Actinobacillosis - Pig

Also known as:Actinobacillosis, A. equuli in swine, Actinobacillus suis septicaemia in horses, Actinobacillus suis septicaemia in pigs, Acute haemorhagic pulmonary infarction and necrotizing pneumonia in horses, Otitis media, externa, interna, middle and inner ear infections

Introduction

Actinobacillosis is caused by the bacteria [[Actinobacillus suis| Actinobacillus suis. 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. Although A.suis mainly affects pigs it has also been linked to septicaemia, acute haemorrhagic pulmonary infarction and necrotizing pneumonia in horses, airsaculitis in waterfowl, neonatal calf pneumonia and localised infections and polyarthritis in alpacas. 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. Excessive temperature fluctuation, high humidity, mixing of pigs of different ages and overcrowding may also have an important role in the development of disease.

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, 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, temors, nystagmus, strabismus, decreased or absent menace response, ptosis, miosis or meiosis, photophobia, headshaking, opisthotonus, facial paralysis, paraparesis and ataxia.

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, both being able to induce a septicaemic infection with 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 organisms.

Differential diagnosis: 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 stabilize antibody levels in the whole population .