Veterinary Preventive Medicine-II

CLINICAL MANIFESTATIONS

• Incubation period is 2 days to 3 weeks. (In pigs, the incubation period is as short as 1-3 days).

Cattle

• The onset is heralded by a precipitate fall in milk yield and a high fever (40-41⁰C) accompanied by loss of appetite, depression. This is followed by appearance of painful stomatitis and the temperature subsides.
• There is profuse salivation, the saliva hanging in long, ropy strings, a characteristic smacking of the lips, and the animal chews carefully.
• Vesicles and bullae (1-2 cm in diameter) appear on the buccal mucosa, dental pad, udder and tongue.

• The vesicles are thin walled contain a straw coloured fluid. Vesicles rupture within 24hrs, leaving a raw painful surface, which heals in about 1 week.
• Vesicles appear on the feet, particularly in the clefts and on the coronet.
• The lesions on the tongue often heal within a few days but those on the feet and nasal cavities are contaminated with bacteria, maggots, which result in lameness and muco purulent discharge.
• Vesicles may also develop on the teats, which results in severe mastitis. The virus does not cross the placenta but the abortion mostly during second trimester of pregnancy mainly due to fever. Morbidity is high (reaches 100%) and mortality is very low (less than 2%). Due to myocarditis the mortality in young calves up to 6 months of age, is very high.

• A sequel to FMD in cattle due to endocrine damage, is a chronic syndrome of dyspnea, deleterious effects on testes causing production of poor quality of semen, anaemia, over growth of hair and lack of heat tolerance described as ‘panting’.

Sheep and goats

• The pronounced clinical sign is sudden and acute lameness.
• The vesicles develop in the interdigital space of the feet, which rupture in about 2-3 days. Sometimes, the upper layer of the hoof is lost. Oral lesions are rare or they may develop only on the tongue and upper palate but there is no salivation.

Pigs

• Large vesicles and bullae occur in the snout and feet and these may rupture to expose large raw surface.
• Lameness is the first sign. The foot lesions are very painful. Vesicles in the mouth are very less prominent.

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