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BACTERIOLOGY - 2 > 28 – Rickettsiales > Flashcards

28 – Rickettsiales Flashcards

1
Q

Microbiological characteristics

A
  • Obligate intracellular parasites
  • ROD shaped
  • Rickettsiacea family: Gram-negative
  • Anaplasmataceae family; lack cell wall components of other Gram negatives
  • Biocontainment levels depends
  • Not possible to culture using ‘standard’ lab methods
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2
Q

Natural host or habitat

A
  • Arthropod associated
  • Replication of organism inside the TICK
  • Sylvatic cycle: back and forth from vector and reservoir
  • Tick to tick transmission
    o Transstadial
    o Verticel
    o Horizontal
  • *ticks tend to be colonized with one species of Rickettsia
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3
Q

Virulence factors

A
  • Not well described
  • *more helpful to think about tissue tropisms
    o Rickettsia: vascular endothelium
    o Anaplasma: erythrocytes, platelets, leukocytes
    o Ehrlichia: leukocytes
    o Neorickettsia: leukocytes
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4
Q

What is the Rickettsia rickettsii the agent of?

A
  • Rocky Mountain Spotted Fever
    o First described in 1890s: ‘trail fever’
    o *affects dogs and people
    o IDed all over N. and S. America
    o Increasing incidence since 1970s
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5
Q

What are the clinical signs of Rocky Mountain Spotted Fever in dogs?

A
  • *fever
  • Edema of extremities
  • May develop petechial or ecchymotic haemorrhages (spots)
  • Joint pain and swellings
  • Myalgia
  • Neurological signs
  • can get necrosis associated with vasculitis
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6
Q

What is the seasonality of Rocky Mountain Spotted Fever?

A
  • March to October
    o Maybe different in SK, due to winter
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7
Q

What is the vector of Rocky Mountain Spotted Fever?

A
  • Hard (Ixodidae) ticks
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8
Q

What is are the possible vectors of Rocky Mountain Spotted Fever in western Canada?

A
  • D. andersoni: SK and AB
  • D. variabilis: SK, MB, western ON
  • *SK is a sympatric zone
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9
Q

What is the clinical significance of Rocky Mountain Spotted Fever in people?

A
  • *RASH
  • Fever, headache, nausea, vomiting, injected conjunctiva
  • Long term consequences: vascular inflammation and thrombosis
    o Hemorrhage or thrombosis of organs or brain
  • *not a reportable disease in Canada
    o In US, it is increasingly common in people (incidence is up, but case fatality rate is DECREASED!)
    o *me
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10
Q

Why decrease in Rocky Mountain Spotted Fever case fatality rate?

A
  • Tetracyclines was invented in 1948
  • *doxycycline in Rocky Mountain Spotted Fever
    o NO tooth staining
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11
Q

What is Rickettsia prowezakii the agent of?

A
  • Epidemic typhus
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12
Q

What is the clinical disease of epidemic typhus from Rickettsia prowezakii?

A
  • Flu like symptoms
  • Rash, neurological signs (headache to coma)
  • Untreated takes 2-3 months to recover fully
  • Mortality rate varies: up to 40%
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13
Q

What is epidemic typhus spread by?

A
  • Pediculus humanus corporis=human body louse
  • *human is reservoir
    o Infected lice die within weeks
  • Associated with flying squirrels in southern USA
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14
Q

When does Epidemic typhus usually occur?

A
  • Miserable conditions
    o Filthy and HIGH density
  • Historical outbreaks: WW1 (Anne Frank)
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15
Q

Where does Bovine Anaplasmosis occur from Anaplasma marginale?

A
  • Between 30 degree S and 40 degree N
    o Not in SK
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16
Q

Bovine Anaplasmosis (Anaplasma marginale) in different aged animals

A
  • Young animals (less than a year: subclinical
  • *disease is more severe the older the animal is
    o More than 2 years old=severe disease
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17
Q

What is seen in severely affected animals with Bovine Anaplasmosis (Anaplasma marginale)?

A
  • Icterus, anemia (extravascular hemolysis)
  • Fever
  • Decreased milk production
  • *can be RAPIDLY FATAL
  • Bos indicus cattle may be more resistant?
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18
Q

How do you treat Bovine Anaplasmosis (Anaplasma marginale)?

A
  • Tetracyclines!
  • Supportive therapy may be necessary
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19
Q

Vaccination for Bovine Anaplasmosis (Anaplasma marginale) is possible

A
  • Exact strategy depends on where you are
  • Some regions: Anaplasma centrale
  • *killed A. marginale vaccine in some to protect against severe disease
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20
Q

What does Anaplasma phagocytophilum cause in dogs?

A
  • Canine granulocytotropic anaplasmosis
  • *also reported in cats, small mammals, horses, mountain lions and coytoes
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21
Q

What is the vector for Anaplasma phagocytophilum in dogs?

A
  • Ixodes ticks
    o Minor distribution of Lyme disease
22
Q

What are the clinical signs of Anaplasma phagocytophilum in dogs?

A
  • Non-specific
  • Pyrexia, lethargy, depression, anorexia
  • Reluctance to move, soreness or weakness
  • Joint pain
23
Q

How do you treat Anaplasma phagocytophilum in dogs?

A
  • Doxycycline
24
Q

How do you control/prevent Anaplasma phagocytophilum in dogs?

A
  • Avoiding exposure to ticks
  • Acaricides
  • NO vaccination available
25
Q

Ehrlichia canis is a multi-systemic disease

A
  • Depression, lethargy
  • Bleeding and petechiation possible
  • Lymphadenopathy and splenomegaly in 20-25% of affected dogs
  • Ocular signs: change in eye colour, blindness
  • Neurological signs
  • Polyarthritis: lameness
26
Q

What can Ehrlichia canis cause in dogs?

A
  • Canine monocytotrophic ehrlichiosis
    o gained attention during Vietnam war: American’s used German shepherds=increased susceptibility to infectious diseases
27
Q

What is the vector of Ehrlichia canis?

A
  • Dermacentor variabilis
  • Rhipicephalus sanguineous
28
Q

What is the treatment for Ehrlichia canis?

A
  • Doxycycline
  • Chloramphenicol
29
Q

What does Neorickettsia helminthoeca cause in dogs?

A
  • Salmon poisoning
  • Highly fatal disease of dogs in California to BC
30
Q

What are the clinical signs of Salmon poisoning (Neorickettsia helminthoeca) in dogs?

A
  • Sudden terrible illness 5-7 days after eating parasitized fish
  • Gradually become hypothermic 4-8 days after signs begin
  • Marked anorexia and wasting
  • Develop diarrhea and vomiting 14 days after signs begin
    o Hematochezia may occur before death
31
Q

What is the life cycle of Nanophyteus salmincola (flukes) in dogs?

A
  • Adult flukes in dog intestine
  • Eggs in feces
  • Cercaria infect fish
  • Metacercaria in fish muscle
  • *as fluke matures it inoculates dog with Neorickettsia helminthoeca
32
Q

How do you treat Salmon poisoning (Neorickettsia helminthoeca) in dogs?

A
  • Tetracyclines
  • Praziquantal: anti-trematode therapy
  • Supportive therapy
    o Fluids
    o Anti-emetics
33
Q

How do you prevent Salmon poisoning (Neorickettsia helminthoeca) in dogs?

A
  • Vaccines NOT effective
  • Prevent exposure=IMPORTANT
    o Organism survives in rotting fish carcases for months
34
Q

What are the clinical signs of Potomac Horse Fever (Neorickettsia risticii)?

A
  • Mild colic
  • Fever
  • Diarrhea: watery
  • Abortion in pregnant mares
  • *case fatality is 5-30%
35
Q

What is the epidemiology of Potomac Horse Fever (Neorickettsia risticii)?

A
  • Thought to involve a yet to be IDed trematode
    o Infection believed to occur following ingestion of insects infected with trematode metacercaria
    o Has been ISOLATED from freshwater snails
36
Q

What is the treatment for Potomac Horse Fever (Neorickettsia risticii)?

A
  • OXYTETRACYCLINE
  • Supportive care
    o NSAIDs?
    o Fluid therapy
37
Q

How do you control Potomac Horse Fever (Neorickettsia risticii)?

A
  • Inactivated vaccines are available
    o Shown to be marginally protective in field trials
  • Heterogeneity in N. risticii strains may complicate vaccination
38
Q

Sample collection and handling

A
  • Blood
  • Blood smears
  • Acute and convalescent serum
  • Feces
  • Biopsies of lesions (R. rickettsii)
  • *unless sending to specialized lab, culture is not a concern
  • *freezing samples for preservation is OK
39
Q

How can you Lab ID R. rickettsii?

A
  • Serology
  • Direct immunofluorescence
  • PCR
40
Q

How does serology work for Lab ID of R. rickettsii?

A
  • Acute and convalescent serum
    o Want to see a 4x increase in Ab titre=indicates response
    o Send at same time! (freeze)
    o Cross reactivity Ab among spotted-fever group
    o Takes time
41
Q

Lab ID for Anaplasma spp.

A
  • ID of circulating morulae in blood
  • PCR on blood
42
Q

Lab ID for Neorickettsia helminthoeca

A
  • Fecal flotation: N. salmincola eggs in feces
  • Seroconversion: acute vs. convalescent
43
Q

Lab ID for Neorickettsia risticii

A
  • Seroconversion: acute vs. convalescent
  • PCR on feces or blood
44
Q

Ehrlichia spp.

A
  • ID of morulae on smears of buffy coat
  • PCR on blood
45
Q

Zoonotic/interspecies transmission

A
  • Many Ricetsiales have BROAD host range
    o Particularly Rocky Mountain Spotted Fever
  • *Transmission to people via vectors AND contract with infectious material in hemolymph
  • Do NOT squish, burn, scratch or rip off ticks
  • Avoid exposure to hemolymph
  • Wear gloves
  • Fine forceps
  • Disinfect wound
46
Q

Client communication with zoonotic/interspecies transmission

A
  • If concerned, GO to physician
  • Don’t panic!
    o Sick dog does NOT equal sick owner
    o Prophylactic treatment not recommended
    o *if signs=seek treatment immediately (Fever, severe headache, rash, nausea)
47
Q

R. akaria: Rickettisalpox (zoonotic/interspecies transmission)

A
  • House mouse reservoir
  • Zoonotic via mites
  • Urban areas
48
Q

R. felis: cat flea typhus (zoonotic/interspecies transmission)

A
  • Opossums IDed as one reservoir
  • Worldwide distribution
  • Zoonotic via cat flea
  • Pathogenicity in cats unclear
49
Q

Is a potential biological weapon due to

A
  • Non-specific initial presentations
  • High morbidity and mortality rate
  • Ability to aerosolize
  • Requires specialized lab to diagnose
  • NOT notifiable disease in Canada
  • Ex. R. prowazekii was weaponized by US, Japan and Soviet Union
50
Q

Treatment options

A
  • Not possible to do susceptibility testing on Rickettsiales
  • *usually tetracyclines
  • People: macrolides, penicillins and aminoglycosides NOT effective
  • *intracellular pathogens
    o Drugs don’t readily cross cell membranes

BACTERIOLOGY - 2 (16 decks)

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