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Tarikh Kemaskini : 10/04/2014

PENYAKIT  KUKU  &  MULUT

(Foot and Mouth Disease)

 Aetiology   Epidemiology   Diagnosis   Prevention and Control   References 

 

AETIOLOGY

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


 

EPIDEMIOLOGY

  • 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


 

DIAGNOSIS

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.


 

PREVENTION AND CONTROL

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

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