MADISON, Wis. — An aggressive tick that can trigger a disease causing fever and fatigue has an increased presence in Wisconsin, bug experts say.

A person in northwestern Wisconsin has contracted a type of ehrlichiosis that is relatively new to the state, according to University of Wisconsin-Madison health officials. The illness is carried by lone star ticks, and although there's no formal effort to track the ticks in Wisconsin, about a dozen have been found in the state, said UW-Madison entomology professor Susan Paskewitz.

"It says to me there actually must be thousands and thousands of them out there," Paskewitz said. "I'm really suspicious now that we may have established populations that are capable of making it through some of our winters."

The insects are abundant in Texas, the "Lone Star State," and other southern states, Paskewitz said. The female tick has a white spot on her back.

The Barron County resident sickened in May by was Wisconsin's third confirmed case of the type of ehrlichiosis associated with lone star ticks, according to the Department of Health Services. Other cases were reported in Chippewa County in 2008, and in Eau Claire County in 2011, the State Journal ( ) reported.

Ehrlichiosis can cause fever, fatigue, headache, muscle pain, confusion and a rash, among other symptoms, and it can be treated with antibiotics, according to the Centers for Disease Control and Prevention. In about 2 percent of cases, the disease is fatal, according to the CDC. Symptoms generally appear one to two weeks after a tick bite.

In rare cases, the infection is thought to cause a meat allergy called alpha-gal, which can result in a dangerous hive-like rash or anaphylactic reaction, according to research presented last year at the American College of Allergy, Asthma & Immunology's annual scientific meeting.