Modelling Initiatives for Campylobacter

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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
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Motivation

• NZs 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

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Conceptual model
Food safety
Animal systems
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Preliminary relative risk model (1)
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Preliminary relative risk model (2)
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Preliminary landscape mitigation model
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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/PreliRelativ
  eriskAssessment.pdf

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(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

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(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

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(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

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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

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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
• Integrativelinking environment health models
• International importance
• Framework will be applicable to other zoonotic
  pathogens transmitted via multiple food and
  environmental pathways

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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?)