Chlamydia and Chlamydophila species

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Chlamydophila psittaci involved in feline rhinotracheitis together with herpes virus 1 C.psittaci more frequently infects the conjunctival epithelium -> chronic conjunctivitis, see feline chlamydiosis

Overview

  • Host adapted and non-host adapted species varying in virulence for different hosts
  • Different species cause specific diseases in particular hosts
  • Repsiratory, enteric, pleural and reproductive diseases in animals and humans
  • Intestinal infections often subclinical and persistent


Characteristics

  • Obligate intracellular bacteria
  • Gram negative bacteria with outer membrane, LPS, ribosomes, DNA and RNA
  • Peptidoglycan cell wall resistant to lysozyme
  • Only grow in presence of living eukaryotic cells
  • Unable to synthesis ATP therefore require intermediates from host cells
  • Grow in embyonated eggs and McCoy cells as well as animal tissues
  • Not stained by Gram stain
  • Kosters (modified Ziehl-Neelson, small red rods) or fluorescent antibody stain required for detection
  • Blue inclusions in cytoplasm of Giemsa-stained cels
  • Antigen detection kits for diagnosis from swabs
  • Two morphological forms
    • Elementary body, the infective extracellular form, which is small, metabolically inert and osmotically stable; surrounded by cytoplasmic membrane, outer membrane with LPS, but no peptidoglycan
    • Retiuculate body: larger, metabolically active, osmotically fragile
  • Elementary body survives in the environment for several days


Pathogenesis and pathogenicity

  • Elementary body enters host epithelial cells by receptor-mediated endocytosis
  • Transformation into larger reticulate body within endosome; known as an inclusion
  • Reticulate body divides by binary fission to form many new chlamydia cells
  • Reticulate bodies mature and condense to form elementary bodies
  • Elementary bodies released from dying host cells after about 72 hours to infect other cells
  • Persistent infections can occur if replication delayed by environmental conditions
  • Many infections subclinical due to intracellular existence of chlamydia preventing inflammatory reactions
  • Chronic infections may fail to induce an immune response, or may repeatedly stimulate the immune system, causing a delayed hypersensitivity reaction and tissue damage
  • Prolonged faecal shedding of organisms
  • Clinical infections occur in non-natural host species
  • CLinical signs depend on route of infection and degree of exposure


Chlamydophila psittaci

  • Causes notifiable psittacosis in birds


Chlamydophila abortus

  • Ovine enzootic abortion
  • Contagious ovine abortion in late pregnancy
  • Infection via ingestion or inhalation causes a bacteraemia
  • Bacteria localise in placenta and cause placentitis, leading to abortion
  • Abortion rates may reach 30%
  • Fertility not impaired
  • Survival of elementary bodies in faeces and wild birds are a source of infection from one lambing season to the next
  • Ewes may be carriers for several years
  • Venereal transmission from infected rams
  • Some immunity develops after infection, protecting ewes from subsequent disease
  • Vaccines prevent infection but will not clear infection from persistently-infected animals
  • Vaccination of ewe lambs


Chlamydophila felis

  • Host adapted species in cats
  • Feline interstitial pneumonia and conjunctivitis
  • Diagnosis by antigen detection in ocular/nasal secretions - ELISA, PCR, Kosters, fluorescent antibody test
  • Vaccine



Diagnosis

Treatments