College of Veterinary Medicine

AAHP Field Disease Investigation Unit (FDIU)

Foodborne Disease Overview


Primarily, we study the foodborne pathogens Escherichia coli O157:H7 (O157), Salmonella enterica serovar Typhimurium definitive type 104 (DT104), and Campylobacter jejuni.  These bacteria inhabit the gastrointestinal tracts of a large variety of species.   Water trough sediments, soil, and animal bedding can also harbor O157 and DT104.  This wide range of habitats and reservoirs, ranging from stagnant ponds to insect guts to domestic pet intestines, makes complete eradication of these pathogens very unlikely.

Animals infected with these bacteria excrete them in feces.  This feces is then transferred by insects, water, or other contact to food products.   Humans ingest the fecal material, and the bacteria along with it.  We call this the fecal-oral route of infection.

Generally, an adult human must ingest a large number of bacteria to cause clinical disease.  The actual number varies between bacteria.  The infectious dose of Salmonella is between 1,000,000 and 10,000,000,000 organisms.  The infectious dose of E. coli O157 can be as low as 10 organisms. 

Children, elderly, and immunocompromised individuals need to ingest fewer organisms to cause disease.  These groups have less active immune systems.   Infants are especially susceptible because their gastrointestinal tracts are not fully developed, and they have no normal flora to compete with the invading bacteria.

Symptoms of these diseases are described more fully in the research section dealing with the organism.

The association of Feed and Water with Salmonella and E. coli O157 prevalence in cattle: A study funded by an FDA grant focuses on feed and water as sources of  E. coli O157 and Salmonella infection

Salmonella:  Investigating the epidemiology and ecology of Salmonella typhimurium DT104 in and around farms.  The ultimate goal is to develop strategies to prevent entry of infection to the farm and to mitigate zoonotic risk

Escherichia coli O157 and Campylobacter:  Studies on zoonotic bacteria Salmonella, Campylobacter jejuni and E. coli 0157. Recent human problems with E. coli 0157 have elevated the need for a descriptive epidemiology, determination of risk factors for herd status, and on farm ecology.

Last Edited: Nov 18, 2009 2:15 PM   

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