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	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.