyclonal rabbit antibodies, which recognize O. ostertagi excretor y/secretory antigens (ES). ES antigens are released by the metabolic active stages of the parasite in the abomasum, and passed in the faeces of the ho st. The detection limit of pure ES material was 30 ng ml(-1) in sample buff er and 125 ng ml(-1) in faecal extract. The test was evaluated using a foll ow up from six artificially infected calves, Elevated levels of Ostertagia coproantigens could be measured from 21 days after infection, indicating th at only the presence of adult parasites can be detected. To evaluate the ca pacity of the assay to measure levels of infection, three groups of cattle were tested: 38 artificially infected calves, 17 naturally infected first g razing season calves and 16 naturally infected adult dairy cows. Optical de nsities were significantly correlated to the worm burdens of the animals an d the ELISA had an overall sensitivity of 91% and a specificity of 45%. The test gave negative readings for faeces of animals carrying patent mono-inf ections with Cooperia oncophora. (C) 2001 Elsevier Science B.V. All rights reserved.