[A study on the occurrence of West Nile virus in mosquitoes (Diptera: Culicidae) on the selected areas in Poland].

West Nile virus (WNV), the etiologic agent of West Nile Fever (WNF), an emerging infectious disease that lately has been rapidly extending its range of occurrence from Africa to Middle East, and to Asia and Southern Europe. In Europe, cases of isolating WNV from mosquitoes representing four genera have been reported from Romania, Portugal, France, southern Russia and what is the most important, from Poland's neighbouring countries as the Czech Republic, Slovakia and southern Ukraine. These data, as well as human and equine cases in the Czech Republic and Belarus, support hypothesis that WNV has already been present also in Poland, the more so, specific antibodies were detected in the sera of birds collected at the Kampinos and Bialowieza Primeval Forests and in human from the vicinity of Bialystok. Mosquitoes were collected in 2004-2009 at indoor and outdoor collection sites in districts: Kujawsko-Pomorskie, Mazowieckie, Podlaskie and Warmińsko-Mazurskie. In total 15400 female mosquitoes were collected in the cow sheds and overwintering in the cellars, and from human bait and CO2 traps. Mosquitoes were sorted by the collecting site, species and sex, and placed in pools of not in more than 50 specimens in special mixture of phenol and chaotropic salts and frozen in -20 degrees C. Altogether, 15400 females were examined. Total RNA were extracted according to protocol of A&A Biotechnology. RT reaction was performed with random primers and 217-nucleotide fragment from the NS5 coding sequence was amplified by heminested PCR. PCR products were analysed on 1.5% agarose gel. The predominant species was Culex pipiens, accounting for over 42% of total insects collection. All obtained results were negative. Further investigations are needed.