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Modelling Initiatives for Campylobacter

Modelling Initiatives for Campylobacter. Graham McBride, Sandy Elliott (NIWA) Peter van der Logt, Lisa Oakley (NZFSA) Rob Lake, Andrew Ball (ESR) Nigel French, Petra Mullner (Massey University) Amanda Hunt (MfE). NZIFST, Wellington, 20 June 2007. Motivation.

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Modelling Initiatives for Campylobacter

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  1. Modelling Initiatives for Campylobacter Graham McBride, Sandy Elliott (NIWA) Peter van der Logt, Lisa Oakley (NZFSA) Rob Lake, Andrew Ball (ESR) Nigel French, Petra Mullner (Massey University) Amanda Hunt (MfE) NZIFST, Wellington, 20 June 2007

  2. Motivation • NZ’s high reported rate of campylobacteriosis (cost ~ $70m p.a.) • Focus to date has been on human exposure, less on sources and transmission (but there is some) • Campylobacter is a zoonotic pathogen; animals are the main “reservoir” • Time to marry environmental models with food and health models, in a quantitative risk framework • Try to identify effective mitigation measures • NZFSA/MfE (supported by MoH) gained CDRP funding for modelling

  3. Campylobacter Ecology: Reservoirs, Amplifiers and Transmission Routes carcass preparation [slaughter house] X - contamin food processing [food industry] Veg/Fruit/Cereal food distribution animal contact [retail] Agriculture & Animal Conservation food preparation [home/cater/service] [Primary Producer] consumption consumption Human drinking - water excreta excreta excreta food recreation drinking sewage treatment sewage treatment aquatic environments aquatic environments drinking drinking - - water water Reservoirs & Amplifiers Environmental treatment treatment Health Transmission Routes Direction of Transmission drinking - water Conceptual model Food safety Animal ‘systems’

  4. Recreational swimming Drinking water Occupational Exposure Food Preparation & Consumption Swim today? Contaminated? Live stock exposure? Contaminated? Amount cross - contamination to preparation Volume water Amount Exposure day? Volume water surfaces ingested prepared ingested Amount Campylobacter Campylobacter Farm Campylobacter transferred t o concentration concentration contaminated? concentration other foods Cooking Amount of Amount of Amount of Amount of Amount of Campylobacter Campylobacter Campylobacter Campylobacter Campylobacter ingested ingested ingested ingested ingested Campylobacter concentration DOSE Dose Response Curve Binomial sampling for Probability of Infection infection cases Infected? (yes or no) Preliminary relative risk model (1)

  5. Preliminary relative risk model (2)

  6. Preliminary landscape mitigation model

  7. Three-Year Research Plan Three components# • Improve existing human exposure models* • Extend existing ecological/environmental models* • Establish the links between the models # www.zoonosesresearch.org.nz/research-priorities/three-year-research-plan-10_8.pdf * www.zoonosesresearch.org.nz/reports/PreliRelativeriskAssessment.pdf

  8. (1) Improve existing human exposure models • Refine occupational contact • Incorporate data on red meat, pets, overseas travel • Incorporate Campylobacter strain typing data • Build in between-group differential immunity • Better identification of exposures via food handling channels

  9. (2) Extend existing ecological & environmental models • Include sheep and poultry farms (cf. dairy only) • Account for animal litter disposal • Incorporate more detailed catchment dynamics • Incorporate disturbance effects (e.g., floods) • Include pathogen carriage and transmission between animals • Incorporate data on sewage and biosolids disposal

  10. (3) Establish the links between the models • Develop generic framework • Progressively update framework details • Liaise with risk managers • mitigation options and deliverables • Model effects of mitigation options • Detailed risk modelling

  11. Strategy • Governance/oversight group to be set up • Use a variety of modelling techniques: • Monte Carlo, Bayesian, mechanistic, statistical, analytical solutions (linear models) • Team meets 3-4 times per year • Ongoing liaison with risk managers • Status paper in prep. for NZ Science Review • Many parallel tasks

  12. Benefits of modelling • Draws on a wide range of published results, and unpublished & in-progress work • Opportunity to be innovative • Maximum use of accumulating typing data • Integrative—linking environment & health models • International importance • Framework will be applicable to other zoonotic pathogens transmitted via multiple food and environmental pathways

  13. Conclusions • Challenging task • Integrative approach offers best prospect of success, especially when married to faecal source-tracking techniques • Some mitigation measures may not be obvious (e.g., animal inoculation?)

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