Bluetongue and epizootic hemorrhagic disease in La Réunion; a burden on ruminant farming

Since 2002, the livestock of Réunion Island has been subject to reoccurring outbreaks of Bluetongue (BT) and Epizootic Hemorrhage Disease (EHD). To find out a solution to this problem, that can have severe financial implications to ruminant farmers, a study was carried out between March and September of 2011. The aims of this study were: (1) to confirm the circulation of the viral agents in relation to both host reservoirs and insect vectors; (2) to assess the health status of Réunion Island's livestock; and (3) to identify major risk factors pertaining to ruminant farming due to these viruses. A total of 254 cows from 51 farms and 206 sheep and goats were chosen randomly for testing. Multiple blood samples were taken from all sampled animals. Farming procedures and environmental conditions were assessed for each farm via a questionnaire. Any animal exhibiting clinical symptoms of viral infection was also tested. Serology was done using commercially available LSIVET kits, viral detection was performed via RT-PCR and genotyping was performed externally. Logistic regression was used to assess potential risk factors after a fist of univariate analysis (Chi2). Serology studies suggested that ~50% of ruminants were positive for Bluetongue and ~40% for EHD. EHDV-1 virus was detected in ~5% of animals and bluetongue variant 2 was detected in ~1%. Statistical analysis showed that the major risk factors for Bluetongue and EHD viral infection of ruminant livestock include; the category of the reared livestock, the presence of organic waste, the presence of a water source and the proximity of another farm. Those results are the first step to a better understanding of what could happen in the futur in Western Europe. (Texte intégral