Intestinal Leakage and Precipitating Antibodies in the Serum of Quillback, Carpiodes cyprinus (Lesueur), Infected with Neoechinorhynchus carpiodi Dechtiar, 1968 (Acanthocephala: Neoechinorhynchidae)

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Abstract
Leakage of the intestine of quillback, Carpiodes cyprinus, infected with Neoechinorhynchus carpiodi was examined using Evans blue (EB) injected into the bloodstream of quillback. The concentration of EB-labeled blood proteins in the intestinal lumen was greatest at the sites of nodule formation and was correlated with size of nodules and number of gravid female worms attached. The intestines of uninfected quillback with no signs of previous infection (no nodules) had the lowest level of protein leakage. Immunoprecipitation bands were observed when sera from infected fish were tested with purified N. carpiodi antigens. These bands were due to specific antibody reactions and not due to C-reactive protein (CRP) or alpha-migrating factor. Antibody titres were not correlated with intensity of infection but the proportion of fish testing positive increased with increasing number of worms. Precipitation reactions were most intense against mature male and gravid female worms and these shared a common antigen. The persistence of nodules and the presence of antibodies suggests that this host-parasite association involves both cellular and humoral components of the fish immune system. This ensures the integrity of nodules and the associated vascularization and leakiness that appear to be important in supplying nutrients to the parasites.