Systematic Veterinary Virology

LESIONS - CATTLE

• The diagnostic lesions are single or multiple vesicles ranging from 2 mm to 10 cm. These can occur at all sites of predilection.

Gross lesions on the tongue

• The lesions usually progress in the following manner
  • A small blanched whitish area develops in the epithelium.
  • Fluid fills the area, and a vesicle (blister) is formed. 
  • Vesicle enlarges and may coalesce with adjacent ones. 
  • Vesicle ruptures.
  • Vesicular covering sloughs leaving an eroded (red) area
  • Gray fibrinous coating forms over the eroded area.
  • Coating becomes yellow, brown or green.
  • Epithelium is restored, but line of demarcation remains; line then gradually fades.
• Occasionally "dry" FMD lesions develop. Instead of forming a vesicle, the fluid is apparently lost as it forms and the upper layers of the epithelium become necrotic and discolored. The lesion therefore appears necrotic rather than vesicular.

Gross Lesions on the Feet

• The vesicle in the interdigital space is usually large because of the stress on the epithelium caused by movement and weight. The lesion at the coronary band at first appears blanched; then there is separation of the skin and horn. When healing occurs, new horn is formed, but a line resulting from the coronitis is seen on the wall of the hoof.

Gross Cardiac and Skeletal Lesions

• Animals that die have grayish or yellowish streaking in the myocardium - degeneration and necrosis. These findings are known as "tiger heart" .