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Yersinia (view source)

Revision as of 13:37, 12 May 2010

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===Overview===

*Cause [[Intestine Pathogens - Pathology|intestinal disease]] in animals and are important zoonoses

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*10 species of which ''Y. pestis, Y. pseudotuberculosis and Y. enterocolitica'' are pathogenic to animals and humans; ''Y. pestis'' is the most pathogenic

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*10 species of which [[Yersinia pestis|''Y. pestis'']], [[Yersinia pseudotuberculosis|''Y. pseudotuberculosis]] and [[Yersinia enterocolitica|''Y. enterocolitica'']] are pathogenic to animals and humans; [[Yersinia pestis|''Y. pestis'']] is the most pathogenic

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*Rodents provide a reservoir of ''Y. pestis'', which is the cause of human plague; fleas transmit the infection to other animals and humans

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*Rodents provide a reservoir of [[Yersinia pestis|''Y. pestis'']], which is the cause of human plague; fleas transmit the infection to other animals and humans

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*''Y. pseudotuberculosis and Y. enterocolitica'' reside in the intestine of domestic and wild animals and birds

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*[[Yersinia pseudotuberculosis|''Y. pseudotuberculosis'']] and [[Yersinia enterocolitica|''Y. enterocolitica'']] reside in the intestine of domestic and wild animals and birds

*Birds may cause mechanical transfer of the organisms

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===Pathogenesis===

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*''Y. enterocolitica and Y. pseudotuberculosis'' enter the intestinal mucosa via M cells of the Peyer's patches

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*''Y. enterocolitica and [[Yersinia pseudotuberculosis|''Y. pseudotuberculosis'']] enter the intestinal mucosa via M cells of the Peyer's patches

*Engulfed by macrphages in the mucosa

*All three invasive species are facultative intracellular organisms and grow inside macrophages

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*Resistant to macrophage killing mechanisms

*Antiphagocytic proteins secreted by the organisms interfere with host [[Neutrophils - WikiBlood|neutrophils]]

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*''Y. pestis is more invasive than the other species and also possesses and antiphagocytic capsule and a plasminogen activator which aids systemic spread; endotoxin also contributes to its pathogenicity

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*[[Yersinia pestis|''Y. pestis'']] is more invasive than the other species and also possesses and antiphagocytic capsule and a plasminogen activator which aids systemic spread; endotoxin also contributes to its pathogenicity

*Transport within macrophages to mesenteric lymph nodes

*Replication in lymph nodes and development of necrotic lesions, with neutrophil invasion

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===Clinical infections===

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*''Yersinia pestis''

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*''[[Yersinia pestis]]''

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**Cause of bubonic plague in humans, transmitted via fleas from infected rats

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**Not a significant veterinary disease

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*''[[Yersinia pseudotuberculosis]]''

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**Disease in rats and other rodents similar to the disease in humans

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**Bubonic form can lead to the pneumonic form, which is highly contagious and usually fatal

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**Humans and domestic and wild animals incidental hosts

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**Plague has rarely been reported in dogs, cats, camels, elephants, deer

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**Cats can acquire the disease from ingesting dead rodents, and show lymphadenopathy and abscesses

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**Fever, lethargy, swelling and abscessation of lymph nodes particularly in head and neck region

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**50% mortality if not treated

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**Possesses 3 plasmids, 2 of which are unique to this species; these encode an endotoxin, and coagulase and fibrinolytic activity

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*''Yersinia pseudotuberculosis''

**Less virulent than ''Y. pestis'' but closely related

**Mainly infect animals

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**Granulomas occur in the gut wall and mesenteric lymph nodes

**Occasional spread from the mesenteric lymph nodes to the liver and [[Spleen - Anatomy & Physiology|spleen]]

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*''Yersinia enterocolitica''

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*''[[Yersinia enterocolitica]]''

**Pathogen of animals and humans

**Found in intestinal tract and oral cavity of animals, eg. pigs, leading to infection of humans via contaminated carcasses

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