Field outbreak investigation methodology

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Field outbreak investigation methodology

• Nick Honhold

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• It sounds easy, and with practice it is
• It is important to collect standard core set of
  data from all outbreaks
• Always use a questionnaire to make sure that the
  important questions are always asked and
  answered.
• Leave room in the questionnaire for non-standard
  but potentially important data and information
• Get to know the questionnaire well so that you
  can ask the questions without keeping your face
  buried in your clipboard

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• Remember you are in an infected site
• FOLLOW BIOSECURITY RIGIDLY
• Do not be responsible for taking the virus to an
  uninfected place
• Leave your vehicle outside the farm or village
• Wear protective clothing and disposable or
  washable boots
• Explain that you are doing this to stop you
  moving the virus, not necessarily to protect
  yourself
• Remember the types of movements between villages
• Dirty to dirty ?
• Clean to dirty ?
• Dirty to clean X

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KEEP CALM

• Yes, its an emergency, but its already happened
• Drive there at a normal pace
• Stay hydrated
• Try and present a calm appearance
• Talk calmly and quietly
• Dont make a problem into a crisis

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KEEP AN OPEN MIND Avoid deciding beforehand what
you think the answer is Remember these
points Viruses dont think, so out-guessing them
is not possible Common things occur
commonly Surprises happen People dont like to
admit to mistakes
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• LISTEN
• If you are doing most of the talking, something
  is wrong with your technique
• Let everyone say what they want
• Pay equal attention to what everyone says
• Absentee owners often say more but have less day
  to day contact with the animals
• Children are keen observers

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• DO NOT CONTRADICT.
• Dont try and tell someone what happened to their
  animals
• Even if you are right, they are unlikely to
  accept it
• If you dont believe something, dont get into an
  argument
• Return later to areas you are not sure about.
• Ask the question in a different way two or three
  times
• Hide behind mental confusion (real enough in my
  case)

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The questions are we trying to answer

• Is the disease present?
• Detailed description of the disease and how long
  it is likely to have been present.
• Detailed description of the affected unit and
  which animals are diseased and which are not
• Where might the disease have come from and by
  what means? (source tracing)
• Where might the disease have spread to and by
  what means? (spread tracing)
• Details of any other affected units (commercial
  farms, villages etc.) in the same area

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• Date of first lesions
• Key parameter
• It is important to establish potential sources
  and spread
• This is often somewhat earlier than initially
  reported
• Be prepared to revise this during the
  investigation
• Look very hard for the oldest lesions. There is
  often a small group of animals (perhaps only one)
  with older lesions
• Examine animals from each epidemiological group
  on the farm

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• Define the epidemiological unit
• Should include all susceptible stock at a similar
  level of risk of exposure
• Usually all the susceptible stock under one
  management system / biosecurity compartment
• Farm if there are boundaries
• Village usually treated as one unit if no
  boundaries
• Not hard and fast, needs judgement
• Always err on the cautious side
• Remember to ask about associated farms/land
  parcels
• Pig farms may be part of a pyramid

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• Define the epidemiological groups
• Within an epidemiological unit there are often
  several epidemiological groups
• Groups of animals grazed together at the time of
  the outbreak
• Different species / ages / purposes / locations
• Dairy vs beef herd
• Heifers vs cows
• Rams
• Weaned lambs
• Dry sows / farrowing shed / weaners

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• Find out the different groups of animals managed
  by a farm or village
• Remember that farms may be made up of several
  separate locations
• If it is claimed that two locations are managed
  separately, look for very strong evidence of this
• ANY link between locations makes them one unit
• Inspect/examine animals in all epidemiological
  groups

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Inspection vs examination

• Inspection means looking at animals for outward
  signs of clinical disease
• Examination means clinically examining animals
• i.e. actually catching and handling them to
  check
• temperature, look for lesions, take
  sample etc
• For cattle, clinical inspection may be adequate.
• For sheep, it is never adequate and leads to
  terms such as sub-clinical or inapparent
  disease

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Clinical examination fro epidemiology

• If possible, this should be done by the
  epidemiologist
• Means must try and be present at time of culling
• The vet responsible for the IP has too many other
  things to do to give this the time it needs
• Epidemiologist likely to have most experience at
  finding and ageing lesions
• Epidemiologist likely to be best placed to spot
  false positives
• Check ALL epidemiological groups
• Check as many animals as you can
• It is dirty, difficult, physically tiring and
  mentally draining job

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• Look for oldest lesion in each group
• Look for prevalence of lesions in each group
• For each epidemiological group you should know
• Where they have been housed and grazed in the
  possible exposure window
• What risk factors have they been exposed to
• Neighbouring stock
• Visits by farmer
• Milk tankers
• Contractors
• etc

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• When you have this information, speak to the
  farmer(s)
• Do not plan on visiting more than three farms in
  one day and preferably only two
• Farmers are often (and often rightly) wary of
  outsiders particularly government officials
• It is vital to establish trust
• Wear informal clothes
• Be patient

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• Try to arrive quietly
• Work in small teams, maximum of two, but
  preferably one. This is non-threatening
• Respect local traditions
• Explain what you are there to do and give your
  name
• Stress that you are not there to blame anyone but
  to gather information to help prevent outbreaks
  in other farms or villages
• Be sensitive. The farmer has just lost a very
  important asset and an important part of his or
  her life

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• Explain what you have found and what you think it
  tells you
• Be prepared to show people what you have written
  down
• Ask if the villagers have any questions to ask
  about FMD
• In villages, look at other sick non-susceptible
  animals if you can. It builds trust and
  co-operation
• Remember that people talk to each other
• What you do today in one farm or village will be
  talked about and relayed to other farms and
  villages where you, or others in your team, may
  need to go in the future

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Outbreak investigation forms

• Detailed information
• Short form..
• How to achieve the two?
• Easy to complete
• Not too formal looking if filled in directly
  during interview

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