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.

Detection of Zoonotic Enteropathogens in Children and Domestic Animals in a Semirural Community in Ecuador

“…Consistent with previous studies (26)(27)(28)(29), our MLST analysis indicated that chickens were an important source of C. jejuni for both humans and domestic animals; this animal species commonly shared the same STs with other species (2 STs in 2 isolates from humans and 5 STs from 7 isolates of domestic animals) (Table 2 and Fig. 1).…”

Global Epidemiology of Campylobacter Infection

“…Data from Canada also support the finding that broiler chickens are a major source of Campylobacter species. There are, however, indications that chicken-associated Campylobacter infections may be more common in urban dwellers than in rural dwellers (326,327). One study reported the levels of thermotolerant Campylobacter species to be three times higher in organic broilers than in conventional broilers (54.2% versus 19.7%) (328), suggesting that the likelihood of purchasing Campylobacter-contaminated broiler meat is higher for organic sources than for conventional sources.…”

Multilocus Sequence Typing (MLST) and Whole-Genome MLST of Campylobacter jejuni Isolates from Human Infections in Three Districts during a Seasonal Peak in Finland

“…The seasonal peak is probably associated with summer activities, including increased outdoor exposures like contacts with animals and soil, barbecuing, consumption of water from private wells, and swimming in natural waters (4,5). On the whole, poultry and poultry products have been shown to be a major source of C. jejuni infections in humans (6)(7)(8)(9).…”

“…In this study, Campylobacter isolates were collected from domestically acquired infections in three midsized districts located outside the metropolitan area. Earlier studies have shown that risk factors and incidences of Campylobacter infections may vary in different geographical areas (6,13).…”