Systematic Veterinary Virology

SYMPTOMS

• Characterized by sudden onset of fever (40° to 41^ºC).
• Affected animals are markedly depressed and appear sleepy. Their hair stands erect giving them a bloated appearance.
• Soon after this stage, a clear watery discharge is noticed from the eyes, nose and mouth, which become thick and yellow as a result of secondary bacterial infection. The discharges wet the chin and the hair below the eye; they tend to dry, causing matting together of the eyelids, obstruction of the nose and difficulty in breathing.
• One to two days after fever has set in, the mucous membranes of the mouth and eyes become very reddened.
• This is followed by pin-point greyish areas on the gums, dental pad, palate, lips, inner aspects of the cheeks and upper surface of the tongue. These areas increase in number and size and join together. In severe cases, the normal membrane may be completely covered by a thick cheesy material. Underneath the dead surface cells shallow erosions are noticed.
• Similar changes may also be seen in the mucous membranes of the nose, the vulva and the vagina. The lips tend to swell and crack and become covered with scabs.
• As the disease progresses, a characteristic foul smell exudes from the mouth. Affected animals resist attempts to open their mouths because of the pain.
• Diarrhoea commonly appears about two to three days after the onset of fever. The faeces are initially soft and then watery, foul-smelling and may contain blood streaks and pieces of dead gut tissue. 
• Affected animals breathe fast exhibiting rocking movements of both the chest and abdominal walls. Severely affected cases show difficult and noisy breathing marked by extension of the head and neck, dilation of the nostrils, protrusion of the tongue and soft painful coughs.
• A common feature in later stages of the disease is the formation of small nodular lesions in the skin on the outside of the lips around the muzzle.