Identifying the seasonal origins of human campylobacteriosis.

Human campylobacteriosis exhibits a distinctive seasonality in temperate regions. This paper aims to identify the origins of this seasonality. Clinical isolates [typed by multi-locus sequence typing (MLST)] and epidemiological data were collected from Scotland. Young rural children were found to have an increased burden of disease in the late spring due to strains of non-chicken origin (e.g. ruminant and wild bird strains from environmental sources). In contrast the adult population had an extended summer peak associated with chicken strains. Travel abroad and UK mainland travel were associated with up to 17% and 18% of cases, respectively. International strains were associated with chicken, had a higher diversity than indigenous strains and a different spectrum of MLST types representative of these countries. Integrating empirical epidemiology and molecular subtyping can successfully elucidate the seasonal components of human campylobacteriosis. The findings will enable public health officials to focus strategies to reduce the disease burden.

Combining risk assessment and epidemiological risk factors to elucidate the sources of human E. coli O157 infection.

E. coli O157 can be transmitted to humans by three primary (foodborne, environmental, waterborne) and one secondary (person-to-person transmission) pathways. A regression model and quantitative microbiological risk assessments (QMRAs) were applied to determine the relative importance of the primary transmission pathways in NE Scotland. Both approaches indicated that waterborne infection was the least important but it was unclear whether food or the environment was the main source of infection. The QMRAs over-predicted the number of cases by a factor of 30 and this could be because all E. coli O157 strains may not be equally infective and/or the level of infectivity in the dose-response model was too high. The efficacy of potential risk mitigation strategies to reduce human exposure to E. coli O157 using QMRAs was simulated. Risk mitigation strategies focusing on food and environment are likely to have the biggest impact on infection figures.

Source attribution, prevalence and enumeration of Campylobacter spp. from retail liver.

Campylobacter prevalence from retail liver (chicken, cattle, pig and sheep) was found to be 81%, 69%, 79% and 78% respectively. Molecular source attribution demonstrated that strains from chicken liver were most similar to those found commonly in humans. This provides further evidence of liver being a probable source of human infection.

The relationship between lay and technical views of Escherichia coli O157 risk.

Here, we bring together and contrast lay (accessible primarily through social science methodologies) and technical (via risk assessment and epidemiological techniques) views of the risk associated with the Escherichia coli O157 pathogen using two case study areas in the Grampian region of Scotland, and North Wales. Epidemiological risk factors of contact with farm animals, visiting farms or farm fields and having a private water supply were associated with postcode districts of higher than average disease incidence in the human population. However, this was not the case for the epidemiological risk factor of consumption of beef burgers, which was independent of disease incidence in the postcode district of residence. The proportion of the population expressing a high knowledge of E. coli O157 was greatest in high-incidence disease districts compared with low-incidence areas (17% cf. 7%). This supports the hypothesis that in high-disease-incidence areas, residents are regularly exposed to information about the disease through local cases, the media, local social networks, etc. or perhaps that individuals are more likely to be motivated to find out about it. However, no statistically significant difference was found between high- and low-incidence postcode districts in terms of the proportion of the population expressing a high likelihood of personal risk of infection (10% cf. 14%), giving a counterintuitive difference between the technical (epidemiological and quantitative microbiological risk assessment (QMRA)) and the lay assessment of E. coli O157 risk. This suggests that lay evaluations of E. coli O157 risk reflect intuitive and experience-based estimates of the risk rather than probabilistic estimates. A generally strong correspondence was found in terms of the rank order given to potential infection pathways, with environment and foodborne infection routes dominating when comparing public understanding with technical modelling results. Two general conclusions follow from the work. First, that integrative research incorporating both lay and technical views of risk is required in order that informed decisions can be made to handle or treat the risk by the groups concerned (e.g. the public, policy makers/risk managers, etc.). Second, when communicating risk, for example, through education programmes, it is important that this process is two-way with risk managers (e.g. including Food Standards Agency officials and communications team, public health infection control and environmental health officers) both sharing information with the public and stakeholder groups, as well as incorporating public knowledge, values and context (e.g. geographical location) into risk-management decisions.

Putative household outbreaks of campylobacteriosis typically comprise single MLST genotypes.

During a 15-month period in Scotland a small but important number of human Campylobacter cases (3·2%) arose from 91 putative household outbreaks. Of the 26 outbreaks with known strain composition, 89% were composed of the same MLST which supports the potential use of MLST in public health epidemiology. The number of cases associated with household outbreaks is much larger than general outbreaks and there is some evidence to indicate that there may be secondary transmission, although this is relatively rare.

A stochastic model simulating the capture of pathogenic micro-organisms by superparamagnetic particles in an isodynamic magnetic field.

The method of immunomagnetic separation (IMS) has become an established technique to concentrate and separate animal cells, biologically active compounds and pathogenic micro-organisms from clinical, food and environmental matrices. One drawback of this technique is that the analysis is only possible for small sample volumes. We have developed a stochastic model that involves numerical simulations to optimize the process of concentration of pathogenic micro-organisms onto superparamagnetic carrier particles (SCPs) in a gradient magnetic field. Within the range of the system parameters varied in the simulations, optimal conditions favour larger particles with higher magnetite concentrations. The dependence on magnetic field intensity and gradient together with concentration of particles and micro-organisms was found to be less important for larger SCPs but these parameters can influence the values of the collision time for small particles. These results will be useful in aiding the design of apparatus for immunomagnetic separation from large volume samples.

Magnetizable needles and wires--modeling an efficient way to target magnetic microspheres in vivo.

The in vivo targeting of tumors with magnetic microspheres is currently realized through the application of external non-uniform magnetic fields generated by rare-earth permanent magnets or electromagnets. Our theoretical work suggests a feasible procedure for local delivery of magnetic nano- and microparticles to a target area. In particular, thin magnetizable wires placed throughout or close to the target area and magnetized by a perpendicular external uniform background magnetic field are used to concentrate magnetic microspheres injected into the target organ's natural blood supply. The capture of the magnetic particles and the building of deposits thereof in the blood vessels of the target area were modeled under circumstances similar to the in vivo situation. This technique could be applied to magnetically targeted cancer therapy or magnetic embolization therapy with magnetic particles that contain anticancer agents, such as chemotherapeutic drugs or therapeutic radioisotopes.