Abstract
To date, studies on host preferences and blood meal identification have been conducted for Culicoides species using molecular-based methods such as PCR techniques to amplify only a fragment from universal vertebrate mitochondrial genes such as cytochrome c oxidase subunit I or cytochrome b (Cyt b). The vertebrate prepronociceptin gene (PNOC) was also tested in this field. However, the choice of molecular marker to identify blood meal is critical. The objective of our study is to compare the ability of Cyt b and PNOC as molecular markers for blood meal identification depending on the stage of blood meal digestion. In order to determine whether these Cyt b and PNOC could provide a positive result, 565 blood-fed females of Culicoides spp were collected and morphologically identified. The samples were collected between 2012 and 2014, in two localities in France. The collection localities were near either livestock or a forest. To catch the specimens, we used UV CDC miniature light traps. PNOC sequence of donkeys (Equus asinus) was sequenced and submitted because it was missing in GenBank. Our findings emphasize that the PNOC marker is not suitable to separate closely related Equid species such as horses and donkeys. The Cyt b marker was able to identify 204 more samples when compared to PNOC (99.55% of specimens). Cyt b appears to be better able to detect the origin of blood meals from females with digested blood in their abdomens. We conclude that Cyt b is a good marker as it increases the accuracy of blood meal identification of engorged females containing digested blood in their abdomens. The host opportunist behavior of Culicoides, especially that of C. obsoletus and C. scoticus, the main vectors of BTV in Europe was also highlighted.
Highlights
The study of host preferences of the native population of hematophagous Culicoides spp is critical in assessing and taking action to prevent infectious disease outbreaks
Sequence editing and Culicoides Species Identification A total of 59,704 Culicoides biting midges [females and males] were collected by the four UV CDC miniature light traps used in this study during the period 2012–2014
The PCR technique based on the cytochrome b (Cyt b) gene of mitochondrial DNA and the prepronociceptin gene (PNOC) was selected for blood meal identification: (i) fully engorged Culicoides, (ii) Culicoides showing an advanced sign of digestion, and (iii) females showing any remainder of blood in their abdomen
Summary
The study of host preferences of the native population of hematophagous Culicoides spp is critical in assessing and taking action to prevent infectious disease outbreaks. A better knowledge of this field could help identify the animal reservoirs for arboviruses. In Europe, before BTV-8 experience, bluetongue was considered an exotic disease that could be controlled by animal movement restriction and vaccination [1]. Since the spread of BTV-8 in northern Europe, despite the absence of C. imicola, the main African vector of BTV, some abundant autochthonous Culicoides species have been suspected and incriminated, mainly species from Obsoletus and Pulicaris groups [2]. In autumn 2011, an unidentified disease of livestock was reported in Germany and, the etiologic agent of this disease was identified as a novel orthobunyavirus and named Schmallenberg virus (SBV) [3]. Midges of the group Obsoletus have been shown to be natural vectors for this virus [4]
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