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Lopez K, Susong K, Irwin P, Paskewitz S, Bartholomay L. Impacts of ground ultra-low volume adulticide applications on Culex pipiens and Culex restuans (Diptera: Culicidae) abundance, age structure, and West Nile virus infection in Cook County, Illinois. JOURNAL OF MEDICAL ENTOMOLOGY 2024; 61:1043-1053. [PMID: 38527268 DOI: 10.1093/jme/tjae041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 03/11/2024] [Accepted: 03/13/2024] [Indexed: 03/27/2024]
Abstract
Since the introduction of West Nile virus (WNV) to the United States over 20 years ago, thousands of cases of human disease and death have been reported. Yearly seasonal outbreaks continue to persist, and the city and suburbs of Chicago, Illinois, is considered a "hot spot" for WNV activity. To interrupt WNV transmission, ground ultra-low volume (ULV) adulticide applications are regularly used to reduce Culex pipiens L. and Culex restuans Theobold (Diptera: Culicidae) abundance and infection. The real-world effectiveness of adulticide applications has not been comprehensively assessed, and prior studies, including our own investigation, have yielded inconclusive or conflicting results. Therefore, we expanded our prior work and evaluated the effects of 5 sequential weekly truck-mounted ULV adulticide applications in large residential areas in the northern suburbs of Chicago, Illinois, in 2019 and 2020. Each day, Cx. pipiens and Cx. restuans host-seeking and gravid mosquitoes were collected to assess abundance, age structure, and WNV infection rates. Adulticide applications resulted in significant reductions of both host-seeking and gravid abundance on the night of treatment. The reduction in host-seeking mosquitoes was followed by a reduction in gravid mosquitoes trapped 3 and 4 days after adulticide application and an increase in the proportion of nulliparous mosquitoes. WNV infection rates were significantly reduced in treatment sites as compared to untreated sites when infection rates were higher in 2020. This large-scale study provides comprehensive evidence that ground ULV adulticide applications are an effective tool in an integrated mosquito management program for combating WNV vectors and infection risk.
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Affiliation(s)
- Kristina Lopez
- Department of Entomology, University of Wisconsin-Madison, Madison, WI, USA
| | - Katie Susong
- Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, WI, USA
| | - Patrick Irwin
- Department of Entomology, University of Wisconsin-Madison, Madison, WI, USA
- Northwest Mosquito Abatement District, Wheeling, IL, USA
| | - Susan Paskewitz
- Department of Entomology, University of Wisconsin-Madison, Madison, WI, USA
| | - Lyric Bartholomay
- Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, WI, USA
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Lopez K, Irwin P, Bron GM, Paskewitz S, Bartholomay L. Ultra-low volume (ULV) adulticide treatment impacts age structure of Culex species (Diptera: Culicidae) in a West Nile virus hotspot. JOURNAL OF MEDICAL ENTOMOLOGY 2023; 60:1108-1116. [PMID: 37473814 DOI: 10.1093/jme/tjad088] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 06/01/2023] [Accepted: 07/14/2023] [Indexed: 07/22/2023]
Abstract
West Nile virus (WNV) invaded the continental United States over 20 years ago and continues to cause yearly seasonal outbreaks of human and veterinary disease. In the suburbs of Chicago, Illinois, ultra-low volume (ULV) truck-mounted adulticide spraying frequently is performed to reduce populations of Culex restuans Theobald and Cx. pipiens L. mosquitoes (Diptera: Culicidae) in an effort to lower the risk of WNV transmission. The effectiveness of this control method has not been rigorously evaluated, and evidence for Culex population reduction after ULV adulticide spraying has been inconclusive. Therefore, we evaluated the results of 5 sequential weekly truck-mounted adulticide applications of Zenivex® E20 (etofenprox) in 2 paired sites located in Cook County, IL, during the summer of 2018. Mosquito population abundance, age structure, and WNV infection prevalence were monitored and compared between paired treatment and nearby control sites. Adulticide treatment did not result in consistent short-term or long-term reductions in target WNV vector Culex abundance. However, there was a significant increase in the proportion of nulliparous females in the treated sites compared to control sites and a decrease in Cx. pipiens WNV infection rates at one of the treated sites. This evidence that ULV adulticide spraying altered the age structure and WNV infection prevalence in a vector population has important implications for WNV transmission risk management. Our findings also underscore the importance of measuring these important indicators in addition to abundance metrics when evaluating the efficacy of control methods.
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Affiliation(s)
- Kristina Lopez
- Department of Entomology, University of Wisconsin-Madison, Madison, WI, USA
| | - Patrick Irwin
- Department of Entomology, University of Wisconsin-Madison, Madison, WI, USA
- Northwest Mosquito Abatement District, Wheeling, IL, USA
| | - Gebienna M Bron
- Department of Entomology, University of Wisconsin-Madison, Madison, WI, USA
- Quantitative Veterinary Epidemiology Animal Science Group, Wageningen University and Research, Wageningen, NL, USA
| | - Susan Paskewitz
- Department of Entomology, University of Wisconsin-Madison, Madison, WI, USA
| | - Lyric Bartholomay
- Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, WI, USA
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Uelmen JA, Lamcyzk B, Irwin P, Bartlett D, Stone C, Mackay A, Arsenault-Benoit A, Ryan SJ, Mutebi JP, Hamer GL, Fritz M, Smith RL. Human biting mosquitoes and implications for West Nile virus transmission. Parasit Vectors 2023; 16:2. [PMID: 36593496 PMCID: PMC9806905 DOI: 10.1186/s13071-022-05603-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 11/30/2022] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND West Nile virus (WNV), primarily vectored by mosquitoes of the genus Culex, is the most important mosquito-borne pathogen in North America, having infected thousands of humans and countless wildlife since its arrival in the USA in 1999. In locations with dedicated mosquito control programs, surveillance methods often rely on frequent testing of mosquitoes collected in a network of gravid traps (GTs) and CO2-baited light traps (LTs). Traps specifically targeting oviposition-seeking (e.g. GTs) and host-seeking (e.g. LTs) mosquitoes are vulnerable to trap bias, and captured specimens are often damaged, making morphological identification difficult. METHODS This study leverages an alternative mosquito collection method, the human landing catch (HLC), as a means to compare sampling of potential WNV vectors to traditional trapping methods. Human collectors exposed one limb for 15 min at crepuscular periods (5:00-8:30 am and 6:00-9:30 pm daily, the time when Culex species are most actively host-seeking) at each of 55 study sites in suburban Chicago, Illinois, for two summers (2018 and 2019). RESULTS A total of 223 human-seeking mosquitoes were caught by HLC, of which 46 (20.6%) were mosquitoes of genus Culex. Of these 46 collected Culex specimens, 34 (73.9%) were Cx. salinarius, a potential WNV vector species not thought to be highly abundant in upper Midwest USA. Per trapping effort, GTs and LTs collected > 7.5-fold the number of individual Culex specimens than HLC efforts. CONCLUSIONS The less commonly used HLC method provides important insight into the complement of human-biting mosquitoes in a region with consistent WNV epidemics. This study underscores the value of the HLC collection method as a complementary tool for surveillance to aid in WNV vector species characterization. However, given the added risk to the collector, novel mitigation methods or alternative approaches must be explored to incorporate HLC collections safely and strategically into control programs.
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Affiliation(s)
- Johnny A. Uelmen
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, 3505 Veterinary Medicine Basic Sciences Building, 2001 S. Lincoln Ave, Urbana, IL 61802 USA
| | - Bennett Lamcyzk
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, 3505 Veterinary Medicine Basic Sciences Building, 2001 S. Lincoln Ave, Urbana, IL 61802 USA
| | - Patrick Irwin
- Northwest Mosquito Abatement District, 147 W. Hintz Rd, Wheeling, IL 60090 USA
| | - Dan Bartlett
- Northwest Mosquito Abatement District, 147 W. Hintz Rd, Wheeling, IL 60090 USA
| | - Chris Stone
- Illinois Natural History Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, Forbes Natural History Building, 1816 S. Oak Street, M/C 652, Champaign, IL 61820 USA
| | - Andrew Mackay
- Illinois Natural History Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, Forbes Natural History Building, 1816 S. Oak Street, M/C 652, Champaign, IL 61820 USA
| | - Arielle Arsenault-Benoit
- Department of Entomology, College of Computer, Mathematical, and Natural Sciences, University of Maryland, 4112 Plant Sciences Building, College Park, MD 20742 USA
| | - Sadie J. Ryan
- Department of Geography, College of Liberal Arts and Sciences, University of Florida, 3141 Turlington Hall, 330 Newell Dr, Gainesville, FL 32611 USA
| | - John-Paul Mutebi
- Division of Vector-Borne Diseases, Arboviral Disease Branch, US Centers for Disease Control and Prevention, 3156 Rampart Rd., Fort Collins, CO 80521 USA
| | - Gabriel L. Hamer
- Department of Entomology. College of Agriculture & Life Sciences, Texas A&M University, TAMU 2475, College Station, TX 77843 USA
| | - Megan Fritz
- Department of Entomology, College of Computer, Mathematical, and Natural Sciences, University of Maryland, 4112 Plant Sciences Building, College Park, MD 20742 USA
| | - Rebecca L. Smith
- Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, 3505 Veterinary Medicine Basic Sciences Building, 2001 S. Lincoln Ave, Urbana, IL 61802 USA
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