Search

BackgroundReunion Island regularly faces outbreaks of epizootic haemorrhagic disease (EHD) and bluetongue (BT), two viral diseases transmitted by haematophagous midges of the genusCulicoides(Diptera: Ceratopogonidae) to ruminants. To date, five species ofCulicoidesare recorded in Reunion Island in which the first two are proven vector species:Culicoides bolitinos,C. imicola,C. enderleini,C. grahamiiandC. kibatiensis. Meteorological and environmental factors can severely constrainCulicoidespopulations and activities and thereby affect dispersion and intensity of transmission ofCulicoides-borne viruses. The aim of this study was to describe and predict the temporal dynamics of allCulicoidesspecies present in Reunion Island.MethodsBetween 2016 and 2018, 55 biweeklyCulicoidescatches using Onderstepoort Veterinary Institute traps were set up in 11 sites. A hurdle model (i.e. 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 ofCulicoides.ResultsAbundance displayed very strong heterogeneity between sites. AverageCulicoidescatch per site per night ranged from 4 to 45,875 individuals.Culicoides imicolawas dominant at low altitude andC. kibatiensisat high altitude. A marked seasonality was observed for the three other species with annual variations. Twelve groups of variables were tested. It was found that presence and/or abundance of all fiveCulicoidesspecies were driven by common parameters: rain, temperature, vegetation index, forested environment and host density. Other parameters such as wind speed and farm building opening size governed abundance level of some species. In addition,Culicoidespopulations were also affected by meteorological parameters and/or vegetation index with different lags of time, suggesting an impact on immature stages. 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%.ConclusionsTo our knowledge, this is the first study to modelCulicoidespopulation dynamics in Reunion Island. In the absence of vaccination and vector control strategies, determining periods of high abundance ofCulicoidesis a crucial first step towards identifying periods at high risk of transmission for the two economically important viruses they transmit.

Background The south-west insular territories of the Indian Ocean have recently received attention concerning the diversity of arthropods of medical or veterinary interest. While a recent study highlighted the circulation of Culicoides-borne viruses, namely bluetongue and epizootic hemorrhagic disease, with clinical cases in Mayotte (comprising two islands, Petite-Terre and Grand-Terre), Comoros Archipelago, no data have been published concerning the species diversity of Culicoides present on the two islands. Results A total of 194,734 biting midges were collected in 18 sites, covering two collection sessions (April and June) in Mayotte. Our study reports for the first time livestock-associated Culicoides species and recorded at least 17 described Afrotropical species and one undescribed species. The most abundant species during the April collection session were C. trifasciellus (84.1%), C. bolitinos (5.4%), C. enderleini (3.9%), C. leucostictus (3.3%) and C. rhizophorensis (2.1%). All other species including C. imicola represented less than 1% of the total collection. Abundance ranged between 126–78,842 females with a mean and median abundance of 14,338 and 5111 individuals/night/site, respectively. During the June collection, the abundance per night was low, ranging between 6–475 individuals. Despite low abundance, C. trifasciellus and C. bolitinos were still the most abundant species. Culicoides sp. #50 is recorded for the first time outside South Africa. Conclusions Our study reports for the first time the Culicoides species list for Mayotte, Comoros Archipelago, Indian Ocean. The low abundance and rare occurrence of C. imicola, which is usually considered the most abundant species in the Afrotropical region, is unexpected. The most abundant and frequent species is C. trifasciellus, which is not considered as a vector species so far, but its role needs further investigation. Further work is needed to describe Culicoides sp. #50 and to carry on faunistic investigations on the other islands of the archipelago as well as in neighboring countries. Electronic supplementary material The online version of this article (10.1186/s13071-019-3379-x) contains supplementary material, which is available to authorized users.