An unwanted companion reaches the country: the first record of the alien mosquito Aedes japonicus japonicus (Theobald, 1901) in Slovakia

BACKGROUND

Invasive mosquitoes of the genus Aedes are quickly spreading around the world. The presence of these alien species is concerning for both their impact on the native biodiversity and their high vector competence. The surveillance of Aedes invasive mosquito (AIM) species is one of the most important steps in vector-borne disease control and prevention.

METHODS

In 2020, the monitoring of AIM species was conducted in five areas (Bratislava, Zvolen, Banská Bystrica, Prešov, Košice) of Slovakia. The sites were located at points of entry (border crossings with Austria and Hungary) and in the urban and rural zones of cities and their surroundings. Ovitraps were used at the majority of sites as a standard method of monitoring. The collected specimens were identified morphologically, with subsequent molecular identification by conventional PCR (cox1) and Sanger sequencing. The phylogenetic relatedness of the obtained sequences was inferred by the maximum likelihood (ML) method. The nucleotide heterogeneity of the Slovak sequences was analysed by the index of disparity.

RESULTS

A bush mosquito, Aedes japonicus japonicus, was found and confirmed by molecular methods in three geographically distant areas of Slovakia-Bratislava, Zvolen and Prešov. The presence of AIM species is also likely in Košice; however, the material was not subjected to molecular identification. The nucleotide sequences of some Slovak strains confirm their significant heterogeneity. They were placed in several clusters on the ML phylogenetic tree. Moreover, Ae. j. japonicus was discovered in regions of Slovakia that are not close to a point of entry, where the mosquitoes could find favourable habitats in dendrothelms in city parks or forests.

CONCLUSION

Despite being a first record of the Ae. j. japonicus in Slovakia, our study indicates that the established populations already exist across the country, underlining the urgent need for intensified surveillance of AIM species as well as mosquito-borne pathogens.

Geographical data on the occurrence and spreading of invasive Aedes mosquito species in Northeast Italy

This article reports data on the occurrence and spread of three invasive mosquito species: Aedes japonicus, Aedes koreicus, and Aedes albopictus in two regions of Northeast Italy; resulting from larval and adult collections performed during the 2011-2020 period in the framework of different projects. Routine species identification was performed using morphological characters and complemented by molecular methods when required. For the years 2019 and 2020, detailed data are reported which update previous information on municipalities and sites where these species have been detected. Geo-referenced information on the presence of invasive mosquitoes is reported and demonstrated on maps. Additional data on the nature of breeding sites and the finding of native mosquito species in the same collections are also provided.

Vector competence of field populations of the mosquito species Aedes japonicus japonicus and Culex pipiens from Switzerland for two West Nile virus strains

Aedes (Hulecoeteomyia) japonicus japonicus (Diptera: Culicidae) (Theobald) is an invasive mosquito species in Central Europe, where it has colonized several areas. In this study, field-collected specimens of Ae. japonicus and Culex pipiens (Diptera: Culicidae) (Linnaeus) from Zürich (Switzerland) were orally exposed to two strains (NY99 and FIN) of the avian zoonotic pathogen West Nile virus (WNV) (family Flaviviridae, genus Flavivirus). Dissemination and transmission of the viruses after incubation for 12-15 days under a fluctuating Central European midsummer temperature regime (24 ± 7 °C) was investigated by detection of viral RNA in homogenates of pools of both head/thorax and saliva by reverse transcription real-time polymerase chain reaction (PCR). Culex pipiens was susceptible to WNV NY99 only, whereas both virus strains could be detected in Ae. japonicus, with the additional isolation of WNV NY99 in Vero cell culture from one saliva pool. Given the high abundances of Ae. japonicus in many newly colonized areas, its recently demonstrated broad host range, including mammalian and avian blood hosts, and its vector competence, this species is a potential key bridge vector of WNV in Central Europe.

First Record of Aedes japonicus In Florida

The presence of Aedes j. japonicus in Florida is reported for the first time. Four adult females were collected by a Mosquito Magnet® X trap baited with pressurized CO₂ in Okaloosa County, FL, in August 2012 and later identified as Ae. japonicus in 2014. Additional adult and larval specimens were collected during 2014-17 from Bay, Leon, Okaloosa, Santa Rosa, or Walton counties, Florida. Notes are provided on the location, general habitats, and mosquito associates that may be found with Ae. japonicus in northwestern Florida. The role of Ae. japonicus in arbovirus transmission within Florida is currently unknown and should be further explored.