Pathomorphological response to Encephalitozoon cuniculi infection in cyclophosphamide-treated rabbits

Abstract

Microsporidia are emerging opportunistic pathogens in immunosuppressed hosts. We have studied the pathomorphological response of cyclophosphamide-treated rabbits with experimental encephalitozoonosis. Forty New Zealand rabbits were used in the experiment. Experimental rabbits were infected intraperitoneally (i.p.) with 5 × 107 E. cuniculi spores. Two weeks after E. cuniculi infection, animals were i.p. injected with cyclophosphamide (CY) of 50 mg/kg and then once weekly with a dose of 15 mg/kg. Control animals were treated with either E. cuniculi or CY, whereas negative controls were left untreated. Rabbits were killed in week 12 after the beginning of the CY treatment. Lesions were found in the brain, liver and kidney of both E. cuniculi infected groups, but they were different. The lymphoplasmacytic lesions of immunocompetent rabbits were consistent with findings previously described in spontaneous encephalitozoonosis. CY-immunosuppressed animals formed almost exclusively granulomatous lesions and rich infiltration with eosinophils within granulomas was also involved. The occurrence of distinct types of lesions indicates that CY modifies the pathomorphological response to E. cuniculi probably via the failure of immune system.