CONTACT: DAVE PEDERSEN
2130 Medical Laboratories
Iowa City IA 52242
(319) 335-8032; fax (319) 335-8034
Release: June 3, 1999
Tick-borne illnesses may be under-recognized, Iowa
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
"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,"
The Hygienic Laboratory's World Wide Web site (www.uhl.uiowa.edu)
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