Abstract
Many wild ruminants such as Spanish ibex (Capra pyrenaica) are susceptible to Bluetongue virus (BTV) infection, which causes disease mainly in domestic sheep and cattle. Outbreaks involving either BTV serotypes 1 (BTV-1) and 8 (BTV-8) are currently challenging Europe. Inclusion of wildlife vaccination among BTV control measures should be considered in certain species. In the present study, four out of fifteen seronegative Spanish ibexes were immunized with a single dose of inactivated vaccine against BTV-1, four against BTV-8 and seven ibexes were non vaccinated controls. Seven ibexes (four vaccinated and three controls) were inoculated with each BTV serotype. Antibody and IFN-gamma responses were evaluated until 28 days after inoculation (dpi). The vaccinated ibexes showed significant (P<0.05) neutralizing antibody levels after vaccination compared to non vaccinated ibexes. The non vaccinated ibexes remained seronegative until challenge and showed neutralizing antibodies from 7 dpi. BTV RNA was detected in the blood of non vaccinated ibexes from 2 to the end of the study (28 dpi) and in target tissue samples obtained at necropsy (8 and 28 dpi). BTV-1 was successfully isolated on cell culture from blood and target tissues of non vaccinated ibexes. Clinical signs were unapparent and no gross lesions were found at necropsy. Our results show for the first time that Spanish ibex is susceptible and asymptomatic to BTV infection and also that a single dose of vaccine prevents viraemia against BTV-1 and BTV-8 replication.
Highlights
Domestic and wild ruminants are thought to be susceptible to bluetongue virus (BTV) infection, which causes bluetongue (BT), a disease that has a high economic impact on animal health
BTV antibodies increased from 4–7 dpi in the non vaccinated ibexes, reaching its maximum at 17 dpi for BTV serotypes 1 (BTV-1), and at 9 dpi for BTV-8, which showed a shorter and faster dynamics than BTV-1
BTV RNA detection both by RT-PCR and RT-qPCR, and BTV isolation without specific clinical signs confirm the susceptibility of Spanish ibex to asymptomatic BTV infection
Summary
Domestic and wild ruminants are thought to be susceptible to bluetongue virus (BTV) infection, which causes bluetongue (BT), a disease that has a high economic impact on animal health. Since 1998, at least eight serotypes (BTV-1, -2, -4, -6, -8, -9, -11 and -16) have been detected in Europe, where BT has expanded its geographical range northwards [6,7,8,9]. The spreading of BTV-8 through Europe since its introduction in 2006 caused severe disease, mainly in cattle, and in sheep, and heavy financial losses in animal industry. BTV-1 infections caused epizootics in southern Europe. BTV-1 and -8 were detected in livestock in Spain in 2007 and 2008, respectively. The target of the vaccination program was to achieve at least 80% coverage of susceptible ruminants [6,8,10]
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