Serological Investigation of Bluetongue Virus Infection by ELISA in Sentinel Cattle Herds in Tunisia

Abstract

Bluetongue (BT) is a non contagious infectious viral disease of domestic and wild ruminants. Isolation of BT virus serotype 2 (BTV-2) was first confirmed in Tunisia in February 2000 and was since detected in several other countries in the Mediterranean region. BTV-1 was detected in November 2006 and in 2007, and several outbreaks were reported in some regions of Tunisia. A structured surveillance study was designed with the aim to determine the dynamics of infection by this virus from June 2006 through July 2008 in 14 sites located throughout Tunisia. In each farm, 10 seronegative calves to BT were identified and monitored monthly for seroconversion by the enzyme-linked immunosorbent assay (ELISA) method. Results showed a differ­ent epidemiologic situation between the two years with a BT seropositivity rate at 1.3% during the first year, reaching 54.3% the second year. The majority of seropositive cases appeared between August and November with only one seroconversion in spring 2008. Detailed results are presented and discussed.