SALMONELLOSIS

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Causative Agent(s)

Salmonella species

There are more than 2400 Salmonella serotypes that have a broad host range.

Some serotypes affect specific hosts; Salmonella typhi (humans), Salmonella dublin (bovine),

Salmonella pullorum/ Salmonella gallinarum (poultry), and Salmonella choleraesuis (swine).

S. typhimurium also causes disease in swine.

Other serotypes of Salmonella occasionally cause transient disease in swine that are debilitated, immunocompromised, or herds that possess a naive immune system and are exposed to very large doses of the pathogen.

Clinical Presentation and Epidemiology

Salmonellosis occurs worldwide as an outbreak.

Salmonella choleraesuis

This organism causes septicaemic salmonellosis in weaned pigs that are less than 5 months of age. The clinical signs observed are fever, inappetence, lethargy, and shallow moist cough, icterus, huddling, reluctance to move, cyanosis of extremities and abdomen, diarrhoea, nervous signs, and death. Pregnant sows may abort.

Salmonella typhimurium

The clinical signs in pigs infected with S. typhimurium are fever, anorexia, unthriftiness, watery, non-haemorrhagic diarrhoea with yellow faeces diarrhoea without mucus, dehydration, rectal strictures, obstipation, and distention of the abdomen.

Other Serotypes

Salmonella Typhisuis and Salmonella Heidelberg are infrequent cause of diarrhoea in affected pigs.

Salmonella Dublin and Enteritidis cause nervous signs in suckling pigs.

Diagnostic Considerations

Diagnosis for this disease is based on clinical signs and pathologic lesions.

Faeces or blood of infected individuals should be collected for bacterial culture and isolation.

The disease is confirmed by culturing the bacteria on brilliant green, bismuth sulphite, blood agar, or MacConkey agar.

It is difficult to culture the organism from animals receiving antimicrobial treatment. Enzyme-linked immunosorbent assay (ELISA) is also used to diagnose the disease.

Polymerase chain reaction (PCR) is expensive for routine diagnosis.

PCR detects DNA from dead Salmonella and therefore the detected organism might not be causing clinical disease.

Management and Treatment

S.Typhimurium and S. Choleraesuis are known to be resistant to many antibacterial agents.

Culture and sensitivity tests of isolates from each outbreak are advised. The following antimicrobials can used to treat salmonellosis.

Gentamicin, 6mg/kg b.w., q24h 3-5 days I.M.

Ceftiofur, 3mg/kg b.w., q24 5 days I.M.

Anti-inflammatory agents such as dexamethasone are sometimes administered to critically ill animals.

Prompt removal and isolation of sick animals. Minimizing exposure to infective materials Thorough biosecurity measures in the piggery.

Restriction of movement of staff from potentially contaminated areas. Decrease crowding of pens and improve pig comfort.