Foot and Mouth Disease Virus

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Foot and Mouth Disease Virus
Farmer kept quiet about disease
February 2001 A Northumberland farmer is found
guilty of animal cruelty and failing to tell
officials of a foot-and-mouth outbreak among
his pigs.
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Cloven-hoofed Animals The Niche of FMD
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FMD or Fast Moving Disease
Devastating to cloven-hoofed animals pigs,
sheep, cattle Economically devastating to
agriculture, travel, and tourism Social and
personal impact
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FMD in GB Case Map
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The Pathogenic Pathway of FMD
In the Animal

• Entry of virus at the Oral / Nasal cavity
• Infection of epithelial cells
• Local lesions, blisters, loss of surfaces
• Transport via blood, viremia ? Fever
• Coronary band, interdigit regions of hooves
• Spread through the body (i.e., meat)
• Infection of the intestinal epithelium

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The Pathogenic Pathway of FMD
The Virus

• A small icosahedral ssRNA virus
• Stable environmentally
• (months to years)

Picornaviridae family
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Virus Lesions on Animals
Result Cannot eat, cannot walk
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The Pathogenic pathway of FMD
And spread of the virus

• from saliva, oral/nasal secretions
• ? other animals
• ? environment ? airborne droplets?
• from the intestine, feces
• ? other animals
• ? environment ? airborne dust?
• from transport and slaughter
• ? other animals ? other countries
• ? environment
• from meat ? wide distribution ? other countries

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The Outbreak in GB A repeat Performance
Fast moving
How is it controlled? Or, is it?
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Spread to Europe(from GB, 2001 ?)

• Cases Slaughtered
• GB 2K 3.7 million (3 mil sheep)
• Ireland 5K
• Belgium 8K
• Netherlands 27K
• France 2 50K

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Prior World Wide Spread 1990 - 2001
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6
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3
1
4
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Control Measures

• Stop Spread and Enable containment
• Animals
• stop movement
• slaughter
• ring slaughter
• sanitary disposal
• Disinfection
• of farm premises
• contaminated items
• Vaccinate?

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Why control efforts failedLessons for the rest
of the World

• Costly delay
• Foot-and-mouth spreads rapidly among pigs, and
  once the disease enters a herd it can cause
  havoc. A mistake was not to place an instant ban
  on the movement of farm animals
• Spreading the infection
• Sheep are often sold informally, without
  entering a market, shuttling sheep the length and
  breadth of Britain, carrying the virus

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Lessons
Manpower needed In the handling of the 1967
outbreak, a report argued for the army to be
brought in early. The government, continued to
believe that it could save the day unaided More
than just Slaughter The government was convinced
it could overcome the outbreak by slaughtering
both infected and potentially infected animals.
But it failed to convince. Animals waited too
long to die, and carcasses waited too long for
burial
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Lessons

• Remedy ignored - Vaccination?
• Foot-and-mouth disease does not often kill
• Vaccinating them can give some protection, even
  though it has to be repeated every six months
• Vaccinating animals in a ring round a source of
  infection might have helped to slow its spread

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Lessons

• Remedy ignored - Vaccination?
• But problems with vaccination
• Which serotype to use (of 7)
• Variation of the virus
• Short term immunity
• All animals vaccinated become sero-positive

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• How to study the effects of control measures on
  an epidemic
• Create a Mathematical Model

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• Creating a Mathematical Model the raw data

Figure 1
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• Creating a Mathematical Model the raw data
• Probability of spread versus distance, pre- and
  post- Stop Movement Order

Figure 2
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• Creating a Mathematical Model the raw data

• The FMD Model took into account such variables
  as
• Number of farms and density of animals
• Distance between farms
• Reporting time
• Probabilities of spread
• Control measures
• And many more estimations
• . In a manner that changing the value of a
  variable would allow plotting the likely change
  in the epidemic curve

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• Creating a Mathematical Model the raw data

The model versus the data obtained from the
outbreak
Figure 3
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• Manipulating the Mathematical Model what if..

Figure 4
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• Manipulating the Mathematical Model what if..

If culling was increased from 55 to 78 If
mean time to slaughter were reduced to 12
hours with 30 culled
Figure 4
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• Manipulating the Mathematical Model what if..

Predicted effect of ring vaccinating, increasing
percent vaccinated
Predicted effect of ring culling, different
ring diameters
Figure 4
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• Manipulating the Mathematical Model what if..

Predicted effect of ring culling, and shorter
time to slaughter
Figure 4
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FMD as a BioWeapon

• Deliberate introduction Animal Agriculture
• Rapid spread
• Delay to recognition of agent
• Delay to action, resistance to mass slaughter
• Economic loss
• Public panic