Monday, November 10, 2014

Culex in Turkey

Arboviruses are a group of viruses that are transmitted by arthropod vectors. The word arbovirus is actually an acronym (arthropod-borne virus) for a rather long list comprising four families of viruses one nastier than the other. The most prominent representatives are Dengue, West Nile, Yellow fever, and Tick-borne encephalitis.

Among the arthropod vectors that are often involved in the transmission of arboviral and parasitic diseases worldwide are mosquitoes of the genus Culex . This genus is huge, with well over 1200 described species which is about one third of all known mosquito species. Culex adults are usually drab, unicolorous mosquitoes which means attempts to identify them on a larger scale involving non-experts are more or less futile. However, a prerequisite to successful control of these diseases is the accurate identification of the mosquito vector species involved. BOLD currently lists about 170 species that have at least one COI Barcode sequence but only 90 of them are publicly available. Now, that I don't understand. I know that colleagues have a long list of reasons for keeping data private although I find most of their justifications not very convincing. In this particular case it simply makes me angry as it is slowing down progress and community interaction both badly need to fight arborviral diseases.

There is no doubt that DNA Barcoding can help not only to identify known mosquitoes on a regular basis as part of preventive measures but also to confirm the identity of invasive or previously undocumented species that local experts are unfamiliar with and are most likely to misidentify.

A good example was just published in Acta Tropica. The study brought together researchers from Turkey and the USA to produce a baseline faunal survey of Culex species in Turkey. Specimens were collected in 11 provinces across Turkey between 2005–2011. Morphologically identified representatives of 10 species (185 specimens) were subjected to an integrated systematics approach using both morphology and DNA barcoding. DNA Barcoding recovered 13 distinct species increasing the Culex of Turkey count to 15 recognised species:

Herein we show that including DNA barcoding in baseline faunal surveys reveals more species than by morphology alone. Our limited study on the Culex of Turkey, clarified the identities of Cx. pipiens and Cx. territans, adding four species to the Turkish faunal list. This included the previously undetected presence of Cx. quinquefasciatus, a highly efficient arboviral vector. Given that we now have quality reference barcode sequences, retrospective vector incrimination by DNA will be much more accurate, even in the absence of voucher specimens. We advocate the use of integrated faunal baseline surveys as precursors to establishing successful mosquito and arbovirus surveillance programmes in future.

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