Evaluation of an ELISA and immunoblotting for studying the humoral immune response in Anguillicola crassus infected European eel Anguilla anguilla

The applicability of an enzyme-linked immunosorbent assay (ELISA) for the d etection of anguillicolosis in feral eels was examined using a crude antige n preparation from the body wall of adult Anguillicola crassus. The screeni ng consisted of samples from 100 feral European eels Anguilla anguilla. As a reference the actual status of infection was determined by dissection of the eels' swimbladders. The ELISA results were compared with a background v alue calculated from the results obtained from 43 non-infected farm eels. T he screened samples had a high prevalence of A. crassus (83 %); however, th e specificity and the negative predictive value of the ELISA were low compa red to the high positive predictive value. Nonetheless, the reproducibility (precision) of the test was satisfactory, and for the non-infected referen ce group specificity was 97.7 %. Although the ELISA, as used in the present study, is not applicable for diagnostic purposes, it represents a useful t ool for the investigation of the specific humoral immune response of eels a gainst A. crassus under controlled experimental conditions. Immunoblots usi ng crude antigen preparations from different parts of adult A. crassus as w ell as a crude somatic third-stage (L-3) antigen preparation illustrated th at only antigens associated with the body wall of adult A. crassus are pote ntially suitable for diagnostic purposes. Despite the fact that antibodies against Raphidascaris acus cross-reacted with 3 body wall antigens of A. cr assus, the most encouraging results were obtained with the antigen preparat ion from the outer cuticle of adult A. crassus which yielded a conspicuous, broad band at about 100 kDa.