Comparison of assays for antibodies to Encephalitozoon cuniculi in rabbits

Two indirect immunofluorescence (IIF) assays, two enzyme-linked immunosorbe nt assays (ELISAs) and the carbon immunoassay (CLA) for determination of an tibodies to Encephalitozoon cuniculi were compared using 210 sera of rabbit s, 135 of which originated from seven infected colonies, while 75 originate d from four uninfected colonies. There was no evidence of a difference betw een the different assays with respect to the number of positive sera. There was a clear correlation between the quantitative response measured by IIF and CIA and the other assays, and between both IIF tests, while no such cor relation was found in the quantitative response measured by ELISAs, which m ight be explained by the less quantitative nature of the ELISA. Therefore q uantitative determination of antibodies to E. cuniculi should be performed by IIF and not by ELISA. The nosographic sensitivities N-1 and specificitie s N-2 of the assays were greater than or equal to 0.94 and greater than or equal to 0.97 respectively. Small differences in N-1 and N-2 between the as says, although not statistically significant, were responsible for differen ces in the calculated predictive values of a positive test and of a negativ e test. As expected, the magnitude of these differences depended on the fra ction of positive sera sampled from a given colony. There was strong eviden ce of such a difference between the fraction of positive sera found in diff erent colonies, hut the sample size from some colonies was too small to all ow any conclusion, whether this was due to differences in the prevalences o f the infection in the colonies or something else. We conclude that any of the assays will be suitable for the routine health monitoring of laboratory rabbit colonies for E. cuniculi infection, as recommended by the Federatio n of European Laboratory Animal Science Associations.