Novel Sampling Method for Assessing Human-Pathogen Interactions in the Natural Environment Using Boot Socks and Citizen Scientists, with Application to Campylobacter Seasonality

Abstract

This paper introduces a novel method for sampling pathogens in natural environments. It uses fabric boot socks worn over walkers' shoes to allow the collection of composite samples over large areas. Wide-area sampling is better suited to studies focusing on human exposure to pathogens (e.g., recreational walking). This sampling method is implemented using a citizen science approach: groups of three walkers wearing boot socks undertook one of six routes, 40 times over 16 months in the North West (NW) and East Anglian (EA) regions of England. To validate this methodology, we report the successful implementation of this citizen science approach, the observation that Campylobacter bacteria were detected on 47% of boot socks, and the observation that multiple boot socks from individual walks produced consistent results. The findings indicate higher Campylobacter levels in the livestock-dominated NW than in EA (55.8% versus 38.6%). Seasonal differences in the presence of Campylobacter bacteria were found between the regions, with indications of winter peaks in both regions but a spring peak in the NW. The presence of Campylobacter bacteria on boot socks was negatively associated with ambient temperature (P = 0.011) and positively associated with precipitation (P < 0.001), results consistent with our understanding of Campylobacter survival and the probability of material adhering to boot socks. Campylobacter jejuni was the predominant species found; Campylobacter coli was largely restricted to the livestock-dominated NW. Source attribution analysis indicated that the potential source of C. jejuni was predominantly sheep in the NW and wild birds in EA but did not differ between peak and nonpeak periods of human incidence.IMPORTANCE There is debate in the literature on the pathways through which pathogens are transferred from the environment to humans. We report on the success of a novel method for sampling human-pathogen interactions using boot socks and citizen science techniques, which enable us to sample human-pathogen interactions that may occur through visits to natural environments. This contrasts with traditional environmental sampling, which is based on spot sampling techniques and does not sample human-pathogen interactions. Our methods are of practical value to scientists trying to understand the transmission of pathogens from the environment to people. Our findings provide insight into the risk of Campylobacter exposure from recreational visits and an understanding of seasonal differences in risk and the factors behind these patterns. We highlight the Campylobacter species predominantly encountered and the potential sources of C. jejuni.

Strain-Specific Differences in Survival of Campylobacter spp. in Naturally Contaminated Turkey Feces and Water

“…Thus, higher relative fitness of C. jejuni in the feces may suggest greater potential for preharvest colonization of turkey flocks with this species. As mentioned earlier, Campylobacter can spread within a turkey house directly via coprophagy or among different turkey houses and farms via vectors such as flies, equipment, and transport crates as well as via human traffic, e.g., through footwear, clothing, and vehicles (10,25,(31)(32)(33). During slaughter and processing, birds that became colonized with Campylobacter at the farm are more likely to lead to contamination of the carcasses with Campylobacter from the birds' intestinal contents (11,45).…”

“…Campylobacter's capacity to colonize chickens is enhanced upon passage through the birds' gastrointestinal (GI) tract and shedding in the fecal droppings (26)(27)(28)(29)(30). Campylobacter in the poultry feces can be then transmitted to other flocks and farms via insects, such as flies, and other vectors, including farm equipment and human traffic, with potential for downstream dispersal and contamination of the natural environment, e.g., surface water and soil (10,25,(31)(32)(33).…”

Food-borne disease and climate change in the United Kingdom

“…However, our understanding of the reasons behind this are limited because unlike other bacteria Campylobacter does not multiple outside the gut. For example the response of Campylobacter cases to season and weather patterns has been attributed in the literature to several factors such as the cycling of the organisms in natural reservoirs and the seasonality of countryside visits exposing the public to Campylobacter in the environment [ 15 ]. Other authors have suggested the importance of seasonal and weather associated changes to food consumption (e.g.…”

Regional differences in presence of Shiga toxin‐producing Escherichia coli virulence‐associated genes in the environment in the North West and East Anglian regions of England

“…This method has been demonstrated to be just as, if not more, sensitive than the older drag swab method developed for use on chicken farms (Buhr et al 2007;Lungu et al 2012). Boot socks have also recently been used to sample for pathogens in the wider environment (Brena et al 2016;Jones et al 2017). The aim of this research was to analyse boot socks generated during the Enigma project for Campylobacter to determine the frequency with which STEC-associated virulence genes were detected in the English countryside (Jones et al 2017).…”