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Clinical Micro > Tick borne infections > Flashcards

Tick borne infections Flashcards

1
Q

Rickettsial bacteria are what type of bacteria?

A

Small pleomorphic, gram negative cocco-bacilli

Obligate intracellular bacteria

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2
Q

How are Rickettsial pathogens transmitted?

A

Zoonotically via an arthropod intermediate

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3
Q

Are Rickettsial pathogens motile?

A

Non-motile because no flagella

- have actin based motility though

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4
Q

What two other bacteria that we discussed in this course display actin based motility?

A

Shigella and listeria monocytogenes

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5
Q

Rickettsial diseases are officially caused by…

A

Obligate intracellular bacteria grouped in the order rickettsiales

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6
Q

Rickettsial diseases are lumped into 3 groups based on clinical symptoms. What are they?

A
  1. Scrub typhus
  2. Typhus
  3. Spotted fever group
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7
Q

What pathogen causes scrub typhus?

A

Orientia tsutsugamushi

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8
Q

What is the reservoir and vector for Orientia tsutsugamushi ?

A

reservoir: rodents
vector: Trombiculid mite = “Chigger”

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9
Q

What are the most important symptoms of scrub typhus?

A
  1. morbilliform rash
  2. Hemorrhaging and intravascular coagulation

all symptoms of vascultitis caused by the pathogen

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10
Q

What is the vector for epidemic vs. endemic typhus?

A
  1. Epidemic - louseborne

2. Endemic - rat flea borne (murine)

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11
Q

What pathogen is responsible for epidemic typhus?

A

Rickettsia prowazekii

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12
Q

What two pathogens are responsible for endemic typhus?

A

Rickettsia typhi and R. felis

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13
Q

Which of epidemic and endemic typhus can be transmitted person to person

A

Epidemic (louse) typhus can be transmitted person to person

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14
Q

What are the reservoirs for epidemic vs endemic typhus?

A

epidemic: humans
endemic: rodents

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15
Q

Where do outbreaks of epidemic typhus tend to occur?

A

In areas where people are living close together with poor sanitation

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16
Q

What are the symptoms of epidemic typhus?

A 
Prolonged high fever 
Severe headache 
Cough 
Myalgias 
Morbilliform rash 
Neurological signs - stupor, sensitivity to light, delirium
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17
Q

What are the symptoms of endemic typhus like?

A

Similar but less severe than epidemic typhus

only see rash and neurological signs in 40-50% of people

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18
Q

Remember!! what do Rickettsia species cause in the body?

A

Vasculitis

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19
Q

What is different between the progression of rash in typhus vs. rocky mountain spotted fever?

A

typhus: rash moves CENTRIFUGALY from torso to extremities

RMSF: rash moves CETRIPETALLY from extremities to torso

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20
Q

What are the symptoms like for RMSF infection?

A

highly variable but include fever, headache, and RASH

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21
Q

What is the rash like for RMSF?

A

variable in presentation

- can be macular, papular, petechial, hemorrhagic and even necrotic

22
Q

What tick(s) is/are responsible for the spread of RMSF?

A

Dermacentor species

  • western US : D. andersoni
  • eastern US: D. variabilis
23
Q

What does transovarian transmission mean? What does this make the tick?

A

The Rickettisial species can be transmitted to oocytes in the female tick
- the tick can then be both a reservoir and a vector

24
Q

What is the reservoir of RMSF?

A

animals like rabbits, squirrels, mice

25
Q

How does a tick become infected with Rickettsial species?

A
  1. Feeds on host with high levels of rickettsia in its blood
  2. Host blood is digested by tick
    • Rickettsia escapes the tick’s gut
  3. Rickettsia get into the salivary glands of the tick and then can infect the next host the tick feeds on
26
Q

What cells and where in the body do Rickettsial species infect?

A

endothelial cells of small blood vessels

27
Q

What leads to vasculitis?

A

Intracellular multiplication –> cell-to-cell spread (actin-based motility) –> inflammation = vaculitis (skin and rash)

28
Q

What is the treatment protocol for Rickettsial disease?

A

emperic treatment with doxycycline or cloramphenicol (if pregnant)

29
Q

What testing is usually done to diagnose rickettsial diseases?

A

PCR and serologic tests

30
Q

When tests are used alongside cell culture to diagnose rickettisal diseases? What kind of sample needs to be obtained for this?

A

DFA or immunoperoxidase

Biopsies of endothelium (not skin) need to be obtained

31
Q

What is the causative agent of Lyme disease?

A

Borrelia burgdorferi

32
Q

What kind of bacteria is Borrelia burgdorferi?

A

Gram negative spirochete

33
Q

What is the vector for Lyme disease?

A

Ixodes ticks

34
Q

What are the two species of Ixodes ticks that transmit lyme disease and where are they found?

A

Central/Eastern: Ixodes scapularis

Western: Ixodes pacificus

35
Q

What is the reservoir for Lyme disease? Preferred host?

A

reservoir: white footed mouse

preferred host: white tailed deer

36
Q

Can there be trans-ovarian transmission for B. burgdorferi?

A

no, tick only acts as the vector

37
Q

What is the distribution of Lyme disease cases?

A

Seasonal- more likely to become infected in late spring and summer

38
Q

How long does a tick need to be attached in order to transmit Borrelia burgdoferi?

A

24-36 hours

39
Q

How is B. burgdoferi transmitted to host?

A

Has migrated to salivary glands of tick
Tick needs to rid itself of water as it feeds so it salivates
- this transmits the spirochete

40
Q

What is the hallmark sign of early lyme disease?

A

Erythema migrans (EM) = bull’s eye rash

41
Q

What results in multiple bulls eye (EM) rashes on the skin?

A

If Lyme disease is left untreated, the spirochetes will spread through the blood resulting in a systemic infection

42
Q

What is the general type of testing for lyme disease

A

Two tiered serology testing

43
Q

What are the two serological tests used for the diagnosis of lyme disease? What are the sensitivities/specificities of each?

A
  1. ELISA (IgG/IgM) screen (first test)
    - highly sensitive but not specific
    - can generate a lot of false positives
  2. Western Blot (IgM and IgG) (second test)
    - highly specific but not sensitive
44
Q

What is the pathogen responsible for Babesiosis?

A

Babesia microti

45
Q

What does Babesia microti infect?

A

red blood cells

46
Q

What disease does Babesiosis look like?

A

malaria

47
Q

What is the vector/reservoir for B. microti?

A

Vector: Ixodes tick
Reservoir: white footed mouse

48
Q

What is the spectrum of symptoms like for Babesiosis?

A

very wide: from asymptomatic to life threatening if you are immunocompromized

49
Q

What is the treatment for babesiosis?

A

Clindamycin/quinine or Atovaquone/azithromycin

50
Q

How do you diagnose Babesiosis?

A

Thick and thin blood smears - looking for parasites inside the RBCs

Serology and molecular methods

51
Q

What are 3 forms of PPE to avoid ticks?

A

Light colored clothing
Covering exposed skin
Repellents such as DEET
- N,N-diethylmetatoluamide

Clinical Micro (28 decks)

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