Mosquitoes are present in Missouri and can pose health risks. Understanding common species, their activity patterns, and effective control methods is important for residents and visitors to protect themselves and their communities.
Mosquito Presence and Seasonal Activity
Missouri’s humid summers and warm temperatures create an environment where mosquitoes thrive. Abundant water sources, including rivers, lakes, wetlands, and small collections of standing water, contribute to their prevalence. Mosquitoes require water for three of their four life stages: egg, larva, and pupa.
The typical mosquito season in Missouri spans from late spring through early fall, aligning with warmer, wetter periods. Mosquito activity increases when temperatures are between 50°F and 80°F. While some species are active during the day, many are most active at dusk and dawn, as these periods offer optimal humidity and cooler temperatures.
Common Mosquito Species and Associated Health Risks
Missouri is home to approximately 50 mosquito species. Culex and Aedes genera are common and transmit diseases. Culex mosquitoes, often called the common house mosquito, are active around dawn and dusk, laying eggs in rafts on stagnant water. Aedes mosquitoes, including the Asian Tiger Mosquito (Aedes albopictus), are known for aggressive daytime biting and distinctive black and white striped bodies. They lay eggs in small, temporary water sources like flowerpots and old tires.
These mosquitoes can transmit several diseases of concern in Missouri. West Nile Virus (WNV) is regularly reported in the state and is transmitted when mosquitoes feed on infected birds and then bite humans. Most WNV infections are asymptomatic, but about one in five may experience mild symptoms such as fever, headache, body aches, and fatigue. More severe cases can lead to encephalitis (inflammation of the brain) or meningitis.
St. Louis Encephalitis (SLE) is another mosquito-borne illness transmitted primarily by Culex species mosquitoes, which acquire the virus from birds. While most SLE infections are asymptomatic, some individuals may develop fever, headache, nausea, and tiredness, with severe cases potentially leading to high fever, neck stiffness, disorientation, and even coma.
Eastern Equine Encephalitis (EEE) is a rare but severe disease, and while less common in Missouri, it is known to be transmissible by some mosquito species. Although locally acquired Zika virus cases have not been reported in Missouri, travel-related cases have occurred, and Aedes mosquitoes, which are present in the state, can transmit the virus if they bite an infected traveler. Symptoms of Zika are often mild and can include fever, rash, joint pain, and red eyes.
Effective Prevention and Control Strategies
Mitigating mosquito issues involves personal protection and property management. Using EPA-registered insect repellents is a primary measure. These repellents contain active ingredients such as DEET, picaridin, IR3535, or oil of lemon eucalyptus. When using both sunscreen and repellent, apply sunscreen first, then the repellent.
Wearing protective clothing, such as long-sleeved shirts and pants, especially during peak mosquito activity hours like dawn and dusk, can also reduce exposure to bites. Staying indoors during these times can further minimize risk.
Property management plays a significant role in reducing mosquito populations by eliminating breeding sites. Mosquitoes lay their eggs in standing water, so removing stagnant water around the home is highly effective. This includes regularly emptying and cleaning items such as flowerpots, bird baths, old tires, and clogged gutters.
For water that cannot be easily removed, such as decorative ponds, introducing water circulation through bubblers or fountains can prevent mosquito breeding, as larvae require still water to breathe. Maintaining window and door screens is also important to prevent mosquitoes from entering indoor spaces. Community-level efforts, such as clean-up events to eliminate breeding areas and vector control programs, also contribute to broader mosquito control.