Experimental Velogenic Viscerotropic Newcastle Disease Virus Infection in Chickens Immunologically Impaired by Treatment with Cyclophosphamide

Abstract

This study investigated whether lymphocytic depletion following chemical bursectomy influenced the severity of infection and development of lesions in chickens challenged with velogenic viscerotropic Newcastle disease virus (vvNDV). Cockerel chickens treated with cyclophosphamide on days 2, 3 and 4 post-hatch showed loss of weight, atrophy and lymphocytic depletion in the bursa of Fabricius and spleen. At 6 weeks of age, the chickens were assigned to four groups- Bursectomized intramuscularly vvNDV inoculated (BI), bursectomized uninfected (BU), non-bursectomized infected (NBI) and non-bursectomized uninfected (NBU) chickens. The BI and NBI chickens showed significant (P < .05) loss of weight than their uninfected controls. Depression, anorexia, greenish diarrhea, listlessness, tremor, and oculo-nasal discharges were observed in both infected groups, but were more severe and frequent in the NBI than in the BI chickens. Total mortalities were 100% and 95.5% for the NBI and BI chickens, respectively (P > .05). Lesions in both infected groups included atrophy of the bursa, spleen and thymus. Hemorrhages in the proventricular mucosa, intestines and cecal tonsils, as well as congestion and enlargement of the kidneys were significantly (P < .05) more severe and frequent in NBI than BI chickens. Histopathology showed necrosis and depletion of lymphocytes in the three lymphoid organs in both infected groups with more severity in the NBI than BI chickens. These results show that depletion of lymphocytes by treatment with cyclophosphamide may influence the severity of infection and development of lesions in vvNDV infection in cockerel chickens.