Difference between revisions of "Chlamydia and Chlamydophila species"

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===Overview===
 
 
 
*Host adapted and non-host adapted species varying in virulence for different hosts
 
*Species cause specific diseases in particular hosts
 
*Repsiratory, enteric, pleural and reproductive diseases in animals and humans
 
*Conjunctivitis, arthritis, abortion, urethritis, enteritis, pneumonia, encephalomyelitis
 
*Manifestation varies from subclinical to severe systemic infections
 
*Intestinal infections often subclinical and persistent
 
*Human infections usualy acquired from infected birds, causing psittacosis or ornithosis, causing respiratory infections
 
 
 
 
 
===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
 
*Not stained by Gram stain
 
*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 such as presence of interferon gamma
 
*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
 
*Epidemiology:
 
**Many wild and domestic birds susceptible
 
**Organisms present in respiratory secretions and faeces of infected birds
 
**Infection via inhalation or ingestion
 
**Subclinical infection common
 
**Intermittent shedding for prolonged periods
 
**Stress precipitates disease outbreaks
 
*Clinical signs:
 
**Generalised infection affecting intestinal and respiratory tracts
 
**Up to 10 day incubation period
 
**Loss of condtion, oculonasal discahrge, diarrhoea and respiratory distress depending on strain
 
**Hepatomegaly, airsacculitis and peritonitis
 
*Diagnosis: stained smears, immunohistochemistry, ELISA, PCR, isolation, antibody detection by ELISA and complement fixation
 
*Treatment: tetracyclines for several weeks
 
*Control: quaranteen imported birds and give tetracyclines; good husbandry
 
*Involved in [[Nasal Cavity Inflammatory - Pathology#In Cats|feline rhinotracheitis]] together with [[Herpesviridae|herpes virus 1]]
 
*Zoonotic by aerosol infection - can cause systemic disease with pneumonia, meningitis or meningoencephalitis
 
 
 
 
 
===''Chlamydophila abortus''===
 
 
 
*Ovine enzootic abortion
 
*Especially in intensive systems
 
*Ewe lambs may acquire infection at birth and abort in their first pregnancy
 
*Pathogenesis:
 
**Infection via ingestion or inhalation causes a bacteraemia
 
**Bacteria localise in placenta and cause placentitis, leading to late abortion or premature weak lambs
 
**Necrosis of cotyledons and oedema of adjacent tissue, as well as dirty pink uterine discharge
 
**Aborted lambs well preserved
 
**Large numbers of chlamydiae shed in placenta and uterine discharges; survive in environment for several days
 
**Abortion rates may reach 30% in susceptible flock
 
**Ewes infected late in pregnancy may not abort, but may abort during the next pregnancy
 
**No other clinical signs in aborting ewes
 
**Fertility not impaired
 
*Transmission:
 
**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
 
*Vaccination:
 
**Live attenuated vaccines prior to breeding or inactivated vaccines during pregnancy
 
**Vaccines prevent infection but will not clear infection from persistently-infected animals
 
**Vaccination of ewe lambs prior to breeding
 
*Treatment: long-acting oxytetracyclines during an outbreak to protect in-contact pregnant ewes
 
*Control: isolate aborted ewes; destroy placentas, thorough cleaning
 
*Also abortion in cattle, goats and pigs
 
*Serious infection in pregnant women
 
 
 
 
 
===''Chlamydophila felis''===
 
 
 
*Host adapted species in cats
 
*[[Respiratory Bacterial Infections - Pathology#Feline Chlamydiosis|Feline chlamydiosis]]
 
*Feline conjunctivitis, rhinitis and rarely interstitial pneumonia
 
*Epidemiology
 
**Up to 10% cats infected
 
**Infection via contact with conjunctival or nasal secretions
 
**Infection may persist with prolonged shedding and clinical relapses
 
**Stress of parturition and lactation may cause shedding of organisms leading to transmission to offspring
 
*Clinical signs:
 
**Incubation period 5 days
 
**Conjunctival congestion, clear ocular discharge, blepharospasm
 
**May have sneezing and nasal discharge
 
**Resolves within a few weeks, or causes persistent infection
 
*Diagnosis:
 
**Intracytoplasmic inclusions in stained conjunctival smears
 
**Antigen detection in ocular/nasal secretions - ELISA, PCR, Kosters, fluorescent antibody test
 
*Modified live vaccines reduce clinical signs but do not prevent infection or shedding
 
 
 
 
 
===''Chlamydophila pecorum''===
 
 
 
*Common inapparent intestinal infection of cattle
 
*Conjunctivitis and arthritis
 
*Sporadic bovine encephalomyelitis:
 
**Usually in cattle under 3 years
 
**Fever, incoordination, depression, excessive salivation, diarrhoea
 
**Recumbency and opisthotonos before death
 
**Up to 50% mortality
 
**Vacular damage in brain
 
**Serofibrinious peritonitis
 
**Treat with high doses tetracyclines and tylosin
 
 
 
 
 
===Diagnosis===
 
 
 
*Direct microscopy of smears and tissues e.g. organs from aborted foetuses, liver/spleen from avian cases
 
*Kosters (modified Ziehl-Neelsen) stain of placental smears shows small red rods
 
*Blue inclusions in cytoplasm of Giemsa-stained cells
 
*Methylene blue stain with darkfield microscopy
 
*Fluorescent antibody stain
 
*Antigen detection kits for diagnosis from swabs
 
*ELISA to detect ''Chlamydophila'' LPS
 
*Isolation in embryonated eggs and McCoy cells as well as animal tissues
 
*PCR to detect chlamydial DNA
 
*Serological tests: complement fixation, ELISA, indirect immunofluorescence
 
 
 
 
 
*May cause [[Joints Inflammatory - Pathology#In Sheep|arthritis in sheep]] and [[Joints Inflammatory - Pathology#In Cattle|arthritis in cattle]]
 

Latest revision as of 10:16, 12 May 2010