Richettsia and Chlamydia

Question 1

General characteristiscs of Richettsia and Chlamydia

Answer 1

Obligate intracellular bacteria (only grow in cells)
Gram negative coccobacilli
Cause persistent infections
Susceptible to tetracycline

Question 2

Different cell types that Richettisa and Chlamydia infect

Answer 2

Richettsia are arthropod transmitted parasites of blood or endothelial cells
Chlamydia are parasites of epithelial cells

Question 3

Rickettsia hosts

Answer 3

Reside in an arthropod host
Rodents and small animals can act as reservoirs
Humans and dogs may develop clinical disease

Question 4

Two groups of Rickettsia infections

Answer 4

Spotted Fever Group

• Rickettsia rickettsia
• Rickettsia felis

Typhus Group

• Rickettsia prowazekii
• Rickettsia typhi
• Orientia tsutsuqamushi

Question 5

Rickettsia rickettsia

Answer 5

Spotted Fever Group
Causes of Rocky Mountain Spotted Fever in humans, dogs
Organism invades and replicates in endothelial cells of smaller blood vessels, initiating platelet activation, intravascular coagulation, and progressive necrotizing vasculitis

Question 6

Rickettsia felis

Answer 6

Spotted Fever Group
Bacterium transmitted by cat flea
Causes flea-borne spotted fever in humans
Causes inapparent infection in cats

Question 7

Richettsia prowazekii

Answer 7

Typhus Group

Louse borne rickettsiosis

Question 8

Rickettsia typhi

Answer 8

Typhus Group
Murine typhus
Opossum/flea cycle

Question 9

Orientia tsutsuqamushi

Answer 9

Typhus Group
Causes scrub typhus
Chigger mites, rodents, birds

Question 10

Piscirickettsia salmonis

Answer 10

In farmed fish

Difficult to control, failure of antibiotic treatment is common, vaccines show variable long term efficacy

Question 11

Rickettsia family Anaplasmataceae 3 genus’

Answer 11

Parasites of haematopoietic (bone marrow derived cells of vertebrate hosts)

Anaplasma
Ehrlichia
Neorickettsia

Question 12

Anaplasma phagocytophilum

Answer 12

Found in neutrophils in the host
Transmitted by Ixodes (deer) ticks
Necrotizing small vessel vasculitis

Question 13

Anaplasma platys

Answer 13

Infects platelets
Infectious cyclic thrombocytopenia
Often asymptomatic or thrombocytopenia

Question 14

Anaplasma marginale

Answer 14

Principal target cell = Erythrocyte
Vector = tick, biting flies, blood contaminated fomites

Causes anaplasmosis in ruminants
Calves are much more resistant to disease than older cattle

Question 15

Ehrlichia canis

Answer 15

Tropical pancytopenia of dogs - “Tropical panleukopenia”
Brown dog tick borne infection
Mononuclear and endothelial cell infection

Question 16

Ehrlichia ruminantium

Answer 16

Heart water disease
Reportable disease

Replicates in macrophages and endothelial cells
Tick vector = amblyoma

Question 17

Ehrlichia ruminantium diagnosis

Answer 17

Demonstration of colonies of organisms in the cytoplasm of capillary endothelial cells (brain squash smear)
Presence of dark purple colonies made up of clusters of individual organisms (granules)

Question 18

Neorickettsia risticii

Answer 18

Potomac Horse Fever
Spread by trematode of brown bats
1st intermediate host = aquatic snails, 2nd intermediate host = aquatic insects

Question 19

Neorickettsia helminthoeca

Answer 19

Salmon poisoning in dogs in Pacific Northwest
Intermediate hosts are snail and fluke
Dogs eat salmon infected with fluke
Infect mononuclear cells
Hemorrhagic diarrhea, lymphadenopathy

Question 20

Unique features of Chlamydia

Answer 20

Dimorphic life cycle:
Intracellular replicating form = Reticulate body
Extracellular non-replicating form = Elementary body

Energy parasites - do not generate ATP

Elementary bodies are the infectious stage and can survive outside the host

Question 21

Chlamydia major diseases of animals

Answer 21

Chlamydia psittaci - avian chlamydiosis; infections are zoonotic
Chlamydia abortus - abortion in ruminants/enzootic abortion of ewes
Chlamydia pecorum - polyarthritic and polyserositis in ruminants/”stiff lamb disease”
Chlamydia felis - conjunctivitis in cats
Chlamydia trachomatis - human chlamydiosis (STD)
Chlamydia pneumonia - conjunctivits, pneumonitis, abortion, arthritis; humans and koala bears

Question 22

Chlamydia psittaci

Answer 22

Avian chlamydiosis
Reportable disease (BSL-3)
Zoonotic disease

Question 23

Chlamydia psittaci pathogenesis

Answer 23

Elementary bodies are shed by carriers (feces) or diseased birds -> inhaled into lungs
Goes through life cycle in epithelial and phagocytic cells

Question 24

Chlamydia pecorum

Answer 24

Ruminants
Polyarthritis in lambs and calves
“Stiff lamb disease”
Sporadic bovine encephalomyelitis (SBE)

Question 25

Chlamydia felis

Answer 25

Agent of feline pneumonitis
Conjunctivitis and rhinitis
Endemic in house cats worldwide

Question 26

Treatment of Chlamydia infections

Answer 26

Chlamydia are susceptible to tetracyclines

Drugs that affect protein and nucleic acid synthesis

Question 27

Control of Chlamydia infections

Answer 27

Isolate and treat infected animals
Disinfect and dispose of infected materials
Cell-mediated immunity is important
Antibodies are an indication of exposure, not protection
Vaccines do not prevent shedding but can reduce incidence and severity of disease

Question 28

Coxiella burnetti

• disease
• hosts

Answer 28

Causes Q (Queensland) fever
-Zoonosis: prolonged serious febrile influenza-like illness

Obligate intracellular pathogen
Endemic in cattle, sheep, and goals

Question 29

Coxiella burnetti transmission

Answer 29

Highly persistant in environment as a resistant ‘“endospore-like” form
Subclinically persists in carrier females
-released around parturition in birth fluids, milk, urine, feces
-spread by inhalation usually