Spatio-temporal impacts of aerial insecticide applications on West Nile virus vectors
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1
University of California, Davis, Davis Arbovirus Research and Training (DART) Lab, Department of Pathology, Microbiology, and Immunology, United States
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2
Pacific Southwest Center of Excellence in Vector-Borne Diseases (PacVec), United States
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3
Institute for Health Metrics and Evaluation, United States
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4
University of California, Davis, Davis Arbovirus Research and Training (DART) Lab, Department of Pthology, Microbiology, and Immunology, United States
Aerial applications of pesticides that target adult mosquitoes are widely used for minimizing transmission of West Nile virus to humans during periods of epidemic risk. However, estimates of efficacy for reducing the abundance of infectious mosquitoes vary widely due to stochastic variation in population dynamics and trapping success unrelated to the treatment. To overcome the limitations of assessing the efficacy of single aerial spray events and capture the spatio-temporal population structure and dynamics, we fitted generalized additive models to mosquito surveillance data from CO2-baited traps in Sacramento and Yolo counties, California from 2006-2017. The models accounted for the expected spatial and temporal trends in the abundance of adult female Culex tarsalis and Culex pipiens in the absence of aerial spraying. Estimates for the magnitude and duration of reduction in relative abundance for each species following aerial spray events were obtained from the model. One week post-treatment, aerial sprays reduced Cx. pipiens by an estimated mean of 39.0% (95% CI: 19.7-55.1%) and Cx. tarsalis populations by an estimated mean of 40.1% (95% CI: 20.5-55.1%). Reductions persisted over several weeks for both species, with longer population suppression for Cx. tarsalis compared to Cx. pipiens. Repeated aerial spraying over multiple weeks was more effective at maintaining reductions in Cx. pipiens populations than in Cx. tarsalis populations. Taken together, our results indicate that aerial adulticides are effective for rapid and sustained reduction of West Nile virus vectors, and further research will consider whether these effects also result in reduced infection prevalence in the same areas.
Acknowledgements
We would like to thank Ruben Rosas, Marcia Reed, and Gary Goodman from Sacramento-Yolo Mosquito & Vector Control District for providing trapping and aerial spray data used in this study. KMH acknowledges funding support from the Floyd & Mary Schwall Fellowship in Medical Research at UC Davis, and KMH & CMB acknowledge support from the Pacific Southwest Center of Excellence in Vector-Borne Diseases funded by the U.S. Centers for Disease Control and Prevention (Cooperative Agreement 1U01CK000516).
Keywords:
Mosquito Control,
Culex mosquitoes,
generalized addtive model,
surveillance,
West Nile virus
Conference:
GeoVet 2019. Novel spatio-temporal approaches in the era of Big Data, Davis, United States, 8 Oct - 10 Oct, 2019.
Presentation Type:
Student oral presentation
Topic:
Spatio-temporal surveillance and modeling approaches
Citation:
Holcomb
KM,
Reiner
RC and
Barker
CM
(2019). Spatio-temporal impacts of aerial insecticide applications on West Nile virus vectors.
Front. Vet. Sci.
Conference Abstract:
GeoVet 2019. Novel spatio-temporal approaches in the era of Big Data.
doi: 10.3389/conf.fvets.2019.05.00097
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Received:
30 May 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
Mx. Karen M Holcomb, University of California, Davis, Davis Arbovirus Research and Training (DART) Lab, Department of Pathology, Microbiology, and Immunology, Davis, United States, kmholcomb@ucdavis.edu