Effect of immunosuppression on the clinicopathological changes in experimental zygomycosis in rabbits

A study was undertaken to investigate the effect of immunosuppression by cyclophosphamide or methylprednisolone on the clinicopathological alterations in respiratory absidiosis in rabbits. Infected rabbits showed respiratory distress that was more severe in immunosuppressed groups. Leukocytosis due to neutrophilia was observed in the non-immunosuppressed group in the initial stages, whereas leukopenia was observed in both the immunosuppressed groups initially, owing to polymorphopenia in the cyclophosphamide-treated group and to lymphopenia in the methylprednisolone-treated group, followed by leukocytosis in both groups. Total serum proteins increased significantly in the non-immunosuppressed group but were significantly decreased in the immunosuppressed groups. Serum creatinine increased significantly in all the infected groups from 20 days post inoculation (DPI) onwards. Blood urea nitrogen increased significantly in the initial stages only in the methylprednisolone-treated group. AST and ALT also showed significant increases in the infected animals. Total serum immunoglobulins and circulating immune complexes increased gradually in all three infected groups, except for an initial significant drop in the immunosuppressed rabbits. Re-isolation of fungus was only achieved from the lungs of infected rabbits up to 15 DPI in the non-immunosuppressed group and 30 DPI in the immunosuppressed groups. Pathological lesions in all the infected groups were found mainly in the lungs and consisted of pyogranulomas. The lesions were most severe in the cyclophosphamide-treated group and least severe in the non-immunosuppressed group.