ISSN 2398-2950      

Salmonella spp

ffelis
Contributor(s):

Richard Walker


Introduction

Classification

Taxonomy

  • Genus Salmonella.
  • Family Enterobacteriaceae.

Etymology

  • Genus discovered by American biologist, Theobald Smith; named after his laboratory chief and co-author, D E Salmon.

Active Forms

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Clinical Effects

Epidemiology

Habitat

  • Reservoir is the gastrointestinal tract of warm- and cold-blooded animals.
  • Sources of infection include:
    • Contaminated soil.
    • Vegetation.
    • Water.
    • Components of animal feeds, eg bone meal, meat meal and fish meal.
    • Foods containing milk, meat or eggs.

Lifecycle

  • Salmonellae adhere to and invade cells in the distal small and proximal large intestine.
  • Multiplication occurs here or in the macrophages of the liver and spleen if septicemia occurs.
  • Multiplication results in endotoxemia.

Transmission

  • Feco-oral.
  • Transovarian and egg transmission occurs in birds.
  • Infection via the mucous membranes of the upper respiratory tract and conjunctivae may occur.

Pathological effects

  • Endotoxin-mediated damage to blood vessels and activation of blood clotting mechanism together with alternate complement pathway   →   disseminated intravascular coagulation, eg ischemic necrosis of distal limbs, ears and tail of calves occuring some weeks after recovery from acute S. Dublin disease.
  • Salmonella fimbriae   →   attachment to cells of distal small intestine   →   disease
  • Some strains produce exotoxins   →   enteritis and diarrhea.
  • Invasive strains   →   multiply within macrophage   →   escape destruction   →   septicemia.
  • The invasiveness of some strains of S. typhimurium is increased by genes carried on a virulent plasmid.

Factors

  • Normal gut flora usually inhibit growth and block access to attachment sites required (competative inhibition); host's susceptibility to infection increased by disruption of normal flora, eg by antibiotics or deprivation of food and water.
  • Stress   →   decreased peristalsis   →   allows multiplication of organisms in intestine.
  • Major pathogens of animals.
  • Animals may be healthy excretors following infection.

Zoonotic Salmonellosis

  • Salmonellosis is an important zoonosis.
  • Contaminated food, mainly of animal origin, is the predominant source.
  • Salmonella strains cause a wide range of human enteric disease:
    • Mild self-limiting gastroenteritis.
    • Severe gastroenteritis with or without bacteremia.
    • Typhoid fever - severe, debilitating and potentially fatal.

Other Host Effects

Some of the diseases caused by Salmonella spp

  • Enteritis or septicemia in cattle, pigs, cats and birds.
  • Abortion in cattle, ewes and mares.
  • Meningitis, osteomyelitis, joint ill and terminal ischemia in calves.
  • Fowl typhoid, fowl paratyphoid and other severe infections in birds may be egg transmitted.
  • Some Salmonella serotypes are host-adapted, eg S. typhi- humans, S. dublin - cattleS. pullorum- birds.

Control

Control via animal

  • Avoidance of stress helps reduce colonization of the gastrointestinal tract.

Control via chemotherapies

Control via environment

  • Salmonellosis is controlled through protocols designed to inhibit spread to susceptible animals and people.
  • Food handlers and the public should be educated in hygiene procedures and methods of cooking food.
  • Observe hygienic precautions after handling animals and educate children to do so.
  • Adequate sanitation and supervision in abattoirs, food-processing plants, butchers' shops, etc.

Diagnosis

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Tauni M A & Osterlund A (2000) Outbreak of Salmonella typhimurium in cats and humans associated with infection in wild birds. JSAP 41 (8), 339-341 PubMed.
  • Lax A J, Barrow P A, Jones P W et al (1995) Current perspectives in salmonellosis. Brit Vet J 151 (4), 351-377 PubMed.
  • Potter M E (1993) The changing face of foodborne disease. JAVMA 201 (2), 250-253 PubMed.
  • Willard M D, Sugarman B, Walker R D et al (1987) Gastrointestinal zoonoses. Vet Clin North Am Small Animal Pract 17 (1), 145-178 PubMed.

Can’t find what you’re looking for?

We have an ever growing content library on Vetlexicon so if you ever find we haven't covered something that you need please fill in the form below and let us know!