Evaluation of Salmonella occurrence in domestic animals and humans in North Dakota (2000-2005).

ABSTRACT

OBJECTIVES: To evaluate the occurrence, serotypes, and antimicrobial susceptibility of Salmonellae from domestic animals and humans in North Dakota. MATERIALS AND METHODS: Salmonellosis data (2000-2005) in humans (n = 286) and animals (n = 258) were extracted from the North Dakota Department of Health (NDDoH) and North Dakota State University Veterinary Diagnostic Laboratory (NDSU-VDL), and analyzed for temporal and spatial trends, and for other associations. Additionally, random samples of 35, 30, and 15 Salmonella isolates from NDSU-VDL, NDDoH, and North Dakota healthy cattle, respectively, were tested for antimicrobial susceptibility. RESULTS: Most animal salmonellosis occurred in cattle (64.7%) sheep (12%), pigs (10.9%), and bison (0.4%) with Salmonella Typhimurium (45.7%) as the predominant serotype; Salmonella Arizona (10.9%) and Dublin (10.5%) were host specific in sheep and cattle respectively. In humans, Salmonella Typhimurium (32.5%) and Salmonella Newport (11.2%) were predominant. Season influenced human (p = 0.027) and animal (p = 0.014) salmonellosis with cases peaking in the spring and summer for animals and humans, respectively. Salmonella Typhimurium case reports in humans were not seasonally related to domestic animals (p = 0.001) nor cattle (p = 0.001). Over time, case reports increased in humans but decreased in domestic animals. Most serotypes from domestic animals were multidrug resistant compared to human isolates. CONCLUSIONS AND APPLICATIONS Many Salmonella serotypes (17) were involved in North Dakota human and animal salmonellosis with case reports closely related in fall and winter, but not during warmer months. Spatial clustering of human and animal cases was similar. Antimicrobial resistance was widespread but lower in human isolates. These data are helpful in determining future policy, research, and control strategies for salmonellosis in humans and domestic animals.