Chiggers are nearly microscopic mites, belonging to the family Trombiculidae, known for their intensely itchy bites. Often called harvest mites or red bugs, their lifecycle includes a parasitic larval stage that feeds on humans and animals. These larvae cause the unpleasant skin reaction associated with chiggers. This article addresses the existence of these pests in Wisconsin, detailing where they are encountered, the biology of their bite, and effective strategies for avoiding and treating the resulting irritation.
Where Chiggers Are Found in Wisconsin
The short answer is that chiggers are indeed present in Wisconsin, although they may not be as universally prevalent as in the southeastern United States. While they are commonly associated with warmer climates, these mites are found throughout the Midwest and in the Great Lakes region. They become active when ambient temperatures range between roughly 77 and 86 degrees Fahrenheit, becoming inactive below 60 degrees.
Chiggers thrive in specific outdoor habitats across the state, particularly in areas with dense vegetation. They are often encountered in tall grassy fields, overgrown weeds, and low-lying, damp areas near lakes and streams. Wooded edges and scrubby areas, where the vegetation is low enough for them to easily transfer to a host, also serve as common locations. Although they are present, their distribution tends to be patchy.
The chigger season in Wisconsin typically aligns with the warm summer months. They do not fly or jump; instead, they crawl onto a host from the tips of low vegetation. This parasitic behavior is limited to the six-legged larval stage, which is the only stage that feeds on people.
Identifying Chiggers and Understanding the Bite
The chigger larva responsible for the bite is barely visible to the naked eye, measuring only about 0.4 millimeters. It has a characteristic chrome-orange or reddish color, though it can appear more yellowish after feeding. Contrary to a common misconception, chiggers do not burrow into the skin or suck blood.
They instead use specialized mouthparts to inject digestive enzymes into the skin. The enzymes break down skin cells, liquefying the tissue which the chigger then ingests. The host’s immune system reacts to these enzymes by hardening the surrounding skin cells, forming a tiny, straw-like feeding tube called a stylostome. The chigger uses this stylostome to continue feeding on the dissolved tissue for several days until it detaches.
The intense itching, known as pruritus, is not felt immediately but typically begins a few hours after the chigger has attached. This reaction is a result of the body’s inflammatory response to the digestive enzymes and the persistent presence of the stylostome. The resulting rash, called chigger dermatitis, appears as red, raised welts, papules, or sometimes blisters. These are often clustered in areas where clothing fits tightly, such as the ankles, waist, or behind the knees.
Strategies for Prevention and Treatment
Preventing chigger bites centers on avoiding high-risk habitats and creating a barrier against the mites. When entering areas like tall grass or wooded edges, wearing long pants and long-sleeved shirts limits exposed skin. Tucking pant legs into socks or boots is recommended, as chiggers typically crawl upward from low vegetation.
Applying EPA-registered insect repellents is an effective preventative step. Repellents containing DEET can be applied to exposed skin. Treating clothing with an insecticide like permethrin is also effective, especially around openings like cuffs and waistbands; permethrin should not be used directly on the skin. A post-exposure measure is taking a hot, soapy shower immediately after spending time in a known chigger area, vigorously scrubbing the skin to dislodge any unattached larvae.
Once bites occur, treatment focuses on symptom relief, as the chigger has usually detached by the time the itching begins. Over-the-counter topical corticosteroids, such as hydrocortisone cream, can be applied to decrease the inflammatory reaction and reduce the itch. Calamine lotion helps to soothe the skin, and oral antihistamines may be taken to help control intense itching, especially if it interferes with sleep. Avoid excessive scratching, which can break the skin and lead to a secondary bacterial infection. The welts typically heal within one to two weeks.