The present study was carried out to investigate the effect of fumonisin B1 (FB1) contaminated feed on the immune response of rabbits to inactivated rabbit pasteurellosis vaccine as well as the pathological changes induced by this toxins in the internal organs of intoxicated rabbits. Feeding of rabbits on Fb1 2.29 and 1 ppm contaminated feed induced immunosuppressive effect on the humeral immunity of theses rabbits and consequently lower their resistance to subsequent challenge with virulent Pasteurellaa multocida organism. The immunosuppressive effect was evidenced by lower antibody titers measured by indirect haemagglutination test ( IHT) in rabbits which received FB1 and vaccinated in comparison with the antibody titer reported in control-fed and vaccinated rabbits. This effect was dose-dependent where , rabbits fed on FB1 2.29 ppm showed lower antibody titers than those fed on FB1 1ppm . Moreover , high mortalities which reached 80 and 40 % were reported in the vaccinated challenged rabbits fed on FB1 in a dose of 2.29 and 1ppm respectively while the deaths in the vaccinated and unvaccinated control fed rabbits were 10 and 100 % respectively.
The pathological pictures in rabbits fed on Fb1 1 ppm and 2.29 ppm were similar . However , the severity of the lesions was more in rabbits fed on higher dose of FB1 than those recorded in rabbits fed on low dose. Severe congestion and enlargement of the liver and kidneys , softening of the brain , together with edematous lungs and small sized spleen were the main gross lesions in both groups. Histopathologically , the recorded lesions consistent heptorenal lesions were represented by degeneration and necrosis with lymphocytic infiltration. The lungs showed severe congestion and inflammatory edema particularly in rabbits which fed on FB1 2.29 ppm. The brain showed congestion , perivascular cuffing , focal hemorrhages and cerebral encephalomalacia. Moreover, cardiac hyalinosis and splenic necrosis were noticed only in rabbits which were fed on higher dose.
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