![]() Clinical cases are almost exclusively reported during or after the rainy season (November–March). Epidemiological investigations highlighted that outbreaks of bluetongue virus (BTV) and epizootic hemorrhagic diseases virus (EHDV) occurred on annual cycles, with BTV being enzootic and EHDV epizootic. Since the 1980’s, clinical cases of two Culicoides-borne viral diseases, bluetongue (BT) and epizootic hemorrhagic diseases (EHD), are observed in sheep and cattle resulting in economic losses. In Reunion Island, Indian Ocean, five Culicoides species are recorded with different altitudinal distributions: C. īiting midges of the genus Culicoides are vector species of economically important viruses affecting livestock. Indeed, daily, seasonal or longer-term changes in meteorological and environmental features can impact their presence and abundance and therefore, the rate of transmission of pathogens they carry. To achieve this, the bionomics and population dynamics of each vector species is a starting point to investigate. Identifying when the transmission is suspected to occur facilitates disease surveillance, vector control implementation and communication to populations and stakeholders. The complex interplay of multiple factors, and their dependence towards extrinsic factors, mean that pathogen transmission is not constant and is often distributed over time and space. Transmission of vector-borne diseases depends on the interaction between hosts (domestic and wild), vectors and pathogens within suitable environmental and climatic conditions. In the absence of vaccination and vector control strategies, determining periods of high abundance of Culicoides is a crucial first step towards identifying periods at high risk of transmission for the two economically important viruses they transmit. To our knowledge, this is the first study to model Culicoides population dynamics in Reunion Island. ![]() Taking into account all the parameters for the final hurdle model, the error rate by Normalized Root mean Square Error ranged from 4.4 to 8.5%. In addition, Culicoides populations were also affected by meteorological parameters and/or vegetation index with different lags of time, suggesting an impact on immature stages. Other parameters such as wind speed and farm building opening size governed abundance level of some species. It was found that presence and/or abundance of all five Culicoides species were driven by common parameters: rain, temperature, vegetation index, forested environment and host density. A marked seasonality was observed for the three other species with annual variations. Culicoides imicola was dominant at low altitude and C. Average Culicoides catch per site per night ranged from 4 to 45,875 individuals. ResultsĪbundance displayed very strong heterogeneity between sites. a presence/absence model combined with an abundance model) was developed for each species in order to determine meteorological and environmental drivers of presence and abundance of Culicoides. Methodsīetween 20, 55 biweekly Culicoides catches using Onderstepoort Veterinary Institute traps were set up in 11 sites. The aim of this study was to describe and predict the temporal dynamics of all Culicoides species present in Reunion Island. Meteorological and environmental factors can severely constrain Culicoides populations and activities and thereby affect dispersion and intensity of transmission of Culicoides-borne viruses. To date, five species of Culicoides are recorded in Reunion Island in which the first two are proven vector species: Culicoides bolitinos, C. Reunion Island regularly faces outbreaks of epizootic haemorrhagic disease (EHD) and bluetongue (BT), two viral diseases transmitted by haematophagous midges of the genus Culicoides (Diptera: Ceratopogonidae) to ruminants.
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