Abstract
Wild and domestic ruminants are susceptible to Bluetongue virus (BTV) infection. Three BTV serotypes (BTV-4, BTV-1 and BTV-8) have been detected in Spain in the last decade. Even though control strategies have been applied to livestock, BTV circulation has been frequently detected in wild ruminant populations in Spain. The aim of the present study is to assess the role for wild ruminants in maintaining BTV after the vaccination programs in livestock in mainland Spain. A total of 931 out 1,914 (48.6%) serum samples, collected from eight different wild ruminant species between 2006 and 2011, were BTV positive by ELISA. In order to detect specific antibodies against BTV-1, BTV-4 and BTV-8, positive sera were also tested by serumneutralisation test (SNT). From the ELISA positive samples that could be tested by SNT (687 out of 931), 292 (42.5%) showed neutralising antibodies against one or two BTV serotypes. For each BTV seroptype, the number of outbreaks in livestock (11,857 outbreaks in total) was modelled with pure autoregressive models and the resulting smoothed values, representing the predicted number of BTV outbreaks in livestock at municipality level, were positively correlated with BTV persistence in wild species. The strength of this relationship significantly decreased as red deer (Cervus elaphus) population abundance increased. In addition, BTV RNA was detected by real time RT-PCR in 32 out of 311 (10.3%) spleen samples from seropositive animals. Although BT outbreaks in livestock have decreased substantially after vaccination campaigns, our results indicated that wild ruminants have been exposed to BTV in territories where outbreaks in domestic animals occurred. The detection of BTV RNA and spatial association between BT outbreaks in livestock and BTV rates in red deer are consistent with the hypothesis of virus circulation and BTV maintenance within Iberian wild ruminant populations.
Highlights
Bluetongue (BT) is a vector-borne infectious disease that has geographically expanded in Europe during the last decades [1,2,3,4,5]
Except for mouflon (Ovis aries musimon), European wild ruminants are mostly asymptomatic to bluetongue virus (BTV) infection [8,9,10], and they have potential to participate in BTV epidemiology [11,12,13,14]
BTV-1 was detected in livestock from Southern Spain in 2007, and as with BTV serotype 4 (BTV-4), both BTV strains reached the Iberian Peninsula probably from infected Culicoides carried by the wind from North Africa [18], and spread in the following years to northern areas
Summary
Bluetongue (BT) is a vector-borne infectious disease that has geographically expanded in Europe during the last decades [1,2,3,4,5]. The causal agent, bluetongue virus (BTV), is transmitted by Culicoides biting midges and both wild and domestic ruminants and camelids are considered susceptible hosts. In Europe, BTV serotype 4 (BTV-4) was firstly detected in 2004 in Southern Spain and was detected in livestock until the end of 2007. BTV-1 was detected in livestock from Southern Spain in 2007, and as with BTV-4, both BTV strains reached the Iberian Peninsula probably from infected Culicoides carried by the wind from North Africa [18], and spread in the following years to northern areas. Vaccination against BTV-4 was compulsory in susceptible domestic ruminants from 2005 to 2008, when the epidemiological situation of BTV-4 in Spain was thought to be controlled, but in 2010 a new compulsory vaccination campaign against this serotype was implemented. Spain is currently considered free from BTV-8 and continues to be considered a restriction zone for BTV-1 and BTV-4, the latter only in Southern Spain [19]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
