MC Nachtigal

Project title: Occupational association of Salmonella and Shiga toxin-producing E. coli cases in Washington State 2005-2016

Degree: MPH | Program: One Health (ONE) | Project type: Thesis/Dissertation
Completed in: 2019 | Faculty advisor: Peter Rabinowitz


Background: Salmonellosis is a common food-borne gastrointestinal infection causing diarrhea, upset stomach, and sometimes vomiting. Each year there are 600-800 cases of salmonellosis reported to the Washington State Department of Health. Shiga toxin-producing Escherichia Coli (STEC) is also a foodborne bacterial illness which can have serious health sequelae, including hemolytic uremic syndrome or death. There are approximately 140-200 cases per year in Washington State. As part of the investigation into reported cases of Salmonella and STEC, DOH asks affected individuals about their occupation. It is suspected that individuals working in some occupations may be at higher risk of salmonellosis than others. Methods: Using Washington State Department of Health notifiable conditions data for Salmonella and Shiga toxin producing E. coli cases and Current Population Survey records through the Employed Labor Force (ELF) query system, we calculated incidence rate ratios for Salmonella and STEC cases reported to WA DOH during the years 2005 through 2016 for each major occupation category using major Standard Occupation Classification, both as total and separated by male and female sex. Results: Women had higher rates of reported infection than men. In Salmonella, employed women and men had similar rates. For STEC, employed women had higher rates than the general population, while men had similar rates in the employed and general population. Overall Salmonella infection rates were highest in Life, Physical, and Social Sciences (IRR 1.84, CI 1.42-2.40), while STEC infections were associated most with the occupational group Arts, Design, Entertainment, and Sports (IRR=2.01, CI 1.41-2.84). Healthcare workers were at increased risk for both Salmonella and STEC (IRR=1.52, CI 1.33-1.73 and 1.73, CI 1.33-2.25 for Salmonella/STEC respectively). Notable gender differences in stratified risk analysis included female construction workers and Salmonella (SIR=3.20, CI 2.05-4.97) males in Farming, Fishing, Forestry for STEC (IRR-2.11, CI 1.18-3.77); and males in Personal Services (IRR=6.67, CI 4.44-10.05) for STEC risk. Discussion: Several categories of increased risk were expected, such as healthcare workers and scientists working in the field. Surprising was the high level of association with not associated with high pathogen exposure such as business/finance or arts and entertainment workers. Future studies should include repeating this method with data of enteric pathogens in other states or regions. Education or care for occupation groups at increased risk for the short- and long-term effects of enteric pathogen infection may be implemented.