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Pasteurellosis - Winter illness in sheep and goats

Written by  Joan Kleynhans
| in Veearts
| August 4, 2014

Pasteurellosis is an often fatal pneumonia which is triggered by stress. It occurs sporadically in sheep and goats.

The causative organisms are Pasteurella haemolytica and P. multocida. They are normally present as commensals in the respiratory system such as the nose, pharynx, trachea and lungs. If animals are compromised by poor body condition aggravated by stressful environmental conditions, the organisms multiply and cause disease.
        Stress may result from weather changes, especially, snow, wind and heavy rain or cold. Animals that have recently been shorn are at increased risk. Severe drought may also cause sufficient stress to cause disease. Other conditions, such as lung worm or “jaagsiekte” (a form of lung cancer caused by a retrovirus) may also predispose to Pasteurella. Chlamydial organisms, which cause enzootic abortion, as well as cold-causing Parainfluenza 3 virus, or choking as a result of dosing, may also be a factor. Crowding of animals in feedlots may also lead to Pasteurellosis and cause significant losses. Exhaustion after being moved large distances on foot as well as long road journeys in poorly ventilated trucks may make animals susceptible.
Untitled-1      Pasteurellosis most commonly presents as pneumonia. Young lambs are most susceptible and losses may be significant. Symptoms seen may include animals lagging behind when the herd is chased, listlessness, a high temperature and lack of appetite. The sheep or goat may cough and pant and have a nasal discharge.
       The pasteurella bacteria may also cause blue udder in ewes.
Rarely it may affect the liver or cause arthritis or meningitis. 

On post mortem the following signs are seen:

      If the skull is opened lengthways, nasal cartilages are very congested and appear dark red to purple in colour. Small haemorrhages may be seen on the inside and outside of the heart’s surface. Kidneys and liver are red and enlarged. However, the most obvious signs in acute cases are seen in the lungs. Significant red areas, some of which feel solid, are very obvious. The lower parts of the anterior lung lobes are usually involved. A third or more of the lung is affected. On occasion there are adhesions between the lungs and chest wall. In chronic cases, lungs may not have the typical “bontlong” appearance, but may be greyish in colour. Although the diagnosis may be made based on history and symptoms, ideally it should be confirmed by histopathology and bacteriology.
      Several vaccines are available in South Africa. Follow the instructions for the product you use carefully. Many strains of P. haemolytica and P.multocida are known to occur in South Africa. Some have been reclassified and renamed. If the problem persists in spite of bi-annual vaccination, further investigation should be done to determine the strain.  Reduction or avoidance of known stressors should also be planned for. Early treatment with certain antibiotics, as well as aggressive supportive treatment with parenteral fluids and anti-inflammatories may succeed in some cases, but is often unsuccessful. About 5% of strains are resistant to tetracyclines. In an outbreak or high risk situation, prophylactic antibiotics given to susceptible lambs, may be useful.