An outbreak of a disease characterised by very high mortality occurred in a
group of nine calves (1B4 months old) in a zero-grazing unit 2-3 weeks aft
er an introduction of an apparently healthy alien sheep into the calf pen.
Five of the six calves which contracted the disease died. The main clinical
signs observed were marked depression, persistently high body temperature
(40,5-41,5 degrees C), copious mucopurulent nasal and ocular discharges, dy
spnoea, bilateral keratoconjunctivitis with corneal opacity, enlargement of
the superficial lymph nodes and marked erythema and/or superficial erosion
s of the buccal mucosae. At necropsy there were lesions in the upper respir
atory and digestive tracts, lymph nodes, brain, eyes, liver, kidneys and th
e urinary bladder. The lesions were histopathologically characterized by fi
brinoid vasculitis which was accompanied by lymphocytic infiltration in the
parenchyma of the affected tissues. Based on the evidence of contact betwe
en the calves and the recently introduced foreign sheep, the characteristic
clinical signs and histopathological findings, a diagnosis of sheep-associ
ated malignant catarrhal fever was made.