Comparative study on hemato-biochemical alterations and selected acute phase protein response in native sheep experimentally infected with bluetongue virus serotypes 10 and 24

Bluetongue (BT) is an infectious, non-contagious, insect-transmitted viral disease of sheep, other domestic, and wild ruminants caused by bluetongue virus (BTV), a prototype species of the genus Orbivirus of the family Reoviridae. The study was designed to determine the hematological and biochemical alterations and acute phase protein response in BTV sero-negative sheep experimentally infected with bluetongue virus serotype-10 and 24. The BTV-infected group comprising of 18 animals, 6 each inoculated with 6 ml of clarified virus containing 1 × 10⁶/ml TCID₅₀ of BTV-10 or 24 by intradermal route, 6 animals inoculated with equal volumes of BTV-10 and 24 and 4 animals with 6 ml of mock infected culture fluid served as uninfected control group. The blood and serum samples were analyzed at 0, 1, 3, 7, 11, and 16 days post-infection (DPI). Hematological findings in this study showed a significant decrease in the total number of white blood cells in BTV-10 infected group, a significant increase in circulating neutrophils decrease in lymphocytes in all the infected groups, in PCV in BTV-24 and co-infected groups, and RBC count in only BTV-24-infected group at 11 DPI. The results of serum biochemical analyses of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) exhibited increased levels in BTV-24 and co-infected animals. A significant rise in the serum level of creatine kinase (CK) was observed from 3 DPI in the infected groups. Serum levels of total proteins decreased significantly at 11 DPI in BTV-24 infected animals. Significant increase in CRP and fibrinogen levels was observed at 7 and 11 DPI in the infected groups. The significantly decreased levels of TLC, hemoglobin, PCV, CK, and acute phase proteins such as fibrinogen and CRP indicated the inflammatory changes associated with the virus replication and the consequent vascular damage and inflammatory changes in the tissues. Further, the variations in the hemato-biochemical and acute phase response observed between the two serotypes BTV-10 and 24 probes to the difference in virulence and pathogenesis of the serotypes in infected sheep.