Pathology of low virulent bluetongue virus serotype 16 in experimentally infected sheep

Bluetongue (BT) is an infectious, non-contagious, arthropod borne disease of ruminants and camelids. The causative agent, Bluetongue virus (BTV) belongs to Reoviridae family and at present at least 27 known serotypes are widespread all over the world. Sheep, being the natural host, exhibit clinical outcome as compared to other hosts. The severity of the disease depends on several factors-like virus, host, vector, environment etc. In the present study, BTV serotype 16, isolated from apparently healthy sheep, was experimentally infected in sheep to study its pathology. Five adult sheep of indigenous breed were used to monitor clinical signs, gross pathology and histopathology to establish the asymptomatic outcome, replicative of its origin. During the experiment, infected animals did not exhibit elevated rectal temperature or any clinical signs. Grossly, pneumonic changes namely emphysema, atelectasis along with multiple pete- chiae over spleen, heart, thymus and pericardium were evident. Histopathologically, variable inflammatory reactions of mild type were observed in lungs, prescapular lymph nodes, skin, spleen, tongue, heart and pulmonary artery. Thus, the infected animals remained apparently healthy imitating the animals from which the present BTV16 strain was isolated.