Actinobacillus pleuropneumonie or ‘Porcine pleuropneumonia’
Actinobacillus pleuropneumonie (APP) in pigs is spread rapidly by airborne droplets over short distances or by direct contact. It causes considerable economic losses due to mortality, hampered growth and the increased need for antibiotics.
Signs of APP
The severity of APP will vary, depending on the strain of the bacteria, immune status of the herd, environmental stressors and levels of exposure. APP can be described as acute or chronic.
Signs of acute APP in pigs:
- Sudden appearance of severely ill animals
- High fever (41.5°C)
- Severe difficulty breathing
- Mouth breathing
- Sitting position
- Foamy blood-tinged discharge through mouth and nostrils
- Blue or purple discolouration of the skin
Chronic APP develops after the disappearance of acute symptoms and will involve:
- Loss of appetite
- Growth retardation
In chronically infected herds there are often diseased animals with no symptoms.
Diagnosis of APP
Diagnosis is confirmed through herd history, the above clinical signs and post-mortem examination.
At post mortem, an acute APP infection will show clearly marked damage and destruction of cells within the respiratory system and the bronchi and trachea are filled with a foamy, blood-tinged mucous exudate. Fibrinous pleurisy is present and the thoracic cavity contains a blood-tinged fluid.
A chronic APP infection will show nodules of different sizes in the diaphragmatic lobes. These nodules are surrounded by a thick capsule of connective tissue. Some areas of adhesive pleurisy are seen. In many cases the lung lesions resolve and only a residual, focal adhesive pleurisy is present. A high incidence of chronic pleurisy at slaughter is highly suggestive of pleuropneumonia.
Treatment and prevention of APP
Good management is essential to controlling APP. Farms free of APP should only introduce stock from APP free herds and new stock should be quarantined. General management principles for controlling respiratory disease are effective.
A good understanding of the herd’s history is important to determining periods of risk. This can be assessed through post mortem examinations, serological testing and clinical examinations.
Vaccination is an effective way to protect against different serotypes of APP using a multivalent inactivated vaccine.
Antibiotic treatment in the initial phases of the disease can help to reduce mortality.
Understanding the bacteria
Actinobacillus pleuropneumonia belongs to the Pasteurellaceae family, which contains the genera Haemophilus, Actinobacillus and Pasteurella.
There are 13 identified serotypes, or varieties. Serotyping is based on capsular polysaccharides (CP) and lipopolysaccharides (LP). Some serotypes show structural similarities between the LP chains. This explains the cross reactions seen between certain serotypes. Each geographical area or country has its own predominant serotype(s).
Differences in virulence between the serotypes or even within the same serotype have often been observed. In general, strains of serovars 1, 5, 9, 10 and 11 are thought to be more virulent than those from other serovars.