Background: Aedes albopictus, the Asian tiger mosquito, has become a prevalent pest in Italy, causing severe nuisance and posing a threat of transmission of arboviruses introduced by infected travelers. In this study, we investigated the influence of weather parameters on the seasonal population density of Aedes albopictus. Methods: A Bayesian approach was employed to identify the best meteorological predictors of species trend, using the eggs collected monthly from 2010 to 2022 by the Emilia-Romagna regional monitoring network. Results: The findings show that the winter–spring period (January to May) plays a crucial role in the size of the first generation and seasonal development of the species. Conclusions: A temperate winter and a dry and cold March, followed by a rainy and hot spring and a rainy July, seem to favor the seasonal development of Ae. albopictus.

In 2011, a new orthobunyavirus, named the Schmallenberg virus (SBV), was discovered in Europe. Like the related Shamonda virus, SBV is an arbovirus (arthropod-borne virus). After its discovery, the virus was detected in a wide area in north-western Europe, an unexpected finding in a territory where climatic conditions would not seem ideal for arbovirus transmission. This sudden expansion suggests the effect of 2011 drought as a key factor that may have triggered SBV circulation. The possible influence of drought, recorded in north-western Europe in early 2011, on virus circulation was evaluated.

Toscana virus (TOSV) is a Phlebovirus transmitted by phlebotomine sand flies and is an important etiological agent of summer meningitis in the Mediterranean basin. Since TOSV infection is often asymptomatic, we evaluated the seroprevalence in blood donors (BDs) in the Bologna and Ferrara provinces (Northeastern Italy)—the areas with the highest and lowest numbers of TOSV neuroinvasive cases in the region, respectively. A total of 1208 serum samples from BDs were collected in April–June 2014 and evaluated for the presence of specific TOSV-IgG by ELISA. The IgG-reactive samples were confirmed by indirect immunofluorescence assay (IIF) and by microneutralization test (MN). Serum samples were defined as positive for anti-TOSV IgG when reactive by ELISA and by at least one second-level test; TOSV seroprevalence was 6.8% in the Bologna province, while no circulation of TOSV was detected in the Ferrara province. Sand fly abundance in 2014 was also estimated by a geographic information system using a generalized linear model applied to a series of explanatory variables. TOSV seroprevalence rate was strongly associated with the sand fly abundance index in each municipality, pointing out the strong association between sand fly abundance and human exposure to TOSV.

Background: Aedes albopictus, the Asian Tiger Mosquito, has become a prevalent pest in Italy, causing severe nuisance and posing a threat of transmission of arboviruses introduced by infected travellers. In this study, we investigated the influence of weather parameters on the seasonal population density of Aedes albopictus. Methods: A Bayesian approach was employed to identify the best meteorological predictors of species trend, using the eggs collected monthly from 2010 to 2022 by the Emilia-Romagna regional monitoring network. Results: The findings show that the winter-spring period (January to May) plays a crucial role in the size of the first generation and seasonal development of the species. Conclusions: A temperate winter and a dry and cold March, followed by a rainy and hot spring and a rainy July, seem to favour the seasonal development of Ae. albopictus.

Background: The Asian tiger mosquito, Aedes albopictus , is an aggressive invasive vector responsible for transmitting important arboviruses. Its global spread has been largely facilitated by human-mediated transport, especially through trade and road networks. Since its first detection in the Netherlands in 2005, repeated introductions have occurred via pathways such as lucky bamboo imports, used tires, aircraft, and ground traffic. Despite ongoing surveillance and elimination efforts, uncertainties remain about the origins, recurrence, and establishment potential of these introductions. Methods: We analyzed 200 Ae. albopictus specimens collected from 21 locations in the Netherlands from 2014 to 2023, including detections in residential areas and points of entry (PoEs). Samples were genotyped at 19 specific microsatellite loci. Genetic diversity and kinship were studied to better understand genetic structure, relatedness between and within locations, and local overwintering. We also determined the presence of Wolbachia endosymbiont strains in the specimens by sequencing Wolbachia markers. Results: Genetic structure and kinship analyses revealed multiple independent introductions, genetic diversity among sites, and evidence of local overwintering at both residential and PoE locations, including used tire storage sites. Close-kin relationships were identified in 63 specimen dyads. Among these, one dyad confirmed overwintering at a used tire storage facility, four indicated kinship within a residential area, and two between two locations. Genetic assignment results also highlighted successful elimination of the species in one Dutch residential area. A total of 16 Dutch locations (76.19%) tested positive for the presence of Wolbachia . Overall, 48.86% specimens analyzed tested positive for at least one strain, and 35 close-kin dyads showed complete concordance in Wolbachia infection status. Conclusions: Our findings highlight the complex invasion dynamics of Ae. albopictus in the Netherlands. Our results demonstrate that microsatellite analysis, combined with kinship assessment, is an efficient approach for investigating kinship among individuals within and between urban areas and PoEs, providing evidence of local overwintering, and assessing the genetic structure of Ae. albopictus at introduction sites. The widespread presence of Wolbachia , which is known to reduce mitochondrial diversity, suggests that mitochondrial DNA (mtDNA)-based population analyses may be limited for the species.