Vector-borne bacterial infections Flashcards
bacilli
disease causing bacteria
what kind of bacilli is rickettsia
gram-negative
what makes rickettsia different from other gram negative rods
- peptidoglycan layer is minimal
2. LPS has weak endotoxin activity
what can you not use for treatment in Rickesttsi? and why?
Beta-lactams because LPD has weak endotoxin activity
obligate intracellular
cannot produce outside of host cell
where does Rickettsia replicate
in cytoplasm of cell
what stain is used to see Rickettsia
Giemsa
Gimenez
what is the common name for Rickettsia rickettsii
Rocky Mountain Spotted Fever (RMSF)
what is the pathogenic factor in Rickettsia rickettsii? how does it work
outer membrane protein A (Omp A)
- adherence to endothelial cells
Rickettsia rickettsii replicates where? this results in what
cytoplasm and nucleus
-vasculitis
how does Rickettsia rickettsii bypass the immune system
intracellular growth protects the bacteria from immune clearance
what is the most common Rickettsia causing human disease in USA
Rickettsia rickettsii
90% of infections occur during what time of year
April - September
what is the vector for Rickettsia Rickettsii? what family do they belong to
Ticks
Ixodeae family
name the 2 forms of ticks that cause Rickettsia Rickettsii
Dermacentor andersoni (wood tick) Dermacentor variablilis (dog tick)
where is Dermacentor andersoni found
rocky mountain states
where is dermacentor variablilis found
Southeast United states
what states had the highest incidence rates for Rocky mountain spotted fever
Arkansas Delaware Missouri North Carolina Oklahoma Tennessee
what is the reservoir for rickettsia rickettsii
ticks via transovarian transmission
what is the process of a tick biting a human
- bit is painless and goes unnoticed
- after 6-10 hours ….????
how long does rocky mountain spotted fever incubate
2-14 days
what are clinical symptoms for rocky mountain spotted fever
fever chills headaches myalgias abdominal pain vomiting hepatitis respiratory failure encephalitis renal failure hypotension myocarditis
when does the pathogenic rash appear for rocky mountain spotted fever
after 3-5 days
where does the pathogenic rash appear for rocky mountain spotted fever? do all victims get this rash
centripetal
palms and soles
no
what does centripetal rash mean
spreads from periphery to center
what happens in 20% of untreated cases for RMSF
fatal, clinical suspicion is key
what will the laboratory findings be for RMSF
Thrombocytopenia coagulopathy anemia normal WBC count hyponatremia Transminitis
Transaminitis what does that mean
Increased ALT/AST levels
could indicate liver damage
for RMSF when is diagnosis idealistic
before the onset of rash is clinical and epidemiological
RMSF, the organism in acute phase is detected how in the lab
- PCR
- Immunohistochemical methods in skin biopsy
- serology but confirmation needed
according to the CDC, when is RMSF notified to them
fever plus any one of the following rash eschar headache myalgia anemia thrombocytopenia hepatic transaminase elevation
how do you confirm RMSF in the lab
- fourfold change in IgG specific titer reactive with R. rickettsii by indirect immunofluoresense assay (IFA) b/w paired serum specimens ( one speciemen taken in 1st week, second 2-4 weeks later )
- detect R. rickettsii DNA in a clinical specimen via amplification of a specific target by PCR asay
- demonstrate rickettsial antigen in biopsy or autopsy speciment by IHC
- Isolation of R. Rickettsii from clinical specimen in cell culture
for laboratory confirmation of RSMF why is IgM not used
lacks specificity and are usually false +
common name for Rickesstia akari
Rickettsailpox
what is the world distribution for Rickettsia Akari
cosmopolitan
how is Rickettsia akari transmitted
mites
what is the reservoir for Rickettsia akari
rodents ( common house mouse)
how does R. akari present
biphasic
what happens in the first phase for R. akari
1 week after bite: papule to ulcer to eschar at site of bite
what happens after the first phase of Rickettsialpox
incubates for 7-24 days
systemic spread
what happens in 2nd phage of R. akari
high fever severe headache photophobia papulovesicular rash, pox-like progression ( vesicles crust over)
when does R. Akari 2nd phase heal
within 2-3 weeks
for clinical symptoms with R. akari and R. Rickittsii which one has a milder course
R. akari
Anthrax
bacterial disease of sheep and cattle, typically affecting the skin and lungs.
- transmitted to humans, causing severe skin ulceration or a form of pneumonia
what is the difference in skin rashes with Anthrax and Rickettsialpox
anthrax patients only have eschar
Rickettsialpox: papule –> ulcer –> eschar
If Rickettsialpox is on the differential diagnosis list what other thing should be on the list
Anthrax
R. Prowazekii has what reservoir
humans
how is R. prowazekii transmitted
during blood meal
- louse defecates highly infective feces
- introduced into by body by scratching/hand contamination/ injured skin or mucous membrane
how long can lice feces remain infectious in R. prowazekii
100 days
how are louse transfered from human to human in R. prowazekii
sharing clothes
what are 2 syndromes for R. prowazekii
acute, potentially severe vasculitis
- Brill-Zinsser disease
when does acute, potentially severe vasculitis occur in R. prowazekii? what other symptoms present
7-14 days after contact with infected lice
fever, centrifugal maculopapular rash, CNS symptoms
what is Brill-Zinsser disease
recrudescent from 10-50 years after primary infection
- milder form, rash, flu-like symptoms, seen in elderly patients WWII refugees
how is R. prowazekii tested in the laboratory
serology (MIF) test
when is R. Prowazekii prevelent in the world
during disaster, war, famine
rare in US
R. prowazekii is transmitted how in the US
usually rare in US
- “flying squirrels”
- squirrels have fleas, fleas bite humans
R. Parkeri common names
American Boutonneuse fever
-Tidewater spotted fever
where does R. Parkeri usually occur
souther United States
what is the vector for R. Parkeri
Amblyomma maculatum ( Gulf Coast Tick)
clinical symptoms for R. Parkeri
fever, headache, myalgias
eschars and rash on PE