Epidemiological study of Middle East respiratory syndrome coronavirus infection in dromedary camels in Saudi Arabia, April-May 2015

A cross-sectional study was conducted in five regions in Saudi Arabia to investigate the epidemiology of Middle East respiratory syndrome coronavirus (MERS-CoV) infection in dromedary camels (Camelus dromedarius) during April and May 2015. Serum and nasal swab samples were tested for MERS-CoV antibodies and ribonucleic acid (RNA) using a recombinant enzyme-linked immunosorbent assay (rELISA) and real-time reverse-transcription polymerase chain reaction (rRT-PCR), respectively. The overall MERS-CoV antibody seroprevalence was 80.5%, whereas the overall viral RNA prevalence was 2.4%. The associations of risk factors with each prevalence were quantified using univariate and multivariate analyses. The multivariate models identified region, age, grazing system, exposure to wild animals and dung removal as factors significantly associated with seroprevalence (p <= 0.05). A higher seroprevalence was more likely to occur in camels from the Riyadh, Eastern, Northern and Makkah regions than those from the Jazan region; camels >= 4 and 1-3 years of age (marginally significant) than calves <1 year; and camels raised in zero grazing and semi-open grazing systems than those raised in an open grazing system. However, the presence of wild animals and daily dung removal were negatively associated with seroprevalence. On the other hand, region and sex were significantly associated with MERS-CoV RNA prevalence (p <= 0.05). A higher viral RNA prevalence was more likely to occur in camels from the Riyadh region and Eastern region (marginally significant) than in those from the Makkah region, and in male camels than female camels. In conclusion, the risk factors identified in this study can be considered to be predictors of MERS-CoV infection in camels and should be taken into account when developing an efficient and cost-effective control strategy.