Abstract
BackgroundCulicoides imicola Kieffer, 1913 is the main vector of bluetongue virus (BTV) and African horse sickness virus (AHSV) in Sub-Saharan Africa. Understanding the population genetic structure of this midge and the nature of barriers to gene flow will lead to a deeper understanding of bluetongue epidemiology and more effective vector control in this region.MethodsA panel of 12 DNA microsatellite markers isolated de novo and mitochondrial DNA were utilized in a study of C. imicola populations from Africa and an outlier population from the Balearic Islands. The DNA microsatellite markers and mitochondrial DNA were also used to examine a population of closely related C. bolitinos Meiswinkel midges.ResultsThe microsatellite data suggest gene flow between Kenya and south-west Indian Ocean Islands exist while a restricted gene flow between Kenya and South Africa C. imicola populations occurs. Genetic distance correlated with geographic distance by Mantel test. The mitochondrial DNA analysis results imply that the C. imicola populations from Kenya and south-west Indian Ocean Islands (Madagascar and Mauritius) shared haplotypes while C. imicola population from South Africa possessed private haplotypes and the highest nucleotide diversity among the African populations. The Bayesian skyline plot suggested a population growth.ConclusionsThe gene flow demonstrated by this study indicates a potential risk of introduction of new BTV serotypes by wind-borne infected Culicoides into the Islands. Genetic similarity between Mauritius and South Africa may be due to translocation as a result of human-induced activities; this could impact negatively on the livestock industry. The microsatellite markers isolated in this study may be utilised to study C. bolitinos, an important vector of BTV and AHSV in Africa and identify sources of future incursions.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-015-1277-4) contains supplementary material, which is available to authorized users.
Highlights
Culicoides imicola Kieffer, 1913 is the main vector of bluetongue virus (BTV) and African horse sickness virus (AHSV) in Sub-Saharan Africa
Of the 75 arboviruses associated with Culicoides, 15 have been isolated from species belonging to C. imicola complex [1]
Cytochrome oxidase I (COI) gene analysis A total of 27 mitochondrial DNA (mtDNA) COI haplotypes were identified in the 94 sequences from both C. imicola and C. bolitinos (Hd = 0.8490) (Table 3)
Summary
Culicoides imicola Kieffer, 1913 is the main vector of bluetongue virus (BTV) and African horse sickness virus (AHSV) in Sub-Saharan Africa. Culicoides imicola is widely distributed in Africa, the Mediterranean, India, Laos, Vietnam and southern China [1, 2, 4, 5]. It is capable of transmitting both bluetongue virus (BTV) and African horse sickness virus (AHSV) [5,6,7] and is considered to be the most important vector of these viruses in Africa [8]. Bluetongue disease was first described in 1903 in Onyango et al Parasites & Vectors (2015) 8:660
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