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There are three major groups of salmonella: host-specific (primarily infects one species of animal), host-adapted (can infect several species but are adapted to live in one), and unadapted serovars with no host preference 1. The foodborne pathogens we study are in the last two groups.

Salmonella is a bacteria which causes a foodborne diarrheal illness in humans. Ingestion of between 1 million and 10 million organisms causes clinical disease in adults. The infectious dose is lower for children, elderly, and immunocompromised individuals 1. Symptoms usually develop within 12 to 14 hours after ingestion and persist for 2-3 days. The average mortality rate by age group is:

  • 0-1 years: 5.8%
  • 1-50 years: 2%
  • over 50: 15%

Up to 5% of patients continue to excrete infectious organisms after symptoms go away. These “carriers” can pass the disease around through poor hygiene and food-handling practices 1.

Salmonella species can cause similar symptoms in infected cattle, especially when those cattle are stressed by overcrowding or extreme temperatures. Resistance to multiple antibiotics makes some salmonella species extremely dangerous 2.

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 DT104 Research Project: Rural America

A grant from the USDA funds research involving Salmonella enterica serovar typhimurium variant DT104. This bacteria is a serious emerging pathogen for humans, wildlife, and farmed animal species in rural areas of the Pacific Northwest. Salmonella DT104 is resistant to multiple antibiotics, including those used to treat human salmonellosis, and is more infective and virulent than other common salmonella species. These features may severely affect domestic and international marketing of the region’s farm products.

In addition to cattle, we have isolated DT104 from numerous species including: horse, goat, emu, cat, dog, elk, mouse, coyote, squirrel, raccoon, chipmunk, pigeon, starling, pine siskin, and flies. We have also isolated DT104 from environmental samples such as soil and cattle bedding. This indicates the organism has many potential routes of movement in the farm ecosystem.

This study investigates the movement of DT104 within the farm ecosystem over a 1-year period of time. We are studying the environmental, farm management, and geospatial factors associated with the introduction and persistence of this agent.

Study goal

Determine the management, environmental, and geospatial factors associated with S. typhimurium DT104 persistence in a herd and the regional and environmental impact. This includes longitudinal sampling in case herds and an evaluation of pathways from movement of S. typhimurium DT104 within the dairy ecosystem.


  1. Jay, J.M. Modern Food Microbiology, Fifth Edition. New York: Chapman and Hall, 1996.
  2. Hancock, D., T. Besser, D. Rice, C. Gay, J. Gay. Pre-harvest food safety interventions on cattle farms.