dArcobacter butzleri has been linked to enteric disease in humans, but its pathogenicity and epidemiology remain poorly understood. The lack of suitable detection methods is a major limitation. Using comparative genome analysis, we developed PCR primers for direct detection and quantification of A. butzleri DNA in microbiologically complex matrices. These primers, along with existing molecular and culture-based methods, were used to detect A. butzleri and enteric pathogens in stools of diarrheic and nondiarrheic people (n ؍ 1,596) living in southwestern Alberta, Canada, from May to November 2008. In addition, quantitative PCR was used to compare A. butzleri densities in diarrheic and nondiarrheic stools. Arcobacter butzleri was detected more often by PCR (59.6%) than by isolation methods (0.8%). Comparison by PCR-based detection found no difference in the prevalence of A. butzleri between diarrheic (56.7%) and nondiarrheic (45.5%) individuals. Rates of detection in diarrheic stools peaked in June (71.1%) and October (68.7%), but there was no statistically significant correlation between the presence of A. butzleri and patient age, sex, or place of habitation. Densities of A. butzleri DNA in diarrheic stools (1.6 ؎ 0.59 log 10 copies mg ؊1 ) were higher (P ؍ 0.007) than in nondiarrheic stools (1.3 ؎ 0.63 log 10 copies mg ؊1 ). Of the 892 diarrheic samples that were positive for A. butzleri, 74.1% were not positive for other bacterial and/or viral pathogens. The current study supports previous work suggesting that A. butzleri pathogenicity is strain specific and/or dependent on other factors, such as the level of host resistance. N early 1.7 billion cases of diarrheal disease are reported globally each year (1), although this is an underestimation of true rates of enteritis, as many afflicted individuals do not have access to or choose not to pursue medical assistance (2). For those seeking diagnosis, the majority of cases of acute enteritis are not linked to an identified etiological agent (3, 4). Ascertaining the etiology of enteric disease is essential for the development of effective therapeutics and preventative mitigation strategies. Direct contact with animals and ingestion of untreated water and/or undercooked animal products are recognized risk factors for acute enteritis (3), which suggests that a significant number of cases of enteritis are caused by unidentified biotic pathogens of human or zoonotic origin. Critical components of the epidemiology of arcobacteriosis and the population structure of Arcobacter butzleri have yet to be resolved, in large part because effective culture and/or molecular-based detection methods for this bacterium have yet to be developed.Arcobacter butzleri is ubiquitous in the environment (e.g., river water contaminated with human and/or nonhuman animal feces) (5-7). That the bacterium is detected in such a variety of sources suggests that pathways for transmission among animals and environmental sources exist, but accurate source tracking of A. butzleri is hampered by a ...