New species Culicoides, possible vector animal diseases, in the Netherlands

Gepubliceerd op
21 januari 2015

CVI chanced upon a new species during its weekly surveillance of Culicoides attacking livestock in the Netherlands during the spring/summer of 2014. The species has a distinct dark wing pattern and has not been described before.

Culicoides scoticus and Culicoides obsoletus sensu stricto, both belonging to the Obsoletus complex, are known to be a vector for Schmallenberg virus (SBV) and very likely Bluetongue virus (BTV). Up to now it is unknown whether this new species, temporarily called ‘dark obsoletus’, is also a possible vector for the above-mentioned viruses. 

Sequences of the genetic material of ‘dark obsoletus’ supports its status as a separate species; the sequences differ significantly from those representing Culicoides obsoletus (Meigen) (90–91% homology) and Culicoides scoticus Downes & Kettle (87–88% homology). In the last decade, several research groups in Europe have encountered ‘mystery species’ related to C. obsoletus and in some instances have made their sequences for various genetic loci available in GenBank. These include a CO1 series submitted from Sweden in 2012 (annotated as ‘obsoletus 01, 02, or 03 MA-2012’) and of which some share a 99% identity with our sequences for ‘dark obsoletus’ found in the Netherlands.

Without doubt, the series from the Netherlands, along with a portion of the Swedish submissions, together represent a single species (‘dark obsoletus’). Whether this species - based solely upon the external morphology of the male - is referable to the Russian Culicoides gornostaevae Mirzaeva recorded recently from Norway, Sweden and Poland is not clear.

Only females of ‘dark obsoletus’ were found in the surveillance. For this surveillance the researchers used amongst others OVI suction light lamps. Less than 1% of the captures are male Culicoides. In the spring/summer of 2014 no SBV or BTV occurred in the Netherlands. Therefore it is not possible to determine whether this new species can be a vector for SBV or BTV.

The presence in Western Europe of multiple undescribed species related to C. obsoletus means that the taxonomy of this important vector complex is not fully resolved; consequently, we know little about these cryptic species with regard to seasonality, geographic range and host preference. This is undesirable given that Culicoides-borne arboviruses causing disease in livestock are moving more regularly out of the tropics and spreading north into temperate latitudes. More studies into possible new species is imperative.

In the next three years CVI continues its weekly Culicoides surveillance near livestock and horses. Besides information obtained of possible shifts in distribution and species of Culicoides during several years, the Culicoides collected can also be tested for the presence of SBV and BTV and possible other “new-emerging” arboviruses.