experience of NaTHNaC indicates that acquisition and coordination of information with health authorities, rapid and direct communication of fi ndings and recommendations to stakeholders, and posting of this information for access by travelers and health professionals can increase communication about global health events.
Source attribution using molecular subtypes has implicated cattle and sheep as sources of human Campylobacter infection. Whether the Campylobacter subtypes associated with cattle and sheep vary spatiotemporally remains poorly known, especially at national levels. Here we describe spatiotemporal patterns of prevalence, bacterial enumeration, and subtype composition in Campylobacter isolates from cattle and sheep feces from northeastern (63 farms, 414 samples) and southwestern (71 farms, 449 samples) Scotland during 2005 to 2006. Isolates (201) were categorized as sequence type (ST), as clonal complex (CC), and as Campylobacter jejuni or Campylobacter coli using multilocus sequence typing (MLST). No significant difference in average prevalence (cattle, 22%; sheep, 25%) or average enumeration (cattle, 2.7 x 10(4) CFU/g; sheep, 2.0 x 10(5) CFU/g) was found between hosts or regions. The four most common STs (C. jejuni ST-19, ST-42, and ST-61 and C. coli ST-827) occurred in both hosts, whereas STs of the C. coli ST-828 clonal complex were more common in sheep. Neither host yielded evidence for regional differences in ST, CC, or MLST allele composition. Isolates from the two hosts combined, categorized as ST or CC, were more similar within than between farms but showed no further spatiotemporal trends up to 330 km and 50 weeks between farm samples. In contrast, both regions yielded evidence for significant differences in ST, CC, and allele composition between hosts, such that 65% of isolates could be attributed to a known host. These results suggest that cattle and sheep within the spatiotemporal scales analyzed are each capable of contributing homogeneous Campylobacter strains to human infections.
Campylobacter species cause a high proportion of bacterial gastroenteritis cases and are a significant burden on health care systems and economies worldwide; however, the relative contributions of the various possible sources of infection in humans are unclear.National-scale genotyping of Campylobacter species was used to quantify the relative importance of various possible sources of human infection. Multilocus sequence types were determined for 5674 isolates obtained from cases of human campylobacteriosis in Scotland from July 2005 through September 2006 and from 999 Campylobacter species isolates from 3417 contemporaneous samples from potential human infection sources. These data were supplemented with 2420 sequence types from other studies, representing isolates from a variety of sources. The clinical isolates were attributed to possible sources on the basis of their sequence types with use of 2 population genetic models, STRUCTURE and an asymmetric island model.The STRUCTURE and the asymmetric island models attributed most clinical isolates to chicken meat (58% and 78% of Campylobacter jejuni and 40% and 56% of Campylobacter coli isolates, respectively), identifying it as the principal source of Campylobacter infection in humans. Both models attributed the majority of the remaining isolates to ruminant sources, with relatively few isolates attributed to wild bird, environment, swine, and turkey sources.National-scale genotyping was a practical and efficient methodology for the quantification of the contributions of different sources to human Campylobacter infection. Combined with the knowledge that retail chicken is routinely contaminated with Campylobacter, these results are consistent with the view that the largest reductions in human campylobacteriosis in industrialized countries will come from interventions that focus on the poultry industry.
The zoonotic association between Campylobacter bacteria in poultry and humans has been characterized by decades of research which has attempted to elucidate the epidemiology of this complex relationship and to reduce carriage within poultry. While much work has focused on the mechanisms facilitating its success in contaminating chicken flocks (and other animal hosts), it remains difficult to consistently exclude Campylobacter under field conditions. Within the United Kingdom poultry industry, various bird genotypes with widely varying growth rates are available to meet market needs and consumer preferences. However, little is known about whether any differences in Campylobacter carriage exist across this modern broiler range. The aim of this study was to establish if a relationship exists between growth rate or breed and cecal Campylobacter concentration after natural commercial flock Campylobacter challenge. In one investigation, four pure line genotypes of various growth rates were grown together, while in the second, eight different commercial broiler genotypes were grown individually. In both studies, the Campylobacter concentration was measured in the ceca at 42 days of age, revealing no significant difference in cecal load between birds of different genotypes both in mixed- and single-genotype pens. This is important from a public health perspective and suggests that other underlying reasons beyond genotype are likely to control and affect Campylobacter colonization within chickens. Further studies to gain a better understanding of colonization dynamics and subsequent proliferation are needed, as are novel approaches to reduce the burden in poultry.
Between 2001 and 2006, the incidence of human Campylobacter infections decreased by 10 and 27% in Scotland and the Grampian region of Scotland, respectively. Contemporaneous collection and analyses of human and retail-chicken isolates from Grampian were carried out over a 10-week period in 2001 and again in 2006 in order to determine whether the fall in the incidence of human infections was related to the retail-chicken exposure route. Rates of carriage of Campylobacter on chicken carcasses from retail outlets in Grampian in 2001 and 2006 were estimated. Chicken-derived Campylobacter isolates from 2001 (n = 84) and 2006 (n = 105) and human-derived isolates from patients with clinical cases of infection in 2001 (n = 172) and 2006 (n = 119) were typed by multilocus sequence typing. We found no evidence for statistically significant changes in prevalence and counts per carcass. We found by rarefaction that although the degree of diversity in humans tended to be higher than that in chickens, these differences were not significant. The genetic distance between chicken and human isolates from 2001 according to sequence type, clonal complex (CC), or allele composition was not significant, whereas the distances between 2006 isolates at the CC and allele levels were significant. This difference was attributable to a lower proportion of CC-21's being found in retail-chicken isolates from 2006 than in chicken isolates from 2001. We conclude that human exposure to Campylobacter via retail chicken is important and that changes in the population structure of campylobacters in this reservoir need to be taken into account in investigating human infection.
We show that a higher incidence of campylobacteriosis is found in young children (age, <5 years) living in rural, compared with urban, areas. Association of this difference with particular animal sources was evaluated using multilocus sequence typing. This evaluation was achieved by comparing Campylobacter isolates originating from these children, retail poultry, and a range of animal sources by use of source attribution and phylogenetic analysis methods. The results indicate that chicken is a major source of infection in young urban children, although not in their rural counterparts, for which ruminant and other avian sources are more important.
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