Pneumonia in Sheep
Pneumonia outbreaks are rarely simple, especially in a group of lambs. The actual infecting agent could be one of a number of bacteria, a mycoplasma or a virus. Many of these organisms are commonly found in the respiratory tract of healthy lambs where they cause no trouble - that is until some predisposing factor stresses the respiratory system. The stressor could be the collection of a group of lambs from grass to a dusty yard for shipping, poor ventilation in a barn, build up of ammonia from a manure pack in a building, high humidity, overcrowding or any combination of these.
The clinical signs will vary with the severity. Early in an outbreak you may realize that there is more coughing in the group than previously; when moving the lambs some may lag behind and be breathing hard. There can be very sick animals which require individual treatments; there may be some deaths. In one New Zealand report of a pneumonia outbreak, 2-3 days after driving 850 lambs from pasture to a dusty collecting yard, 24 were dead; another 12 died in the next two weeks. There were sporadic cases of pneumonia in the survivors every time that they were handled.
Treatment of individual lambs is difficult except in the small flock. Treatment must be aimed at the cause of the secondary infection to attempt to save the animals, and to reduce lung damage. Because of the variety of agents that can be implicated, an accurate identification of the infectious agent is a must.
To prevent a serious pneumonia outbreak, attack the predisposing factors. If the collecting yard is very dusty, lay the dust before the sheep come. Drive them slowly. In the winter good air movement through a barn or shed is essential; stale humid air fosters pneumonia.
There are economic losses too. Lambs with chronic pneumonia, although they may appear normal have a slowed growth rate. These are after there have been deaths and expensive treatments have been used.
Remember that the most common cause of a chronic pneumonia in sheep, three or more years old, is maedi-visna. This is a progressive viral pneumonia in which the functioning lung tissue is lost. Ewes with maedi-visna lose condition and have less milk from mastitic udders.
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