ISSN 2398-2993       Transformation '' not found.

Salmonella spp

obovis

Synonym(s): enterobacteriaceae


Introduction

Classification

Taxonomy

  • Family: enterobacteriaceae.
  • Genus: salmonella.

Etymology

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

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Clinical Effects

Epidemiology

Habitat

  • Reservoir is the gastrointestianl 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 Disease transmission: overview.
  • Transovarian and egg transmission occurs in birds.
  • Also endogenous infection following alterations of intestinal microenvironment.
  • Infection via the mucous membranes of the upper respiratory tract and conjunctiva may occur but is rare.

Pathological effects

  • Specific local antibodies prevent attachment.
  • Circulating antibodies encourage phagocytosis.
  • 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 occurring some weeks after recovery from acute S. dublin disease.
  • Salmonellae 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 plasmid.
Factors
  • Normal gut flora usually inhibit growth and block access to attachment sites required; 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 and birds.Salmonellosis
  • Abortion Abortion & Stillbirths in cattle, ewes and mares.
  • Meningitis, osteomyelitis, joint ill and terminal appendage 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- cattle, S. pullorum- birds.

Control

Control via animal

  • Avoidance of stress helps reduce colonization of the gastrointestinal tract.
  • Implementation of a closed herd policy.
  • Isolation of affected animals.
  • Restriction on movement of animals.

Control via chemotherapies

  • Antibiotic treatment of the invasive diseases is indicated in conjunction with antimicrobial susceptibility testing.
  • Fluid and electrolyte therapy is necessary to avoid dehydration and shock. Fluid therapy.

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 hygienic procedures and through cooking of 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.
  • Careful disposal of dead animals and contaminated bedding/food.

Vaccination

  • Vaccines are available.

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Blanchard P C (2012) Diagnostics of dairy and beef cattle diarrhea. Vet Clin North Am Food Anim Pract 28 (3), 443-64 PubMed.
  • Costa L F, Paixão T A, Tsolis R M, Bäumler A J & Santos R L (2012) Salmonellosis in cattle: advantages of being an experimental model. Res Vet Sci 93 (1), 1-6 PubMed.
  •  Foster D M & Smith G W (2009) Pathophysiology of diarrhea in calves. Vet Clin North Am Food Anim Pract 25 (1), 13-36 PubMed.
  • Mohler V L, Izzo M M, House J K (2009) Salmonella in calves. Vet Clin North Am Food Anim Pract 25 (1), 37-54 PubMed.
  • Methner U (2005) Situation of bovine salmonellosis in Germany from 1995-2003 according to the data from the National Animal Disease Reporting System. Berl Munch Tierarztl Wochenschr 118 (11-12), 449-55 PubMed.
  • Lax A J, Barrow P A, Jones P W & Wallis T S (1995) Current perspectives in salmonellosis. Br Vet J 151 (4), 351-377 PubMed.
  • Vanduijkeren E et al (1994) Equine salmonellosis in a Dutch veterinary teaching hospital.Vet Rec 135 (11), 248-250 PubMed.
  • Potter M E (1992) The changing face of foodbourne disease. JAVMA 201 (2), 250-252 PubMed.

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