Abstract
BackgroundThe Culicoides obsoletus species complex (henceforth ‘Obsoletus complex’) is implicated in the transmission of several arboviruses that can cause severe disease in livestock, such as bluetongue, African horse sickness, epizootic hemorrhagic disease and Schmallenberg disease. Thus, this study aimed to increase our knowledge of the composition and genetic diversity of the Obsoletus complex by partial sequencing of the cytochrome c oxidase I (cox1) gene in poorly studied areas of Spain.MethodsA study of C. obsoletus populations was carried out using a single-tube multiplex polymerase chain reaction (PCR) assay that was designed to differentiate the Obsoletus complex sibling species Culicoides obsoletus and Culicoides scoticus, based on the partial amplification of the cox1 gene, as well as cox1 georeferenced sequences from Spain available at GenBank. We sampled 117 insects of the Obsoletus complex from six locations and used a total of 238 sequences of C. obsoletus (ss) individuals (sampled here, and from GenBank) from 14 sites in mainland Spain, the Balearic Islands and the Canary Islands for genetic diversity and phylogenetic analyses.ResultsWe identified 90 C. obsoletus (ss), 19 Culicoides scoticus and five Culicoides montanus midges from the six collection sites sampled, and found that the genetic diversity of C. obsoletus (ss) were higher in mainland Spain than in the Canary Islands. The multiplex PCR had limitations in terms of specificity, and no cryptic species within the Obsoletus complex were identified.ConclusionsWithin the Obsoletus complex, C. obsoletus (ss) was the predominant species in the analyzed sites of mainland Spain. Information about the species composition of the Obsoletus complex could be of relevance for future epidemiological studies when specific aspects of the vector competence and capacity of each species have been identified. Our results indicate that the intraspecific divergence is higher in C. obsoletus (ss) northern populations, and demonstrate the isolation of C. obsoletus (ss) populations of the Canary Islands.Graphical abstract
Highlights
The Culicoides obsoletus species complex ( ‘Obsoletus complex’) is implicated in the trans‐ mission of several arboviruses that can cause severe disease in livestock, such as bluetongue, African horse sickness, epizootic hemorrhagic disease and Schmallenberg disease
Three of the Aguilar‐Vega et al Parasites Vectors (2021) 14:351 arboviruses of the genus Orbivirus—bluetongue virus (BTV), African horse sickness virus (AHSV) and epizootic hemorrhagic disease virus (EHDV) [3]—can have an impact on livestock welfare and cause significant economic losses, and are listed as notifiable diseases by the World Organization for Animal Health [4]
Our polymerase chain reac‐ tion (PCR) allows the differentiation of C. obsoletus from C. scoticus within the Obsoletus complex, without the need for sequencing derived from the use of generic primer pairs such as LCO/HCO [60], C1-J-1718/C1-N-2191 [61, 62], and Lep [63], ObL primers showed a lack of specificity for the amplification of C. montanus, which we discuss below
Summary
The Culicoides obsoletus species complex ( ‘Obsoletus complex’) is implicated in the trans‐ mission of several arboviruses that can cause severe disease in livestock, such as bluetongue, African horse sickness, epizootic hemorrhagic disease and Schmallenberg disease. Three of the Aguilar‐Vega et al Parasites Vectors (2021) 14:351 arboviruses of the genus Orbivirus (family Reoviridae)—bluetongue virus (BTV), African horse sickness virus (AHSV) and epizootic hemorrhagic disease virus (EHDV) [3]—can have an impact on livestock welfare and cause significant economic losses, and are listed as notifiable diseases by the World Organization for Animal Health [4]. Despite not being reported in the European Union, EHDV outbreaks have been declared in Mediterranean Basin countries [9]. This proximity suggests a risk of introduction of EHDV into the EU, as has occurred with AHSV [10] and BTV [10, 11]
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