In the sweltering summer heat of Las Vegas, while many insects struggle for survival, mosquitoes have been thriving in the Las Vegas Valley. The situation is escalating as these pests are developing immunity to commonly used pesticides.
Trishan Wickramasinghe from UNLV’s Parasitology & Vector Biology Laboratory notes that despite regular pesticide application, the eradication efforts targeting mosquitoes, particularly those that carry the West Nile virus, are proving ineffective in areas like Summerlin and Henderson.
Wickramasinghe indicated that preliminary studies show certain mosquito species continue to withstand pesticide exposure, even at levels 100 times higher than standard recommendations.
The rapid adaptation of these insects poses a significant challenge, as Louisa Messenger, assistant professor at UNLV’s School of Public Health, highlighted that new generations of mosquitoes can quickly evolve resistance to these chemicals.
Mosquitoes thriving in areas with frequent pesticide application, like water hazards on golf courses, are particularly of concern. The combination of stagnant water and high pesticide exposure appears to foster the development of these defensively evolved mosquitoes.
As mosquito season reaches its peak in Clark County, public health officials are ramping up surveillance efforts, especially following a record spike in mosquito activity earlier in summer 2024. The Southern Nevada Health District and Clark County Vector Control are actively monitoring the area’s mosquito population for disease, particularly given the looming threat posed by West Nile virus.
As of mid-July, health officials had yet to report any positive samples for arboviruses such as West Nile virus. However, Senior Environmental Health Specialist Christian De Haan cautioned that the public health threat from mosquitoes will continue until the season ends in late October.
De Haan warned that without a concerted community effort, the mosquito situation will likely worsen. He mentioned, “If you’ve got one person with an untreated, stagnant swimming pool on the end of the road, they’re just gonna be seeding mosquitoes back into the community.”
To address the growing mosquito populations, two mosquito species have emerged as primary concerns among environmental and public health experts in the Las Vegas Valley: Culex quinquefasciatus and Aedes aegypti.
Culex quinquefasciatus, the predominant mosquito species in Southern Nevada, prefers damp locales such as wetlands and is known to transmit West Nile virus. In 2023, the health district reported 26 human cases of the virus, marking the disease’s introduction to the valley in 2004.
In contrast, Aedes aegypti, a highly aggressive and resilient species, was first identified in the valley in 2017. Bites from these mosquitoes can cause severe skin reactions and may transmit diseases such as dengue fever, chikungunya, yellow fever, and Zika. While no Aedes aegypti carrying these viruses have been reported yet, health experts believe it is only a matter of time before such cases emerge, particularly given the annual influx of approximately 40 million visitors to Las Vegas.
Messenger expressed concern over potential outbreaks, as the current environmental conditions in the valley are conducive for mosquitoes to breed, especially following Hurricane Hilary’s rains that contributed to increased mosquito activity.
The proliferation of Aedes aegypti is alarming; the species has expanded from being identified in four ZIP codes in 2017 to 57 ZIP codes by last year. Current predictions, using mathematical models based on existing data, suggest that Aedes aegypti could be located in as many as 75 ZIP codes by 2030.
De Haan noted that fluctuating mosquito population sizes are often contingent on yearly weather patterns. The increased rain in 2023 resulted in a surge in mosquito numbers, but subsequent high temperatures and dry months led to a substantial decrease as the season progressed.
To mitigate mosquito bites, De Haan recommends several precautions, such as using insect repellent, wearing clothing that covers arms and legs, removing standing water sources around properties, and ensuring windows and doors are screened. He emphasized, “We have mosquitoes in town … and they’re not going anywhere. But everyone can take steps to reduce the number of mosquitoes around them, as well as take steps to prevent them from biting them.”
Efforts in mosquito abatement vary widely across Clark County, as there is currently no centralized control program. Local municipalities handle mosquito management independently, which may diminish the effectiveness of eradication efforts across the region.
Clark County Vector Control works to manage mosquito populations in public areas, utilizing mosquito-eating fish and insecticides in washes and storm drains. However, the division does not offer abatement services for private property, opting instead for educational outreach to inform homeowners about mosquito control.
Messenger has faced skepticism from local governments regarding the establishment of a county-wide mosquito abatement program. In response, she conducted a survey to gauge public sentiment towards the creation of an abatement program, aiming to present the findings to decision-makers.
With a strong desire to improve community awareness, Messenger stated, “The best thing we can do is have the community tell us,” indicating that community input could be instrumental in advocating for necessary interventions to control the rising mosquito populations.
As Las Vegas grapples with its ongoing mosquito challenge, experts reinforce the need for increased collaboration and community engagement, combined with effective prevention strategies to combat the threat posed by these resilient pests.
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