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Release: June 3, 1999

Tick-borne illnesses may be under-recognized, Iowa researchers say

IOWA CITY, Iowa -- The prevalence of tick-borne illnesses in Iowa and other states in the upper Midwest may be an under-recognized -- and thus underreported -- public health concern, according to a study led by scientists at the University of Iowa Hygienic Laboratory.

The findings were presented June 2 at the annual meeting of the American Society for Microbiology in Chicago. Researchers from the UI, led by Tom Gahan, public health microbiologist, and Mary Gilchrist, Ph.D., director, at the Hygienic Laboratory, worked with Patricia Quinlisk at the Iowa Department of Public Health to conduct the study.

The researchers analyzed 760 human blood samples collected last year by physicians and other health care providers in Iowa. The majority of samples (668) were initially submitted to Hygienic Laboratory scientists for testing for one of several tick-borne organisms than can cause illness. An additional 92 samples were tested that were originally submitted -- and found to be negative -- for enterovirus infections. Enteroviruses cause illnesses with symptoms similar to those of some tick-borne diseases.

When the blood samples were first sent to the Hygienic Laboratory, researchers tested for only one tick-borne illness -- usually Lyme disease -- as requested by the physician who submitted the sample. Using these stored blood samples, the researchers then performed a retrospective study, testing for antibodies against six tick-borne diseases whose agents are known to exist in parts of Iowa and pose potential health risks to humans. In addition to Lyme disease, these diseases included Rocky Mountain spotted fever, typhus fever, human granulocytic ehrlichiosis (HGE), human monocytic ehrlichiosis (HME) and babesiosis.

Of the 760 samples, 54 (7.1 percent) had elevated antibody levels indicating exposure to at least one of the six possible tick-borne agents. Of those 54, 19 showed evidence of a current or recent infection. Thirteen of the 19 were considered unexpected cases, since a tick-borne agent other than the agent initially requested for testing by the physician came back positive. Seven of the 19 infections detected were part of the enterovirus group.

"Our findings suggest that tick-borne illnesses may be under-recognized by health care providers in Iowa," Gahan said. "The public is somewhat aware of the risk of Lyme disease associated with tick bites, but it's less well known that a number of other diseases are attributed to organisms carried by ticks. Our hope is that physicians will become more aware of these other tick-borne agents, which will lead to more requests for laboratories like ours to test for these agents and get a better sense of what's out there."

Gahan noted that the areas in the upper Midwest usually associated with Lyme disease are in Minnesota and Wisconsin. "However, I think other states that border the endemic areas may be experiencing the same thing we've found here in Iowa. There just aren't a lot of requests from health professionals for testing for HGE, HME and some of the lesser-known tick-borne illnesses at this time," he said.

Part of the problem for physicians may lie in diagnosing tick-borne diseases. For example, the "bull's eye" rash commonly associated with Lyme disease actually occurs in slightly more than half of the patients with the disease. It's a similar situation with HGE and HME. These and other tick-related disease symptoms -- low-grade fever, headache, malaise and a possible rash -- may resemble a flu-like illness, making initial recognition of a tick-borne disease less than clear-cut. Since HGE and HME were discovered only in the past 10-15 years, many health care practitioners may be unfamiliar with their occurrence and symptoms.

It's not known how long each of the six of the tick-borne agents studied by the researchers have been present in Iowa, but an increased prevalence may be partly due to an explosion in the deer population over the past several decades. With more deer come more deer ticks, for example, which carry the organisms that cause Lyme and other diseases.

Deer serve as sentinels in tick-borne disease detection, since they typically stay within a small geographic region and receive hundreds of tick bites each year. Hygienic Laboratory researchers have studied deer blood samples to assess the prevalence of tick-borne agents in Iowa.

"The key is to raise awareness among health professionals and the public, which will lead to better surveillance as well as prevention," Gahan said.

The Hygienic Laboratory's World Wide Web site ( contains information on tick control, prevention and tick removal, as well as maps that detail the prevalence of the Lyme disease and HME in Iowa by county.