Serological and molecular evidence of bluetongue in sheep and goats in Uttar Pradesh, India

Abstract

Cross-sectional experimental study was conducted with the objective to estimate the seroprevalence on the basis of antibodies to VP7 protein of bluetongue virus by competitive enzyme linked immunosorbent assay (c-ELISA), to test the neutralizing ability of the antibody to reference strains of 4 BTV serotypes (BTV-1, 2, 10 and 23) by micro serum neutralization assay (m-SNT), to check the presence of BTV dsRNA and to isolate and characterize bluetongue virus (BTV). A total of 91 serum and 26 whole blood samples were obtained from sheep and goat. The study was conducted between September and November, 2012 when the culicoides midges’ activity is maximal. The animals were observed for clinical signs of BTV infection and serum samples were obtained from all animals for c-ELISA and m-SNT. Further, blood samples were collected from the c-ELISA positive animals and subjected to virus isolation and nested RT-PCR. Out of 91 animals tested, 26 (28.6%) were found to be seropositive by c-ELISA and one sheep showed neutralizing antibody against BTV-1 serotype at a titer of 1.2 log10. Multivalent logistic regression analysis of risk factors like age, sex, body condition and species of animals were considered during the serological study and found that species of animal had significant influence (χ2 = 17.111, P<0.05) in seropositivity of BTV. Goats showed more seropositivity to bluetongue as compared to sheep (OR = 0.233). Other risk factors had no significant influence (P>0.05) on seropositivity. It was worth enough to conclude that higher seroprevalence among goats indicated that goats would be the most important animals in the epidemiology of BTV with less clinical manifestation due to development of acquired immunity as the result of continuous exposure.

Keywords: Bluetongue virus (BTV), competitive enzyme linked immunosorbent assay (c-ELISA), goat, seroprevalence, sheep, micro serum neutralization assay (m-SNT), nested reverse transcription polymerase chain reaction (RT-PCR)

African Journal of Biotechnology Vol. 12(19), pp. 2699-2705