Neuropathology mediated through caspase dependent extrinsic pathway in goat kids naturally infected with PPRV

Peste des petits ruminant (PPR), a highly contagious viral disease of small ruminants, is characterized by erosive stomatitis and pneumo-enteritis. However, its neurovirulence potential as observed with other morbilliviruses has not been fully investigated. The present study describes the neuropathological alterations induced by PPR virus through apoptotic pathway. A total number of 12 carcasses of local breed goat kids of either sex were received for postmortem examination. The clinical history was described as symptoms of mucopurulent nasal discharge, high to low grade fever, erosive stomatitis, dyspnoea and profuse watery diarrhoea followed by mortality of 35 goat kids within a week. The pathoanatomical lesions and immunohistochemical demonstration of PPRV antigen in lungs, intestine, spleen and lymph nodes confirmed PPR disease in goats. Grossly, five brain specimens showed moderate to severe leptomeningeal congestion during necropsy. Microscopically, brain sections showed leptomeningitis and nonsuppurative encephalitis characterized by vascular congestion, haemorrhages in the parenchyma, perivascular cuffing with mild to moderate mononuclear cells (mainly lymphocytes and few macrophages), focal to diffuse microgliosis, neuronal degeneration, satellitosis and neuronophagia. Immunolabelling of viral antigen was observed in the cytoplasm of neurons and glial cells. The RT-PCR amplification of N gene fragment also confirmed the presence of PPRV in the brain. The strong immunoreactivity of Caspase-3, Caspase-8 and comparatively lower expression of caspase-9 along with the absence of any reactivity for Apaf-1 antigen in the brain sections indicated the role of caspase dependent extrinsic pathway in inducing neuropathological changes. The presence of apoptotic neurons in the brain by TUNEL assay further confirmed the apoptosis and strong immunoreactivity of iNOS in neurons which suggested the generation of oxidative stress, that might have induced the apoptosis. The overall findings confirm the neurovirulence potential of PPR virus, via the extrinsic pathway of apoptosis, in natural cases of PPR disease in goat kids.