Role of eco-climatic factors in the distribution of bluetongue in endemic areas in Tunisia.

Background: Bluetongue (BT) is an important infectious, non-contagious, OIE-listed viral disease of domestic and wild ruminants. The disease is transmitted among susceptible animals by a few species of an insect vector in the genus Culicoides. Recently, during the fall of 2020 (September and October), a Bluetongue virus-4 epizootic marked the epidemiological situation in several delegations of Tunisia with clinical cases recorded in sheep and cattle. Aim: Determine the eco-climatic variables most likely associated with delegations reporting BT cases. Methods: A logistic regression model (LRM) was used to examine which eco-climatic variables were most likely associated with delegations reporting BT cases. Results: Based on the LRM, our findings demonstrated that the key factors contributing significantly to BT cases' distribution among delegations in Tunisia included day land surface temperatures (DLST), night land surface temperatures (NLST) and normalized difference vegetation index (NDVI). A positive correlation between sheep distribution and rainfall amounts was demonstrated. Statistical analysis focusing on the most affected delegations during the BT epidemic (the Sahel and the Centre of Tunisia) demonstrated that the epidemic situation seems to be a consequence of the combination of the following environmental parameters: NDVI with values ranging between 0.16 and 0.2, moderate rainfall 2-4-fold above the normal (10-50 mm) and DLST values between 32°C and 34°C in September. Conclusion: These findings suggest and develop a robust and efficient early warning surveillance program in risk areas based on eco-climatic risk factors.

West Nile disease in Tunisia: an overview of 60 years.

West Nile virus (WNV) is an arthropod borne virus of public health importance. The virus is a member of the genus Flavivirus and belongs to the Japanese encephalitis virus (JEV) antigenic complex under the Flaviviridae family. The WNV is continuously spreading across Tunisia especially in the coastal and Southern area of the country. The first human West Nile disease (WND) epidemic in Tunisia occurred in 1997, since then, the quantity and the extension of spillover effects increased constantly. However, the existing knowledge of factors triggering such events continues to be rather poor. The last epidemic WNV human meningitis and meningoencephalitis recorded in 2012, with 86 cases and 6 deaths, confirmed the failure of the current system in predicting new cases. This review, based on analysis of scientific papers published between 1970 and 2015, summarises the state of knowledge on WNV in Tunisia and highlights the existing knowledge and research gaps that need to be addressed.