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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
How does a tick become infected with Rickettsial species?
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
What cells and where in the body do Rickettsial species infect?
endothelial cells of small blood vessels
27
What leads to vasculitis?
Intracellular multiplication --> cell-to-cell spread (actin-based motility) --> inflammation = vaculitis (skin and rash)
28
What is the treatment protocol for Rickettsial disease?
emperic treatment with doxycycline or cloramphenicol (if pregnant)
29
What testing is usually done to diagnose rickettsial diseases?
PCR and serologic tests
30
When tests are used alongside cell culture to diagnose rickettisal diseases? What kind of sample needs to be obtained for this?
DFA or immunoperoxidase Biopsies of endothelium (not skin) need to be obtained
31
What is the causative agent of Lyme disease?
Borrelia burgdorferi
32
What kind of bacteria is Borrelia burgdorferi?
Gram negative spirochete
33
What is the vector for Lyme disease?
Ixodes ticks
34
What are the two species of Ixodes ticks that transmit lyme disease and where are they found?
Central/Eastern: Ixodes scapularis Western: Ixodes pacificus
35
What is the reservoir for Lyme disease? Preferred host?
reservoir: white footed mouse preferred host: white tailed deer
36
Can there be trans-ovarian transmission for B. burgdorferi?
no, tick only acts as the vector
37
What is the distribution of Lyme disease cases?
Seasonal- more likely to become infected in late spring and summer
38
How long does a tick need to be attached in order to transmit Borrelia burgdoferi?
24-36 hours
39
How is B. burgdoferi transmitted to host?
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
What is the hallmark sign of early lyme disease?
Erythema migrans (EM) = bull’s eye rash
41
What results in multiple bulls eye (EM) rashes on the skin?
If Lyme disease is left untreated, the spirochetes will spread through the blood resulting in a systemic infection
42
What is the general type of testing for lyme disease
Two tiered serology testing
43
What are the two serological tests used for the diagnosis of lyme disease? What are the sensitivities/specificities of each?
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
What is the pathogen responsible for Babesiosis?
Babesia microti
45
What does Babesia microti infect?
red blood cells
46
What disease does Babesiosis look like?
malaria
47
What is the vector/reservoir for B. microti?
Vector: Ixodes tick Reservoir: white footed mouse
48
What is the spectrum of symptoms like for Babesiosis?
very wide: from asymptomatic to life threatening if you are immunocompromized
49
What is the treatment for babesiosis?
Clindamycin/quinine or Atovaquone/azithromycin
50
How do you diagnose Babesiosis?
Thick and thin blood smears - looking for parasites inside the RBCs Serology and molecular methods
51
What are 3 forms of PPE to avoid ticks?
Light colored clothing Covering exposed skin Repellents such as DEET - N,N-diethylmetatoluamide

Clinical Micro (28 decks)

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