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PubMed This is a summary of 18 peer-reviewed journal articles Updated
Pediatrics

Prevention, Mosquito Control, and Source Reduction

At a Glance

The best way to prevent La Crosse encephalitis (LACV) is by eliminating breeding sites for the Eastern Tree-hole mosquito, such as tree holes, old tires, and standing water. Because this mosquito bites during the day, use DEET or picaridin repellents whenever children are outdoors.

Because there is no vaccine or specific medication for La Crosse encephalitis (LACV), the most effective way to protect your family is through “source reduction”—eliminating the environments where the virus thrives [1][2]. Understanding the unique biology of the mosquito that carries this virus is key to keeping your home safe.

The “Tree-Hole” Mosquito

The primary carrier of LACV is the Aedes triseriatus, commonly known as the Eastern Tree-hole mosquito [3][4]. Unlike many other mosquitoes that are most active at dawn and dusk, this species is an aggressive diurnal (daytime) biter that prefers shaded, wooded areas [5][6].

A unique and challenging feature of LACV is transovarial transmission. This means a female mosquito can pass the virus directly to her eggs [3][7]. These infected eggs can survive through freezing winters, hatching in the spring as already-infected mosquitoes ready to spread the virus [7][8]. Because the virus is “built-in” to the next generation, simply waiting for winter is not enough to clear the risk.

Actionable Source Reduction

Source reduction means removing the specific habitats where these mosquitoes lay their eggs. Aedes triseriatus prefers small, dark “containers” that hold stagnant water [9][5].

1. Manage Tree Holes

Natural cavities in trees are the primary breeding ground for these mosquitoes.

  • Filling: If you have trees with holes that collect water, you can fill them with sand or non-toxic expanding foam to prevent water from accumulating [10].
  • Drainage: In some cases, drilling a small hole to allow water to drain naturally from the cavity is recommended [10].

2. Remove Old Tires

Discarded tires are one of the most dangerous artificial breeding sites for Aedes triseriatus [11]. They are dark, hold heat, and collect water and leaf litter, making them a perfect nursery for mosquito larvae [12].

  • Dispose of old tires through local recycling programs.
  • If tires must stay on your property (e.g., tire swings), drill large drainage holes in the bottom.

3. Clear Peridomestic Containers

“Peridomestic” refers to the area immediately around your home. High densities of artificial containers are directly linked to increased LACV risk [5].

  • Weekly Check: Walk your yard every week to dump standing water from toys, buckets, flowerpot saucers, and birdbaths.
  • Gutters: Clean gutters regularly to ensure they don’t become “elevated tree holes” filled with soggy leaves and stagnant water.

Personal Protection Measures

In addition to managing your yard, personal protection is essential when your child is in wooded or shaded areas:

  • Effective Repellents: Use topical repellents containing DEET or picaridin, which are highly effective against these mosquitoes [13][14].
  • Protective Clothing: When possible, have children wear long sleeves and pants in wooded areas. Clothing treated with permethrin (an insecticide that stays on fabric) can provide an extra layer of protection by repelling or killing mosquitoes on contact [15][16].
  • Daytime Awareness: Remember that protection is needed all day long, not just in the evenings, due to the daytime biting habits of the vector [6].

By combining yard maintenance with personal protection, you can significantly reduce the “focal” risk of LACV on your property [17][18].

Common questions in this guide

Why is the mosquito that carries La Crosse encephalitis unique?
The Eastern Tree-hole mosquito is an aggressive daytime biter, unlike many mosquitoes that bite at dusk. Additionally, infected females can pass the virus directly to their eggs, which survive the winter and hatch already infected in the spring.
How can I reduce mosquitoes that spread La Crosse virus in my yard?
The best method is source reduction, which means eliminating stagnant water where mosquitoes lay eggs. Focus on filling or draining tree holes, removing discarded tires, and emptying water from toys, gutters, and flowerpots.
What kind of bug spray is best for preventing La Crosse encephalitis?
Use topical repellents containing DEET or picaridin, which are highly effective against the mosquitoes that carry the virus. For extra protection, children can wear long sleeves and pants treated with permethrin.
Do I need to worry about La Crosse mosquitoes during the day?
Yes. The primary carrier of the virus is a diurnal biter, meaning it is highly active and bites aggressively during the daytime. Protection is needed all day long, especially in shaded or wooded areas.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Are there any specific regions or zip codes in our area that have been identified as 'high risk' for LACV this season?
  2. 2.What is the best way to report unusual mosquito activity or a suspected LACV case to local public health authorities?
  3. 3.Are there specific pediatric-safe repellents you recommend for a child who has already survived one neuroinvasive illness?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (18)
  1. 1

    West Nile Virus and Other Nationally Notifiable Arboviral Diseases - United States, 2023.

    Padda H, Jacobs D, Gould CV, et al.

    MMWR. Morbidity and mortality weekly report 2025; (74(21)):358-364 doi:10.15585/mmwr.mm7421a1.

    PMID: 40504766
  2. 2

    La Crosse virus encephalitis in children.

    Ouellette CP

    Current opinion in infectious diseases 2024; (37(5)):419-424 doi:10.1097/QCO.0000000000001042.

    PMID: 39079177
  3. 3

    Characterizing oogenesis and programmed cell death in the eastern tree hole mosquito Aedes (Protomacleaya) triseriatus.

    Airs PM, Nazarchyk MJ, Tucker BJ, Bartholomay LC

    Frontiers in insect science 2022; (2()):1073308 doi:10.3389/finsc.2022.1073308.

    PMID: 38468807
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    La Crosse Virus: A Comprehensive Review of Its Emerging Public Health Importance.

    Feng S, Feng X, Zhu W, et al.

    Viral immunology 2025; (38(4)):137-147 doi:10.1089/vim.2024.0088.

    PMID: 40274395
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    Peridomestic conditions affect La Crosse virus entomological risk by modifying the habitat use patterns of its mosquito vectors.

    Tamini TT, Byrd BD, Goggins JA, et al.

    Journal of vector ecology : journal of the Society for Vector Ecology 2021; (46(1)):34-47 doi:10.52707/1081-1710-46.1.34.

    PMID: 35229580
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    Snow-Covered Tires Generate Microhabitats That Enhance Overwintering Survival of Aedes albopictus (Diptera: Culicidae) in the Midwest, USA.

    Susong KM, Tucker BJ, Bron GM, et al.

    Environmental entomology 2022; (51(3)):586-594 doi:10.1093/ee/nvac023.

    PMID: 35552675
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    Vertical Transmission of Zika Virus in Aedes aegypti Mosquitoes.

    Thangamani S, Huang J, Hart CE, et al.

    The American journal of tropical medicine and hygiene 2016; (95(5)):1169-1173 doi:10.4269/ajtmh.16-0448.

    PMID: 27573623
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    Survival and Replication of Zika Virus in Diapause Eggs of Aedes Albopictus From Beijing, China.

    Zhang Q, Jiang Y, Li C, et al.

    Frontiers in microbiology 2022; (13()):924334 doi:10.3389/fmicb.2022.924334.

    PMID: 35875521
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    Are they there, how many, and how big? Investigating potential trap biases in the surveillance of La Crosse virus vectors.

    Day CA, Trout Fryxell RT

    Journal of medical entomology 2025; (62(1)):189-198 doi:10.1093/jme/tjae126.

    PMID: 39441803
  10. 10

    PERSISTENCE OF AEDES TRISERIATUS DESPITE THE INVASION OF AEDES JAPONICUS IN WESTERN WISCONSIN.

    Lysaker DT, Tucker BJ, Osmundson T, et al.

    Journal of the American Mosquito Control Association 2025; (41(2)):69-76 doi:10.2987/24-7211.

    PMID: 40675590
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    MOSQUITO SPECIES DISTRIBUTION IN TIRES IN RURAL AND URBAN LANDSCAPES ACROSS NORTHERN KENTUCKY.

    Parker AT, Murray BA, Miller AL

    Journal of the American Mosquito Control Association 2024; (40(4)):182-185 doi:10.2987/24-7189.

    PMID: 39527708
  12. 12

    Effects of tire leachate on the invasive mosquito Aedes albopictus and the native congener Aedes triseriatus.

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    PeerJ 2017; (5()):e3756 doi:10.7717/peerj.3756.

    PMID: 28890855
  13. 13

    Failure of Permethrin-Treated Military Uniforms to Protect Against a Laboratory-Maintained Knockdown-Resistant Strain of Aedes aegypti.

    Estep AS, Sanscrainte ND, Cuba I, et al.

    Journal of the American Mosquito Control Association 2020; (36(2)):127-130 doi:10.2987/19-6906.1.

    PMID: 33647125
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    New mosquito repellency bioassay for evaluation of repellents and pyrethroids using an attractive blood-feeding device.

    Morimoto Y, Kawada H, Kuramoto KY, et al.

    Parasites & vectors 2021; (14(1)):151 doi:10.1186/s13071-021-04656-y.

    PMID: 33691776
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    Chemical and Plant-Based Insect Repellents: Efficacy, Safety, and Toxicity.

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    Wilderness & environmental medicine 2016; (27(1)):153-63.

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    Field evaluation of personal protection methods against outdoor-biting mosquitoes in Lao PDR.

    Tangena JA, Thammavong P, Chonephetsarath S, et al.

    Parasites & vectors 2018; (11(1)):661 doi:10.1186/s13071-018-3239-0.

    PMID: 30558671
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    Notes from the Field: Spatially Associated Coincident and Noncoincident Cases of La Crosse Encephalitis - North Carolina, 2002-2017.

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    Persistent spatial clustering and predictors of pediatric La Crosse virus neuroinvasive disease risk in eastern Tennessee and western North Carolina, 2003-2020.

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This page provides environmental and mosquito control strategies for educational purposes. It does not replace professional medical advice or official guidance from your local public health authority.

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