Equis ISSN 2398-2977

Intestine: salmonellosis

Contributor(s): Rachel Murray, Prof Jonathon Naylor

Introduction

  • Salmonella infections are common in horses. A spectrum of infection is seen - from asymptomatic carriers to peracute death.
  • Cause: a number of serotypes are responsible - most commonlySalmonella typhimurium  Salmonella spp  .
  • Signs: in mild infection - pyrexia, anorexia, dullness and diarrhea. Acute colitis, septicemia and asymptomatic carrier forms also occur.
  • Diagnosis: identification ofSalmonellaisolates in fecal samples, post-mortem tissues, septicemic blood samples or by detection of antibodies from recovered animals.
  • Treatment: oral/parenteral antibiotics and intravenous fluids where indicated.
  • Prognosis: depends upon severity of infection - >50% mortality in acute salmonellosis; chronic carrier state exists. Prevention and control of spread of disease crucial.

Pathogenesis

Etiology

  • Salmonella typhimurium  Salmonella spp  is the most frequently isolated serotype.
  • Other Group B serotypes includingS. agona.
  • S. dublin,S. heidelberg,S. giveandS. newportalso occur.
  • Carriers ofSalmonellaspp are important in epidemiology of disease.
  • Up to 10-20% of adult horses are inapparently infected withSalmonellaspp.
  • Many carriers are clinically normal.
  • Carriers may be intermittent excretors of the organism (active carriers) or non-excreting (passive carriers).
  • Active carriers may act as potential sources of infection for other animals particularly when they or in-contact animals are stressed, eg in hospitals.
  • Carriers may or may not become ill when stressed.

Predisposing factors

General
  • Management factors.
  • Stress.

Specific

  • General anesthesia.
  • Gastrointestinal surgery.
  • Pre-existing disease, especially gastrointestinal disease.
  • Transportation.
  • Concurrent disease or immunosuppression.
  • Antimicrobial therapy.
  • Dietary change.
  • High ambient temperatures.
  • Excessive withdrawal of feed, especially if other stress factors.

Pathophysiology

  • Similar to that in other species.
  • Often seen following stress, eg operations, transport, strongyle infections, parturition.
  • Development of clinical disease influenced by:
    • Bacterial virulence factors including adherence to and invasion of mucosal lining, and affect on inflammatory response.
    • Host immune status.
    • Gastrointestinal defense mechanisms, ie motility and normal gut flora, gastric pH.
    • Environmental factors.
  • Salmonellaspp are invasive organisms with the ileum, cecum and proximal large colon the main sites of infection.
  • Infection   →   severe mucosal inflammation, enterocolitis, protein-losing enteropathy   Protein losing conditions  , diarrhea and endotoxemia.
  • Bacteremia via the reticuloendothelial system may   →    disseminated infection elsewhere in the body.
  • Septicemia can   →    rapid death.

Epidemiology

  • Carrier states.
  • Persistence ofSalmonellaspp in host and environment.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Kim L M, Morley P S, Traub-Dargatz J L, Salmon M D & Gentry-Weeks C (2001)Factors associated with Salmonella shedding among equine colic patients at a veterinary teaching hospital.JAVMA218(5), 740-748 PubMed.
  • Newton-Clarke M (1995)Principles of prevention and control of salmonellosis.Equine Vet Educ7(2), 67-69 VetMedResource.
  • Pace L Wet al(1995)Salmonella septicemia with pulmonary abscesses and osteomyelitis in a foal.Equine Vet Educ7(2), 64-66 Wiley Online Library.


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