Abstract
The continuous circulation of West Nile virus (WNV) in Central, South and East Europe and its recent detection in several dead birds and two horses in Germany highlights the need for information on WNV vector competence of mosquitoes from Central Europe. Therefore, three common Culex species (Culex pipiens biotype pipiens, Culex pipiens biotype molestus and Culex torrentium) from Germany were orally infected with WNV and kept at 18 °C, 21 °C, 24 °C or 27 °C for 14 or 21 days post infection (dpi). Thereafter viable WNV was present in the saliva in all tested taxa, but only at incubation temperatures of 24 °C or 27 °C and predominantly at the extended incubation period of 21 dpi. Highest transmission efficiency rates of 17 % (24 °C) and 24% (27 °C) were found for Cx. torrentium. Culex p. pipiens and Cx. p. molestus showed low transmission efficiencies with a maximum of only 3%. Consequently, temperatures above 21 °C support transmission of WNV, which matches the predominant distribution of human WNV cases around the Mediterranean Sea and in South-East Europe. Culex torrentium has been identified as a potent vector for WNV in Central and Northern Europe, which highlights the need for surveillance of mosquito-borne viruses north of the Alps.
Highlights
West Nile virus (WNV) belongs to the genus Flavivirus within the family Flaviviridae [1]
All three investigated Culex taxa were susceptible to WNV (Table 1), i.e. viral titres of mosquito bodies reached at least the detection limit of the quantitative real-time PCR (qRT-PCR) of 10,000 RNA copies per mosquito specimen
Culex torrentium had higher infection rate (IR) compared to Cx. p. pipiens and Cx. p. molestus (Tukey’s post-hoc tests, p < 0.05), while no differences were found between Cx. p. pipiens and Cx. p. molestus (Tukey’s post-hoc test, p > 0.05)
Summary
West Nile virus (WNV) belongs to the genus Flavivirus within the family Flaviviridae [1]. WNV is a zoonotic pathogen with an enzootic cycle between mosquitoes as vectors and birds as the primary, amplifying host. Equines and other vertebrates are incidental hosts [2,3]. WNV infections can range from asymptomatic or mild clinical symptoms to severe outcomes due to neuroinvasive manifestations [2]. There is no specific treatment or licensed vaccine for human use. WNV has a high epidemic potential as illustrated by its rapid spread after a single
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