Use of a 14.2 kDa recombinant Cooperia oncophora protein in an ELISA for herd health monitoring of nematode infections in first grazing season calves

An ELISA using a recombinant 14.2 kDa excretory/secretory Cooperia oncophor a protein (CoES14.2 ELISA) was evaluated for estimating level of cumulative exposure to infective Cooperia larvae in first grazing season calves. Data from one experiment were used to obtain a quantitative relationship betwee n IgG levels and cumulative exposure. That relationship was validated again st data from another experimental study and from natural field studies. The latter included different pasture management strategies with or without an anthelmintic treatment. Validation involved 'predicting' cumulative exposu re for the groups of calves in the latter two datasets based on observed Ig G levels measured with the CoES14.2 ELISA, and subsequently comparing those 'predictions' with observed cumulative exposures. Generally, 'predicted' c umulative exposures correlated well to observed exposures (r values of 0.7- 0.9). However, 'predicted' cumulative exposures underestimated observed exp osures in the natural field studies. Anthelmintic treatments in some of the groups of the natural field studies reduced the 'prediction' accuracy of t he CoES14.2 ELISA. This suggests that cumulative exposure in relation to Ig G levels is more accurately defined by the total amount of host-parasite co ntact than by the cumulative number of larvae ingested. It is concluded tha t IgG levels measured with the CoES14.2 ELISA allow evaluating how much exp osure to infection calves have experienced in the first grazing season. (C) 2000 Elsevier Science B.V. All rights reserved.