NEW YORK -- Preliminary research, to be released here this morning,
suggests that at least one in three people may be genetically
susceptible to travelers' diarrhea.
That may be one reason travel medicine expert Dr. David Shlim
reports that taking standard precautions (avoiding certain foods
and drinking bottled water) doesn't make a lot of difference in
heading off the ailment. As a result, he said, obtaining
antibiotics in advance of a trip may be the most practical course
to pursue.
The study and Dr. Shlim's related breakout session on prevention
of the common disorder are on today's schedule at the International
Society of Travel Medicine (ISTM) worldwide conference under way
here though May 11.
The research, undertaken at the University of Texas, was
described by ISTM as the first to find a likely genetic basis for
some travelers' susceptibility to enteroaggregative E. coli (EAEC)
-- one of two bacteria that cause most cases of travelers'
diarrhea.
The study looked at health results among 69 Americans who spent
five weeks in Mexico. Among the 69, about one-third tested positive
for the EAEC bacteria and a specific gene. However, another third
tested positive for the gene, meaning that nearly two-thirds of the
group had the genetic marker.
However, among those who contracted EAEC-caused diarrhea, 87%
tested positive for the gene, while among those who showed no signs
of illness, 41% had the gene.
Dr. Herbert DuPont, a co-author of the study and a travel
medicine expert at Houston's St. Luke's Episcopal Hospital, said
doctors may one day be able to test quickly for the gene to
identify travelers who should take antibiotics as a
preventative.
Next up, he said, will be a study to determine if there is a
genetic link between travelers' diarrhea and the second bacteria
that is a major cause of the syndrome.
Meanwhile, Dr. Shlim will give a talk at the ISTM conference
called Can Travelers' Diarrhea Be Prevented by Food & Water
Precautions? His answer is -- in a word -- no.
The doctor, who is medical director of Jackson Hole (Wyo.)
Travel and Tropical Medicine, said studies suggest there is no
correlation between failing to follow common guidelines and
contracting the diarrhea.
"The rate of people who get diarrhea in the first few weeks of a
trip has not changed in 50 years," said Dr. Shlim said. Studies
show, he continued, that "there's not much you can do to avoid
acquiring travelers' diarrhea."
Therefore, he recommends that travelers "be prepared to
self-diagnose and treat the diarrhea with antibiotics." The ailment
will go away eventually on its own, but he said, antibiotics can
shorten the illness from several days to several hours -- and save
a vacation.
Only about 10% of cases have causes other than bacteria and are
not treatable with antibiotics, he said.
Dr. Shlim also recommended an over-the-counter medicine called
loperamide to treat symptoms although it does not cure the
diarrhea.
Finally, he said, the risk of contracting diarrhea and its
severity depend on the amount of bacteria in the offending food or
water, how much of the food or water was taken and the person's
previous exposure to the organisms. Also, the ailment's frequency
among travelers to underdeveloped countries varies widely by
country, from 20% to 70%; the incidence for Mexico is about 35%,
ISTM said.