In 2011, the Minnesota Department of Health (MDH) became part of the Upper Midwest Agriculture Safety and Health Center, one of 10 national centers for agricultural disease and injury research, education, and prevention. Previous research has quantified the occurrence of fatal injuries and other non-infectious health threats among agricultural workers, but research on zoonotic diseases among agricultural workers is sparse. Since 2012, MDH has prospectively collected systematic, detailed data on animal agriculture exposures in Minnesota residents with reportable enteric pathogen infections.
METHODS:
Campylobacter, Cryptosporidium parvum, Salmonella, E. coli O157, and non-O157 Shiga toxin-producing E. coli (STEC) infections are reportable to MDH. Cases reported during 2012-2014 were interviewed with a standard hypothesis-generating questionnaire. Cases reporting animal agriculture exposures were re-interviewed in more detail about their agricultural exposure. Cases were excluded if they were part of an outbreak, traveled internationally, or were lost-to-follow-up.
The total number and proportion of cases reporting an animal agriculture exposure were calculated, and demographics, clinical illness, and agricultural exposure characteristics were evaluated. Cases were assigned to one of three exposure tiers: 1) lived or worked on farm; 2) visited a farm; or 3) visited a fair, petting zoo, or other venue with food production animals.
RESULTS:
From 2012-2014, 26% of Campylobacter cases, 51% of Cryptosporidium parvum cases, 13% of Salmonella cases, 32% of E. coli O157:H7 cases, and 8% of STEC cases reported an animal agriculture exposure during their incubation period. Campylobacter (n = 518) caused the highest absolute number of illnesses attributable to agricultural exposures, followed by Salmonella (n = 192) and C. parvum (n = 157). The incidence of Campylobacter infections in the general Minnesota population was 16.7 per 100,000 person-years, but among Tier 1 cases was 81.6 per 100,000 person-years. In other words, those who live or work on a farm were 4.9 times more likely to get a Campylobacter infection than the general population. Similarly, people who live or work on a farm in Minnesota were 1.8 times more likely to get a Salmonella infection and 7.2 times more likely to get a C. parvum infection.
CONCLUSIONS:
Data we have collected represent the most comprehensive and detailed disease data set on agricultural workers in the United States. Enteric zoonoses are much more common among agricultural workers than previously documented. Current estimates of the burden of zoonoses are underappreciated and the proportion of cases of enteric zoonoses currently attributed to foodborne transmission are likely overestimated.