Corynebacterium pseudotuberculosis infection in goats. I. Evaluation of two serological diagnostic tests

The bacterial agglutination test (BAT) and the hemolysis inhibition test (HIT) were employed and evaluated.The threshold value between positive and negative antibody titres in BAT and HIT was determined on the basis of titration results for sera from 25 adult goats infected with Corynebacterium pseudotuber-culosis (positive), and sera from 25 adult goats from a herd in which caseous lymphadenitis did not occur (negative).Antibody titres were expressed as logio to the reciprocal value of the highest positive serum dilution in both tests. Positive titre (T) in BAT was stipulated as T ≥ 2.1 and in HIT as T > 0.6. The sensitivity and specificity was 0.96 in both tests in the material used. Twenty-three of the 25 goats infected with G. pseudotuberculosis were positive in both BAT and HIT.The reproducibility in both tests was described by the use of correlation coefficient and coefficient of variation. The values were estimated using duplicate determination of titres of 155 serum samples. Correlation coefficients were 0.87 for BAT and 0.95 for HIT. Coef-ficients of variation were 26.4 % for BAT and 14.1 % for HIT. The coefficient of variation was related to titres. It was highest for BAT at low titres.It was concluded that both tests can be used for seroepidemio-logical investigations of C. pseudotuberculosis infection in goats.