Ovine pulmonary adenocarcinoma

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Case history - Observations

• A purchased yearling ram presents in poorer body condition (BCS 2.0; scale 1 to 5) compared to rams in the group (BCS 3-3.5).
• The ram is bright and alert and has a normal appetite.
• The ram is afebrile (39.6 C) but tachypnoeic (48 breaths per minute) with an abdominal component to his breathing.
• Auscultation of the chest reveals some wheezes and antero-ventrally on both sides of the chest.
• The heart rate is 88 beats per minute.

Typically, ultrasonographic examination of the chest in OPA reveals very sharply-defined hypoechoic areas representing the tumour mass(es). Small OPA lesions, measuring less than 1-2 cm are readily detected when they involve the pleural surface.

The prognosis for OPA is hopeless and affected sheep must be culled immediately for welfare reasons and to limit further disease spread within the flock.

Control measures include purchase of flock replacements from known OPA-free sources.

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During winter housing, when the risk of aerosol transmission is greatly increased, group sheep in age cohorts not upon keel marks (anticipated lambing date) to limit spread of OPA.

When sheep are grouped by age, infection acquired by older sheep does not present such a problem because these ewes would be voluntarily culled at the end of their productive lives before significant lung pathology had time to develop. Isolate suspected cases immediately and cull as soon as the diagnosis has been established.

There is presently no commercially available serological test for OPA. If there is a high prevalence of OPA in one group of sheep, the advice would be to cull that group. Cull progeny of all clinical cases of OPA.