Bluetongue virus detection in new <i>Culicoides</i> species in Sardinia, Italy

Abstract

Bluetongue is an infectious disease transmitted by <i>Culicoides</i> biting midges. <i>Culicoides imicola</i> is considered the main vector in the Mediterranean basin but other species have been implicated in the Bluetongue virus (BTV) transmission. During 2017, BTV serotype 4 re-occurred in Sardinia causing outbreaks in sheep farms. A survey was carried out on affected farms with the aim to detect the virus in field-collected <i>Culicoides</i> Biting midges were morphologically identified, pooled and then assayed with a real time RT-PCR. To evaluate BTV dissemination, some <i>Culicoides</i> were dissected and head, thorax and abdomen were tested singly by PCR. A total of 173,738 <i>Culicoides</i> adults were collected. Viral RNA was detected in 68 out of 77 pools and all species analysed resulted positive. Detection of BTV in parous female body regions (head, thorax and abdomen) confirmed the full dissemination of BTV in all species analysed. During this study, the vector competence of <i>C imicola</i>, <i>C newsteadi</i> s.l. and Obsoletus complex was confirmed. The authors found two new <i>Culicoides</i> species BTV positive, <i>C paolae</i> never associated with BTV transmission and <i>C circumscriptus</i> only recently found BTV positive in Turkey, which could be considered potential vectors.