Actinobacillus suis


Other names

This has historically been classed as a secondary agent or even normal inhabitant of the mouth and throat, but as herd health has improved it is possible that specific disease/characteristics may be associated with Actinobacillus suis

Causal agent

Actinobacillus suis a bacteria. Distinctive from Actinobacillus pleuropneumoniae does not require NAD

Age group

Sows with mastitis. Piglets with sudden death. Growing pigs with respiratory problems

Clinical signs

Adult sows

A. Suis has been associated with chronic mastitis and a few other abscessations

Nursery pigs

Septicaemia and sudden death

Recent problems

Pig found dead. High fever, lethargy and anorexia. Some skin discoloration.



Carried in the tonsils and nostrils of healthy pigs of any age

It has also been found in the vagina

Stress factors


It is likely that all of the stress factors involved in the post weaning respiratory complex is also going to be involved in the demonstration of clinical signs

Post-mortem Lesions

Acute necrohaemorrhagic lesions scattered throughout the lung. There may be pleurisy, pericarditis, peritonitis and septicaemia. The lesions look very much like acute pleuropneumoniae.

The mastitis lesions can be very extensive.



Culture of the organism

Histopathology of the lesion



Because of the rapid onset of the disease in grow finish animals treatment can be difficult

With sows with chronic mastitis cull from herd

Common differentials


Actinobacillus pleuropneumonia. Other causes of mastitis

Zoonotic implications


There are no zoonotic implications