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Chlamydiales and rickettsiales
i.e. intracellular bacteria
28
Veterinary Medicine
Undergraduate 3
06/04/2012

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Term
Chlymadiales and rickettsiales - similarities
Definition
-both IC survival -have all the enzymes and machinery they need -but unable to synthesise all precursors (missing some cofactors and so unable to make sufficient E) -therefore totally reliant on host
Term
Chlymadiales - spp
Definition
-Chlamydia spp.
-Chlamydophilia psittaci (avian chlamydiosis / grannies dz)
-Chylamydiolphilia abortus (EAE)
-Chylamydiophila felis (feline chlamydiosis)
Term
Chlamydiales - intracellular survival
Definition
-live in endosome - modify the compartment - insert proteins into endosome membrane so doesn't become fully acidified
Term
Chlamydiales - extracellular transmission
Definition
totally reliant on the host, can not be transmitted by traditional routes.
There are distinct forms of chlamydiales
Elementary body (EB) is the infectious form - it is dehydrated, w. a R wall and is metabolically inactive i.e. spore like
The reticulate body (RB) is the intracellular form which is active and replicates
Term
Chlamydiales - life cycle
Definition
-EB attaches to host cell and stimulates uptake by PIE and favourable conditions
-EB --> RB i.e. wall softens, rehydrates
-RB undergoes binary fission and there is formation of inclusion bodies
-RB reaches certain point , condenses --> EB
-cell lysis and EB released
Term
Chlamydiales - dz. trends
Definition
-associated w. MM resp, GIT, conjunctival and UGT
- some can cross and give rise to systemic dz (esp GIT) - arthritis, encephalomyelitis
-subclinical persistence and clinical flare-ups over years
Term
Chlamydophilia psittaci - dz
Definition
Avian chlamydiosis
-resp and intestinal inf. w. high mortality
Term
Chlamydophilia psittaci - source
Definition
-EB shed in faeces
-subclinical carriers shed when stresed
Term
Chlamydophilia psittaci - sequence of events
Definition
inhalation of EB --> acute systemic dz --> ocular / nasal discharges and green bloody diarrhoea --> high mortality
Term
Chlamydophilia psittaci - zoonoses
Definition
psittascosis "grannies dz / parrot fever"
-generally associated w. pet birds
-inhalation of EB w. dried faeces, esp when cleaning cage
-resp inf / pneumonia and poss systemic spread
-death in 20% untreated cases (NB: generally older population associated)
Can also get in association w. turkeys / pigeons.
Term
Chlamydophilia abortus - main dz
Definition
Enzootic Abortion of Ewes (EAE) - cause of ~90% ovine abortion in UK
Term
Chlamydophilia abortus - source
Definition
ingestion of EBs in placentas / uterine discharge / environment
Term
Chlamydophilia abortus - infection late pregnancy
Definition
no abortion
BUT may abort next pregnancy or ewelambs may be subclinically infected and then abort
Term
Chlamydophilia abortus - infection early pregnancy
Definition
abortion in late pregnacy
or premature / weak lambs which if ewelambs may be subclinically infected and then abort
Term
Chlamydophilia felis - disease
Definition
Feline chlamydiosis - conjunctivitis, rhinitis
-endemic - low mortality and usually self limiting
-but persists subclinically so get relapses
Term
Chlamydial infection - tx
Definition
- difficult!
- need antibiotics to be clinically effective IC
-antibiotics usually oxytetracyline for 2-3 weeks, NOT penicillin (affects bact. cell wall but unable to lyse it, so may push IC)
Term
Chlamydial infection - prevention
Definition
-detergents - due to high lipid content EBs are sensitive - should be rel. easy to remove from cage
-vaccines are available
- feline chlamydiosis vacc (but largely ineffective)
-avian chlamydiosis - regulated dz (NB this does not mean notifiable!)
-EAE - live attenuated vacc. used pre-breeding, or inactivated in preg
-as avian chlamydiosis is regulated, imported birds muct be quarantined for 35-45 days
Term
Rickettsiales - families
Definition
-Ehrlichiaceae
-Rickettsiaeae
Term
Rickettsiales - intracellular survival
Definition
-entry via PIE
-Ehrlichia live in endosome
-Rickettsia escape from endosome - have lipases which degrade the endo. wall an so escape and survive in cytoplasm
Term
Chlamydiales - cell type
Definition
mucous membrane epithelial cells
+/- macrophages if penetrate
Term
Rickettsiales - cell type
Definition
Ehrlichia - RBC and WBC (multiple in vaculoles)
Rickettsia - capillary endothelial cells, mutliple in cytoplasm
Term
Rickettsiales - transmission
Definition
totally reliant on the host, can not be transmitted by traditional routes.
-transmitted by blood-sucking arthropod vectors
Can be mechanical or biological vectors
Term
Rickettsiales - tx
Definition
-very similar to chlamydials
-plus blood transfusion if necessary
Term
Rickettsiales - prevention
Definition
-very similar to Chlamydiales
-plus vector control
Term
Chlamydial and rickettsial infection - dx
Definition
-ID bact in lesion smear - Giemsa stain / IF show inclusion bodies w. RBs
-PCR
-serology on paired sera from several birds - ELISA, indirect IF
-isolation - tissue cultures / embryonated eggs (won't grow on normal agar)
Term
Ehrlichia phagocytophila - dz
Definition
tick borne fever - initially fever then chronic immunosuppression
Term
Ehrlichia phagocytophila - spp affected
Definition
ruminants - esp. in tick-infected areas affecting lambs
Term
Ehrlichia phagocytophila - sequence of events
Definition
infects granulocytes --> fluctuating fever for a few days
persistence of organism --> relapses --> chronic immunosuppression --> susceptible to other serious infections
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