Foot and Mouth Disease

Question 1

Economic, social and environmental impacts of FMD.

Answer 1

Severe productivity losses.
Disruptions in a wide range of agricultural, industrial and social activities.
Major threat to food supply/food security.
Threat to worldwide trade.

Question 2

1. What type of virus is FMD caused by?
2. Serotypes?
3. Cross immunity?
4. What subtype was the 2001 outbreak caused by?
5. 2 dangerous factors of strain?

Answer 2

1. A picorna virus. Most infectious agent known.
2. 7 incl. A, O, C, Asia1, SAT1-3.
3. No.
4. Sub-type O Pan-Asiatic strain.
5. Highly contagious and able to survive outside hosts.

Question 3

1. Temperature and length of survival?
2. pH of inactivation?
3. Resistance to disinfectants?
4. How long can it persist in contaminated fodder?
5. Length of survival in slurry?
6. Length of survival in dries faeces?
7. How is the virus killed?

Answer 3

1. 4C, for months, progressively inactivated at temperatures above 50C.
2. <6.0 or >9.0 – destroyed in muscle when pH <6.0 i.e. after rigor mortis, but will survive in LNs and bone marrow at neutral pH.
3. Resistant to iodophores, quaternary ammonium compounds, hypochlorite and phenols, esp. in presence of organic matter.
4. Up to ~a month (3d summer, 30d winter).
5. 6 months.
6. 2 weeks.
7. Killed by UV light and desiccation.

Question 4

Transmission.

Answer 4

• Direct or indirect contact – droplets.
• Animate vectors – humans etc., (birds), poss. hedgehogs, rats and other small animals.
• Inanimate vectors – vehicles, implements.
• Airborne, esp. in temperate zones – claimed to be 60km over land and 300km over sea.

Question 5

Sources of the virus.

Answer 5

• Clinically affected animals in breath, saliva, faeces, urine, milk, semen.
• Incubating animals (can be up to 4 days before clinical signs).
• Meat and meat by-products in which pH has remained above 6.0.
• Carriers: plenty of evidence for carrier status but dubious evidence as to transmission.

Question 6

What is the infectious dose of FMD virus for cattle?

Answer 6

Aerosol infective dose = ~10 tissue culture infectious units.
There are 10,000,000 tissue culture infectious doses/ml in vesicle fluid.

Question 7

1. Incubation period?
2. Clinical presentation in cattle?
3. Recovery?

Answer 7

1. 3-8 days.
2. Early signs of pyrexia (40C-41C), anorexia, depression, reduced milk yield.
   Shivering, lameness, salivation.
   Vesicles on buccal MMs and/or between claws and coronary band.
   Vesicles rupture quickly leaving erosions which become secondarily infected.
3. Recovery within 8-15days but rapid loss of condition.

Question 8

Clinical complications of FMD virus in cattle.

Answer 8

• Super-infection in lesions.
• Mastitis and permanent impairment of milk production.
• Abortion.
• Permanent weight loss.
• Loss of efficient thermoregulation.
• Myocarditis esp. in young stock.

Question 9

Clinical presentation of FMD in sheep.

Answer 9

Become lame, often lie down.
Foot lesions may go unrecognised due to sheep being prone to lameness anyway.
Lesions in dental pad.
Myocarditis fatal in many lambs.
Major problem with differential diagnosis, esp. w/ Orf.

Question 10

Clinical presentation of FMD in pigs.

Answer 10

Foot lesions often first sign.
Lameness may be severe or painful.
Often high mortalities.
Pigs produce a lot of virus!

Question 11

FMD diagnosis.

Answer 11

Clinical signs.
Vesicular epithelial sample.
- Virus isolation – culture.
- Serotype specific Ag-capture ELISA.
- NA detection: serotype-specific RT-PCR.
- Genotyping.
Blood sample.
- Serotype specific liquid-phase blocking-ELISA.
- Virus neutralisation assay.
World Reference Laboratory, Pirbright, UK.

Question 12

1. What is the biggest factor that may reintroduce FMD in future?
2. What has been banned in order to stop FMD reintroduction?

Answer 12

1. Illegal imports of meat and meat products.
2. Swill feeding pigs.

Question 13

1. How many illegal international consignments of meat are intercepted in the UK every month?
2. What weight of this in hand luggage annually?
3. How many tonnes in containers annually?

Answer 13

2. 730t.
3. 67t.

Question 14

1. How many animals were slaughtered as infected, suspicious, dangerous contacts or as a contiguous cull?
2. How many slaughtered on welfare grounds?
3. Number of premises that had all livestock slaughtered?
4. When was the last case of FMD seen?

Answer 14

1. 4,124,000 – (600,000 cattle, 3,187,000 sheep, 147,000 pigs).
2. 2,048,769.
3. 10,178.
4. 30th September 2001.

Question 15

Disease control policy.

Answer 15

• Slaughter of infected animals, animals in direct contact, animals perceived to be dangerous contacts and normal animals within exclusion zones surrounding an outbreak.
• Cull animals on infected farms within 24h.
• Cull animals on contiguous premises within 48h.
• Removal of dangerous contact animals.
• Movement restrictions – whole of GB became Controlled Area under 1983-Foot and Mouth Disease Order, prohibiting all movements of livestock except under license.

Question 16

Sequence if events under a “stamping out” policy for FMD on the infected place (IP).

Answer 16

• Notification.
• Quarantine.
• Diagnosis.
• Movement control.
• Appraisal.
• Slaughter/disposal.
• Disinfection.
• Restocking.

Question 17

1. What is the estimated number of sheep moved after the disease entered the country and before the movement ban on 23 Feb?
2. How many livestock markets exist today?
3. How many licensed abattoirs are there today in the UK?

Answer 17

1. 2 million.
2. <170.
3. <450.

Question 18

How was sero-surveillance carried out afterwards?

Answer 18

1. Big sheep bleeding program.
   – look for antibodies.
   – prove virus gone.

Question 19

1. How were animals disposed of?
2. Biosecurity?

Answer 19

1. burnt.
2. Decontamination of people and infected areas.
   – need to use Virkon etc.

Question 20

1. What was the purpose of serological testing after the FMD outbreak?
2. 2 tests most widely used in FMD?
3. Antibody response to FMD?

Answer 20

1. To prove there was no infection left.
2. Serotype specific virus neutralisation (VN) and ELISA. – ELISA titre >1:40 considered positive.
3. Response detected abput 7-10 days after initial infection and will last for up to 12 months.

Question 21

Is contiguous culling necessary?

Answer 21

yes.
80% of IPs in hotspots were within 3km of previous IP and 30-40% of all IPs are within 1.5km of a previous case.
Need expert and LOCAL risk assessment.

Question 22

How important id speed of culling and carcass disposal?

Answer 22

Essential to cull clinically affected animals immediately!
Direct contacts w/in 24h.
Proven dangerous contacts ASAP.
Disposal of disinfectant treated carcass important but not if interferes w/ logistical support.

Question 23

Why not vaccinate?

Answer 23

• Control of FMD in endemic countries relies on mass use of multivalent inactivated vaccines.
• Major costs of FMD in endemic countries are reduced productivity, regular vaccination and reduced access to global markets.

Question 24

Arguments for vac?

Answer 24

• Strategy of slaughter = barbaric.
• FMD was eliminated from mainland Europe by 1989 w/ the help of vac.
• FMD free status is a high risk with globalisation of trade.
• Europe holds 30 million doses of vac “for an emergency”, what constitutes an emergency?
• Could use for ring fencing an outbreak.
• Could use for genetically valuable stock.
• Works w/ other diseases such as smallpox and polio.

Question 25

Arguments against vac.

Answer 25

Can still get carrier status after infection.
Will need multivalent vacs.
Need 6 monthly vacs.
2 shots necessary.
Vaccinated still susceptible.
Vaccinated may carry virus.
Who will vaccinate in a logistical crisis.
High mutation rate of FMD virus.
Cannot export stock or meat products.
Pariah in Europe?!!

Question 26

Welfare issues of FMD?

Answer 26

Were the means and mechanisms of euth. appropriate?
What was the effect of the movement ban on animal welfare?
How could we have utilised vaccinated stock?
Welfare considerations in the human population.

Question 27

Why was 2001 epidemic so extensive?

Answer 27

Delayed notification.
Difficult detection in sheep.
Peak time of year for marketing of sheep and high frequency of sheep movements.
Marketing of infected sheep before FMD recognised in country.
Large sheep population in UK.
Cool weather.
Inadequate vet force.