Pathological Investigation of Newcastle Disease and Infectious Bursal Disease Co-infection in Broiler Chickens in Kaduna State

Co-infections between Newcastle disease virus (NDV) and infectious bursal disease virus (IBDV) are increasingly recognised as a significant cause of flock mortality in commercial poultry operations across Nigeria. This study investigated the gross and histopathological features of NDV and IBDV co-infection in commercial broiler farms in Kaduna State, North West Nigeria, during the 2023 production cycle. A total of 55 broiler chickens from five affected farms exhibiting signs of respiratory distress, bloody diarrhoea, and sudden death were submitted for necropsy. Tissues from the bursa of Fabricius, thymus, spleen, proventriculus, brain, and intestines were processed for histopathological examination. Gross findings included bursal enlargement with gelatinous oedema in early IBDV cases, progressing to bursal atrophy, alongside haemorrhagic proventricular erosions and caecal tonsil necrosis consistent with NDV. Microscopically, severe lymphoid depletion and follicular necrosis of the bursa confirmed IBDV, while perivascular lymphocytic encephalitis and intestinal lymphoid necrosis were indicative of concurrent NDV infection. Immunosuppression mediated by IBDV likely exacerbated NDV pathology, contributing to increased mortality rates above 40 percent in affected flocks. These findings are consistent with recent reports of dual viral pathology in intensively managed poultry systems in West Africa. Improved biosecurity, vaccination timing, and routine diagnostic monitoring are urgently recommended. Keywords: Newcastle disease, Gumboro, co-infection, broiler, histopathology