Chlamydia and Chlamydophila species

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

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 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
Clinical infections occur in non-natural host species

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

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

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