Foot and Mouth Disease
Aetiology
Epidemiology
Diagnosis
Prevention and Control
References
Classification of the causative agent
A virus of the family Picornaviridae, genus
Aphthovirus.
Seven immunologically distinct serotypes: A, O, C, SAT1,
SAT2, SAT3, Asia1
Resistance to physical and chemical action
| Temperature: |
Preserved by refrigeration and freezing and progressively inactivated
by temperatures above 50°C
|
| pH: |
Inactivated by pH <6.0 or >9.0
|
| Disinfectants: |
Inactivated by sodium hydroxide (2%), sodium carbonate (4%), and
citric acid (0.2%). Resistant to iodophores, quaternary ammonium
compounds, hypoclorite and phenol, especially in the presence of organic
matter
|
| Survival: |
Survives in lymph nodes and bone marrow at neutral pH, but destroyed
in muscle when is pH <6.0 i.e. after rigor mortis. Can persist
in contaminated fodder and the environment for up to 1 month,
depending on the temperature and pH conditions |
- One of the most contagious animal diseases, with important economic losses
- Low mortality rate in adult animals, but often high mortality in young due
to myocarditis
Hosts
- Bovidae (cattle, zebus, domestic buffaloes, yaks), sheep, goats, swine,
all wild ruminants and suidae. Camelidae (camels, dromedaries, llamas,
vicunas) have low susceptibility
Transmission
- Direct or indirect contact (droplets)
- Animate vectors (humans, etc.)
- Inanimate vectors (vehicles, implements)
- Airborne, especially temperate zones (up to 60 km overland and 300 km by
sea)
Sources of virus
- Incubating and clinically affected animals
- Breath, saliva, faeces, and urine; milk and semen (up to 4 days before
clinical signs)
- Meat and by-products in which pH has remained above 6.0
- Carriers: particularly cattle and water buffalo; convalescent animals and
exposed vaccinates (virus persists in the oropharynx for up to 30 months in
cattle or longer in buffalo, 9 months in sheep). African Cape buffalo are the
major maintenance host of SAT serotypes
Occurrence
FMD is endemic in parts of Asia, Africa, the Middle East and
South America (sporadic outbreaks in free areas)
For detailed information on
occurrence, see recent issues of World Animal Health and the OIE
Bulletin
Incubation period is 2-14 days
Clinical diagnosis
Cattle
- Pyrexia, anorexia, shivering, reduction in milk production for 2-3 days,
then
- smacking of the lips, grinding of the teeth, drooling, lameness,
stamping or kicking of the feet: caused by vesicles (aphthae) on buccal and
nasal mucous membranes and/or between the claws and coronary band
- after 24 hours: rupture of vesicles leaving erosions
- vesicles can also occur on the mammary glands
- Recovery generally occurs within 8-15 days
- Complications: tongue erosions, superinfection of lesions, hoof
deformation, mastitis and permanent impairment of milk production,
myocarditis, abortion, death of young animals, permanent loss of weight, loss
of heat control ('panters')
Sheep and goats
- Lesions are less pronounced. Foot lesions may go unrecognised. Lesions in
dental pad of sheep. Agalactia in milking sheep and goats is a feature. Death
of young stock
Pigs
- May develop severe foot lesions particularly when housed on concrete. High
mortality in piglets a frequent occurrence
Lesions
- Vesicles or blisters on the tongue, dental pad, gums, cheek, hard and soft
palate, lips, nostrils, muzzle, coronary bands, teats, udder, snout of pigs,
corium of dewclaws and interdigital spaces
- Post-mortem lesions on rumen pillars, in the myocardium, particularly of
young animals (tiger heart)
Differential diagnosis
Clinically indistinguishable:
- Vesicular stomatitis
- Swine vesicular disease
- Vesicular exanthema of swine
Other differential diagnosis:
- Rinderpest
- Mucosal disease
- Infectious bovine rhinotracheitis
- Bluetongue
- Bovine mammillitis
- Bovine papular stomatitis
- Bovine viral diarrhoea
Laboratory diagnosis
Procedures
| Identification of the agent |
- ELISA
- Complement fixation test
- Virus isolation: inoculation of primary bovine thyroid cells and
primary pig, calf and lamb kidney cells; inoculation of BHK-21 and
IB-RS-2 cell lines; inoculation of mice
|
Serological tests |
- ELISA
- Virus neutralisation test
|
(prescribed tests in the
Manual) | |
Samples
- 1 g of tissue from an unruptured or recently ruptured vesicle. Epithelial
samples should be placed in a transport medium which maintains a pH of 7.2-7.4
and kept cool (see Manual)
- Oesophageal-pharyngeal fluid collected by means of a probang cup Probang
samples should be frozen to below -40°C immediately after collection
| NB!! |
Special precautions are required when sending perishable suspect
FMD material within and between countries. See Manual,
Chapter 1.4. | |
Sanitary prophylaxis
- Protection of free zones by border animal movement control and
surveillance
- Slaughter of infected, recovered, and FMD-susceptible contact animals
- Disinfection of premises and all infected material (implements, cars,
clothes, etc.)
- Destruction of cadavers, litter, and susceptible animal products in the
infected area
- Quarantine measures (Code Chapter 2.1.1.)
Medical prophylaxis
Inactivated virus vaccine containing an adjuvant.
Immunity:
6 months after two initial vaccinations, 1-month apart, depending on the
antigenic relationship between vaccine and outbreak strains
| REFERENCES AND OTHER
INFORMATION |
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Updated:
30/08/2000
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