Evidence of exposure to bluetongue and epizootic haemorrhagic disease viruses in the ruminant population of Mauritius and Rodrigues Islands.

Bluetongue (BT) and epizootic haemorrhagic disease (EHD) are vector-borne viral diseases causing significant economic losses in livestock systems across the globe, with particular relevance to tropical regions. This study investigates the seroprevalence of BT virus (BTV) and EHD virus (EHDV) in ruminants on the islands of Mauritius and Rodrigues. We performed serological analyses using commercial ELISA kits for BTV and EHDV, testing samples from 2017/2018 that were collected from cattle, small ruminants (sheep and goats) and native deer. In Mauritius, BTV antibody prevalence in cattle was estimated at 59.3% (95% CI [52.1–66.6]), 15.0% (95% CI [10.3–20.9]) in small ruminants and 9.8% (95% CI [6.0–13.6]) in deer. EHDV antibody prevalence was estimated at 91.4% (95% CI [87.9–95.0]) in deer, 60.4% (95% CI [53.2–67.7]) in cattle, 1.1% in small ruminants (95% CI [0–2.6]). In Rodrigues, BTV antibody prevalence in cattle was 0.5% (1/191), 11.1% in goats (4/36) whereas EHDV antibodies were absent in each of the three animal species tested (cattle, sheep and goats). These findings show that the antibody prevalence of both BTV and EHDV is higher in Mauritius than in Rodrigues, indicating a more widespread exposure to these viruses in Mauritius. Furthermore, the data suggest that both viruses currently circulate in local animal populations despite no reported clinical outbreaks.