Immunohistochemical characterization of polyclonal antibodies against E nteromyxum leei and E nteromyxum scophthalmi ( M yxozoa: M yxosporea), intestinal parasites of fish

The enteric myxozoan parasites E nteromyxum leei ( D iamant, L om et D yková) and E nteromyxum scophthalmi P alenzuela, R edondo et Á lvarez‐Pellitero are responsible for high weight loss in infected fish, which leads to subchronic disease and low mortality rates in gilthead sea bream ( GSB ), S parus aurata L ., and to high mortality rates in turbot, P setta maxima ( L .). The detection of initial parasite stages in histological sections is particularly difficult, but can be simplified by means of specific antibodies. Rabbit polyclonal antibodies (p A bs) were raised against E . scophthalmi and E . leei , and direct enzyme‐linked immunosorbent assay ( ELISA ) and immunohistochemistry were used to characterize their sensitivity and specificity. Both p A bs were adsorbed (ap A b) with non‐infected intestines to avoid non‐specific labelling of fish tissues and to improve their specificity. The highest titre obtained in ELISA was 1: 32 000 for ap A b‐ E leei and 1:16 000 for ap A b‐ E scoph. Working dilutions in immunohistochemistry were 1:1000 for ap A b‐ E leei and 1:8000 for ap A b‐ E scoph. Both ap A bs labelled proliferative and sporogonic stages with high specificity. ap A b‐ E scoph was very specific, whereas ap A b‐ E leei cross‐reacted with S phaerospora dicentrarchi S itjà‐ B obadilla et Á lvarez‐ P ellitero and S phaerospora testicularis S itjà‐ B obadilla et Á lvarez‐ P ellitero, suggesting the presence of shared antigens. These p A bs stand as new tools for antigenic characterization and the diagnosis of both E nteromyxum species.