South Dakota drought ends, West Nile season begins

West Nile cases 2007
A map from the U.S. Geological Survey of the 3,630 cases of West Nile virus reported in 2007.
Courtesy USGS

There are millions of mosquitoes buzzing around -- about 44 different species of them. But unless a person has microscopic vision, it's not easy to detect differences between a West Nile carrier and a less harmful - but still pesky - mosquito.

According to South Dakota's state epidemiologist Lon Kightlinger, the West Nile carriers are just starting to lay eggs and feed off of infected birds. He says the peak time for West Nile starts in a few weeks.

"We are anticipating because we have more water, more breeding sites. What we're looking at now is the flood water mosquito and that is not the primary carrier of West Nile," he says. "It'll be later in the summer when the culex mosquito starts coming out in full force that we'll really be at high risk for West Nile in South Dakota."

This is the seventh year for West Nile in South Dakota. In that time more than 1,600 people have gotten sick with the disease and 26 people have died.

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The Culex tarsalis mosquito is the only mosquito that carries the West Nile virus. Researchers identify them by the white bands around the proboscis and around the legs.
Photo courtesy of South Dakota State University

Eighty percent of the people bitten don't show any symptoms. Kightlinger says it can take up to two weeks after a bite to show signs of West Nile.

Often it's flu-like symptoms; a fever, swollen lymph glands. Some of the more severe cases are when the virus infects the brain and people become disoriented and have intense body aches. In some cases, it can lead to a coma.

Kightlinger calls South Dakota and the upper Great Plains the epicenter of West Nile because the culex tarsalis mosquito winters here.

There's much more known now than in 2002 when the first cases were identified. Back then, Kightlinger says people didn't know if the virus was spread through food or coughing.

Now, it's clear that people have made the connection between West Nile and mosquitoes.

"The first year, you could find a little bit of mosquito repellent scattered around the state. Now every store stocks mosquito repellent," he says. "As people know how the disease is spread, they know how to protect themselves. It's just as with all preventative health measures it's getting people to actually follow through and do those things."

Studies show the peak time of night for the culex tarsalis mosquito is between 8 p.m. and midnight. Kightlinger says people should protect themselves with clothing and repellent.

The state of South Dakota has awarded a total of $412,000 in grants for every city in the state to help with mosquito control.