Thameur Ben Hassine

Epizootic hemorrhagic disease (EHD) is a non-contagious arthropod-transmitted viral disease and a World Organization for Animal Health (WOAH)-listed disease of domestic and wild ruminants since 2008. EHDV is transmitted among susceptible animals by a few species of midges of genus Culicoides. During the fall of 2021, a large outbreak caused by the epizootic hemorrhagic disease virus (EHDV), identified as serotype 8, was reported in Tunisian dairy and beef farms with Bluetongue virus (BTV)-like clinical signs. The disease was detected later in the south of Italy, in Spain, in Portugal and, more recently, in France, where it caused severe infections in cattle. This was the first evidence of EHDV-8 circulation outside Australia since 1982. In this study, we analyzed the epidemiological situation of the 2021–2022 EHDV outbreaks reported in Tunisia, providing a detailed description of the spatiotemporal evolution of the disease. We attempted to identify the eco-climatic factors associated with infected areas using generalized linear models (GLMs). Our results demonstrated that environmental factors mostly associated with the presence of C. imicola, such as digital elevation model (DEM), slope, normalized difference vegetation index (NDVI), and night-time land surface temperature (NLST)) were by far the most explanatory variables for EHD repartition cases in Tunisia that may have consequences in neighboring countries, both in Africa and Europe through the spread of infected vectors. The risk maps elaborated could be useful for disease control and prevention strategies.

Bluetongue (BT) is an OIE-listed disease of ruminants caused by a Bluetongue virus (BTV) of the Orbivirus genus within the family Reoviridae and transmitted by biting midges of the genus Culicoides. BTV circulation has been described in North African countries and many BTV emergences in Europe were related to the wind-driven dissemination of infected midges from those countries. During the fall of 2020 (September and October), an epizootic of BT linked to BTV4 marked the epidemiological situation in several delegations of Tunisia with clinical cases recorded in sheep and cattle. Eco-climatic variables are known to influence the Culicoides presence and abundance and, therefore, the probability of occurrence of BT. A logistic regression model (LRM) was used to examine which eco-climatic variables were most likely associated with delegations reported BT cases. Eco-climatic variables included: Normalized Difference Vegetation Index (NDVI), Day Land Surface Temperature (DLST), Night Land Surface Temperature (NLST), precipitation, elevation, cattle and sheep distribution. Our findings, based on the LRM, demonstrate that the key factors that contributed significantly to BT cases distribution among delegations in Tunisia included DLST and NDVI. 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 0.16-0.3, moderate rainfall 2-4-fold above the normal (10-50 mm) and DLST values between 32 and 34°C.

Epizootic hemorrhagic disease (EHD) is a Culicoides-borne disease of domestic and wild ruminants caused by EHD virus (EHDV). This virus circulates in multiple serotypes. In late September 2021, a novel strain belonging to EHDV-8 was reported in cattle farms in Central–Western Tunisia, and in the fall of 2022, the same virus was also detected in Italy and Spain. In the present study, we described EHDV-8 occurrence in deer and, a preliminary identification of the potential Culicoides species responsible for virus transmission in selected areas of Tunisia. EHDV-8 was identified in deer carcasses found in 2021 and 2022 in the national reserve of El Feidja, Jendouba, Northwestern Tunisia, and isolated on cell culture. Instead, insect vectors were collected in October 2021 only in the areas surrounding the city of Tozeur (Southern Tunisia) where EHDV-8 cases in cattle were confirmed. Morphological identification showed that 95% of them belonged to the Culicoides kingi and Culicoides oxystoma species and both species tested positive for EHDV-8 RNA. C. imicola was not detected in this collection and EHDV-8 RNA was not evidenced in vector pools collected in 2020, prior to official EHDV-8 emergence. EHDV whole genome sequences were also obtained directly from infected biological samples of deer and positive vectors. EHDV-8 sequences obtained from deer and vectors share a nucleotide identity ranging from 99.42 to 100% and amino acid identity from 99.18 to 100% across all genome segments with the EHDV-8/17 TUN2021 reference sequence.

Epizootic haemorrhagic disease (EHD) is a Culicoides-borne viral disease caused by the epizootic haemorrhagic disease virus (EHDV) associated with clinical manifestations in domestic and wild ruminants, primarily white-tailed deer (Odocoileus virginianus) and cattle (Bos taurus). In late September 2021, EHDV was reported in cattle farms in central/western Tunisia. It rapidly spread throughout the country with more than 200 confirmed outbreaks. We applied a combination of classical and molecular techniques to characterize the causative virus as a member of the serotype EHDV-8. This is the first evidence of EHDV- 8 circulation since 1982 when the prototype EHDV-8 strain was isolated in Australia. This work highlights the urgent need for vaccines for a range of EHDV serotypes.

Epizootic haemorrhagic disease (EHD) is a Culicoides-borne viral disease caused by epizootic haemorrhagic disease virus (EHDV) and associated with clinical manifestations in cervids and bovids. In late September 2021, EHDV was reported in cattle farms in central/western Tunisia. It rapidly spread throughout the country with more than 200 confirmed outbreaks. A combination of classical and molecular techniques was applied to characterize the causative virus as a member of EHDV-8 serotype. This is the first evidence of EHDV- 8 circulation since 1982 when the prototype EHDV-8 strain was isolated in Australia. This work highlights the urgent need for vaccines for a range of EHDV serotypes.

Background: Tunisia has experienced several West Nile virus (WNV) outbreaks since 1997. Yet, there is limited information on the spatial distribution of the main WNV mosquito vector Culex pipiens suitability at the national level.Objectives: In the present study, our aim was to predict and evaluate the potential and current distribution of Cx. pipiens in Tunisia.Methods: To this end, two species distribution models were used, i.e. MaxEnt and Random Forest. Occurrence records for Cx. pipiens were obtained from adult and larvae sampled in Tunisia from 2014 to 2017. Climatic and human factors were used as predictors to model the Cx. pipiens geographical distribution. Mean decrease accuracy and mean decrease Gini indices were calculated to evaluate the importance of the impact of different environmental and human variables on the probability distribution of Cx. pipiens.Results: Suitable habitats were mainly distributed next to oases, in the north and eastern part of the country. The most important predictor was the population density in both models. The study found out that the governorates of Monastir, Nabeul, Manouba, Ariana, Bizerte, Gabes, Medenine and Kairouan are at highest epidemic risk.Conclusions: The potential distribution of Cx. pipiens coincides geographically with the observed distribution of the disease in humans in Tunisia. Our study has the potential for driving control effort in the fight against West Nile vector in Tunisia.

Background: Bluetongue (BT), a vector‐borne disease of wild and domestic ruminants, is responsible for severe economic losses in flocks. To reduce this impact, a surveillance and control plan was implemented in Tunisia. However, the epidemiological situation of BT remains incompletely understood, especially for the circulating serotypes.Objective: The aim of this survey was to determine the seroprevalence, to identify the circulating serotypes and to identify the associated risk factors for bluetongue virus (BTV) circulation in Tunisia using risk‐based sampling (RBS).Methods: A total of 3314 blood samples were randomly collected from 67 sectors using risk‐based sampling and screened by competitive enzyme‐linked immunosorbent assays (c‐ELISAs). Out of the 1330 positive samples, 200 samples were analysed by serum neutralization test (SNT) to identify circulating BTV serotypes.Results: Of 3314 sera, 1330 were c‐ELISA‐positive (40.1%) for antibodies against the BTV structural protein VP7. The result of SNT showed the presence of BTV‐1, BTV‐2, BTV‐3, BTV‐4 and, for the first time in Tunisia, BTV‐26. The logistic regression model revealed that older animals had nearly two times the odds of being infected with BTV compared to younger animals. Flocks with a history of BT were almost 1.5 times more likely to be at risk for contracting BTV infection. The flock size, housing indoors and intensive production system were significant protective factors.Conclusions: High seroprevalence of BTV among sheep was highlighted in Tunisia. The neutralization test showed the presence of the following BTV serotypes: BTV‐1, BTV‐2, BTV‐3, BTV‐4 and, for the first time in Tunisia, BTV‐26. Age, production system and flock size were important variables associated with BTV infection in sheep. This finding is crucial, as it will allow the adjustment of the BT control programme in Tunisia.

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. Determine the eco-climatic variables most likely associated with delegations reporting BT cases. A logistic regression model (LRM) was used to examine which eco-climatic variables were most likely associated with delegations reporting BT cases. 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. These findings suggest and develop a robust and efficient early warning surveillance program in risk areas based on eco-climatic risk factors.

The increasing threat of vector-borne diseases (VBDs) represents a great challenge to those who manage public and animal health. Determining the spatial distribution of arthropod vector species is an essential step in studying the risk of transmission of a vector-borne pathogen (VBP) and in estimating risk levels of VBD. Risk maps allow better targeting surveillance and help in designing control measures. We aimed to study the geographical distribution of Culicoides imicola, the main competent vector of Bluetongue virus (BTV) in sheep in Tunisia. Fifty-three records covering the whole distribution range of C.imicola in Tunisia were obtained during a 2-year field entomological survey (August 2017 – January 2018 and August 2018 – January 2019). The ecological niche of C. imicola is described using ecological-niche factor analysis (ENFA) and Mahalanobis distances factor analysis (MADIFA). An environmental suitability map (ESM) was developed by MaxEnt software to map the optimal habitat under the current climate background. The MaxEnt model was highly accurate with a statistically significant area under curve (AUC) value of 0.941. The location of the potential distribution of C. imicola is predicted in specified regions of Tunisia. Our findings can be applied in various ways such as surveillance and control program of BTV in Tunisia.