Culicoides biting midges are tiny, -haematophagous insects that act as a vector of important human and domestic animal diseases. Because of the lack of proper identification systems, the ecology of Culicoides larvae is poorly understood. We previously determined partial mitochondrial sequences of 19 Japanese Culicoides species by using adult midges, which can be easily identified with morphological keys. Based on these sequences, we designed a universal primer set to amplify the partial sequence of the mitochondrial cytochrome c oxidase I gene (cox1), which contains a highly variable region amongst different Culicoides species. Direct sequencing was performed for the polymerase chain reaction product amplified from DNA extracted from Culicoides larvae using the primer set. Species identification for 243 specimens of field-collected larvae was performed based on the variation in cox1 using this molecular identification system. These specimens were identified as 10 species, including C. oxystoma, C. arakawae, and C, brevitarsis. C. oxystoma and C. arakawae are incriminated vectors of ruminant arboviruses and an avian pathogenic protozoan, respectively, and their larvae were recovered from paddy fields. On the other hand, C. brevitarsis, which is a possible vector of arboviruses, was found to breed in cattle dung in pastures. A more comprehensive understanding of larval habitats of Culicoides biting midges employing our molecular identification system will be useful in devising measures for the control of Culicoides larvae and for estimating the risk of Culicoides-borne pathogen spread based on the assessment of environmental factors prevalent in the habitat of these species.
(Subtropical Disease Research Division)
References:
Yanase, T. et al (2013) J. Med. Entomol. 50:1105-1110
