Population genetic structure of the Asian bush mosquito, Aedes japonicus (Diptera, Culicidae), in Belgium suggests multiple introductions

Abstract

Background Aedes japonicus japonicus has expanded beyond its native range and has established in multiple European countries, including Belgium. In addition to the population located at Natoye, Belgium, locally established since 2002, specimens were recently collected along the Belgian border. The first objective of this study was therefore to investigate the origin of these new introductions, which were assumed to be related to the expansion of the nearby population in western Germany. Also, an intensive elimination campaign was undertaken at Natoye between 2012 and 2015, after which the species was declared to be eradicated. This species was re-detected in 2017, and thus the second objective was to investigate if these specimens resulted from a new introduction event and/or from a few undetected specimens that escaped the elimination campaign. Methods Population genetic variation at nad4 and seven microsatellite loci was surveyed in 224 and 68 specimens collected in Belgium and Germany, respectively. German samples were included as reference to investigate putative introduction source(s). At Natoye, 52 and 135 specimens were collected before and after the elimination campaign, respectively, to investigate temporal changes in the genetic composition and diversity. Results At Natoye, the genotypic microsatellite make-up showed a clear difference before and after the elimination campaign. Also, the population after 2017 displayed an increased allelic richness and number of private alleles, indicative of new introduction(s). However, the Natoye population present before the elimination programme is believed to have survived at low density. At the Belgian border, clustering results suggest a relation with the western German population. Whether the introduction(s) occur via passive human-mediated ground transport or, alternatively, by natural spread cannot be determined yet from the dataset. Conclusion Further introductions within Belgium are expected to occur in the near future, especially along the eastern Belgian border, which is at the front of the invasion of Ae. japonicus towards the west. Our results also point to the complexity of controlling invasive species, since 4 years of intense control measures were found to be not completely successful at eliminating this exotic at Natoye.

Japanese Encephalitis Virus Interaction with Mosquitoes: A Review of Vector Competence, Vector Capacity and Mosquito Immunity

“…However, although Culex pipiens is not considered a primary vector, given its high abundance in temperate zones (including Europe) and its competence for JEV, the potential contribution of this vector species to the spread of JEV upon introduction should not be underestimated. In this respect, Aedes japonicus also might play a role as it is known to be abundant in certain regions [ 123 , 124 , 125 , 126 , 127 ] and present far beyond its endemic zone ( Figure 3 ). It is one of the world’s most invasive Culicidae species, with a confirmed presence in Europe.…”

Aedes koreicus, a vector on the rise: pan-European genetic patterns, mitochondrial and draft genome sequencing

“…albopictus (41,42) and Ae. japonicus (43,44) were undertaken over the last decades, to date, for Ae. koreicus only morphological characterizations are available from Belgium (7) and Germany (20).…”

From a long-distance threat to the invasion front: a review of the invasive Aedes mosquito species in Belgium between 2007 and 2020

“…The collected polystyrene pieces from OT were checked for the presence of IMS eggs in the laboratory by using a stereomicroscope. From 2007 to 2010 and from 2013 to 2019, a subsample of the eggs from the polystyrene piece (1–5 eggs per side) was always DNA-barcoded [ 18 , 26 , 27 , 36 , 40 ]. In 2012 and 2020 the positive polystyrene pieces or wooden paddles were immerged in water in secured containers, which were stored in a secured mosquito breeding room (2012 [ 25 ]) or climate controlled cupboard (2020).…”

“…japonicus spread again in southwest direction as it was the case in 2012. It seems that the small forest located southwest of the tyre company forms a good ‘green corridor’ for the spread of the mosquito [ 40 , 72 ]. At the northeast side, the company is surrounded by open meadows, which possibly hamper the spread of the population in that direction.…”

“…An investigation of the genetic variation at seven microsatellite loci indicated that remnants of the original population were still present, although no detections were done in 2015 and 2016 during the control campaign [ 70 ]. Natural or cryptic larval habitats (tree holes, plastic sheet covering wood, plastic waste) in the small forest probably played a role as ‘refuge’ [ 22 , 40 , 73 ]. The current admixed population displayed a higher allelic richness than the original population, which points towards at least one re-introduction of Ae.…”