Seroprevalence and risk factors: A comprehensive seroepidemiological study of epizootic hemorrhagic disease and bluetongue in Northwestern Tunisia

Epizootic hemorrhagic disease (EHD) and Bluetongue (BT) are vector-borne diseases that commonly circulate among wild and domestic ruminants. The epidemiological situation of EHD in Tunisia remains poorly documented, despite several studies having been conducted on BT. To assess the seroprevalence of the EHD and BT in northern Tunisia, 394 bovine serum samples were collected and tested for anti-VP2 antibodies using a competitive ELISA. The seroprevalence of EHD and BT at the individual level was estimated at 51.2% and 81% respectively. Herd-level seroprevalence reached 93% for EHDV and 100% for BTV. No statistically significant differences in prevalence were observed between governorates for EHD (p-value = 0.169). However, the prevalence of BT across governorates was found to be statistically significant (p-value = 0.00000). A multivariable mixed-effects logistic regression were conducted to identify risk factors for EHD and BT. The final model revealed that risk factors associated with EHD and BT seroprevalence may include only age where an age-related increase in seroprevalence was noted for both diseases. Local animal husbandry practices and herd management were not found to be associated with the dynamics of the two diseases. The findings of this study highlight the geographical extent of the disease in the northwestern region and its associated risk factors. It is therefore imperative that further investigations be conducted on vectors and their abudance in order to gain a comprehensive understanding of the current situation.