PASTEURELLOSIS

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Causative Agent(s)

Pasteurella multocida

Four subspecies are known to cause disease: multocida, septica, gallicida, and tigris.

However the subspecies causing the most problem is Pasteurella multocida subspecies multocida. Subspecies; gallicida and septica have been occasionally reported in some infections.

Pasteurella multocida is gram-negative nonmotile rod or coccobacillus approximately 1.0–2.0 µm in length.

The bacterium is a facultative anaerobe that exhibits a distinct bipolar staining characteristic.

Clinical Presentation and Epidemiology

Pasteurella multocida is a zoonotic agent occurring in all regions of the world.

It causes a respiratory disease in pigs as progressive atrophic rhinitis and pneumonia occurring as moderate to severe outbreaks.

Atrophic rhinitis eventually leads to total disappearance of the nasal turbinates which is caused by toxigenic strains of Pasteurella multocida either alone or in combination with Bordetella bronchiseptica.

Pneumonic pasteurellosis is the common final stage of enzootic pneumonia or porcine respiratory disease complex (PRDC), a syndrome which is the most widespread spread disease of pigs raised under confinement.

Progressive Atrophic Rhinitis

The signs noticed are sneezing and snuffling in piglets, serous to muco-purulent nasal and ocular discharges, epistaxis, shortened upper jaw in relation to the lower jaw, lateral deviation of the snout may be observed.

Pneumonia

Pneumonic pasteurellosis commonly occurs in grower and finisher pigs together with mycoplasmosis contributing to Porcine respiratory disease complex.

Clinical signs vary depending on the pathogens involved and the stage or severity of the disease. However, coughing, intermittent fever, depression, anorexia, dyspnoea, cyanosis of tips of the ears are observed.

Septicaemic Pasteurellosis

Septicaemic pasteurellosis has a sudden onset. The clinical signs noticed are fever, dyspnoea and prostration, oedema of the throat and lower jaw, and cyanosis of the abdomen.

Diagnostic Considerations

The samples for bacterial isolation are swabs of the nose and tonsils. Although the bacteria can be isolated in healthy animals.

Swabs should be transported to the laboratory within 24 hours in a medium containing sterile phosphate buffered saline.

For cases of pneumonia, nasal swabs, swabs of tracheobronchial exudate are sufficient.

For dead animals, affected lung tissue from the border area between affected and normal tissue should be taken.

All samples should be refrigerated until cultured.

In the case of Progressive Atrophic Rhinitis, a definitive diagnosis depends on clinical and pathological signs, culture, isolation of the organism and histopathology of affected tissues.

Radiography and computed tomography can also be used if available however the pigs must be sedated or restrained physically.

The use of serology in diagnosis has been a problem because toxigenic and nontoxigenic strains of the bacteria possess similar cross-reacting antigens however enzyme-linked immunosorbent assays (ELISAs) can be used.

For septicaemic pasteurellosis, blood of infected animals and affected lung tissues are good samples for diagnosis.

The bacteria should be cultured on blood agar and isolated.

Biochemical tests can be done to identify the organism. Diagnosis can also be achieved by Polymerase chain reaction.

Management and Treatment

Penicillin, 20,000 IU/kg b.w., q24h 5 days, I.M. Enrofloxacin, 5mg/kg b.w., q24h 3-5 days, I.M. Ceftiofur, 3mg/kg b.w., q24h 5 days I.M.

Due to resistance to Ceftiofur, antimicrobial sensitivity tests will be required