Tick Borne Infections Flashcards
Rickettsial Pathogens
Small, pleomorphic Gram negative coccobacilli
Obligate INTRAcellular bacteria
Zoonoses via arthropod intermediate
Non-motile (no flagella) but do have actin based motility
3 pathogens that have actin based motility
Listeria
Shigella
Rickettsia
Endemic vs epidemic typhus host
En: fleas
Epi: lice
Orientia tsutsugamushi (what does it cause, where is it found, reservoir, vector, main symptoms)
Scrub typhus
Similar to other forms of typhus
Endemic in india, south east asia, australia
Reservoir: rodents
Vector: trombiculid mite (chigger)
Main symptoms: morbilliform rash, hemorrhage and intravascular coagulation (systemic disease)
What pathogens cause a morbilliform rash?
Measles Rubella Roseola Scrub typhus Rickettsia prowazekii
EPIdemic typhus
causative agent, transmission, vector, reservoir, epidemics or sporadic
Rickettsia prowazekii Transmitted person to person Vector is human body lice Causes epidemics- from poor sanitation/crowding Reservoir is humans More severe manifestation
ENdemic typhus
causative agents, transmission, vector, reservoir, epidemics or sporadic
Rickettsia typhi and R. felis No person to person transmission Vector is rat flea - from bite or feces Cases are sporadic Reservoir is rodents Usually milder
Rocky Mountain Spotted Fever
Rickettsia produces a vasculitis throughout the body
Symptoms can be highly variable
Rash starts on extremities and moves inward
Have to treat right away
Difference in rash between RMSF and Typhus
RMSF: centripetal progression (starts on extremities, and then to trunk)
Typhus: centrifugal progression (starts on trunk and then moves out)
Where is Dermacentor andersoni vs Dermacentor variabilis found in the US?
andersoni: west coast
variabilis: east coast
Rickettsial disease treatment
Should be empiric!
Doxycycline
Best way to diagnose rickettsial diseases
Serology - but by the time you’ve mounted an immune response its too late (have to treat first)
Can also do PCR
Or DFA but need good biopsy of endothelium
Lyme disease
causative agents, morphology, vector
Borrelia burgdorferi
Gram negative spirochete
Vector is Ixodes ticks
Where is Ixodes scapularis vs Ixodes pacificus found?
scap: Central/eastern
paci: western
Lyme disease reservoir and preferred host
Res: white footed mouse
PH: white-tailed deer
What disease does not have transovarian transmission?
Lyme disease
What is a good diagnostic clue for early Lyme disease
Eryhtemia migrans = bull’s eye rash
Anywhere in the skin
2 tiered testing for Lyme disease
- ELISA (IgG/IgM) screen: very sensitive, but not specific
- Western Blot (IgM and IgG): very specific but not sensitive
Need 5-10 bands for IgG and 3-5 for IgM to be positive
Babesiosis
caused by, vector, reservoir, treatment
Caused by a parasite that infects RBCs
Most human cases are caused by Babesia microti
Vector: Ixodes ticks
Reservoir: white footed mouse
Treatment: clindamycin/quinine, atovaquone/azithromycin
Babesia vs Plasmodium
Babesia is smaller, and there could be multiple ring forms inside the RBCs
