Abstract
Salmonella has been detected in the feces of many wildlife species, including raccoons (Procyon lotor), but little is known about the epidemiology of Salmonella in wildlife living in different habitat types. Our objective was to investigate demographic, temporal, and climatic factors associated with the carriage of Salmonella in raccoons and their environment on swine farms and conservation areas. Using a repeated cross-sectional study design, we collected fecal samples from raccoons and environmental samples (soil, manure pits, dumpsters) on 5 swine farms and 5 conservation areas in Ontario, Canada once every five weeks from May to November, 2011–2013. Salmonella was detected in 26% (279/1093; 95% CI 22.9–28.2) of raccoon fecal samples, 6% (88/1609; 95% CI 4.5–6.8) of soil samples, 30% (21/69; 95% CI 20.0–42.7) of manure pit samples, and 23% (7/31; 95% CI 9.6–41.0) of dumpster samples. Of samples testing positive for Salmonella, antimicrobial resistance was detected in 5% (14/279; 95% CI 2.8–8.3) of raccoon fecal, 8% (7/89; 95% CI 3.2–15.5) of soil, 10% (2/21; 95% CI 1.2–30.4) of manure pit, and 0/7 dumpster samples. Using multi-level multivariable logistic regression analyses, we found location type (swine farm or conservation area) was not a significant explanatory variable for Salmonella occurrence in raccoon feces or soil (p > 0.05). However, detection of Salmonella in raccoon feces was associated with rainfall, season, and sex with various interaction effects among these variables. We detected a variety of Salmonella serovars that infect humans and livestock in the feces of raccoons indicating that raccoons living near humans, regardless of location type, may play a role in the epidemiology of salmonellosis in livestock and humans in southwestern Ontario.
Highlights
Salmonella enterica is one of the most important foodborne pathogens in the world [1] and is the 3rd most important cause of bacterial foodborne illness in Canada [2]
Using a repeated cross-sectional study conducted over 3 years, our objectives were to: 1) compare Salmonella prevalence, Salmonella serovars, and antimicrobial resistance patterns detected in Salmonella from raccoon and environmental samples on swine farms and conservation areas; and 2) assess the impact of seasonal, climatic, annual, location, and raccoon demographic factors on the occurrence of Salmonella in raccoon fecal and environmental samples
Salmonella prevalence in raccoon fecal and soil samples on farms and conservation areas may not have differed in our study because did all of the study sites have some level of human use, but they all were located within the boundaries of the Grand River watershed in Ontario, which is heavily impacted by agriculture and humans [39]
Summary
Salmonella enterica is one of the most important foodborne pathogens in the world [1] and is the 3rd most important cause of bacterial foodborne illness in Canada [2]. Antimicrobial resistant Salmonella infections in humans have been associated with increased risk of extraintestinal infections, hospitalization, longer duration of illness [5, 6], and an excess number of cases [7], compared to susceptible isolates. Transmission of Salmonella from animals to humans typically occurs via the fecal-oral route through consumption of contaminated food products [8, 9], water [10,11,12], or direct contact with animals [13]. Wildlife may ingest Salmonella through consumption of contaminated animal feed or water, or through contact with contaminated farm buildings, manure, or direct contact with other animals carrying the bacteria [15]. Salmonella diversity and abundance in water samples is strongly influenced by seasonal precipitation and water temperature [22], and detection in soil samples is associated with moisture [23], and human and animal activity [18]
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