Williston Vector Control Director Fran Bosch looks at a scoop of water from a ditch of standing water in Trenton not too far from Trenton Lake in this 2015 file photo. Checking various traps helps Vector Control decide when to begin spraying for mosquitoes.

West Nile has arrived early in North Dakota this year, with the state reporting its first human case of infection for the season, and Williston Vector Control reporting its first C. tarsalis in mosquito traps.

Additionally, a pool of mosquitoes captured in Grand Forks has also tested positive for West Nile virus.

The person infected with West Nile virus lives in Ramsey County. The person was not hospitalized for the illness.

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C. tarsalis can both carry and transmit West Nile virus, but usually doesn’t start appearing in Williston until the last half of June.

“I know we just crossed that point today, but we have been finding them for the past couple of weeks now,” said Fran Bosch, director of Williston Vector Control. “That’s out of the ordinary.”

There have not been enough C. tarsalis in Williston’s traps to test for West Nile virus so far, Bosch said. But he expects to be doing so soon.

The first few mosquitoes that show up in Williston’s trap are generally the only early warning sign that the population of C. tarsalis is about to suddenly take off.

This is because the female mosquito overwinters with eggs that she is ready to lay as soon as she gets that first blood meal.

The mosquito doesn’t start liking it until the days get into the 80s. They don’t love it until the days hit the 90s.

“They also love hot humid nights,” Bosch said. “We haven’t really had any of those yet, but the (C. tarsalis) are out there already. They will become much more active when it heats up a little more.”

While West Nile virus does not cause symptoms for most people, it can lead to serious complications and even death for some. In 2017, North Dakota Department of Health reported 62 cases of human infection with West Nile virus. Thirty-five percent of the cases resulted in hospitalizations, and two in death.

“This first human infection is being reported earlier than what we usually see in North Dakota,” said Jenny Galbraith, with the Division of Disease Control. “People need to take measures to avoid contracting the virus, by protecting themselves from mosquito bites.”

These precautions include:

• Using a repellent such as DEET, picaridin, IR3535, oil of lemon eucalyptus (or PMD), or permethrin. Apply according to manufacturer instructions;

• Wearing protective clothing, including long-sleeved shirt and pants;

• Limiting outdoor activity between dusk and dawn, when mosquitoes are most likely to bite;

• Eliminating stagnant water in containers around homes, where mosquitoes can lay eggs, such as buckets, flowerpots, old tires, wading pools and birdbaths;

• Keeping grass around your home trimmed.

Williston Vector Control has begun ground and aerial adulticide treatments over Williston and the city of Ray now through June 21. The Air Force is also coming into town next week, possibly as early as Tuesday, to help spray in Williston and Watford City areas.

The spraying is necessary to help control mosquitoes in general, including C. tarsalis, which carries West Nile virus.

With record numbers of C. tarsalis last year, Bosch has been fearful there will again be a high population of West Nile mosquitoes again this year.

Williston Vector Control asked voters to approve expanding the agency’s mosquito control perimeter by 2 miles around Williston for the next two years, which was approved during the June primary.

Bosch recommended that residents get rid of any standing water, to help reduce the number of such mosquitoes that can propagate in residential areas.

“They are famous for hanging out in tires and flooded ditches,” Bosch said. “And they are down in those boggy, marshy areas along the river.”


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