What the risk of mosquito-borne diseases? | News

Summer is halfway over, but yet mosquitoes season is still buzzing along.

For the last leg of this summer, here is some tips to keep those pests at bay.

According to Dave Neitzel, a vector-borne disease epidemiologist at the Minnesota Department of Health, mid-July to mid-September is high-risk season for mosquito-borne diseases.

Neitzel said that the main mosquito-borne viruses in the Rice County area include the West Nile virus and La Crosse encephalitis.

According to the Minnesota Department of Health, last year there were 30 cases reported of the West Nile virus in the state; in 2016, there were 83. Since 1985, there have been 147 cases of the La Crosse encephalitis virus in 22 Minnesota counties, mainly in the southwestern part of the state. 

According to Neitzel, West Nile first appeared in Minnesota in 2002, with 48 human cases, two of them from the Rice County area. Culex tarsalis, the mosquito that transmits the West Nile virus is seen in open agricultural areas.

According to the Minnesota Department of Health, people will typically be asymptomatic or experience flu-like symptoms. There are two forms of West Nile: West Nile fever and West Nile encephalitis. Twenty percent of those bitten will contract West Nile fever, while one out of 150 people will contract the severe form of West Nile, encephalitis.

With West Nile fever, people may experience a headache, high fever, sore throat, vomiting, nausea, muscle aches, a rash, fatigue, and swollen lymph nodes. According to Neitzel, people who typically contract the disease are middle-age or older. When it affects younger patients, it is typically not as serious.

People who contract West Nile encephalitis may experience a change in mental status, vomiting, light sensitivity, altered reflexes, seizures (less frequent), and acute flaccid paralysis (occurs infrequently in patients with severe case). Less than 1 percent of people will experience neurological symptoms that is typically seen in encephalitis or meningitis.

Culex tarsalis, the mosquito that transmits the West Nile virus, is typically present at dusk and dawn. According to Elizabeth Shiffman, an epidemiologist at the Minnesota Department of Health, this mosquito typically lays its eggs in semi-permanent bigger and open places such as a drainage ditches, with their eggs on top of the water, sticking together like a raft.

Most who become infected will not experience symptoms. Severe cases will include symptoms such as headache, fever, lethargy and nausea. The illness may progress into symptoms such as disorientation, coma or seizures.

The La Crosse disease is typically seen in children. Neitzel said children who contract the disease are more severely impacted. When adults contract it, they tend to be able to fight it off more easily.

La Crosse encephalitis is transmitted by the treehole mosquito, according to Neitzel. The treehole mosquito is seen in the day and in wooded areas. The Treehole mosquito tend to lay their eggs in different places, usually containers such as a bucket or a tree hole, with their eggs just above the water line.

When it comes to both diseases, there is no treatment, except supportive care until the illness subsides.

When it comes to fending off mosquitoes, Neitzel recommended mosquito repellent that contains DEET and lemon eucalyptus oil. Both Neitzel and Schiffman noted the importance of maintaining yards and making sure that there is no standing water for mosquitoes to lay their eggs in. Schiffman said that mosquitoes can lay eggs in something as small as a plastic water cap.

Schiffman said that people should be encouraged to go outside and enjoy themselves, but to be aware of the risks, and to lessen the risks by using bug repellent and making sure there is no standing water outside.

Reach Reporter Clare Bender at 507-333-3128 or follow her on Twitter @FDNclare.

© Copyright 2018 APG of Southern Minnesota. All rights reserved.