The objective of this work was to verify the occurrence of sheep serologically positive for bluetongue virus (BTV) in the state of Ceará, Brazil, and analyze immunogenic proteins of circulating viral strains in these flocks. The agar gel immunodifusion test (AGID) was used to examine 271 serum samples from 16 herds. The results demonstrated that 27.3% (74/271) of the analyzed samples presented antibodies for the agent, and that 68.8% (11/16) of the properties presented positive animals. Immunoblotting (IB) was used to analyze the immunogenic proteins of BTV derived from AGID positive sera. Sera showed strong reaction against viral protein VP2. Of the seven BTV structural proteins, VP2 is the major protein to elicit protective immune responses. It was concluded that bluetongue (BT) seropositivity in sheep flocks studied in Ceará is high, despite that the animal's do not show clinical signs, indicating that it occurs in an endemic form. The animals' resistance to the disease may be related to the strong immune response to the protein VP2. Therefore, further studies are needed to better clarify the epidemiological situation of BT in Brazilian sheep flocks, through the identification of viral vectors and serotypes circulating in different regions.
Orbivirus; ruminants; semiarid; VP2