Disease Risk from Ticks in Urban Green Spaces

About

Public health risks from tick-borne disease are increasing in the U.S., particularly in the Midwest. Some tick-borne diseases (e.g. Lyme disease) cause life-long illness with diverse symptoms ranging from extreme fatigue to meningitis. Others can be fatal if not treated promptly (e.g. Rocky Mountain spotted fever). According to the CDC, both of these diseases are increasing in the Midwest due to shifts in tick distribution. In Illinois, the distribution of the blacklegged tick (Ixodes scapularis; vector for Lyme Disease) has doubled in 20 years while cases of Lyme have increased seven-fold from 2000 to 2016. Cases of Rocky Mountain spotted fever have increased over 20-fold in the past 20 years in Illinois as the lone star tick (Amblyomma americanum) emerged in the Midwest.

Lincoln Park Zoo staff are investigating the relationship between mammal host communities, tick densities, and tick-borne disease. They are also examining risk of Lyme disease for people within recreational green spaces along an urban gradient by surveying for ticks at green spaces throughout the Chicago metropolitan area. Staff are using data collected by the Urban Wildlife Biodiversity Monitoring Project, which measures medium and large mammal activity via wildlife field cameras, to relate tick densities and the presence of bacteria that cause tick-borne diseases with the diversity and activity of urban mammals. The presence and activity of urban mammals is an important factor to study as opossums might lower the risks from ticks because they are known to eat about 95 percent of ticks that try to parasitize them and they aren’t good hosts for tick-borne diseases, while deer are an important resource for ticks to reproduce.

Additionally, the collected ticks are sent to collaborators at the Illinois Natural History Survey Medical Entomology Lab for species identification and diagnostic testing for common pathogens as part of their statewide tick surveillance program funded by the Illinois Department of Public Health. Together, we hope to reduce disease risk from ticks for people across Chicagoland.

Study Objectives

To better understand how urban sprawl affects human risk of tick-borne disease, Urban Wildlife Institute researchers are attempting to answer the following questions:

1. Which types of ticks and tick-borne pathogens are present in Chicago recreational greenspaces?
2. How does tick density and pathogen prevalence in Chicago recreational green spaces relate to the community of mammals using those greenspaces?
3. When are blacklegged ticks (the Lyme Disease vector) most active in the Chicagoland region?

Techniques

Researchers survey for ticks using a “drag cloth” method that consists of dragging a flannel cloth over vegetation and leaf litter. This mimics the movement of an animal through the space, so ticks questing (looking for a host to bite) will latch onto the cloth. Researchers examine the cloth periodically and remove any ticks on the cloth with forceps. Collected ticks are then placed in vials of ethanol for preservation until pathogen testing.

How to Avoid Tick-borne Disease

Many people worry that the presence of ticks means they can’t safely enjoy outdoor spaces; however, there are many ways to reduce your risk of tick bites in outdoor spaces!

Know where you might encounter a tick
Ticks live in grassy, brushy, or wooded areas and are typically most active when the weather is warm during spring through fall. When hiking, walking your dog, camping, or engaging in other outdoor activities in these areas, you can take preventative measures to protect yourself from ticks.

Wear the right clothing
Wearing a long-sleeved shirt and long pants can limit your exposure to ticks. Tucking pant legs into your socks provides added protection from ticks that might otherwise climb up inside pant legs. Light-colored clothing will also make it easier to see ticks on your body.

Use insect repellent
Insect repellents that contain DEET, picaridin, IR3535, or oil of lemon eucalyptus can be used on skin and clothing to repel ticks and prevent tick bites. Permethrin products can be used to treat boots, clothing, and camping gear and remains protective through several washings.

Check for ticks
You should inspect your body, outdoor gear, and pets following outdoor activity in spaces where you might encounter ticks. Conduct a full body check by inspecting under the arms, in and around the ears, inside the belly button, behind the knees, in and around hair, between the legs, and around the waist. Showering within two hours of coming indoors has also been shown to reduce your risk of getting Lyme disease, as it may help wash off unattached ticks; it also creates a great opportunity to check your body for ticks.

More Information

For more information on tick-borne diseases, how to prevent them, and what to do if you find a tick on yourself see the following resources:

Centers for Disease Control and Prevention

Illinois Department of Public Health