title: Culicoides species composition and environmental factors influencing African horse sickness distribution at three sites in Namibia.
abstract: African horse sickness (AHS) is one of the most lethal infectious, non-contagious, vector-borne disease of equids. The causative agent, African horse sickness virus (AHSV) is transmitted via Culicoides midges (Diptera: Ceratopogonidae). AHS is endemic to Namibia but detailed studies of Culicoides communities and influencing environmental parameters are limited. This study aims to determine the Culicoides species composition at three different sites and to assess environmental parameters influencing the geographical distribution of AHS in Namibia. Weekly collections of Culicoides were made during the AHS peak season from January to May for 2013 and 2014 using the Onderstepoort 220V UV-light trap. Out of 397 collections made, 124 collections (3287 Culicoides) were analysed for AHSV presence with RT-qPCR. A total of 295 collections were analysed for total Culicoides (all collected Culicoides individuals) and in 75% of these collections the Culicoides were identified to species level. C. imicola was the dominant species with proportional representation of 29.9%. C. subschultzei, C. exspectator and C. ravus each contribute more than 10% to the species composition. The lowest number of Culicoides was collected at Aus 9980, a total of 21819 at Windhoek and the highest number at Okahandja 47343. AHSV was present at all three sites during 2013 but only in Windhoek and Okahandja during 2014. Multivariate analyses of data from the two year survey indicate the environmental parameters in order of importance for the distribution of AHS in Namibia as precipitation>temperature>clay>relative humidity>NDVI. The implication of these findings is that any precipitation event increases Culicoides numbers significantly. Together with these results the high number of species found of which little is known regarding their vector competence, add to the complexity of the distribution of AHS in Namibia.
authors.affiliation: Unit for Environmental Sciences and Management, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa. Electronic address: Danica.LiebenbergWeyers@nwu.ac.za.
authors.forename: Danica
authors.initials: D
authors.lastname: Liebenberg
authors.affiliation: Unit for Environmental Sciences and Management, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa.
authors.forename: Stuart
authors.initials: S
authors.lastname: Piketh
authors.affiliation: Parasites, Vectors and Vector Borne diseases, Agricultural Research Council- Onderstepoort Veterinary Institute, Private Bag X5, Onderstepoort, 0110, South Africa.
authors.forename: Karien
authors.initials: K
authors.lastname: Labuschagne
authors.affiliation: Parasites, Vectors and Vector Borne diseases, Agricultural Research Council- Onderstepoort Veterinary Institute, Private Bag X5, Onderstepoort, 0110, South Africa.
authors.forename: Gert
authors.initials: G
authors.lastname: Venter
authors.affiliation: Unit for Environmental Sciences and Management, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa.
authors.forename: Telane
authors.initials: T
authors.lastname: Greyling
authors.affiliation: Unit for Environmental Sciences and Management, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Mienie
authors.affiliation: Unit for Environmental Sciences and Management, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa.
authors.forename: Tania
authors.initials: T
authors.lastname: de Waal
authors.affiliation: Unit for Environmental Sciences and Management, North-West University, Potchefstroom Campus, Private Bag X6001, Potchefstroom 2520, South Africa.
authors.forename: Huib
authors.initials: H
authors.lastname: van Hamburg
mesh_terms: D000355:African Horse Sickness / Q000453:epidemiology*; D000356:African Horse Sickness Virus / Q000254:growth & development*; D000538:Aluminum Silicates; D000818:Animals; D002519:Ceratopogonidae / Q000821:virology*; D000077215:Clay; D006736:Horses; D006801:Humans; D006813:Humidity; D009276:Namibia / Q000453:epidemiology; D012367:RNA, Viral / Q000032:analysis*; D060888:Real-Time Polymerase Chain Reaction; D012621:Seasons; D013696:Temperature
chemical_list: D000538:Aluminum Silicates; D012367:RNA, Viral; D000077215:Clay
keywords: Culicoides imicola; Precipitation; RT-qPCR; Temperature