FOOT AND MOUTH DISEASE

Etiology

  • This disease is caused by Picorna virus.
  • The strains of this virus are ‘O’, ‘A’, ‘SAT-1’, ‘SAT-2’, ‘SAT-3’, ‘Asia-1’ and ‘C’.

Mode of Transmission

  • Direct contact
  • Ingestion
  • Air borne spread (nocturnal spread as humidity is high during the night time)
  • Spread is more during the cooler seasons.
  • Infection through fomites.
  • All the secretions and infections from the animals remain infective.
  • The carrier cattle may harbor the virus in the esophageal fluid for 6 to 24 months.

Pathogenesis

  • The virus initially settles in the cells of the dorsal surface of the soft palate or on the lateral wall of the pharynx following the entry. But, they do not produce any lesions in these areas.
  • They affect the mucous membrane of the mouth cavity and invade the basal layer of the stratified epithelium of the tongue and produce primary vesicles causing pyknotic changes in the nucleus of the cells with leukocytic infiltration.
  • Heart muscles may show acute degeneration of the myocardial cell fibres in calf.
  • Musculature will have striped appearance which is termed as “tiger heart” (Graham, 1959)

Clinical Findings

  • Morbidity is 100% but mortality is less in indigenous cattle and comparatively more in pure and cross bred cattle.
  • Incubation period: 2-8 days to 2-3 weeks.
  • Temperature may reach 104-1060F
  • This is accompanied with generalized malaise, depression, dejection and apathy to food and water.
  • Reduction in milk yield.
  • Vesicular stomatitis.
  • Reduction of temperature is seen after reaching the peak temperature.
  • Drooling of foamy, roapy salivation and protrusion of the tongue are the features in this stage.
  • Vesicles may rupture due to jaw movements.
  • Animals refuse to eat due to pain in oral mucosa.

Lesions

  • The characteristics lesions comprise of vesicles and ulcerations.
  • Vesicular lesions become apparent when sufficient amount of fluids accumulate inside.

Treatment

  • Symptomatic treatment is done.
  • Potassium permanganate, sodium carbonate, boric acid and glycerin may be applied over mouth lesions.
  • Antiseptic or antibiotics may be given on foot lesions and lesions on mammary tissues.

Control

  • Regular vaccination must be done.
  • Healthy animals must not be allowed to mix with affected animals.
  • Visitors must not be allowed during the vulnerable season.