Pathological and molecular investigations of systemic form of camelpox in naturally infected adult male dromedary camels in India

Camelpox is a wide-spread infectious viral disease of camelids. An outbreak of camelpox was reported in 15 adult male dromedary camels aged between 10 to 16 years of an organized herd in winter season. The infected camels showed clinical signs of fever, anorexia, lachrymation, pendulous lips, excessive salivation and pock lesions on the skin of head, neck, mouth, lips, extremities, thigh, abdomen, scrotum and inguinal region. Mortalities were recorded in three infected camels after 10–12 days of infection and showed systemic pox lesions characterized by vesicles, papules, ulcerations and raised pock lesions in the mucous membranes of the mouth, tongue, tracheal mucosa, lung, abomasum and liver. Histopathology study revealed characteristic pox lesions with intracytoplasmic eosinophilic inclusion bodies in tongue. Lung showed lesion of interstitial pneumonia (n = 2) and bronchointerstitial pneumonia (n = 1). Liver showed infiltration of mononuclear cells around central veins and degenerative changes of hepatocytes. The abomasum and intestine showed ulcerations, marked capillary congestion and areas of lymphocyte infiltration in mucosa and submucosa. The presence of camelpox virus (CMLV) was confirmed in viral DNA isolated from formalin fixed paraffin embedded (FFPE) tissues of tongue, lung, abomasum, liver, heart and intestine of infected camels by C18L gene PCR. The sequencing of viral DNAs showed phylogenetic relatedness with other CMLV isolates from India and other countries. Thus, our study confirmed the rare severe form of systemic camelpox outbreak in adult male dromedary camels hence future attention should be given for studies on virulence, strain identification and molecular epidemiology of CMLV for planning of effective preventive and control strategies.