Blacklegged or “deer” tick (Ixodes scapularis)

The blacklegged tick (also known as the deer tick) is present everywhere in Wisconsin where there is forested habitat. This tick can spread Lyme disease, anaplasmosis, babesiosis, ehrlichiosis (due to Ehrlichia muris eauclairensis) and Powassan virus.

Distribution

In recent years, the distribution of Ixodes scapularis in Wisconsin has changed dramatically, so that these ticks can now be found in many parts of eastern Wisconsin where they had not been seen before (Lee et al. 2013).

Student teams hit the woods each summer to collect deer tick nymphs and then determine how many are infected. The map above shows that a range of 11-30% of the nymphs were infected in 2016-17 but the average was about 15-20%.

Life Stages

Deer ticks have three life stages:The larva becomes a nymph which then becomes an adult. This takes about 2 years. Nymphs are of greatest public health concern, because they are just 2 millimeters (1/10 of an inch) long and are hard to spot and remove quickly.

Here is a picture of a blood fed nymph that was attached for 4 days:

References

X. Lee, K. Hardy, D. H. Johnson, S. M. Paskewitz, Hunter Killed Deer Surveillance to Assess Changes in the Prevelance and Districution of Ixodes scapularis (Acari: Ixodidae) in Wisconsin, Journal of Medical Entomology, Volume 50, Issue 3, 01 May 2013, Pages 632-639, https://doi.org/10.1603/ME12234