West Nile research creates buzz


Brookings Street Department workers fog the mosquitoes at Pioneer Park on Tuesday, Aug. 31


Two professors at South Dakota State University and their partners are attempting to take the sting out of mosquito bites.

Mike Hildreth and Mike Wimberly are collaborating with the South Dakota Department of Health, National Aeronautics and Space Administration (NASA) and communities across South Dakota to create an early warning system to prevent the West Nile Virus. 

The researchers also want South Dakotans to be more concerned about West Nile than Zika.

“South Dakota has the highest risk of human West Nile Disease in the U.S.,” said Wimberly, professor of natural resource management and a senior scientist with the Geospatial Sciences Center of Excellence. “Most people don’t realize that because you don’t think of South Dakota being a mosquito hotspot.”

As of Aug. 30, there have been 79 human cases of West Nile Virus reported to the South Dakota Department of Health. Out of those 79 cases, there has been one death associated with the virus.

According to the United State Geological Survey and Center for Disease Control, there have been 427 reported cases of West Nile Virus nationally as of Aug. 30.

Brookings County, as of Aug. 30 according to the South Dakota Department of Health, has four reported cases of West Nile Virus. 

The street department workers in Brookings work to prevent more cases by capturing mosquitoes in mosquito traps, counting the mosquitos and, if there are more than 100 in the trap, the street department workers will fog or spray the city.

The City of Brookings has been fogged more than eight times over the summer, said Josh McClain, an advanced equipment operator for the City of Brookings.

Hildreth, professor in biology, microbiology and veterinary science, began working with the South Dakota Department of Health to prevent West Nile Virus in 2001 before it came to South Dakota. Wimberly arrived in South Dakota in 2005 and started assisting in the West Nile Research in 2007.

“It’s really been a fun, cooperative effort between state agencies, universities, local communities,” Hildreth said, “and we ended up with a NASA grant that allows all of this integration to be brought to a whole other level.”

Collaborative West Nile Virus Research

“Our research is focused on using the best information we can find and looking at it scientifically to give us a better picture of where and when people are at risk,” Wimberly said.

According to Wimberly, communities can use the information produced in the research to effectively perform mosquito control and inform the public about the risk of West Nile Virus.

Weather patterns, past findings and surveillance of mosquitoes across the state shape their research. Wimberly leads his team in using models to locate where the risk may be for West Nile Virus across the state.

“We do various types of modeling, of building essentially computer simulations that put this all together and produce a prediction, an assessment of what the current West Nile Virus risks are and whether they’re likely to be a week or two into the future,” Wimberly said.

Hildreth spearheads the team that test mosquitoes in South Dakota.

South Dakota towns place mosquito traps, which are then emptied and the mosquitos are counted in the trap. Those mosquitos are then sent to a testing facility to see if those caught in the trap are carriers of West Nile Virus.

Hildreth and Wimberly are assisted by Justin Davis, Jeffrey Vincent and Brianna Lind at SDSU.

The information found by the teams are then used to create a weekly report that states the risk of West Nile Virus in South Dakota. The most recent report was published on Aug. 30, and it can be found at www.mosquito.sdstate.edu. There is additional information also included in the report.

Hildreth warned that West Nile Virus remains a concern until the first hard frost of the season. Cases of West Nile Virus will continue to pop up after the frost because those individuals were bitten prior to the frost.

The researchers struggle to balance the false signals of West Nile risk, the lag time between West Nile Virus transmission and the appearance of symptoms.

“One of the problems that we have is that many of the things that we observe, that we can easily observe, give us the wrong information,” Wimberly said.

There is one type of mosquito transmitting West Nile, but the problem is that there is a false sense of risk. Sometimes there are many mosquitos and none of them are the species of mosquito that transmits the disease. Whereas there are situations where there are very few mosquitos, but all of the mosquitoes transmit West Nile Virus.

Human cases of West Nile Virus tend to be a “lagging indicator” because there is a delay between when the individuals get the virus, develop symptoms, get sick, visit the doctor, the doctor reports the signs and the health department checks the symptoms.

“By the time we really notice that [human cases],” Wimberly said, “it’s kind of too late because there are already a lot of people who have already been infected, but they just haven’t been counted and included in the tally of cases yet.”

Risk or lack of risk for Zika in South Dakota

South Dakotans are at a low risk of being infected with Zika in South Dakota. However, if a person travels to a tropical area, they are able to be bitten by a mosquito that transmits Zika.

“You’re not going to be bitten by a mosquito that will give you Zika virus in South Dakota. The mosquitos that are known to transmit have never ever been found in South Dakota,” Hildreth said. “The risk has to do with travel.”

Individuals traveling to a tropical area are advised by Hildreth to watch the travel advisories and to be vigilant when it comes to protecting themselves against mosquitos bites. Zika can also be transmitted sexually.

“We’ve got a long ways to go before you could start seeing mosquito transmission of Zika,” Hildreth said. “We’re going to have at least a year’s advanced warning for that and right now it doesn’t look like it’s even possible in South Dakota.”

There are two types of mosquito that transmit Zika, and neither of those mosquitos are in South Dakota.

There are 43 species of mosquitoes in South Dakota. Of those 43 species, 20 species are found regularly and three or four species are the most common.

Overall, Hildreth and Wimberly are pleased by the success of their research and they hope they can continue to make strides in preventing West Nile.

“The hope is we would like to keep increasing our scientific understanding,” Wimberly said. “There is still a lot we don’t know about the ecology and the transmission cycles and stuff in South Dakota.”