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

• May cause arthritis in sheep and arthritis in cattle

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

Pathogenesis and pathogenicity

• Elementary body, the infective form, phagocytosed and internalised into host epithelial cells
• Transformation into larger reticulate body
• Reticulate body divides by binary fission to form many new chlamydia cells
• Reticulate body has un-crosslinked peptidoglycan, which is cross-linked to form elementary bodies
• Elementary bodies released from dying host cells to infect other cells
• Persistent infections
• Many infections subclinical due to intracellular existence of chlamydia preventing inflammatory reactions
• Clinical infections occur in non-natural host species

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