Association between environmental risk factors and campylobacter infections in Sweden

Abstract

Campylobacter sp. is the most common cause of acute bacterial gastroenteritis in Sweden and the incidence has been increasing. Case-control studies to identify risk factors have been conducted in several countries, but much remains unexplained. The geographical distribution of campylobacter infections varies substantially, and many environmental factors may influence the observed pattern. Geographical Information Systems (GIS) offer an opportunity to use routinely available surveillance data to explore associations between potential environmental risk factors showing a geographical pattern and disease incidence, complementing traditional approaches for investigating risk factors for disease. We investigated associations between campylobacter incidence and environmental factors related to water and livestock in Sweden. Poisson regression was used to estimate the strength of the associations. Positive associations were found between campylobacter incidence and average water-pipe length per person, ruminant density, and a negative association with the percentage of the population receiving water from a public water supply. This indicates that drinking water and contamination from livestock may be important factors in explaining sporadic human campylobacteriosis in Sweden, and that contamination occurring in the water distribution system might be more important than previously considered.

Impact of Rurality, Broiler Operations, and Community Socioeconomic Factors on the Risk of Campylobacteriosis in Maryland

“…Nygard et al (2004) remind us that data collected for populations, rather than for individuals, do not necessarily reflect associations at the individual level. This can lead data analysis to a potential "ecological fallacy" in which a risk factor derived from aggregate data and subsequently ascribed to individuals does not, in fact, reflect the biological effect at the individual level (Morgenstern, 1998: Nygard, 2004.…”

“…Similarly, in a Swedish prospective case-control study, which examined domestically acquired C. jejuni and C. (Michaud, 2004). Similarly, an ecological study conducted among municipalities in Sweden found a slightly protective effect of having a public water supply instead of a private supply (IRR 0.93; 95%CI= 0.90-0.95 (Nygard, 2004). A population-based surveillance case-control study among infants 0-6 months of age, using U.S. FoodNet data, found that drinking well water (OR 4.4;CI, brought with it an increased risk of Campylobacter infection among infants (Fullerton, 2007).…”

“…Better data availability on poultry density would lead to more precise measures of exposure, especially insofar as occupational exposure is concerned . In Denmark, Nygard et al (2004) found similar limitations when examining the association of environmental factors and campylobacter incidence in municipalities of Sweden, 1998Sweden, -2000. In terms of animal density, they found an IRR of 1.03 (95%CI=1.01,1.05) for poultry and found an IRR of 1.08 (95% CI= 1.05, 1.11) for ruminant density.…”

“…Similarly, Nygard (2004) suggests that a water-animal-water cycle may be involved with ruminants such as cattle citing a British study revealing cattle as a source of contamination for ground water (Stanley, 1998). In a Finnish study, cattle exposed to…”

“…But they pointed out an increased risk of campylobacteriosis in high-animal density areas could originate from higher rates of direct transmission from cattle and small ruminants. Since measuring indirect transmission from animals through water is difficult to do, they suggest further research combining data from individual based studies with the data on environmental factors (Nygard, 2004).…”