Actinobacillus Pleuropneumonia

Elimination programme

Investigation into Cases

 

Other names

APP, Haemophilus Pleuropneumonia (HPP)

Causal agent

Actinobacillus pleuropneumoniae a bacteria.

There are currently 15 varieties (serovars) described.  The severity of the clinical signs differ between the different serovars and presence of other factors.

Serovars 1, 5, 9, 10 and 11 are considered to be more virulent than others but there are a lot of local variations.

Serovars  3, 6 and 8 predominate in the UK. In the US 1,5 and 7 most important.

Cross reactions with 1,9 and 11; 2, 6 and 8; 4 and 7. Note Actinobacillus suis may also cause some cross-reaction complicating diagnosis. PCR will help classification. Bacteriological culture generally requires NAD – from a staphylococcus streak.  A. pleuropneumoniae demonstrates satellitisim.

Age group

All ages are susceptible, mostly 20 to 100 kg pigs show the disease on farms

Clinical signs  (varying from death to nothing)

Peracute

Pleuropneumonia gross 1

Sudden illness.  May occur in individuals only first.   The animals lie down a lot and have a high rectal temperature of 41.5•C.  The animals are anorexia and generally do not drink.  Their extremities become cyanotic (purple) and are cold to the touch.  The cyanosis can spread to the whole of the body.  Severe breathing difficulties, often with mouth breathing, develops before the animal dies.  Blood stained froth can be seen at the mouth and nostrils.  Death generally occurs within 24 to 48 hours

Acute

Several animals in the group (may be 70%) present  depressed and lie down a lot.  They have a high rectal temperature of 40.5 to 41•C. They are anorexia and often do not drink either.  The animals present with severe respiratory distress often with a cough and mouth breathing.  Cyanosis is apparent, particularly if the animal is asked to move.  Vomiting may be seen.   Abortion can occur in sows

Subacute

There can be an intermittent cough in a group of pigs.  There is a general loss of appetite resulting in reduced growth.  With serovar type 3 arthritis, endocarditis (heart valve lesions) and abscesses may be seen

Chronic

In chronically affected herds (most herds), daily weight gain may not be affected.  An intermittent cough may be heard

Implications of the disease

 

From 15 to 30% of pigs are affected in a group and at times up to 100% may die.  Depending on the severity of the disease daily gain may be reduced by up to 30%

Infectivity

 

The disease is mainly spread by pig to pig contact

Airborne spread via droplets is possible over a short distance

Survival in the environment is very short unless protected by mucus or organic material, when it can be extended to a few days

Recovered pigs can act as carriers

Stress factors

 

Moving pigs

Mixing pigs

Overcrowding

Rapid changes in temperature, insufficient ventilation, high Relative Humidity

Taking blood and other tests


 

Incubation period

 

Very variable, high exposure can result in death within a few hours, other cases can take a few days

Post-mortem Lesions

 

Most of the lesions are confined to the respiratory tract.

In the peracute and acute cases there is the presence of well demarcated focal dark and solid pneumonic areas particularly in the caudal area of the lung, but lesions can be found also in the cranial lobe.  Lesions may have a red haemorrhagic outer edge and a necrotic (dead) centre.   Pleurisy is generally very obvious and may be seen adherent to the lesion.   Fluid around the heart (pericardial effusion) may also be seen.

In the subacute form, there may be pleurisy with no other lung lesions

In the chronic form, there may be a few individuals with pleurisy, but most pigs demonstrate no gross changes.

There are three known toxins ApxI strong haemolysin and cytotoxic, ApxII is weak haemolysin and mildly cytotoxic and ApxIII is a strong cytotoxin

 

 

Distribution of the lesions

 

Gross appearance of the lung

Cross section of the lung showing the yellow necrotic areas

Pleurisy – tag demonstrated

In the drawing the shaded area indicates the area of lung generally diseased by pleuropneumonia.  Illustration of an acute pleuropneumonia lesion

Diagnosis

 

Bacteriological confirmation needed in peracute, acute and subacute cases.

Pleurisy can occur through other diseases, notably Glässer's.

Detection of antibodies generally unrewarding clinically, but may be worth considering when needing to tract the disease through a herd.  Note pigs can go serologically negative after a while.

To investigate an outbreak of APP a thorough clinical examination of the farm will be necessary.  An example checklist.

Treatment

Individuals affected

Individual Antimicrobial injections, but you must be vigorous and quick in peracute and acute outbreaks.  Treat other pigs in the same area as well.  Tulathromycin and Ceftiofur are very effective.

In-feed and water medication may be ineffective as the seriously affected pigs do not eat or drink

Short acting medicines such as ceftiofur are very effective initially, followed up by long acting amoxycillin.   Tulathromycin is very effective. Once the animals start to eat and drink other medication routes can be considered

Control

All-in/All-out programmes

Purchase breeding stock from farms with good health programmes.  Possibly purchase stock negative to specific serotypes – APP 1 for example.

All purchased stock to go through isolation facilities

Partial depopulation may be needed in herds with repeated acute or subacute problems. 

Vaccines may be useful either autogenous or commercial, but do require a farm specific programme to be worked out.   Commercial vaccines can be very disappointing

Elimination of genetic stock is possible by hysterectomy or medication methods using tulathromycin

Common differentials

 

Swine Fevers,  Erysipelas, Salmonellosis, Streptococcal septicaemia, Glässers disease and other abscess forming organisms in the chronic forms.

Zoonotic implications

 

There are no zoonotic implications.