MISET: an immunological technique for the serodiagnosis of Cryptobia salmositica (Sarcomastigophora: Kinetoplastida) infection in Oncorhynchus mykiss.

A serodiagnostic technique, microscopic immuno-substrate-enzyme technique (MISET), is described using the Cryptobia-Oncorhynchus mykiss system. The reactions of specific antibodies, phosphatase-labeled antibody, and substrate with subsequent color development on the parasite (cell membrane, flagella, kinetoplast, and nucleus) are observed using light microscopy. Using this technique, humoral response to Cryptobia salmositica was detected in 2 of 10 O. mykiss 7 days after infection. Subsequently, antibodies were detected in all 10 infected fish. Parasites cultured in minimum essential medium or from experimentally infected pink salmon, Oncorhynchus gobuscha, worked equally well. Antibodies eluted from antisera or whole blood dried on filter paper (stored at -20 C) gave similar reactions as those from antisera stored in containers. MISET is at least as sensitive as the indirect fluorescent antibody technique. When MISET is modified and adapted for other parasitic diseases (e.g., for those of medical and or of economic importance), it may be useful especially in smaller centers or in developing countries where equipment cost, maintenance of equipment, operating costs, and well trained personnel are important considerations. Because MISET worked with dried whole blood or serum on filter paper it may also be a useful field technique for large scale seroepidemiological surveys.