CONTACT: LESLIE LOVELESS
(319) 335-4436; fax(319) 335-8034
CONTACT: DAVE PEDERSON
2130 Medical Laboratories
Iowa City IA 52242
(319) 335-8032; fax(319) 335-8034
Release: Aug. 7, 2000
UI researchers track new tick-borne disease in Iowa
IOWA CITY, Iowa -- With the help of more than 2,000 Iowa deer hunters, researchers
at the University of Iowa have tracked the migration of a new tick-borne disease
An article in a recent issue of Emerging Infectious Diseases, a journal
published by the Centers for Disease Control and Prevention, features this
unusual collaboration between scientists and game hunters to trace the route
of this potentially fatal disease.
Human monocytic ehrlichiosis (HME) is a newly recognized disease caused
by the bacterium Ehrlichia chaffeensis and carried by the Lone Star tick.
The tick's preferred host is the white-tailed deer, but it does occasionally
bite humans. Deer are not affected by Ehrlichia, but they do produce antibodies
to the bacteria when bitten by an infected tick.
HME, a potentially life-threatening disease if not treated early, was first
recognized in Arkansas in 1986. Human cases of this disease have been reported
in Illinois, Missouri and several other states south of Iowa, but it has not
yet been reported in Iowa.
Deer hunters from across Iowa were asked by researchers to collect small
samples of blood from white-tailed deer and record the location where the
deer was killed. The samples were then mailed to the UI Hygienic Laboratory
and tested for antibodies. The deer survey, done in 1994 and again in 1996,
showed an increase in the prevalence of seropositive deer -- deer that have
been exposed to Ehrlichia -- especially in Iowa's southern counties.
"These data indicate that Ehrlichia may be moving north into Iowa from
Missouri," said Peter Thorne, professor of occupational and environmental
health in the UI College of Public Health.
In fact, a map of the prevalence of deer exposed to Ehrlichia shows a gradient
running from south to north, with the highest rates in Iowa's southernmost
counties. Prevalence also increased from 1994 to 1996. The figures are adjusted
for changes in deer population by region.
Symptoms of HME range from a mild, flu-like syndrome to a severe, life-threatening
illness. It is difficult to diagnose, but can be treated with antibiotics
once a diagnosis is made. Because of its vague symptoms, tracking Ehrlichia
in deer, rather than in humans, made sense to researcher Linda Mueller-Anneling,
who was at the UI Hygienic Lab at the time of the study.
"By looking at antibodies in deer, you can follow the disease, even
if deer don't get sick from it," Mueller-Anneling said. "Now we
know that there are definitely ticks in Iowa that carry Ehrlichia, and we
can take appropriate measures to protect humans.