The excessive rainfall that deluged the southern Plains during spring and into summer may set the stage for a boom in mosquito populations and possible cases of West Nile Virus this summer.
Frequent heavy rounds of rain in May and early June followed by dry periods have created the perfect breeding grounds for Culex mosquitoes, the main species that carries West Nile Virus.
In addition to Culex mosquitoes, the Aedes mosquito is another species that will be abundant this summer. While this species does not carry any harmful viruses in the United States, they can still be very bothersome to humans.
After several major rainstorms hit the western Gulf Coast this spring, flooding became a major problem for states like Texas and Oklahoma.
"Alice, Texas, received more than their summer's worth (June-August) of rainfall from Tropical Storm Bill alone," said AccuWeather Meteorologist Brian Edwards.
Due to these the copious amounts of rain, the Culex and Aedes species will thrive differently.
The Culex, or vector mosquito, is a "container mosquito," meaning it needs areas filled with standing water such as birdbaths, flowerpots or tarps in order to live. When these areas are inundated with rainwater, it provides the female mosquitoes an area to lay their eggs and feed off the stagnant water.
Within a week, the eggs turn to flying adult mosquitoes.
Since container areas have recently been filled due to persistent rainfall, the Culex mosquitoes currently have the perfect environment to thrive. But too much rain can be a bad thing for these vector mosquitoes, said Dr. Gabriel Hamer, assistant professor for the Department of Entomology at Texas A&M.
Hamer explained that if the "container habitats" are continually flooded, the mosquito's habitats repeatedly get washed out, and they are unable to lay eggs without the nourishment. They need these rainy periods to subside and drier weather to move in, so that the Culex can lay their eggs.
The Aedes mosquitoes, on the other hand, are more of a nuisance than a threat to humans in the United States. They are known as nuisance or floodwater mosquitoes because they live in areas that are frequently flooded, like riverbeds, low-lying areas and streams, and adapt to these frequent floods.
"With all this rain, there are a ton of nuisance, biting mosquitoes that are harassing people," Hamer said. "There is an abnormal amount of these mosquitoes that are just becoming a nuisance. They are not a vector (meaning they don't carry West Nile Virus) so fortunately, they are not a huge problem, they are just annoying."
Hamer noted that the mosquito population this year is just about average, but that their peak season is between July and September. However, populations can be expected to settle above average. He also emphasized there is no reliable way to forecast the activity of West Nile Virus this year.
Dr. Michael Merchant of Texas A&M AgriLife Extension Service noted that the Aedes mosquitoes are active and will continue to be as the floodwaters recede. As rains depart, the Culex mosquitoes will become more abundant.