Difference between revisions of "Category:Rickettsiales"

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===Overview===
 
===Overview===
  
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[[Haemobartonella canis]]
 
[[Haemobartonella canis]]
  
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[[Coxiella burnetti]]
  
  
===Q fever===
 
 
*Caused by ''Coxiella burnetti''
 
*Influenza-like disease of humans in contact with farm animals
 
*Transmitted to humans by inhalation from parturient sheep, goats and cattle
 
*Organisms replicate in female genital tract and mammary glands of ruminants
 
*Shedding occurs in uterine discharges, foetal fluid and milk
 
*Infections in animals usually subclinical
 
*Sporadic abortions occur in sheep, goats, cattle, cats
 
*Infertility may result in ruminants, as well as placentitis or endometritis
 
*Hepatitis, myocarditis and interstitial pneumonia may occur in affected foetuses
 
*Diagnosis: MZN-stained smears of placental tissue and uterine discharges; immunofluorescence; PCR; culture; serology
 
*Control: disposal of infected placenta and separation of pregnant ruminants; inactivated vaccines
 
 
[[Category:Infectious_Agents]]
 
[[Category:Infectious_Agents]]

Revision as of 20:46, 14 May 2010



Overview

  • Cause systemic diseases in animals
  • Usually use arthropod vectors
  • Host and cell type specificity
  • Q fever and Rocky Mountain spotted fever are zoonoses

Characteristics

  • Non-motile, pleomorphic Gram-negative organisms
  • Obligate intracellular pathogens
  • Require live cells for culture such as tissue culture cells or embryonated eggs
  • Require Romanowsky stains
  • Include two families, Rickettsiaceae and Anaplasmataceae
  • Rickettsiaceae have cell walls that contain peptidoglycan; they target endothelial cells and leukocytes
  • Anaplasmataceae lack cell walls; they target erythrocytes

Epidemiology

  • Rickettsiae replicate in gut epithelial cells of arthropod vectors and spread to other organs such as salivary glands and ovaries
  • Transmission occurs during feeding on the animal host
  • Transovarial or trans-stadial transmission occurs in the arthropod vectors
  • Most ricketsiae have limited survival in the environment, apart from Coxiella burnetii, which undergoes aerosol transmission

Pathogenesis and pathogenicity

  • Many rickettsiae target endothelial cells of small blood vessels; they produce phospholipase which damages phagosome membranes, escaping into the cytoplasm
  • Ehrlichia target leukocytes or platelets, and inhibit phagosome/lysosome fusion
  • Anaplasmataceae localise within vacuoles or on the surface of red blood cells; they may alter red cell antigens causing immune-mediated damage. Anaemia may result from haemolysis or removal of red blood cells

Identification

  • Giemsa-stained blood or tissue smears identify blue/purple organisms
  • Fluorescent antibody technique for specific identification
  • Isolation in embryonated eggs or tissue culture lines
  • Nucleic acid probes and PCR
  • Inoculation of susceptible animals

Rickettsia rickettsii

Ehrlichia canis

Ehrlichia platys



Ehrlichia risticii

Ehrlichia equi

Ehrlichia ondiri

Ehrlichia phagocytophila

Cowdria ruminantium

Anaplasma marginale


Mycoplasma haemofelis

Haemobartonella canis

Coxiella burnetti