The Potential Risk Associated with Foodborne Pathogens in Watersheds: <i>Salmonellap</i> spp. in Dairy Cattle

Abstract

Salmonella spp. is one of the most important food- and waterborne pathogens implicated in human and animal disease. A repeat cross-sectional study was performed to assess the occurrence of Salmonella in dairy herds in a watershed and determine the factors that play a role in the likelihood of perpetuation of this organism among animals on these farms. A convenience sample of herds in the Delaware County watershed was selected based on farmers’ willingness to participate. Fecal samples were collected per rectum from a representative sample of cattle in these herds and tested for the presence of Salmonella using a combination of culturing and molecular detection methods. The significance of association between the putative risk factors and the likelihood of Salmonella spp. was evaluated using the logistic regression analysis. A total of 34 dairy farms were enrolled in the study and 1987 samples were collected coinciding with seasonal variation. Salmonella spp. was detected in 44% (15/34) of the herds in the study population ( i.e ., from at least one animal in these herds). However, only a small fraction of the entire sampling population (1.7%) was found to be shedding Salmonella. Risk factors that were found to be associated with the presence of the pathogen on the farm in the final multivariable model included concrete flooring for calves, prevention of calf access to the dam, and the lack of a designated calving pen. Two serovars, Salmonella enterica serovar Infantis and Salmonella enterica serovar Oranienburg, were identified among the isolates recovered in this study. Our study demonstrated that there was a potential risk of watershed degradation from Salmonella associated with cattle.