Comparative pathology of Aflatoxicosis in the duck and fish with special reference to the immune system

Abstract

Pathological responses of ducklings and juvenile Indian carps Labeo rohita in experimental aflatoxicosis were studied. Both the ducklings and fishes were given sublethal toxic levels of aflatoxin B1. The ducklings and fishes were exposed to aflatoxin B1 for 2, 4, 6 and 8 weeks respectively and they were sacrificed at the end of the experiment and samples for haematological, serum protein profile, histological and ultrastructural investigations were collected. Pathological changes were studied with special reference to the humoral and cell – mediated immune responses. Among the haematological parameters, total erythrocyte count, total leucocyte count and packed cell volume were found to be reduced in fishes. The reduction was directly proportional to the duration of aflatoxin treatment. In the fishes, there was moderate fall in the total proteins and the albumin. The electrophoretic picture of the serum of the fishes also showed fall in the albumin fractions. In the ducks there was severe reduction in the albumin level and this was reflected in the electrophoretic picture as well as A: G ratio. In both the ducks and the fishes humoral immune response was suppressed due to aflatoxin treatment. Antibody titres against sheep RBC fell in the experimental groups of the ducks and the fishes. The cell - mediated immunity was assessed in the ducks and the fishes by intradermal PHA – M response, count of ANAE positive lymphocytes in the peripheral blood and leucocyte migration inhibition test. In the ducks and the fishes of the aflatoxin treated groups, there was significant fall in the skin sensitivity response and also in the number of ANAE positive lymphocyte. These findings clearly established that CMI was suppressed by aflatoxin . The histological and electron microscopic studies revealed severe degenerative and necrotic changes in the hepatocytes in the ducks and fishes. However, hepatosis was more severe in the fishes whereas in the ducks biliary proliferation was a prominent feature. The hepatic changes could be correlated with the changes in the plasma protein profile in the duck and the fish. The lymphoid organs of the duck and the fish (thymus, spleen, bursa of Fabricius and anterior kidney) showed extensive necrosis and degenerative changes. These changes clearly established the reason for the immunosuppression and low leucocytic counts observed in the aflatoxin fed ducks and fishes. The kidneys of the duck and the fish exhibited nephrotic changes. Degenerative changes were also observed in the brain and the heart of the two species. The pathologic changes due to aflatoxicosis were comparable in the ducks and fishes.