“While all mosquitoes may potentially be exposed to West Nile Virus from birds and horses, not all mosquitoes can actively transmit the virus,” said Dr. Joseph Mehus, associate professor of biology at Mayville State University.

“Mosquitoes are not born with WNV, they have to pick it up from an infected blood meal,” Mehus said.

Mehus is a mosquito researcher and also the founder of the Mehus Mosquito Lab, where a North Dakota IDeA Network of Biomedical Research Excellence (ND INBRE) project was started by Mehus and is currently advised by him.

Many people may not realize there are more than 40 different species of mosquito in North Dakota according to historical records. Mehus’ research team primarily covers Steele County and Traill County and they have found around 20 of those species between the two N.D. counties.

According to Mehus’ research, for some mosquito species, even if the WNV is ingested, the virus cannot spread throughout the mosquito’s body and will thus not infect the salivary glands of these mosquitoes, which means these mosquitoes will not be contagious to humans and other organisms.

When the virus does infect the mosquito’s salivary glands after the mosquito has fed on an infected organism, the mosquito becomes an infectious transmitter of WVN.

A common misconception about mosquitoes is that they sting. Although the bites might produce a “stinging” sensation, mosquitoes themselves do not have stingers and do not sting like bees or yellowjackets, instead using their mouths to drink blood.

“Their mouth is really composed of six individual parts that work to hold the skin, cut into the skin, and then pierce into a blood vessel,” Mehus said.

Birds are one of the organisms mosquitoes typically pick WNV up from; however, many species of mosquito do not actively seek out birds to feed on.

“Viruses mutate very quickly and often move from one species to another,” Mehus said. “West Nile Virus is primarily an avian virus. It affects different bird species to differing degrees. Corvid birds (crows, blue jays, magpies) and hawks and owls are especially susceptible and often die when they get WNV. Other birds that can get it are passerine birds such as robins and blackbirds. WNV has also been found in horses, llamas, dogs, cats, chipmunks, squirrels, black howler monkeys, mountain gorillas and others. Horses often do not fare well upon exposure to WNV.”

Mehus’ research group at Mayville State University is currently investigating population dynamics of local mosquito species. Each mosquito species has its own peak season of activity, but from this research some generalizations can be made about North Dakota’s mosquito season as a whole.

“It is very safe to say that throughout the state of North Dakota, millions of mosquitoes are active every day during the mosquito season,” Mehus said.

“If we throw all the species together and just say when mosquito season is, or peak numbers, that would be from about mid-May through October, or a good freeze. We typically see a boost in mosquito populations in the first week of June, then larger increases in the third week of July,” Mehus said.

Culex tarsalis is North Dakota’s number one WNV transmitting mosquito. “We see more Culex tarsalis in the fall,” Mehus said.

Once there is a good freeze and the temperatures get closer to winter, some mosquitoes will enter diapause, similar to hibernation.

“Some mosquito species will overwinter as adults inside of trees and bark, under the eaves of houses, cracks in foundation, or buried in leaf litter. Other mosquitoes will overwinter in their egg stages. These species need spring rains or snow melt to cover the eggs and start the hatching process. A third group of species overwinter as larvae within the mud of ponds in association with cattail roots. Freezing during the diapause stage doesn’t typically kill the mosquitoes, hence why we have mosquitoes in early spring,” Mehus said.

It is actually the female mosquitoes who need to digest blood meals so they can use the iron and additional protein in the blood to develop their eggs. “WNV is transmitted to humans via the bite of the female mosquito that is infected. Males simply feed off plant juices and nectar,” Mehus said.

In most cases, those previously infected with WNV will have immunity from the virus. This does not mean a person cannot get WNV again, however, which is true of other viruses as well. Immunity simply means the body will have developed antibodies to better fight against the virus after first infection.

“Upon re-exposure to the same strain of the virus, you will have a series of white blood cells that are familiar with how to rid the virus from your body. It still takes a day or two for your immune system to ramp up and get those antibodies flowing,” Mehus said. “Having been previously exposed severely cuts down the symptoms and time of recovery.”

Between 70-80% of people who contract WNV are asymptomatic, or show no symptoms of infection.

“WNV, like most other viruses and pathogens, really applies pressure to small children whose immune systems are still developing, or our older populations of people. People who are ‘generally’ healthy may feel fatigue, body aches, or just general malaise. These individuals may only feel symptoms for a few hours to a day or two,” Mehus said.

Mehus’ current project through ND INBRE is in its fifth year but Mehus himself has been researching mosquitoes for more than 20 years.

There are currently two faculty members at Mayville State University who conduct ND INBRE research, including Mehus. However, Mehus is the only mosquito researcher. Mehus began his research at the University of North Dakota when he was obtaining his doctorate.