Lyme Disease in Wisconsin
Yes, ticks in Wisconsin absolutely carry Lyme disease, and Wisconsin is a well-established endemic area with significant disease burden. Wisconsin is specifically identified as part of the upper north-central region where approximately 90% of all U.S. Lyme disease cases are reported 1.
The Vector and Geographic Distribution
The blacklegged tick (Ixodes scapularis) is the primary vector of Borrelia burgdorferi (the causative agent of Lyme disease) in Wisconsin 1. This same tick species also transmits other pathogens including Anaplasma phagocytophilum (causing anaplasmosis) and Babesia microti (causing babesiosis), making co-infections a significant concern 1, 2.
- The distribution of I. scapularis has been spreading slowly throughout the northeastern and upper north-central United States over recent decades, with Wisconsin being a core endemic area 1.
- In highly endemic areas of Wisconsin, approximately 15%-30% of I. scapularis nymphs carry B. burgdorferi 3.
- Historical data from Wisconsin shows the density of infected ticks has increased substantially over time, with the percentage of deer carrying I. dammini (now I. scapularis) increasing from 24% in 1979 to 38% in 1981 4.
Disease Burden in Wisconsin
Wisconsin has a substantial burden of Lyme disease and related tickborne illnesses:
- Anaplasmosis (formerly human granulocytic ehrlichiosis) has been identified as a major cause of unexplained fever during tick season in Wisconsin, with evidence suggesting the incidence may be even higher than in neighboring Minnesota 1.
- A prospective study in northwestern Wisconsin found that 27% of patients presenting with nonspecific febrile illness during tick season had laboratory evidence of tickborne infection, including 11% with Lyme disease and 13% with anaplasmosis 5.
- Lyme disease cases in Wisconsin occur throughout 22 different counties, demonstrating widespread geographic distribution 4.
Seasonal Risk Pattern
Peak transmission occurs during late spring and early summer when nymphal ticks are most active:
- The majority of Lyme disease cases (73%) occur during June-July 4.
- All confirmed cases occur during May-November 4.
- Nymphal ticks, which are responsible for most human infections, feed predominantly in late spring and early summer 3.
Critical Clinical Consideration: Co-infections
A major pitfall in Wisconsin is failing to recognize potential co-infections, which significantly impacts treatment decisions:
- Because I. scapularis transmits multiple pathogens, simultaneous infections with A. phagocytophilum and B. burgdorferi have been documented 1.
- This is clinically crucial because amoxicillin can treat early Lyme disease but is completely ineffective for anaplasmosis 1, 2.
- If co-infection is suspected (particularly if the patient has leukopenia or thrombocytopenia), doxycycline should be used instead of amoxicillin 2.
Prevention Strategies for Wisconsin Residents
Personal protective measures are highly effective when consistently applied:
- Wear light-colored clothing to spot ticks more easily, tuck pants into socks, and use DEET-containing repellents 3.
- Apply permethrin to clothing and perform daily tick checks after outdoor activities 3.
- Environmental modifications around homes include removing leaf litter and brush, and creating barriers between wooded areas and lawns 3.
Post-Exposure Prophylaxis
Single-dose doxycycline prophylaxis should be considered within 72 hours of tick removal if:
- The tick is identified as I. scapularis 3
- The tick was attached for ≥36 hours 3
- The bite occurred in a highly endemic area (which Wisconsin clearly is) 3
This prophylaxis recommendation is particularly relevant for Wisconsin residents given the high prevalence of infected ticks in the state.