Seasonal Phenological Patterns and Flavivirus Vectorial Capacity of Medically Important Mosquito Species in a Wetland and an Urban Area of Attica, Greece

Sterile Insect Technique (SIT) field trial targeting the suppression of Aedes albopictus in Greece

The sterile insect technique (SIT) involves releasing large numbers of sterile males to outcompete wild males in mating with females, leading to a decline in pest populations. In the current study, we conducted a suppression trial in Greece against the invasive dengue vector mosquito Aedes albopictus (Skuse) through the weekly release of sterile males for 22 weeks from June to September 2019. Our approach included the long-distance transport of sterile mosquitoes, and their release at a density of 2,547 ± 159 sterile males per hectare per week as part of an area-wide integrated pest management strategy (AW-IPM). The repeated releases of sterile males resulted in a gradual reduction in egg density, reaching 78% from mid-June to early September. This reduction remained between 70% and 78% for four weeks after the end of the releases. Additionally, in the SIT intervention area, the ovitrap index, representing the percentage of traps containing eggs, remained lower throughout the trial than in the control area. This trial represents a significant advance in the field of mosquito control, as it explores the viability and efficacy of producing and transporting sterile males from a distant facility to the release area. Our results provide valuable insights for future SIT programmes targeting Ae. Albopictus, and the methodology we employed can serve as a starting point for developing more refined and effective release protocols, including the transportation of sterile males over long distances from production units to intervention areas.

Winter survival of adults of two geographically distant populations of Aedes albopictus in a microclimatic environment of Athens, Greece

Overwintering capacity is a major step towards establishment of invasive mosquitoes from the tropics in temperate zone areas and one of the main elements determining next seasons' population size that regulates disease transmission of competent invasive vector species. The Asian tiger mosquito, Aedes albopictus (Skuse) (Diptera: Culiciidae) is an aggressive invasive species that has greatly expanded its geographical boundaries over the last few decades. The species' ability to induce photoperiodic-based egg diapause allows its overwintering in temperate regions, which favors its establishment in higher latitudes. In warmer temperate areas winter survival can be accomplished in the adult stage as well especially in human-made shelters. Aedes albopictus is already showing signs of adaptation to colder climates which may result in disease transmission in new areas. Although the Asian tiger mosquito has invaded Greece since 2003-4, little is known regarding its overwintering capacity in the country, especially as far as adults are regarded. We studied the survival of Ae. albopictus adults during winter in a protected shelter in Athens, the capital city of Greece. The study involved two geographically isolated populations originating from Chania (Crete, most southern part of Greece), and Palaio Faliro (Athens, Central Greece). We exposed different cohorts of F3 adults of the above two populations that emerged from field collected eggs to "winter condition" from November 2018 to beginning of January 2019. in a protected microclimatic environment. Adult mortality was recorded systematically until the death of the last individual in the cohort. Results demonstrated evidence of winter survival of adults for both populations. Longevity of both females and males of the Palaio Faliro population was longer than that of the Chania population for almost all installation dates. Survival curves, regardless of the date of installation, were steeper for females of the Chania population compared to those from Palaio Faliro. In conclusion, overwinter survival of both populations in the adult stage highlights the need for future studies, considering local and microclimatic condition that vary significantly between regions. Winter climatic conditions play vital role in adult survival of this highly important public health species concerning distribution limits and knowledge on winter survival of Ae. albopictus transmitted viruses.

Field Evaluation of Commonly Used Adult Mosquito Traps in Greece

Background: Entomological monitoring activities are a major part of mosquito and mosquito-borne diseases surveillance. Several trapping methods are implemented worldwide, aiming to gather data on species composition and their abundance in various study areas. Methods: Several methodological modifications, such as trapping systems baited with attractants or carbon dioxide, have been proposed to increase trap efficiency. The aim of this study was to test different trap types, commonly used in Greece to collect mosquitoes, with the addition of the Biogents Sentinel lure. Moreover, traps were placed in two distinct land types and two different heights above the ground to compare their efficacy. West Nile Virus is endemic in Greece, so we also aimed to detect viral presence and circulation in selected mosquito pools. Results: Adult mosquitoes of Aedes albopictus, Culex pipiens s.l., and Culiseta longiareolata were collected in both study areas. The trap type had a significant impact on the total collections, while the trap position and interaction between trap and position did not significantly affect mosquito catches. WNV was detected in Cx. pipiens s.l. pools examined from the two study areas. Conclusion: This study emphasizes the role of trapping methods as a key component for monitoring and surveillance of adult mosquito populations, reflecting that several trap types present with different mosquito species capture and catch rates.

Entomological Surveillance Activities in Regions in Greece: Data on Mosquito Species Abundance and West Nile Virus Detection in Culex pipiens Pools (2019-2020)

Human cases of West Nile virus (WNV) infections have been recorded in Greece since 2010, with seasonal outbreaks (summer-autumn) on an almost annual basis, caused mainly by the WNV lineage 2 strain (Nea Santa-Greece-2010). National Public Health Organization (NPHO) in Greece is annually implementing enhanced surveillance of human WNV infection, in order to promptly identify human cases of WNV infection and monitor distribution in terms of time and place. Entomological surveillance activities were carried out on a national basis in 2019 and 2020, under NPHO coordination and the collaboration of several private subcontractors, along with the Unit of Medical Entomology, Laboratory for Surveillance of Infectious Diseases (LSID). The aim was to monitor mosquito species composition, abundance, and WNV circulation in mosquito pools of Culex pipiens s.l. species. Adult mosquito traps were placed in selected sites; collected samples were morphologically characterized and pooled by date of collection, location, and species types. Female Culex pipiens s.l. pools were tested for WNV and WNV infection rates (MIR and MLE) were estimated. Highest mean number of female Culex pipiens s.l. species was recorded in Central Macedonia both for 2019 and 2020. Six hundred and fifty-nine mosquito pools (147 in 2019 and 512 in 2020) of female Culex pipiens s.l. were examined for WNV presence. The highest MLE was detected in Western Macedonia in 2019 and in Thessaly in 2020. Here, we present data on the mosquito species composition in the studied areas and WNV detection in mosquitoes from areas in Greece where the specific national mosquito surveillance program was implemented, for two years, 2019 and 2020.

Knowledge, Attitudes and Perception of Mosquito Control in Different Citizenship Regimes within and Surrounding the Malakasa Open Accommodation Refugee Camp in Athens, Greece

The study aims to evaluate the Knowledge, Attitude and Perception (KAP) of different societal groups concerning the implementation of targeted community-based mosquito surveillance and control interventions in different citizenship regimes. Targeted surveys were carried out within Malakasa camp for migrants and refugees, neighboring residential areas and urban areas in the wider Athens metropolitan area to investigate different knowledge levels and the role that both local and migrant communities can play in the implementation of community-based interventions based on their attitudes and perceptions. A scoring system was used to rate the collected responses. Results indicate different levels of KAP among the various groups of respondents and different priorities that should be considered in the design and execution of community interventions. Findings indicate a lower level of Knowledge Attitudes and Perceptions for the migrants, while the rate of correct answers for Perception significantly improved for migrants following a small-scale information session. The study highlights disparities in the levels of knowledge for certain public health issues and the feasibility of certain approaches for alleviating health-related challenges such as mosquito-borne diseases. Findings suggest that essential preparedness is needed by public authorities to respond to public health challenges related to migration and the spread of vector-borne diseases.

Spatial and Temporal Dynamics of Aedes albopictus Populations in Rural and Agricultural Areas in Chania, Greece, After Its Invasion

Aedes albopictus, also known as the Asian tiger mosquito, is an aggressive invasive mosquito species that transmits parasites that cause several major human diseases such as dengue, Chikungunya, and Zika. Its recent establishment in many European countries and the reported autochthonous cases of Aedes-transmitted arboviral diseases highlight the importance of effective surveillance programs to plan and implement efficient mosquito-control interventions. Aedes albopictus invaded the Greek island of Crete in 2014 and rapidly spread throughout; however, there are no comprehensive population-related data yet available. Our study focused on spatial and temporal dynamics of Ae. albopictus populations in rural and agricultural areas in Chania (western part of the Crete Island). An oviposition surveillance network, consisting of 51 ovitraps, was established in 2017 and systematically inspected for 2 years. Thirty ovitraps were established in rural areas and 21 in the surrounding agricultural areas. Eggs were collected weekly and transferred to the laboratory for counting and assessment of hatching rates. The spatial and temporal egg distribution was assessed by using geographical information systems and spatial statistical analysis tools. Kernel density and hot spot analysis were employed to identify clusters of high populations of eggs. Oviposition activity (eggs in traps) was recorded during April–May and December (of both years), while the maximum egg-laying rates were observed during September–October. The proportion of traps with eggs was similar between rural and agricultural areas, while the higher number of eggs was recorded in rural compared to agricultural areas during 2017. Egg hatch rates were high (>90%) until the end of September. The proportion of diapausing non-hatched eggs rapidly increased at the end of November. All hatched larvae were identified as Ae. Albopictus, indicating a negative effect of the invasion on the population of the local species Ae. cretinus. This was a systematic attempt to monitor the seasonal and spatial patterns of the Asian tiger mosquito in the island of Crete, the southernmost area of Europe, and a study in Europe that assessed temporal and spatial dynamics of Ae. albopictus soon after its invasion and establishment in an area.