Animal Health Research Reviews

Review Article

Explaining unexplained diarrhea and associating risks and infections

Donna M. Dennoa1, Eileen J. Kleina2, Vincent B. Younga3a4, James G. Foxa3a4, David Wanga5 and Phillip I. Tarra6 c1

a1 Departments of Health Services and Pediatrics, University of Washington School of Medicine, Seattle, WA, USA

a2 Children's Hospital and Regional Medical Center, Department of Pediatrics, University of Washington, Seattle, WA, USA

a3 Department of Internal Medicine and Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA

a4 Massachusetts Institute of Technology, Massachusetts Ave., Cambridge, MA 02139, USA

a5 Department of Molecular Microbiology and Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA and

a6 Department of Pediatrics and Department of Molecular Microbiology, Campus Box 8208, 660 South Euclid Avenue, St. Louis, MO 63110, USA


Gastrointestinal illnesses are common afflictions. However, knowledge of their etiology is often lacking. Moreover, most cases of infections with reportable enteric pathogens (Campylobacter jejuni, Escherichia coli O157:H7, Salmonella, Shigella, Yersinia, Cryptosporidia and Giardia) have sporadic modes of acquisition, yet control measures are often biased towards mitigation of risks discerned by outbreak analysis. To determine the etiology of unexplained diarrhea it is important to study populations that can be matched to appropriate controls and to couple thorough classic microbiologic evaluation on receipt of specimens with archiving and outgrowth capabilities. Research evaluations should address the potential roles of a broad panel of candidate bacterial pathogens including diarrheagenic E. coli, Listeria monocytogenes, Helicobacters and jejuni Campylobacters, and also apply novel massively parallel sequencing and nucleic acid detection technologies that allow the detection of viral pathogens. To fill voids in our knowledge regarding sources of known enteric pathogens it will be critical to extend case-control studies to assess risk factors and exposures to patients with non-epidemic illnesses and to appropriate controls. By filling these gaps in our knowledge it should be possible to formulate rational prevention mechanisms for human gastrointestinal illnesses.

(Received May 30 2007)

(Accepted June 04 2007)


c1 Corresponding author. E-mail: