Evaluation of an ELISA for Dictyocaulus viviparus-specific antibodies in cattle.

An ELISA using a protein extract from adult Dictyocaulus viviparus as antigen was evaluated with respect to its quality and suitability as a diagnostic method for epidemiological studies on dictyocaulosis. In experimentally infected animals, D. viviparus-specific antibodies were first detected between 30 and 44 days post-infection (dpi) and persisted until 107-128 dpi (end of examination), i.e. eight or more weeks longer than the patency period of the infections. Based on parasitological and serological results given by 16 first-year grazing cattle infected with D. viviparus and gastrointestinal nematodes and on the results given by 32 first-year grazing cattle infected only with gastrointestinal nematodes under field conditions, the D. viviparus ELISA showed sensitivities ranging between 69 and > 99% and specificities ranging between 91 and 97% from 8 weeks after turnout until time of housing (21 weeks after turnout). For this part of the grazing season, positive predictive values estimated for 33, 50, 67 and 80% prevalences of infection ranged between 79 and 99% and negative predictive values between 42 and > 99%. High values (> 90%) for all four test characteristics were observed from 13 to 17 weeks after turnout. Positive predictive factors ranged between 0.90 and 0.97 and negative predictive factors between 0.83 and > 0.99 from 8 weeks after turnout until the end of the grazing season and were still as high as 0.88 and 0.74, respectively, at the time of housing. Hence the ELISA appeared to be a very suitable diagnostic method for epidemiological studies on dictyocaulosis.