— PUBLIC HEALTH
Mosquito Borne Diseases in Wisconsin
Wisconsin mosquitoes carry more than an itchy bite. The diseases they spread can cause serious illness and are more widespread than most residents realize.
Mosquito-Borne Diseases in Wisconsin
Ah, Wisconsin summers – the smell of bratwurst on the grill, weekends at the lake, campfires under the stars … and the unmistakable buzz of an uninvited guest: the mosquito. Warm temperatures and humid conditions create the perfect environment for these pesky insects to thrive, especially from May through September. Unfortunately, mosquitoes aren’t just an annoyance; they can also carry serious diseases like West Nile virus and La Crosse encephalitis, both of which have been reported in Wisconsin in recent years.
But don’t worry – arming yourself with a bit of knowledge (and a lot of bug spray) can go a long way in keeping you and your family safe. So grab your citronella candles and let’s dive into what you need to know about mosquito-borne illnesses in Wisconsin and how to fight back against the bite!
IN THIS ARTICLE
- West Nile Virus
- La Crosse Encephalitis
- Jamestown Canyon Virus
- Eastern Equine Encephalitis
- The Role of Climate
- Mosquito Bite Prevention
Protect Your Family from Mosquitoes with Safe, Effective Lawn Treatments
Illnesses Spread by Mosquitoes in Wisconsin
While not every mosquito bite leads to illness, it’s still important to understand the diseases they may transmit and take steps to prevent bites.
West Nile Virus
The most commonly reported mosquito-borne illness in Wisconsin is West Nile Virus. On average, 18 cases are reported each year in the state, according to the Wisconsin Department of Health Services (WDHS). It is primarily spread to humans through the bite of an infected Culex mosquito, which becomes infected after feeding on birds carrying the virus. Most people infected with WNV won’t experience any symptoms, but about 1 in 5 may develop fever, headaches, and body aches. In rare cases, particularly among older adults or individuals with weakened immune systems, West Nile Virus can lead to severe neurological illness, such as encephalitis. No antiviral or human vaccine exists, so prevention is the key.
La Crosse Encephalitis
Named after La Crosse, Wisconsin, where it was first identified, this disease is commonly carried by the Aedes triseriatus mosquito. Mosquitoes become infected with the La Crosse encephalitis virus by feeding on infected small mammals, such as chipmunks and squirrels. Most people infected with LACV do not show noticeable symptoms. Mild cases usually have flu-like signs such as fever, fatigue, and headache. The WDHS states that “severe illness is more common in children under 16. Serious symptoms can include encephalitis, seizures, coma, paralysis, and lasting neurological issues.”
Jamestown Canyon Virus
Jamestown Canyon virus is a rare but emerging illness in Wisconsin, transmitted when mosquitoes pick up the virus, often from infected white‑tailed deer, and then bite humans. Most people who get the virus experience no symptoms, but some may develop mild flu-like illness, including fever, headaches, muscle aches, and fatigue. In more severe cases, the virus can cause neurological problems such as encephalitis or meningitis. Wisconsin has seen an increase in reported JCV cases over the past decade, especially in the northern part of the state. According to the WDHS, the state reported 13 confirmed or probable cases in 2023, with 144 total from 2011 to 2023. Jamestown Canyon virus is the second most common mosquito-borne disease in Wisconsin.
Eastern Equine Encephalitis
Eastern equine encephalitis is a rare but severe illness spread by the bite of an infected mosquito. Only five human cases of EEE have been reported in Wisconsin from 1964 to 2020, according to the WDHS. Mosquitoes become infected with the virus by feeding on infected birds. While human cases are rare, infected individuals may develop flu-like symptoms, including fever, chills, headache, and fatigue. In severe cases, the virus can cause encephalitis, with symptoms such as seizures, confusion, and neurological impairment. EEE has a case fatality rate of 30 to 40 percent, and many survivors are left with permanent neurological disabilities. Since no vaccine or treatment exists for humans, prevention is essential.
The Role of Climate in Changing Risk
Wisconsin’s mosquito season is not what it used to be. Warmer springs are arriving earlier, causing mosquito activity to begin in early May or even April, rather than late May in particularly warm years. Milder autumns extend the season into October. Unpredictable weather patterns, like drought followed by heavy rain, cause rapid swings in mosquito populations. Dry spells temporarily reduce numbers, but when standing water returns, populations rebound quickly and can reach high levels.
This is especially significant for mosquito-borne diseases. Longer seasons increase the period during which transmission can occur. Higher temperatures accelerate viral replication in mosquitoes, shortening the time between a mosquito feeding on an infected bird and its ability to infect a human. As a result, diseases previously found in southern states are gradually spreading further north.
Wisconsin public health authorities have observed a gradual northward spread of West Nile Virus activity across the state over the past decade, with northern counties now reporting cases that were once almost exclusively seen in the southern half of the state.
Mosquito Bite Prevention
Effective mosquito prevention involves a combination of personal protection and eliminating mosquito breeding habitats in your yard. To reduce your risk of mosquito bites, follow these tips:
-
Use Insect Repellent: Apply an EPA-registered repellent containing DEET or picaridin to your skin and clothing when spending time outdoors.
-
Wear Protective Clothing: Dress in long sleeves, long pants, and socks, especially during dawn and dusk when mosquitoes are most active.
-
Eliminate Standing Water: Empty or clean out birdbaths, gutters, flower pots, old tires, and any containers that can collect water.
-
Mosquito Lawn Treatment: Advanced Wildlife and Pest Control offers safe and effective mosquito control lawn treatment applications.
-
Maintain Your Yard: Keep grass short, trim shrubs, and remove leaf litter where mosquitoes can hide.
-
Install or Repair Screens: Ensure windows and doors have tight-fitting screens to keep mosquitoes from getting indoors.
-
Use Fans Outdoors: Mosquitoes are weak fliers, so a fan on a porch or deck can help keep them away.
Implementing these prevention tips can greatly reduce mosquito activity around your home and protect your family from mosquito bites and mosquito-borne illnesses.
Professional Mosquito Control in Milwaukee, WI
While mosquitoes may be a familiar part of Wisconsin summers, the diseases they carry are no joke. While not every bite results in illness, it’s important to stay informed and take proactive steps to reduce your risk. The good news? You don’t have to fight the bite alone. Our professional mosquito control lawn treatments are designed to significantly reduce mosquito populations around your home – giving you peace of mind and a yard you can actually enjoy. Whether you’re hosting a backyard gathering or just relaxing on the porch, we’ll help keep your outdoor space safer, healthier, and mosquito-free.
Ready to take back your yard? Contact us today at (262) 292-1497 to schedule your mosquito treatment and enjoy a bite-free summer!
— PUBLIC HEALTH
Histoplasmosis:
The Hidden Danger in Bat Guano
Removing bats is only half the job. The guano they leave behind can also pose a serious health risk long after they’re gone.
Mosquito-Borne Diseases in Wisconsin
Ah, Wisconsin summers – the smell of bratwurst on the grill, weekends at the lake, campfires under the stars … and the unmistakable buzz of an uninvited guest: the mosquito. Warm temperatures and humid conditions create the perfect environment for these pesky insects to thrive, especially from May through September. Unfortunately, mosquitoes aren’t just an annoyance; they can also carry serious diseases like West Nile virus and La Crosse encephalitis, both of which have been reported in Wisconsin in recent years.
But don’t worry – arming yourself with a bit of knowledge (and a lot of bug spray) can go a long way in keeping you and your family safe. So grab your citronella candles and let’s dive into what you need to know about mosquito-borne illnesses in Wisconsin and how to fight back against the bite!
IN THIS ARTICLE
- West Nile Virus
- La Crosse Encephalitis
- Jamestown Canyon Virus
- Eastern Equine Encephalitis
- The Role of Climate
- Mosquito Bite Prevention
Protect Your Family from Mosquitoes with Safe, Effective Lawn Treatments
West Nile Virus
The most commonly reported mosquito-borne illness in Wisconsin is West Nile Virus. On average, 18 cases are reported each year in the state, according to the Wisconsin Department of Health Services (WDHS). It is primarily spread to humans through the bite of an infected Culex mosquito, which becomes infected after feeding on birds carrying the virus. Most people infected with WNV won’t experience any symptoms, but about 1 in 5 may develop fever, headaches, and body aches. In rare cases, particularly among older adults or individuals with weakened immune systems, West Nile Virus can lead to severe neurological illness, such as encephalitis. No antiviral or human vaccine exists, so prevention is the key.
La Crosse Encephalitis
Named after La Crosse, Wisconsin, where it was first identified, this disease is commonly carried by the Aedes triseriatus mosquito. Mosquitoes become infected with the La Crosse encephalitis virus by feeding on infected small mammals, such as chipmunks and squirrels. Most people infected with LACV do not show noticeable symptoms. Mild cases usually have flu-like signs such as fever, fatigue, and headache. The WDHS states that “severe illness is more common in children under 16. Serious symptoms can include encephalitis, seizures, coma, paralysis, and lasting neurological issues.”
- Fever and chills
- Chest pain or discomfort
- Shortness of breath
- Dry or nonproductive cough
- Headache
- Night sweats
- Fatigue and general malaise
- Muscle aches
- Loss of appetite
Where Does Histoplasmosis Come From?
Histoplasma thrives in damp, organic-rich soil, and it grows especially well in material loaded with bat guano or bird droppings. The nitrogen content in droppings essentially fertilizes it. In the United States, the fungus is very common in Midwestern states, including Wisconsin.
Attics with Bat Colonies
Years of accumulated guano in a warm, enclosed space with poor ventilation is the most common area of exposure.
Old Barns & Outbuildings
Rural properties often have decades of bat and bird waste in haylofts, rafters, and grain areas.
Chimneys & Soffits
Chimney swifts, starlings, and bats nest in these tight cavities, and droppings pile up directly above living spaces.
Pigeon & Starling Roosts
Ledges, signage, rooftop HVAC units, and warehouse rafters on Milwaukee-area commercial buildings.
Chicken Coops
Backyard flocks are increasingly common in Wisconsin, and coop cleanout stirs up exactly the kind of dust that carries spores.
Caves & Demolition Sites
Caving, spelunking, and tearing down or remodeling old structures all disturb long-settled material.
One more detail worth noting: spores can remain viable in guano for years. A colony that moved out three summers ago doesn’t mean the attic is safe. The droppings are still a hazard.
What Are the Health Risks?
Here’s the honest picture, because both extremes get exaggerated. Most people who inhale Histoplasma spores never get sick at all or feel mildly under the weather and recover on their own without ever knowing why. That’s the common outcome.
But the dose matters enormously. A homeowner who spends a weekend shoveling out an attic full of guano without a respirator is inhaling a far heavier load of spores than someone who walks through a park. Heavy exposure in a confined space is what turns a non-event into a real illness — and it’s also how you get clusters where several people in the same household get sick at once.
Histoplasmosis shows up in a few different forms:
How Is Histoplasmosis Treated?
Diagnosis typically involves a urine or blood antigen test, sometimes paired with chest imaging, blood work, or a culture. It usually takes a few days to a couple of weeks to receive results. Treatment depends entirely on severity:
How to Prevent Histoplasmosis
It’s hard to avoid breathing in microscopic fungal spores. But you can take the following steps to reduce your risk of infection.