Minnesotans are well acquainted with the itchy, red bumps resulting from pesky mosquito bites after a summer evening outdoors. For those susceptible to skeeter syndrome and mosquito-borne viruses, however, the symptoms are more than just a nuisance.
Allergist-immunologist Dr. Allan Stillerman with the Allergy & Asthma Network says while regular mosquito bites are considered non-allergenic, inflammatory responses to irritation, skeeter syndrome is an allergic reaction local to the site of the sting or spread throughout the body. Larger than normal, swollen, itchy sores can develop within hours of contact and can become infected.
“When a person is bitten, the salivary proteins of the female mosquito are deposited into the victim’s skin, which causes a local, itchy and inflammatory response that sometimes can swell up profusely,” Stillerman said. “The forearm could swell up to the size of an American football.”
According to Stillerman, as adults get repeated stings throughout life, they build up immunity to the mosquito bite protein and become desensitized. Young children and seniors are more vulnerable to skeeter syndrome because they have considerably lower levels of immunity, he says.
While rare, Stillerman says maybe every five to 10 years, a group of around 10 patients will report anaphylactic reactions to mosquito bites. These more serious cases involve swelling of the throat, difficulty breathing, rashes and blood pressure drop.
“In terms of testing for this problem, there are no FDA-approved tests and certainly no treatments for desensitizing patients who have either skeeter syndrome or a generalized reaction,” he said.
Skeeter syndrome is more common than anaphylaxis – but it’s not a common entity in itself, Stillerman explains, compared to how many people actually get mosquito bites.
“I think I’ve had one patient in 40 years with skeeter syndrome,” he said. “That doesn’t mean it doesn’t exist, but it’s very rare.”
Stillerman recommends treating swollen, itchy areas with calamine lotion followed by an over-the-counter topical corticosteroid applied twice a day and oral antihistamines such as Benadryl, Claritin or Zyrtec. He also warns against scratching the area, as it can lead to bacterial infections such as cellulitis.
Mosquito borne viruses
There are also two mosquito-borne viruses found in Minnesota that residents should be aware of, according to University of Minnesota School of Public Health Assistant Professor Jon Oliver. The first is the West Nile virus, which is transmitted by culex mosquitoes and found throughout the state.
“West Nile virus was big news a few years back, and we’ve had hundreds of cases,” Oliver said. “Things have winded down in terms of that, and now we have a few dozen cases a year. There’s been a little bit of an increase here in Minnesota. I think in 2017 we had about 80 cases.”
Oliver says while only about one-fifth of those who contract West Nile virus are hospitalized and/or develop severe symptoms, La Crosse encephalitis, the second mosquito-borne virus found in Minnesota, can be fatal. The virus, named after the city in Wisconsin, is spread by tree hole mosquitoes that live in forested areas.
“We usually get about half a dozen or so cases of La Crosse encephalitis each year, and those tend to be very severe,” Oliver said. “They mainly affect children and it can often be fatal or can cause long term or permanent damage. Like West Nile, they can cause inflammation of the brain.”
Oliver recommends wearing insect repellent to prevent mosquito-borne viruses, citing DEET (diethyltoluamide) as the best studied and most effective repellent. According to Oliver, DEET is safe in concentrations of up to 30 percent, even for children, and has been well-studied in terms of effectively keeping away mosquitoes. For those who spend time in wooded areas, Oliver suggests permethrin, which will keep off mosquitoes and black flies.
In terms of reducing the number of mosquitoes in the backyard, Oliver says the most effective way is to make sure there is no debris holding water in the yard. This means cleaning out bird baths, storing buckets, and not leaving out wrinkled up tarp, all of which can provide areas for mosquito larvae to grow, he says.