Gene might underlie travelers' diarrhea.

Having a particular form of the gene that encodes the natural compound lactoferfin could predispose some people to travelers' diarrhea, a study finds. Normally, lactoferrin binds to some bacteria, thwarting their capacity to cause disease.

Roughly 40 to 60 percent of U.S. visitors to Mexico get diarrhea, usually from ingesting viruses or bacteria such as Escherichia coli, salmonella, and shigella, says Jamal A. Mohamed, a molecular biologist at the University of Texas Medical School in Houston. In search of genetic factors common to these individuals, Mohamed and his colleagues identified 718 people from the United States while they were on short-term stays in Mexico between 2002 and 2005.

There, 362 of the travelers became sick enough with diarrhea to visit a clinic. Four-fifths of the cases of diarrhea stemmed from bacterial infections, stool samples showed.

Blood samples from the travelers revealed that the sick ones were significantly more likely than the healthy ones to harbor a particular form of the gene encoding lactoferrin. The gene variant, called the TT allele, also showed up more often in white travelers than in blacks or Asians.

However, the form of a person's lactoferrin gene had no effect on how likely that person was to get sick from the diarrhea-causing norovirus, the researchers found.--N.S.