Actinobacillosis - Pig

Also known as: Actinobacillosis — Actinobacillus suis septicaemia in pigs — A. equuli in swine — Otitis media, externa, interna, middle and inner ear infections

Introduction

Actinobacillosis is caused by the bacteria Actinobacillus suis. The disease affects suckling, weanling and fattening pigs, and adult pigs and it is thought that it colonises piglets within the first three weeks of life.

In piglets aged 1 to 8 weeks old the organism causes acute and rapidly fatal septicaemia, and localized infections such as endocarditis, polyarthritis, and respiratory distress may also been seen with additional neurological signs.

Adult pigs can suffer pneumonia-like symptoms, see clinical signs for more details. It is not considered a zoonosis but there has been a report of human infection after a pig bite .

Signalment

High health status herds with lower immune challenges are more at risk then conventional herds. Piglets from high health status herds can suddenly die without any premonitory signs. Disease progression can be exaccerbated by excessive temperature fluctuation, high humidity, mixing of pigs of different ages and overcrowding. Genetic make up and immune status can also influence infectivity rate and clinical signs.

Clinical Signs

Clinical signs vary from fever, lethargy, depression, erysipelas-like lesions, abscesses, haemorrhage, vomiting/regurgitation and lameness and multiple joint swelling. More serious cases progress to pneumonia (clinical signs similar to A. pleuropneumoniae) and sudden death.

Cardiorespiratory signs include tachycardia, heart murmurs, purulent or serous occulonasal discharges, sneezing, coughing, abnormal lung sounds, dyspnoea, cyanosis changes in heart rate and open mouthed breathing.

Aural purulent mucoid discharge and increased amounts of wax are present along with a foul odour. Pigs can become deaf and are often found rubbing and scratching their ears.

Affected animals are in a lot of pain and discomfort and suffer from dysphagia, lymphadenopathy, anorexia, and unthriftiness. In sows it can cause agalactia, mastitis, abortions, still births or weak piglets.

Neurological signs include head tilt, circling, tremors, nystagmus, strabismus, decreased or absent menace response, ptosis, miosis or meiosis, photophobia, headshaking, opisthotonus, facial paralysis, paraparesis and ataxia. Further occular signs associated with this disease is corneal oedema and ulceration.

Diagnosis

Actinobacillus suis Gram stain

Diagnosis can be difficult as its clinical signs are similar to other pathogens, such as Streptococcus suis and Haemophilus parasuis, which also cause septicaemic infection and sudden death. Infection can be confirmed by the isolation of A. suis, from culturing infected tissue.

On post-mortem serous or fibrinous exudates can be found in the thorax and pericardium and ecchymotic haemorrhages can be seen in kidneys, lungs, liver, spleen and other organs.

Differential diagnoses: A. pleuropneumoniae, Erysipelas, Glasser’s disease, Streptococcus suis, and Mulberry heart disease.

Treatment

A.suis has good sensitivity to ceftioufur, gentamicin and trimethoprim/sulfadiazine, and moderate sensitivity to ampicillin, neomycin, sulfadimethoxine and tiamulin. Culture and sensitivity is recommended.

Control

Routine biosecurity and disinfection should be followed and maintained. At present there is no commercial vaccine for A. suis but there is evidence that autogenous vaccines in a herd could help stabilise antibody levels in the whole population .

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