CONTACT: DAVE PEDERSEN
283 Medical Laboratories
Iowa City IA 52242
(319) 335-8032; fax (319) 335-8034
University Hygienic Laboratory monitoring tick-borne diseases in
IOWA CITY, Iowa -- Warmer weather soon will have Iowans gearing up for
outdoor activities such as camping, hiking and fishing. But being outdoors
also means being exposed to the potential health risks associated with
tick bites. Increased awareness among the public and health professionals
is key to detection, say researchers at the University of Iowa Hygienic
Around 15 years ago, Lyme disease succeeded Rocky Mountain Spotted Fever
as the most recognized tick-borne disease in Iowa. In addition, human monocytic
ehrlichiosis (HME) and human granulocytic ehrlichiosis (HGE) have been
identified as illnesses attributed to organisms carried by ticks. Tick-borne
diseases typically begin with a low-grade fever, headache, malaise and
possibly a rash. Left untreated, the symptoms may progress to serious and
even life-threatening conditions. However, many cases may resolve without
treatment and remain unrecognized.
"Our detection system is such that when we detect tick-borne infections
we immediately report them. Overall, there has not been a lot of evidence
of human disease in Iowa," says Dr. Mary Gilchrist, director of the
UI Hygienic Laboratory. "However, the public and many physicians in
the state are perhaps not as familiar with the more recently identified
tick-borne diseases like HME and HGE. So part of our job is to make the
public and health professionals aware of what's out there, which helps
in our detection efforts."
In Iowa, Hygienic Laboratory research gathered from deer blood samples
from 1994 and 1996 (conducted in collaboration with researchers at Iowa
State University, the Iowa Department of Natural Resources and the Iowa
Department of Public Health) has indicated a modest frequency of the organism
that causes HME among Lone Star ticks in the southern tier of Iowa counties,
especially in the southeast portion of the state. Deer serve as sentinels
in tick-borne disease detection, since they typically stay within the same
geographic area and receive hundreds of tick bites each year. The Lone
Star tick is responsible for transmitting HME in Iowa.
HGE is transmitted by bites from the deer tick, the same tick that is
responsible for transmitting Lyme disease, and is found mainly in northeastern
Iowa and in counties bordering the Mississippi River. So far the HGE organism
has not been prevalent in Iowa, but Gilchrist notes that it has been detected
in deer samples from those counties.
As for Lyme disease, researchers know that the northeast counties of
the state are the main areas for tick-borne exposure. More recent data
suggests, however, a newly evolving focus of Lyme disease among the deer
population in the more forested northwestern counties in Iowa, particularly
around the Lake Okoboji area.
"The signal of a tick-borne infection in the deer population generally
leads us to expect to see the disease in humans, too," Gilchrist says.
"We already have a modest amount of tick-borne illnesses, especially
Lyme disease, in Iowa. We suspect there may be a similar amount of ehrlichiosis
in Iowa, but it's just not been recognized."
Part of the reason for this, Gilchrist says, is that one of the early
signs of Lyme disease--a bulls eye-like ring that develops at the site
of the tick bite--is not present following a bite from a tick carrying
ehrlichiosis. "You don't have that kind of red flag. Ehrlichiosis
produces a flu-like illness, with or without a generalized rash. People
with this may think they simply have a rash due to allergy." Gilchrist
notes that ehrlichiosis typically does not progress to chronic complications
such as arthritis or central nervous system symptoms, as can be the case
with Lyme disease, and adds that people tend to recover from the illness.
The Hygienic Laboratory has just released maps on its World Wide Web
page (www.uhl.uiowa.edu) that show the prevalence of the bacteria that
cause Lyme disease and HME in deer in each Iowa county. Viewers can "click"
a county on the maps and find a table of positive deer serology results
from 1994 and 1996. The laboratory's Web page also has information on tick
bite prevention and how to safely remove a tick from the skin.
Hygienic Laboratory researchers continue to accept and identify ticks
submitted by the public for tick-borne diseases. The researchers also will
conduct tick-borne disease surveillance among the state's deer population
in 1998. For more information, call (319) 335-4500.