Rickettsias And Coxiella

Question 1

What are rickettsias?

Answer 1

Obligate, intracellular bacteria
Gram negative- two membranes with no lipopolysaccharides
some have absence of peptidoglycan

Question 2

What is the intracellular lifecycle of rickettsiales

Answer 2

• Ricketssia enters
• Phagosome lysis
• Replication throughout the cytoplasm
• Then either direct transfer into the adjacent cell or host cell lysis and release

Question 3

What are the two main pathogenic species of Anaplasmataceae

Answer 3

Ehrlichia & Anaplasma
- they cycle between animal and tick hosts

Question 4

What kind of host cells do anaplasmatacae target?

Answer 4

• Eythrocytes
• Platelets
• Neutrophils, eosinophils,
• monocytes, macrophages, lymphocytes
• vascular endothelium

Question 5

What happens when the rickettsia are in the dense core?

Answer 5

They are infectious but not-dividing

Question 6

What happens when the rickettsia are in the reticulate part of the developmental cycle?

Answer 6

They are dividing but not infectious

Question 7

What are the three ticks that primarily transmis anaplasmatcae?

Answer 7

• Ixodes ricinus
• Dermacentor
• Amblyomma

Question 8

What is the three-host tick cycle of rickettsia and coxiella?

Answer 8

• 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

Question 9

What are the symptoms of bovine anaplasmosis?

Answer 9

• anaemia
• fever #
• jaundice
• weight-loss
• breathlessness
• abortion

Question 10

What causes bovine anaplasmosis?

Answer 10

• 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

Question 11

What is anaplasma centrale?

Answer 11

• Milder version of bovine anaplasmosis
• also affects sheep, wild ruminants

Question 12

What is anaplasma centrale used as immunisation for?

Answer 12

A.marginale- does not prevent the disease but reduces symptoms

Question 13

What is anaplasma platys?

Answer 13

• Causes cyclic thrombocytopenia
• targets platelets

Question 14

What are the clinical signs of anaplasma platys?

Answer 14

• anaemia
• diarrhoea
• weight loss

Question 15

What do anaplasma ovis and anaplasma bovis cause?

Answer 15

• 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

Question 16

What is anaplasma phagocytophilum?

Answer 16

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

Question 17

What does infection of cells with A. phagocytophilum lead to?

Answer 17

Cell lysis
often combined with immunosupression and secondary infections
leads to abortion
can convert to a carrier state

Question 18

What is the diagnosis and treatment of anaplasma infections?

Answer 18

• Clinical signs
• Microscopy
• immunofluorescence assays
• serology
• culture
• molecular tests

Question 19

What is important about Ehrlichia species?

Answer 19

• Tick-borne
• targets a wide range of hosts
• targets white blood cells primarily

Question 20

What does erhlichia canis cause?

Answer 20

• causes canine ehrlichosis, canine pancytopenia
• lethargy, inappetence, pancytopenia
• targets monocytes, macrophages and lymphocytes

Question 21

What tick transmits Ehrlichia canis?

Answer 21

Rhipcephalus sanguineous

Question 22

What are the clinical signs of canine Erhrlichiosis?

Answer 22

• fever, oedema, haemorrhage
• leukopenia, hypergammaglobulaemia
• there is presence of inclusion bodies (morula) in blood smears
• Growth in tick cell lines

Question 23

Where is E. chaffensis primarily found?

Answer 23

primarily found in deer, can cause human ehrlichosis
similiar to E.canis
-monocytes, macrophages, lymphocytes

Question 24

What is the name of the tick that transmits E.chaffensis?

Answer 24

Amblyomma americanum

Question 25

Where is E. ewingii primarily found?

Answer 25

It is primarily found in dogs and humans

Question 26

What does Ehrlichia ruminantium cause?

Answer 26

heartwater, cowdriosis
targets the vascular endothelium throughout the body and granulocytes

Question 27

What are the clinical signs of cowdriosis?

Answer 27

• Dependent on age and breed
• fever, death within a few hours
• convulsions, respiratory distress, anorexia, exaggerated blinking, chewing or stiffening of the limbs

Question 28

How might you diagnose cowdriosis?

Answer 28

• Brain smears- using Diff-quik staining
• Serology
• PCR

Question 29

How can you control and treat Cowdriosis?

Answer 29

• tick control
• farming resistant shock
• antibiotic treatment
• immunisation
• vaccines

Question 30

Main points surrounding Rickettsia species

Answer 30

• 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
  *

Question 31

What are two other bacteria that infect blood cells?

Answer 31

• Mycoplasma species
• Bartonella species (cat-scratch disease, trench fever)

Question 32

What is coxiella burnetti?

Answer 32

• 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

Question 33

What are the clinical signs of Q fever?

Answer 33

• 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

Question 34

What is the transmission of coxiella?

Answer 34

• 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

Question 35

How could you diagnose Q fever?

Answer 35

• Placenta, ammniotic fluid
• only handled by specialist laboratories
• can be cultured with cell lines or embryonated eggs

Question 36

How can you treat Q fever?

Answer 36

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)

Question 37

What are some of the sources of human infection in Q fever?

Answer 37

• Contact with
  infected animals
• Contact with
  infected animal
  secretions
• Consumption of
  infected animal
  products
• Aerosols (transport,
  bedding)
• Ticks/vectors?

Question 38

What are some of the control measures of Q fever?

Answer 38

• Safe disposal of animal secretions
• pasteurisation/ sterilisation of milk
• public awareness
• separate aborting animals