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Buzz Killers Unite: How Mosquito Abatement Districts are Waging War Against the World's Deadliest Animal

By Kristin Withrow posted 04-19-2024 01:58 PM


By Kristin Withrow, CSDA Communications Specialist

Mosquito abatement goes far beyond ensuring your backyard barbecue isn't spoiled by mosquitoes as the sun goes down. Mosquito abatement districts canvas their territories trapping, testing and mitigating blooms of mosquitos across the state. The risks posed by mosquitoes are real and can have significant impact on people's lives.

Broadly, some of the diseases mosquitos are capable of spreading, and that are present in California, include dengue, chikungunya, Zika, yellow fever, St. Louis encephalitis. While rare, these diseases are a threat to human populations. West Nile Virus was first noted in California in the early 2000's and recently spiked in 2023 with 7,500 cases reported and 300 deaths. Beyond that, approximately 80% of cases will be asymptomatic, making it harder to detect until patients report illness. In 2023, cases surpassed the five-year average in California. West Nile Virus does not spread between humans and is more deadly to other animals, including birds and horses. In service to the public health, mosquito abatement districts coordinate with the Department of Public Health (CDPH). 

"California is fortunate to have over 60 local mosquito and vector control districts. These special districts are the front line in protecting California residents and visitors from mosquito-borne diseases, such as West Nile virus," stated Dr. Vicki Kramer, Chief of Vector-Borne Disease Section at CDPH.  "In collaboration with the California Department of Public Health, districts use sophisticated surveillance and control methods to quickly target mosquito populations, reduce disease transmission risk, and protect public health."

Somewhat new to California is the non-native Aedes mosquito that can spread yellow fever, dengue, chikungunya, and Zika to humans. The Aedes aegypti was first detected in 2013 in Clovis and Madera, and now has been detected in 24 counties up to the Oregon border. Aedes albopictus was first detected in southern California in 2011 and was found as far north as Shasta County in 2020.  These mosquitoes require very little water to lay their eggs. Aedes aegypti is an aggressive daytime biter and thrives in residential areas where its preferred food source (humans) and abundant egg-laying habitat make survival easy. Additionally, their eggs resist drying out and can lay dormant in dry conditions for up to nine months. In addition to the nuisance pressure from these invasive mosquitoes, they are also capable of transmitting imported diseases such as chikungunya, Zika, yellow fever, and dengue.  In 2023, to much alarm, the first two cases of locally-acquired dengue were reported in the Los Angeles area.

Wide area larviciding is deployed to cascade micro-droplets down in residential areas. This enables products specifically targeted to Aedes aegypti to reach small surface areas such as gutters and accumulated sprinkler runoff. This technique is used in a targeted manner in areas where these aggressive daytime biters have been reported.  There are also several sterile insect strategies that are currently being evaluated, including releasing irradiated male mosquitoes incapable of reproducing but still compete with other male mosquitoes to drive down the population.  Mosquito abatement districts continue to explore a number of innovative technologies and control strategies, hoping to turn the tide on this rising public health threat. 

Two men on a boat sampling water from Tulare Lake

With the wave of floodwaters that poured down on California in 2023, mosquito abatement districts have had their hands full trying to suppress the populations of mosquitoes that had abundant waters in which to reproduce. In addition to the reemergence of Tulare Lake, fields, orchards and pasture lands were flooded to divert water away from the communities in the region. The subsequent wet conditions provided perfect breeding grounds for mosquitoes. 

Aerial Larviciding, a technique used to cover expansive areas like Tulare Lake, has been utilized at a massive scale to stop reproduction. Mosquito abatement districts target different life stages of mosquitoes with an overall goal to prevent as many immature mosquitoes as possible from becoming biting adults and reduce the risk of transmission of mosquito borne diseases. 

Districts have seen their budgets blown out of the water, with some reporting expenditures of over $500,000. Intensive techniques have been deployed, new equipment, technology and innovation has been required to combat the bloodthirsty threat. Mosquito abatement districts are funded by set sources, such as property taxes, and do not have a rate payer structure to increase billing based on demand in an area. Yet the Mosquito and Vector Control Association of California (MVCAC) is tackling some of the same issues that the National Special Districts Coalition has addressed -- without a formally adopted definition of special districts, mosquito abatement districts often struggle to be included in emergency funding. Additionally, the vector threat lingers beyond the initial disaster declaration and cleanup of debris.  Districts are seeking relief from the Federal Emergency Management Agency and CalOES, but the road to funding is fraught with unknowns. 

“Extreme flood events or local transmission of imported diseases, both of which occurred in the last year, have the potential to financially devastate a vector control district.  It is vital that we establish a clear path to support before these emergencies arise and ensure sufficient funds are dedicated to promote an immediate, effective, and sustainable response," stated MVCAC President Conlin Reis.  

As these districts continue to grapple with evolving threats, a collaborative effort involving government support, regulatory clarity, and innovative solutions is essential to protect public health and ensure the success of mosquito abatement endeavors. Our health, and the fate of backyard barbecues everywhere, is in the hands of mosquito abatement district professionals deploying strategic biological science to protect us all.