English abstract
This is the first large-scale study on the seroprevalence of bluetongue disease in camels in
the Sultanate of Oman. Bluetongue (BT) is an infectious, non-contagious, vector-borne
viral disease that affects domestic and wild ruminants, including cattle, buffaloes, camels,
sheep, goats, and deer. The causative agent of the BT is a member of the Orbivirus genus,
and it belongs to the Reoviridae family. This study aimed to estimate the seroprevalence
and potential risk factors of BTV in Omani camels in northern Oman. The study also
aimed to estimate the molecular prevalence of BTV in Omani camels. A cross-sectional
study was conducted in the northern regions of Oman and Sera samples from 439 camels
and out of them 100 blood samples were collected from five governorates from October
2016 to March 2017. Competitive enzyme-linked immunosorbent assay (c-ELISA) was
used for screening serum for BTV antibodies and real-time reverse transcription polymerase chain reaction (RT-qPCR) was used for detecting BTV genomic RNA in
blood. Data of risk factors associated with BTV were collected using a structured
questionnaire. Statistical analysis was performed using the chi-squared test and binary
logistic regression. The overall seroprevalence of BTV was 56.04%. BTV seropositivity
was significantly associated with location, age of camels, sex, participation in events, and
outbreak history whereas, tick infestation in farms and abortion history were not
significant. The highest seroprevalence was in A'Dhahirah 81.08% and the lowest was in
Al Buraimi 40.63%. The finding revealed the BTV seroprevalence was higher in camels
older than 10 years (80%) than camels younger than 4 years old (18.27%) and camels
aged between 4 to 10 years old (65.36%). Further, it was found that BTV seropositivity
was higher in female camels (59.33%) than male camels (32.08%). Notably, camels that
were mixed with small and large ruminants had a seroprevalence of 67.21%, while
camels that were kept alone had a seroprevalence of 40.86%. The seroprevalence of BTV
in camels that had outbreak history was 36.54% and 54.26% in aborted camels. The
overall molecular prevalence in the regions was 26%. The highest active infection
revealed by RT-qPCR was in Ash Sharqiyah (22%), A'Dhahirah (21.05%), and Al
Batinah (27.78%). There was a good agreement between c-ELISA and RT-qPCR (kappa
value = 0.794). The results of the present study showed that the BTV in northern Oman is
enzootic, widely distributed and it is believed BT is an asymptomatic or sub-clinical
disease in camels. Further investigation is required to determine the BTV serotypes that
are circulating in the Sultanate of Oman.
