Mosquitoes are a confirmed presence throughout the Las Vegas valley and Clark County. While this might seem counterintuitive given the arid Mojave Desert climate, these insects thrive by adapting to the environment created by human habitation. The significant mosquito population is sustained not by natural desert features, but by extensive water management and residential practices. The constant introduction of water for landscaping, recreation, and sanitation provides the necessary standing water sources for mosquitoes to complete their life cycle.
Mosquito Activity in the Desert Climate
Mosquito season in Southern Nevada begins in the late spring, typically around March or April, and continues through early fall, sometimes lasting into October. The peak period of activity occurs during the hottest summer months, specifically from May through September, with the highest concentration in July and August. This extended period is directly related to sustained high temperatures that accelerate the mosquito life cycle.
The presence of mosquitoes is entirely dependent on man-made habitats that collect water. Residential and commercial properties often contain the specific breeding sites these insects require. Abandoned or neglected swimming pools, often referred to as “green pools,” are prolific breeding grounds, offering large, undisturbed volumes of water. Other smaller, less obvious sources contribute significantly to the population, including leaky irrigation systems, ornamental ponds, and any container that holds water for more than a week. This includes small items like children’s toys, plant saucers, and discarded tires that collect water from sprinklers or infrequent rainfall.
Disease Risk and Specific Species
The primary public health concern in Clark County is the transmission of West Nile Virus (WNV), which is actively monitored by local health officials. The main carriers of WNV are native Culex species, such as the Southern House Mosquito (Culex quinquefasciatus) and the Western Encephalitis Mosquito (Culex tarsalis). These mosquitoes are most active during the cooler hours of dawn and dusk, and they frequently feed on birds, which act as a reservoir for the virus.
A more recent concern is the invasive Aedes aegypti, an aggressive daytime biter first identified in Clark County in 2017. While this species can also carry WNV, it is primarily monitored for its capacity to transmit other serious diseases, including Dengue, Chikungunya, and Zika viruses. This species prefers to bite humans and breeds in very small amounts of water, increasing the threat of disease transmission in dense urban settings.
Managing Mosquito Populations in Clark County
The Southern Nevada Health District (SNHD) operates a Mosquito Surveillance Program that actively monitors the population across Clark County. Health officials set thousands of traps annually to collect mosquitoes, which are then tested for arboviruses like West Nile Virus and St. Louis Encephalitis. This surveillance identifies disease activity and guides the response of abatement agencies.
Clark County Vector Control manages control efforts in public areas, including using larvicides in flood channels and stocking neglected water sources with mosquito fish (Gambusia affinis). Residents and visitors play a significant role in prevention by eliminating standing water around their homes, which is the most effective control measure. Personal protection involves using EPA-registered insect repellents and ensuring that window and door screens are intact to prevent mosquitoes from entering indoor spaces.