Abstract
The mosquito Aedes albopictus is expanding across Europe, raising concerns due to its ability to transmit arboviruses. The larvicide Bacillus thuringiensis subsp. israelensis (Bti) plays a central role in controlling the spread of Ae. albopictus. The objective of this study is to assess the temporal effectiveness of Bti as a control method using fine-scale spatiotemporal data and a distributed lag non-linear modelling framework. We analyzed 1,320 ovitrap observations from 195 traps alongside records of 4,387 Bti treatments and local environmental conditions for the entire 2023 mosquito season in Heidelberg, Germany. Bti treatments produced a clear reduction in egg counts, with the strongest marginal effects occurring 6–13 days after treatment with efficacy diminishing thereafter at lower treatment counts, while higher counts demonstrated sustained effects. Cumulatively, Bti was highly effective at reducing egg counts even at moderate treatment levels, and a counterfactual no Bti scenario suggested that Bti treatments reduced seasonal egg production by an estimated 41.9% (95% CI 24.4% – 58.5%) and prevented total establishment across the study site. These results demonstrate that Bti can substantially reduce Ae. albopictus populations in urban settings, though its limited temporal efficacy underscores the need for repeated interventions to prevent establishment and spread.
Data availability
The materials and datasets generated and analyzed during this study are available from the corresponding author upon reasonable request. Restrictions apply only to the sharing of entomological surveillance data collected by the ICYBAC Mosquito Control GmbH on behalf of the city of Heidelberg, for which access should be granted directly from there. Meterological data from HYRAS is available at: https://www.dwd.de/DE/leistungen/hyras/hyras.html. Air temperature from city of Heidelberg can be found here: https://ckan.datenplattform.heidelberg.de/de/dataset/environment_main_barani. Green space data was directly sourced from OpenStreetMap using the Ohsome API.
Code availability
The code to reproduce the models and figures can be found at: https://github.com/cstarob/Temporal-Spatial-Bti-Albopictus.
References
Jourdain, F. et al. From importation to autochthonous transmission: Drivers of chikungunya and dengue emergence in a temperate area. PLoS Negl. Trop. Dis. 14, e0008320 (2020).
Kraemer, M. U. G. et al. Past and future spread of the arbovirus vectors Aedes aegypti and Aedes albopictus. Nat. Microbiol. 4, 854–863 (2019).
Rocklöv, J. & Dubrow, R. Climate change: An enduring challenge for vector-borne disease prevention and control. Nat. Immunol. 21, 479–483 (2020).
Barman, S. et al. A climate and population dependent diffusion model forecasts the spread of Aedes Albopictus mosquitoes in Europe. Commun. Earth Environ. 6, 276 (2025).
Nationale Expertenkommission „Stechmücken als Überträger von Krankheitserregern“. Friedrich-Loeffler-Institut https://www.fli.de/de/kommissionen/nationale-expertenkommission-stechmuecken-als-uebertraeger-von-krankheitserregern/.
Farooq, Z. et al. Impact of climate and Aedes albopictus establishment on dengue and chikungunya outbreaks in Europe: A time-to-event analysis. Lancet Planet Health. 9, e374–e383 (2025).
Haider, N. et al. Global dengue epidemic worsens with record 14 million cases and 9000 deaths reported in 2024. Int. J. Infect. Dis. 158, 107940 (2025).
Seasonal surveillance for chikungunya virus disease in the EU/EEA for 2025. https://www.ecdc.europa.eu/en/chikungunya-virus-disease/surveillance-and-updates/seasonal-surveillance (2025).
Liu-Helmersson, J. et al. Climate change and Aedes vectors: 21st century projections for dengue transmission in Europe. EBioMedicine 7, 267–277 (2016).
Van Daalen, K. R. et al. The 2024 Europe report of the Lancet Countdown on health and climate change: Unprecedented warming demands unprecedented action. The Lancet Public Health https://doi.org/10.1016/S2468-2667(24)00055-0 (2024).
Ravasi, D., Parrondo Monton, D., Tanadini, M. & Flacio, E. Effectiveness of integrated Aedes albopictus management in southern Switzerland. Parasit. Vectors. 14, 405 (2021).
Land, M., Bundschuh, M., Hopkins, R. J., Poulin, B. & McKie, B. G. Effects of mosquito control using the microbial agent Bacillus thuringiensis israelensis (Bti) on aquatic and terrestrial ecosystems: A systematic review. Environ. Evid. 12, 26 (2023).
López-de-Felipe, M. et al. Integrated Control of Aedes albopictus in a Residential Area Through a Community-Based Approach: NESCOTIGER, a Large-Scale Field Trial in Valencia, Spain. Pathogens https://doi.org/10.3390/pathogens14040367 (2025).
European Centre for Disease Prevention and Control. Vector control with a focus on Aedes aegypti and Aedes albopictus mosquitoes: Literature review and analysis of information. (ECDC, 2017).
Lee, Y. W. & Zairi, J. Susceptibility of laboratory and field-collected Aedes aegypti and Aedes albopictus to Bacillus thuringiensis israelensis H-14. J. Am. Mosq. Control Assoc. 22, 97–101 (2006).
Ravasi, D., Monton, D. P., Tanadini, M., Campana, V. & Flacio, E. Efficacy of biological larvicide VectoMax® FG against Aedes albopictus and Culex pipiens under field conditions in urban catch basins. J. Eur. Mosq. Control Assoc. 42, 51–60 (2023).
Uragayala, S., Kamaraju, R., Tiwari, S., Ghosh, S. K. & Valecha, N. Field testing & evaluation of the efficacy & duration of effectiveness of a biolarvicide, Bactivec® SC (Bacillus thuringiensis var. israelensis SH-14) in Bengaluru, India. Indian J. Med. Res. 147, 299–307 (2018).
Boyce, R. et al. Bacillus thuringiensis israelensis (Bti) for the control of dengue vectors: Systematic literature review. Trop. Med. Int. Health 18, 564–577 (2013).
Giatropoulos, A. et al. Efficacy Evaluation of Oregano Essential Oil Mixed with Bacillus thuringiensis israelensis and Diflubenzuron against Culex pipiens and Aedes albopictus in Road Drains of Italy. Insects 13, 977 (2022).
Ferraguti, M. et al. Spatial distribution and temporal dynamics of invasive and native mosquitoes in a large Mediterranean city. Sci. Total Environ. 896, 165322 (2023).
Virgillito, C. et al. Evaluation of Bacillus thuringiensis Subsp. Israelensis and Bacillus sphaericus Combination Against Culex pipiens in Highly Vegetated Ditches. J. Am. Mosq. Control Assoc. 38, 40–45 (NaN/NaN/NaN).
Fontoura, P. S. et al. Field Efficacy of VectoMax FG and VectoLex CG Biological Larvicides for Malaria Vector Control in Northwestern Brazil. J. Med. Entomol. 57, 942–946 (2020).
Guidi, V., Lüthy, P. & Tonolla, M. Comparison between diflubenzuron and a Bacillus thuringiensis israelensis– and Lysinibacillus sphaericus–based formulation for the control of mosquito larvae in urban catch basins in Switzerland. J. Am. Mosq. Control Assoc. 29, 138–145 (2013).
Cetin, H., Oz, E., Yanikoglu, A. & Cilek, J. E. Operational Evaluation Of Vectomax® WSP (Bacillus thuringiensis Subsp. israelensis Bacillus sphaericus) Against Larval Culex pipiens in Septic Tanks1. J. Am. Mosq. Control Assoc. 31, 193–195 (2015).
Yang, D. et al. Semi-field life-table studies of Aedes albopictus (Diptera: Culicidae) in Guangzhou, China. PLoS ONE 15, e0229829 (2020).
Delatte, H., Gimonneau, G., Triboire, A. & Fontenille, D. Influence of temperature on immature development, survival, longevity, fecundity, and gonotrophic cycles of Aedes albopictus, vector of chikungunya and dengue in the Indian Ocean. J. Med. Entomol. 46, 33–41 (2009).
Manica, M., Rosà, R., della Torre, A. & Caputo, B. From eggs to bites: Do ovitrap data provide reliable estimates of Aedes albopictus biting females?. PeerJ 5, e2998 (2017).
Virgillito, C. et al. Lessons learned exploiting a multi-year large-scale data set derived from operational quality assessment of mosquito larval treatments in rain catch basins. Pest Manag. Sci. 81, 6630–6638 (2025).
Sun, D. et al. Taming a tiger in the city: Comparison of motorized backpack applications and source reduction against the Asian tiger mosquito, Aedes albopictus. J. Am. Mosq. Control Assoc. 30, 99–105 (2014).
Reuss, F. et al. Knowledge on exotic mosquitoes in Germany, and public acceptance and effectiveness of Bti and two self-prepared insecticides against Aedes japonicus japonicus. Sci. Rep. 10, 18901 (2020).
Sotelo, F., Lévesque, A., Larouche, M., Dupras, J. & Turgeon, K. Social Perspectives on Larvicide-Based Mosquito Control in Urban Quebec. 2025.10.20.683413 Preprint at https://doi.org/10.1101/2025.10.20.683413 (2025).
Krähenmann, S., Walter, A., Brienen, S., Imbery, F. & Matzarakis, A. High-resolution grids of hourly meteorological variables for Germany. Theor. Appl. Climatol. 131, 899–926 (2018).
Karaman, Z. CDSE: ‘Copernicus Data Space Ecosystem’ API Wrapper. 0.3.0 https://doi.org/10.32614/CRAN.package.CDSE (2023).
Frick, C. et al. Central European high-resolution gridded daily data sets (HYRAS): Mean temperature and relative humidity. Meteorol. Z. 23, 15–32 (2014).
NDVI, the Foundation for Remote Sensing Phenology | U.S. Geological Survey. https://www.usgs.gov/special-topics/remote-sensing-phenology/science/ndvi-foundation-remote-sensing-phenology (2018).
Marini, F. et al. Estimating spatio-temporal dynamics of Aedes albopictus dispersal to guide control interventions in case of exotic arboviruses in temperate regions. Sci. Rep. 9, 10281 (2019).
Gasparrini, A., Armstrong, B. & Kenward, M. G. Distributed lag non-linear models. Stat. Med. 29, 2224–2234 (2010).
Hastie, T. J. & Tibshirani, R. J. Generalized Additive Models (Routledge, 2017). https://doi.org/10.1201/9780203753781.
Farajollahi, A. et al. Assessment of a direct application of two Bacillus thuringiensis israelensis formulations for immediate and residual control of Aedes albopictus. J. Am. Mosq. Control Assoc. 29, 385–388 (2013).
Gasparrini, A. Distributed lag linear and non-linear models in R: The package dlnm. J. Stat. Softw. 43, 1–20 (2011).
Wood, S. N. Fast Stable Restricted Maximum Likelihood and Marginal Likelihood Estimation of Semiparametric Generalized Linear Models. J. R. Stat. Soc. Ser. B Stat. Methodol. 73, 3–36 (2011).
Acknowledgements
We are grateful to the city of Heidelberg for sharing their vector control and mosquito population data.
Funding
Open access funding provided by Umea University. JR received financial research support from the Alexander von Humboldt foundation. CH receives support from the Helmholtz Information & Data Science School for Health (HIDSS4Health). The study received partial support from the IDAlert project which has received funding from the European Union’s Horizon Europe programme under Grant Agreement 101057554.
Author information
Authors and Affiliations
Contributions
CH and JR conceptualized this study. CH was responsible for data curation. CH conducted the formal analysis. CH, PL, JB, and PS were responsible for the methodology. JR, MB, and AZ supervised the study. CH, AT, and NB accessed and verified the data. CH was responsible for data visualization. CH wrote the original draft manuscript. All authors reviewed and edited the manuscript. All authors had full access to all the data in the study and had final responsibility for the decision to submit for publication.
Corresponding author
Ethics declarations
Competing interests
Authors AT and NB are employees of ICYBAC Mosquito Control GmbH, which provided the data used in this study. They did not contribute to the study design, statistical analysis, interpretation of results, or the decision to publish. The remaining authors declare no competing interests.
Additional information
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Information
Supplementary Information. (download DOCX )
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Reprints and permissions
About this article
Cite this article
Hatfield, C.R.S., Stiles, P.C., Liyanage, P. et al. Fine-scale temporal and spatial dynamics of Ae. albopictus response to larviciding with Bacillus thuringiensis israelensis in Heidelberg, Germany.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-46094-9
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41598-026-46094-9
Source: Ecology - nature.com
