A Comparison of Adult Mosquito Trapping Methods to Assess Potential West Nile Virus Mosquito Vectors in Greece during the Onset of the 2018 Transmission Season

Abstract

West Nile virus (WNV) threatens the health of humans and equines worldwide. Culex (Cx.) pipiens complex mosquitoes are major vectors but numerous other species have been implicated. Due to variations in blood-feeding behaviour, Cx. pipiens biotypes and hybrids influence transmission, from enzootic cycles (between mosquitoes and birds), to spill-over transmission to humans and equines. In this study, mosquitoes were collected in May–June 2018 during the early period of the transmission season from two regional units of Greece, where WNV cases had been reported in the previous four years (Palaio Faliro and Argolida). A total of 1062 mosquitoes were collected with Biogents Sentinel 2 traps collecting both a greater number of all mosquito species and the Cx. pipiens complex than CDC miniature light traps or Heavy Duty EVS traps. Molecular identification confirmed additional species including Aedes albopictus. The proportion of Cx. pipiens biotypes in Palaio Faliro was 54.5% pipiens, 20.0% molestus and 25.5% hybrids. In Argolida, the collection comprised 68.1% pipiens biotype, 8.3% molestus biotype and 23.6% hybrids. Screening resulted in WNV detection in three females of the pipiens biotype and in one hybrid. As hybrids play a role in spill-over transmission, these findings highlight the importance of entomological surveillance programs incorporating molecular xenomonitoring as an early warning before human cases at the onset of the transmission season.

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

“…In this study, mosquito screening for WNV showed that the majority of positive samples for WNV were detected in the East Attica, followed by the South Sector of Attica (Table 4). In the RU of PF, WNV-positive pools in mosquitoes were detected in both years, while in the study of Bisia et al (2020) [18], no positive pool was detected in 2018. The region of MS has a warm temperate climate with hot dry summers and mild winters and displays characteristics to sustain WNV transmission cycles [96].…”

“…The installation and circulation of WNV in Greece is a fact, while extensive studies have been performed on its circulation since 2010 [10][11][12]14,18,23,30,[33][34][35]. However, predicting periods and circulation areas of the virus are difficult due to complex interactions of multiple involved factors [23,38,100].…”

“…The BG-sentinel trap (BGs) (Biogents AG, Regensburg Germany) baited with CO 2 and BG-Lure [69], which is considered an effective method for mosquito diversity and abundance characterization [2,18,32], was selected as the main monitoring tool.…”

“…Entomological studies conducted in many regions of Greece [8][9][10][11][12][13][14] and in other European countries [15][16][17] demonstrate the importance of mosquito surveillance for transmitted viruses that can be a powerful tool as a part of an effective early-warning system [10,12,14,18,19]. Testing Culex mosquitoes for WNV, especially in high-risk areas is helpful for gaining insight into the virus circulation; it is a significant confirmation in cases where WNV was detected in mosquitoes before the symptoms' onset in the human cases [14,20,21].…”

“…It is continuously circulating in Europe with a recent increasing trend of incidence in several countries [3,31,32]. Greece is one of the most WNV-affected European countries with outbreaks of the virus being recorded since 2010 [13,14,18,30,[33][34][35][36]; since then, the cases of WNV remain high on an annual basis [37][38][39].…”