Mosquito numbers climbing

Mosquito numbers in Jamestown are still low but anticipated to climb, according to Harold Sad, Jamestown street foreman who supervises the city's vector control department.

"The averages are still down," he said, "... but I think it will explode shortly. July and August are the worst months."

Vector control department staff check about eight mosquito traps on a daily basis. So far, the average count has been about 20 mosquitoes. The city's protocol calls for fogging the city with insecticides if the count exceeds an average of 125 mosquitoes.

The warmer weather normal to July and August not only increases the overall number of mosquitoes but is prime breeding conditions for the culex tarsalis mosquito, which is the species most commonly associated with the spread of West Nile virus in this area, according to Michelle Dethloff, an epidemiologist with the North Dakota Department of Health.

"The primary vector of transmission of West Nile virus to people is increasing," she said, referring to recent results of mosquito trapping in North Dakota. "It's not really high yet but as the weather warms, those numbers climb."


The first reported human case of West Nile virus this season in North Dakota was announced last week. The Centers for Disease Control and Prevention reported 201 cases of West Nile virus resulting in two deaths in North Dakota during 2018.

Dethloff said the culex tarsalis mosquito lays its eggs in standing water. As the temperatures rise, the eggs hatch into larvae that mature into the flying mosquitoes at a quicker rate than during cooler weather. This causes more generations of mosquitoes to be active and feeding at any time.

The warm weather of July and August increases the numbers of many mosquito species and it is impossible to tell the difference between species with the naked eye, Dethloff said.

Sad said the best precautions are to remove as many breeding areas for mosquitoes as possible.

"With the warmer weather and the ground saturated, we're getting a lot of puddles," he said. "People need to be draining any water that is standing in any debris in their yards."

Things like old tires, planters or even eave troughs on homes that don't completely drain are prime spots for mosquitoes to breed. The North Dakota Department of Health recommends dumping and cleaning any receptacle that holds water, such as bird baths and kiddie pools, once a week as another way to limit mosquito population growth.

"That's one of the things we can control," Sad said.

The city has been active since spring putting larvacide in standing water in Jamestown and within a one-mile radius around the city. Larvacide is placed in standing water and kills the mosquito larvae before it can develop into an adult.


Because no mosquito control program is 100% effective, people are urged to use other precautions, Dethloff said.

Wearing long shirts and pants and applying an insect repellant approved by the Environmental Protection Agency when outdoors helps reduce bites. The Department of Health also recommends wearing light-colored clothing and staying indoors between dusk and dawn when mosquitoes are most active.

Mosquito Biting.jpg
A mosquito fills up with blood from its host as seen in this file photo. John M. Steiner / The Sun

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