Integrated control of Aedes albopictus in Southwest Germany supported by the Sterile Insect Technique

Media type: E-Article
Title: Integrated control of Aedes albopictus in Southwest Germany supported by the Sterile Insect Technique
Contributor: Becker, Norbert; Langentepe-Kong, Sophie Min; Tokatlian Rodriguez, Artin; Oo, Thin Thin; Reichle, Dirk; Lühken, Renke; Schmidt-Chanasit, Jonas; Lüthy, Peter; Puggioli, Arianna; Bellini, Romeo
Published: Springer Science and Business Media LLC, 2022
Published in: Parasites & Vectors, 15 (2022) 1
Language: English
DOI: 10.1186/s13071-021-05112-7
ISSN: 1756-3305
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Description: <jats:title>Abstract</jats:title><jats:sec> <jats:title>Background</jats:title> <jats:p>The invasive species <jats:italic>Aedes albopictus</jats:italic>, commonly known as the Asian tiger mosquito, has undergone extreme range expansion by means of steady introductions as blind passengers in vehicles traveling from the Mediterranean to south-west Germany. The more than 25 established populations in the State of Baden-Württemberg, Palatine and Hesse (south-west Germany) have become a major nuisance and public health threat. <jats:italic>Aedes albopictus</jats:italic> deserves special attention as a vector of arboviruses, including dengue, chikungunya and Zika viruses. In Germany, <jats:italic>Ae. albopictus</jats:italic> control programs are implemented by local communities under the auspices of health departments and regulatory offices.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>The control strategy comprised three pillars: (i) community participation (CP) based on the elimination of breeding sites or improved environmental sanitation, using fizzy tablets based on<jats:italic> Bacillus thuringiensis israelensis</jats:italic> (fizzy Bti tablets; Culinex® Tab plus); (ii) door-to-door (DtD) control by trained staff through the application of high doses of a water-dispersible Bti granular formulation (Vectobac® WG) aimed at achieving a long-lasting killing effect; and (iii) implementation of the sterile insect technique (SIT) to eliminate remaining <jats:italic>Ae. albopictus</jats:italic> populations. Prior to initiating large-scale city-wide treatments on a routine basis, the efficacy of the three elements was evaluated in laboratory and semi-field trials. Special emphasis was given to the mass release of sterile <jats:italic>Ae. albopictus</jats:italic> males.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>More than 60% of the local residents actively participated in the first pillar (CP) of the large-scale control program. The most effective element of the program was found to be the DtD intervention, including the application of Vectobac® WG (3000 ITU/mg) to potential breeding sites (10 g per rainwater container, maximum of 200 l = maximum of approx. 150,000 ITU/l, and 2.5 g per container < 50 l) with a persistence of at least 3 weeks. In Ludwigshafen, larval source management resulted in a Container Index for <jats:italic>Ae. albopictus</jats:italic> of < 1% in 2020 compared to 10.9% in 2019. The mean number of <jats:italic>Aedes</jats:italic> eggs per ovitrap per 2 weeks was 4.4 in Ludwigshafen, 18.2 in Metzgergrün (Freiburg) (SIT area) and 22.4 in the control area in Gartenstadt (Freiburg). The strong reduction of the <jats:italic>Ae. albopictus</jats:italic> population by Bti application was followed by weekly releases of 1013 (Ludwigshafen) and 2320 (Freiburg) sterile <jats:italic>Ae. albopictus</jats:italic> males per hectare from May until October, resulting in a high percentage of sterile eggs. In the trial areas of Ludwigshafen and Frieburg, egg sterility reached 84.7 ± 12.5% and 62.7 ± 25.8%, respectively; in comparison, the natural sterility in the control area was 14.6 ± 7.3%. The field results were in line with data obtained in cage tests under laboratory conditions where sterility rates were 87.5 ± 9.2% after wild females mated with sterile males; in comparison, the sterility of eggs laid by females mated with unirradiated males was only 3.3 ± 2.8%. The overall egg sterility of about 84% in Ludwigshafen indicates that our goal to almost eradicate the <jats:italic>Ae. albopictus</jats:italic> population could be achieved. The time for inspection and treatment of a single property ranged from 19 to 26 min depending on the experience of the team and costs 6–8 euros per property.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusions</jats:title> <jats:p>It is shown that an integrated control program based on a strict monitoring scheme can be most effective when it comprises three components, namely CP, DtD intervention that includes long-lasting Bti-larviciding to strongly reduce <jats:italic>Ae. albopictus</jats:italic> populations and SIT to reduce the remaining <jats:italic>Ae. albopictus</jats:italic> population to a minimum or even to eradicate it. The combined use of Bti and SIT is the most effective and selective tool against <jats:italic>Ae. albopictus</jats:italic>, one of the most dangerous mosquito vector species.</jats:p> </jats:sec><jats:sec> <jats:title>Graphical Abstract</jats:title> </jats:sec>
Access State: Open Access

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