Tick borne infections Flashcards
Rickettsial bacteria are what type of bacteria?
Small pleomorphic, gram negative cocco-bacilli
Obligate intracellular bacteria
How are Rickettsial pathogens transmitted?
Zoonotically via an arthropod intermediate
Are Rickettsial pathogens motile?
Non-motile because no flagella
- have actin based motility though
What two other bacteria that we discussed in this course display actin based motility?
Shigella and listeria monocytogenes
Rickettsial diseases are officially caused by…
Obligate intracellular bacteria grouped in the order rickettsiales
Rickettsial diseases are lumped into 3 groups based on clinical symptoms. What are they?
- Scrub typhus
- Typhus
- Spotted fever group
What pathogen causes scrub typhus?
Orientia tsutsugamushi
What is the reservoir and vector for Orientia tsutsugamushi ?
reservoir: rodents
vector: Trombiculid mite = “Chigger”
What are the most important symptoms of scrub typhus?
- morbilliform rash
- Hemorrhaging and intravascular coagulation
all symptoms of vascultitis caused by the pathogen
What is the vector for epidemic vs. endemic typhus?
- Epidemic - louseborne
2. Endemic - rat flea borne (murine)
What pathogen is responsible for epidemic typhus?
Rickettsia prowazekii
What two pathogens are responsible for endemic typhus?
Rickettsia typhi and R. felis
Which of epidemic and endemic typhus can be transmitted person to person
Epidemic (louse) typhus can be transmitted person to person
What are the reservoirs for epidemic vs endemic typhus?
epidemic: humans
endemic: rodents
Where do outbreaks of epidemic typhus tend to occur?
In areas where people are living close together with poor sanitation
What are the symptoms of epidemic typhus?
Prolonged high fever Severe headache Cough Myalgias Morbilliform rash Neurological signs - stupor, sensitivity to light, delirium
What are the symptoms of endemic typhus like?
Similar but less severe than epidemic typhus
only see rash and neurological signs in 40-50% of people
Remember!! what do Rickettsia species cause in the body?
Vasculitis
What is different between the progression of rash in typhus vs. rocky mountain spotted fever?
typhus: rash moves CENTRIFUGALY from torso to extremities
RMSF: rash moves CETRIPETALLY from extremities to torso
What are the symptoms like for RMSF infection?
highly variable but include fever, headache, and RASH
What is the rash like for RMSF?
variable in presentation
- can be macular, papular, petechial, hemorrhagic and even necrotic
What tick(s) is/are responsible for the spread of RMSF?
Dermacentor species
- western US : D. andersoni
- eastern US: D. variabilis
What does transovarian transmission mean? What does this make the tick?
The Rickettisial species can be transmitted to oocytes in the female tick
- the tick can then be both a reservoir and a vector
What is the reservoir of RMSF?
animals like rabbits, squirrels, mice
How does a tick become infected with Rickettsial species?
- Feeds on host with high levels of rickettsia in its blood
- Host blood is digested by tick
- Rickettsia escapes the tick’s gut
- Rickettsia get into the salivary glands of the tick and then can infect the next host the tick feeds on
What cells and where in the body do Rickettsial species infect?
endothelial cells of small blood vessels
What leads to vasculitis?
Intracellular multiplication –> cell-to-cell spread (actin-based motility) –> inflammation = vaculitis (skin and rash)
What is the treatment protocol for Rickettsial disease?
emperic treatment with doxycycline or cloramphenicol (if pregnant)
What testing is usually done to diagnose rickettsial diseases?
PCR and serologic tests
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
What is the causative agent of Lyme disease?
Borrelia burgdorferi
What kind of bacteria is Borrelia burgdorferi?
Gram negative spirochete
What is the vector for Lyme disease?
Ixodes ticks
What are the two species of Ixodes ticks that transmit lyme disease and where are they found?
Central/Eastern: Ixodes scapularis
Western: Ixodes pacificus
What is the reservoir for Lyme disease? Preferred host?
reservoir: white footed mouse
preferred host: white tailed deer
Can there be trans-ovarian transmission for B. burgdorferi?
no, tick only acts as the vector
What is the distribution of Lyme disease cases?
Seasonal- more likely to become infected in late spring and summer
How long does a tick need to be attached in order to transmit Borrelia burgdoferi?
24-36 hours
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
What is the hallmark sign of early lyme disease?
Erythema migrans (EM) = bull’s eye rash
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
What is the general type of testing for lyme disease
Two tiered serology testing
What are the two serological tests used for the diagnosis of lyme disease? What are the sensitivities/specificities of each?
- ELISA (IgG/IgM) screen (first test)
- highly sensitive but not specific
- can generate a lot of false positives - Western Blot (IgM and IgG) (second test)
- highly specific but not sensitive
What is the pathogen responsible for Babesiosis?
Babesia microti
What does Babesia microti infect?
red blood cells
What disease does Babesiosis look like?
malaria
What is the vector/reservoir for B. microti?
Vector: Ixodes tick
Reservoir: white footed mouse
What is the spectrum of symptoms like for Babesiosis?
very wide: from asymptomatic to life threatening if you are immunocompromized
What is the treatment for babesiosis?
Clindamycin/quinine or Atovaquone/azithromycin
How do you diagnose Babesiosis?
Thick and thin blood smears - looking for parasites inside the RBCs
Serology and molecular methods
What are 3 forms of PPE to avoid ticks?
Light colored clothing
Covering exposed skin
Repellents such as DEET
- N,N-diethylmetatoluamide
