Kristýna Venclíková

West Nile virus lineage 2 isolated from Culex modestus mosquitoes in the Czech Republic, 2013: expansion of the European WNV endemic area to the North?

We report the detection and isolation of four almost identical strains of West Nile virus (WNV) lineage 2from Culex modestus mosquitoes collected at three fish ponds in South Moravia, Czech Republic, during August 2013. Phylogenetic analysis demonstrated that the Czech WNV strains isolated are closely related to Austrian, Italian and Serbian strains reported in 2008,2011 and 2012, respectively. Our findings show the current northernmost range of lineage 2 WNV in Europe.

Zoonotic Dirofilaria repens (Nematoda: Filarioidea) in Aedes vexans mosquitoes, Czech Republic

The surveillance of vectors for arthropod-borne pathogens is nowadays an important tool in surveillance programmes throughout Europe. Whereas many studies have been performed to screen arthropods for viruses or bacterial pathogens, only limited information is available concerning the geographical distribution and vector range of pathogenic filariae in Central Europe. To consider the prevalence of filarial parasites in mosquito vectors, we performed a molecular survey of mosquitoes for filarial DNA. Mosquito collection was conducted at six study sites in the South Moravian region (Czech Republic) close to the borders with Slovakia and Austria from 2009 to 2011. Molecular screening of mosquitoes was conducted using conventional PCR with primers designed to amplify the mitochondrial cytochromoxidase subunit I gene as well as the partial 5.8S ribosomal RNA gene. A total of 13,222 mosquitoes belonging to six species were captured and distributed into 237 pools with different numbers of individuals. Overall, four pools were positive for Dirofilaria repens (a minimum infection rate 0.03 %) at two study sites (both natural and urban). Another filarial parasite detected during a study into Aedes vexans mosquitoes revealed the closest homology to Setaria spp. We detected specific D. repens DNA in Ae. vexans mosquitoes for the first time in the Czech Republic and confirmed the circulation of Dirofilaria spp. in a natural focus of infection providing an epidemiological link between autochthonous canine cases and mosquito vectors in the area studied.

Co-circulation of Usutu virus and West Nile virus in a reed bed ecosystem

BackgroundMosquito-borne flaviviruses are a major public health threat in many countries worldwide. In Central Europe, West Nile virus (WNV) and Usutu virus (USUV), both belonging to the Japanese encephalitis virus group (Flaviviridae) have emerged in the last decennium. Surveillance of mosquito vectors for arboviruses is a sensitive tool to evaluate virus circulation and consequently to estimate the public health risk.MethodsMosquitoes (Culicidae) were collected at South-Moravian (Czech Republic) fishponds between 2010 and 2014. A total of 61,770 female Culex modestus Ficalbi mosquitoes, pooled to 1,243 samples, were examined for flaviviruses by RT-PCR.ResultsOne pool proved positive for USUV RNA. Phylogenetic analysis demonstrated that this Czech USUV strain is closely related to Austrian and other Central European strains of the virus. In addition, nine strains of WNV lineage 2 were detected in Cx. modestus collected in the same reed bed ecosystem.ConclusionsThis is the first detection of USUV in Cx. modestus. The results indicate that USUV and WNV may co-circulate in a sylvatic cycle in the same habitat, characterised by the presence of water birds and Cx. modestus mosquitoes, serving as hosts and vectors, respectively, for both viruses.

West Nile virus in overwintering mosquitoes, central Europe

BackgroundWest Nile virus (WNV) is currently the most important mosquito-borne pathogen spreading in Europe. Data on overwintering of WNV in mosquitoes are crucial for understanding WNV circulation in Europe; nonetheless, such data were not available so far.ResultsA total of 28,287 hibernating mosquitoes [27,872 Culex pipiens, 73 Anopheles maculipennis (sensulato), and 342 Culiseta annulata], caught in February or March between 2011 and 2017 in a WNV-endemic region of South Moravia, Czech Republic, were screened for the presence of WNV RNA. No WNV positive pools were found from 2011 to 2016, while lineage 2 WNV RNA was detected in three pools of Culex pipens mosquitoes collected in 2017 at two study sites.ConclusionsTo the best of our knowledge, this is the first record of WNV RNA in overwintering mosquitoes in Europe. The data support the hypothesis of WNV persistence in mosquitoes throughout the winter season in Europe.

Human pathogenic borreliae in Ixodes ricinus ticks in natural and urban ecosystem (Czech Republic)

A total of 1279 field-collected Ixodes ricinus ticks were screened for Borrelia burgdorferi sensu lato (s.l.) in a natural and an urban ecosystem of Ostrava city (Czech Republic) by using molecular methods. Minimal prevalence rate for Borrelia burgdorferi s.l. in ticks for the urban park Bělský les was found to be 13.8% (17.6% in males, 17.8% in females and 11.7% in nymphs), similarly for the natural site Proskovice was minimal prevalence 15% (12.5% in males, 20% in females and 14.9% in nymphs). Six proven human pathogenic genomic species have been recorded in the study: B. afzelii, B. garinii, B. burgdorferi s.s., B. valaisiana, B. lusitaniae, and B. spielmanii. Emerging B. spielmanii was detected for the first time in Ixodes ricinus ticks in the region. Our results highlight the need for surveillance of zoonotic tick-borne pathogens even in urban areas.

Isolation of Tahyna Virus (California Encephalitis Group) From Anopheles hyrcanus (Diptera, Culicidae), a Mosquito Species New to, and Expanding in, Central Europe.

ABSTRACT Two strains of Tahyna virus (TAHV; Orthobunyavirus, Bunyaviridae) were isolated from 4,568 (92 pools) female Anopheles hyrcanus Pallas (Diptera, Culicidae) mosquitoes collected on the fishponds in South Moravia (Czechland, central Europe) during July–August 2013. This is the first isolation of TAHV from An. hyrcanus in Europe. An. hyrcanus is a species new to Czechland since 2007; its population density was very high in the year 2013 at these ponds. The virus isolation procedure was based on intracerebral inoculation of newborn mice; moreover, the positive pools were also tested by polymerase chain reaction and found to contain TAHV RNA. An. hyrcanus, feeding preferentially on mammals including humans, may be a new potential vector for TAHV in Europe.

Overwintering of Uranotaenia Unguiculata Adult Females in Central Europe: A Possible Way of Persistence of the Putative New Lineage of West Nile Virus?

We report the overwintering of Uranotaenia unguiculata adult females in Central Europe (Czech Republic, Hungary, Austria). This finding suggests a potential mode of winter persistence of putative novel lineage of West Nile virus in the temperate regions of Europe.

First report of Rickettsia raoultii and Rickettsia helvetica in Dermacentor reticulatus ticks from the Czech Republic

Tick-borne rickettsioses nowadays present a significant health threat among emerging tick-borne infections. In the study, we screened a total of 997 questing adult Dermacentor reticulatus ticks (576 females and 421 males) collected in Southern Moravia (Czech Republic) from April to September of 2010 and 2011 for the presence of human pathogenic rickettsiae. Here we provide the first evidence on the occurrence of human pathogenic Rickettsia raoultii in the local D. reticulatus population indicating possible future emergence of Dermacentor-borne necrotic erythema and lymphadenopathy (DEBONEL) in the region.