title: Campylobacteriosis in urban versus rural areas: a case-case study integrated with molecular typing to validate risk factors and to attribute sources of infection.
abstract: Campylobacter infection is a leading cause of bacterial gastroenteritis worldwide, and most clinical cases appear as isolated, sporadic infections for which the source is rarely apparent. From July 2005 to December 2007 we conducted a prospective case-case study of sporadic, domestically-acquired Campylobacter enteritis in rural versus urban areas and a prevalence study of Campylobacter in animal and environmental sources in the Eastern Townships, Quebec. Isolates were typed using Multilocus Sequence Typing (MLST) to reinforce the case-case findings and to assign a source probability estimate for each human isolate. The risk of human campylobacteriosis was 1.89-fold higher in rural than urban areas. Unconditional multivariate logistic regression analysis identified two independent risk factors associated with human Campylobacter infections acquired in rural area: occupational exposure to animals (OR = 10.6, 95% CI: 1.2-91, p = 0.032), and household water coming from a private well (OR = 8.3, 95% CI: 3.4-20.4, p<0.0001). A total of 851 C. jejuni isolates (178 human, 257 chicken, 87 bovine, 266 water, 63 wild bird) were typed using MLST. Among human isolates, the incidence rates of clonal complexes (CC) CC-21, CC-45, and CC-61 were higher in rural than urban areas. MLST-based source attribution analysis indicated that 64.5% of human C. jejuni isolates were attributable to chicken, followed by cattle (25.8%), water (7.4%), and wild birds (2.3%). Chicken was the attributable source for the majority of cases, independent of residential area, sex and age. The increased incidence in rural compared to urban areas was associated with occupational exposure to animals, particularly cattle among those aged 15-34 years, and with consumption of private well water. Both bovine and water exposure appeared to contribute to the seasonal variation in campylobacteriosis. These results provide a basis for developing public education and preventive programs targeting the risk factors identified.
authors.affiliation: Department of Microbiology and Infectious Diseases, Faculté de Médecine de l'Université de Sherbrooke, Québec, Canada.
authors.forename: Simon
authors.initials: S
authors.lastname: Lévesque
authors.affiliation: Laboratoire de santé publique du Québec, Institut national de santé publique du Québec, Sainte-Anne-de-Bellevue, Québec, Canada.
authors.forename: Eric
authors.initials: E
authors.lastname: Fournier
authors.affiliation: Centre de Recherche Clinique Étienne-Le Bel du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, Québec, Canada.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Carrier
authors.affiliation: Department of Microbiology and Infectious Diseases, Faculté de Médecine de l'Université de Sherbrooke, Québec, Canada ; Centre de Recherche Clinique Étienne-Le Bel du Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, Québec, Canada.
authors.forename: Eric
authors.initials: E
authors.lastname: Frost
authors.affiliation: Infectious Diseases Section, Tufts University School of Medicine, Boston, Massachusetts, United States of America.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Arbeit
authors.affiliation: Department of Microbiology and Infectious Diseases, Faculté de Médecine de l'Université de Sherbrooke, Québec, Canada.
authors.forename: Sophie
authors.initials: S
authors.lastname: Michaud
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D002167:Campylobacter / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D002169:Campylobacter Infections / Q000453:epidemiology* / Q000382:microbiology* / Q000635:transmission; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D008875:Middle Aged; D058885:Multilocus Sequence Typing; D011446:Prospective Studies; D011792:Quebec / Q000453:epidemiology; D012307:Risk Factors; D012424:Rural Population; D012621:Seasons; D012737:Sex Factors; D014505:Urban Population; D055815:Young Adult