Rickettsias And Coxiella Flashcards
What are rickettsias?
Obligate, intracellular bacteria
Gram negative- two membranes with no lipopolysaccharides
some have absence of peptidoglycan
What is the intracellular lifecycle of rickettsiales
- Ricketssia enters
- Phagosome lysis
- Replication throughout the cytoplasm
- Then either direct transfer into the adjacent cell or host cell lysis and release
What are the two main pathogenic species of Anaplasmataceae
Ehrlichia & Anaplasma
- they cycle between animal and tick hosts
What kind of host cells do anaplasmatacae target?
- Eythrocytes
- Platelets
- Neutrophils, eosinophils,
- monocytes, macrophages, lymphocytes
- vascular endothelium
What happens when the rickettsia are in the dense core?
They are infectious but not-dividing
What happens when the rickettsia are in the reticulate part of the developmental cycle?
They are dividing but not infectious
What are the three ticks that primarily transmis anaplasmatcae?
- Ixodes ricinus
- Dermacentor
- Amblyomma
What is the three-host tick cycle of rickettsia and coxiella?
- Hatches and quests on the grass
- attachment and feeding to a dog
- Drops off/ moults then attaches to cattle
- then drops off and attaches to a human/ deer
What are the symptoms of bovine anaplasmosis?
- anaemia
- fever #
- jaundice
- weight-loss
- breathlessness
- abortion
What causes bovine anaplasmosis?
- Type of ricketssia
- caused by anaplasma marginale
- transmitted by a variety of ticks- dermacenter and rhipcephalus
- infects erythrocytes
- leads to anaemia
- infected animals serve as a reservoir
- worldwide/ tropical/sub tropical
What is anaplasma centrale?
- Milder version of bovine anaplasmosis
- also affects sheep, wild ruminants
What is anaplasma centrale used as immunisation for?
A.marginale- does not prevent the disease but reduces symptoms
What is anaplasma platys?
- Causes cyclic thrombocytopenia
- targets platelets
What are the clinical signs of anaplasma platys?
- anaemia
- diarrhoea
- weight loss
What do anaplasma ovis and anaplasma bovis cause?
- A ovis causes ovine anaplasmosis in sheep, goats and wild ruminants
- targets erythrocytes
- A.bovis generally causes mild disease and targets monocytes
*they both have worldwide distribution
What is anaplasma phagocytophilum?
Combines E.equi, E.phagocytophillia and HGE agent
it is transmitted by hard ticks Ixodes
targets neutrophils, eosinophils, and sometimes monocytes
causes tick-borne fever (cattle, sheep, goats, equine anaplasmosis in the US)
it is characterised by high fever, neutropenia and leukopenia
What does infection of cells with A. phagocytophilum lead to?
Cell lysis
often combined with immunosupression and secondary infections
leads to abortion
can convert to a carrier state
What is the diagnosis and treatment of anaplasma infections?
- Clinical signs
- Microscopy
- immunofluorescence assays
- serology
- culture
- molecular tests
What is important about Ehrlichia species?
- Tick-borne
- targets a wide range of hosts
- targets white blood cells primarily
What does erhlichia canis cause?
- causes canine ehrlichosis, canine pancytopenia
- lethargy, inappetence, pancytopenia
- targets monocytes, macrophages and lymphocytes
What tick transmits Ehrlichia canis?
Rhipcephalus sanguineous
What are the clinical signs of canine Erhrlichiosis?
- fever, oedema, haemorrhage
- leukopenia, hypergammaglobulaemia
- there is presence of inclusion bodies (morula) in blood smears
- Growth in tick cell lines
Where is E. chaffensis primarily found?
primarily found in deer, can cause human ehrlichosis
similiar to E.canis
-monocytes, macrophages, lymphocytes
What is the name of the tick that transmits E.chaffensis?
Amblyomma americanum
Where is E. ewingii primarily found?
It is primarily found in dogs and humans
What does Ehrlichia ruminantium cause?
heartwater, cowdriosis
targets the vascular endothelium throughout the body and granulocytes
What are the clinical signs of cowdriosis?
- Dependent on age and breed
- fever, death within a few hours
- convulsions, respiratory distress, anorexia, exaggerated blinking, chewing or stiffening of the limbs
How might you diagnose cowdriosis?
- Brain smears- using Diff-quik staining
- Serology
- PCR
How can you control and treat Cowdriosis?
- tick control
- farming resistant shock
- antibiotic treatment
- immunisation
- vaccines
Main points surrounding Rickettsia species
- Arthropod transmission e.g ticks, lice etc.
- Do not grow outside of cells- found in tissue culture or embryonated chicken eggs
- targets the vascular endothelium and circulating blood cells
*
What are two other bacteria that infect blood cells?
- Mycoplasma species
- Bartonella species (cat-scratch disease, trench fever)
What is coxiella burnetti?
- Small gram-negative coccobacillus
- initially thought to be a rickettsia
- it cannot be stained using standard gram-staining
- does not grow in labs
- causative agent of Q-fever in humans
- large animal reservoir
- transmission is linked to ticks
What are the clinical signs of Q fever?
- First described in 1937 as outbreak of febrile illness among slaughterhouse workers,
- can then progress to chronic febrile illness
- endocarditis with negative blood culture
- significant morbidity
- may lead to abortion
- may be asymptomatic in 90% of cases
*- high fever, malaise, pneumonia, hepatitis
What is the transmission of coxiella?
- Highly infectious, one particle may be enough for transmission
- it is found in a variety of wild and domestic animals
- transmission via aerosol, ingestion or direct contact
- shed in large quantities in placenta and ammniotic fluid of aborting animals
How could you diagnose Q fever?
- Placenta, ammniotic fluid
- only handled by specialist laboratories
- can be cultured with cell lines or embryonated eggs
How can you treat Q fever?
Endocarditis: Combination of doxycycline (200 mg/day) with
hydroxychloroquine (200 mg / 3 times/day)
* Hydroxychloroquine > raise pH in the pseudolysosomal vacuole to restore
doxycycline activity
* Vascular infections: same + surgical resection affected tissues
* Treatment often very long (18-24 months)
What are some of the sources of human infection in Q fever?
- Contact with
infected animals - Contact with
infected animal
secretions - Consumption of
infected animal
products - Aerosols (transport,
bedding) - Ticks/vectors?
What are some of the control measures of Q fever?
- Safe disposal of animal secretions
- pasteurisation/ sterilisation of milk
- public awareness
- separate aborting animals
