Other Tick Borne Infections Flashcards
What microorganism causes RMSF?
Rickettsia rickettsii
WHat is the morphology of Rickettsia rickettsii?
intracellular gram negative rod
What are the tick bectors for rickettsia rickettsii?
dermacenter (wood tick)
amblyomma americanum (lone star tick)
rhipicephalus sanguineus (brown dorg tick - AZ only so far)
DUring what life stage can the dermacenter tick bit humans and infect them?
only the adult - so it’s transmitted trans-stadially
What are two reservoir mammal hosts?
rodents and dogs
What is the incubation tie for RMSF?
3-12 days
What is the mortality rate if left untreated?
20%
Describe the clinical signs of RMSF.
- abrupt onset of influenza like illness with fevers, chills, myalgias, and headache
- somtimes nause and vomiting
- CENTRIPETAL rash observed by day 4 (no echar at bite site). rash is typically petechiae but sometimes extensive purpura - neither will blanch under pressure
- Splenomegaly in 50% of patients
What will lab tests show in RMSF?
- platelet count reduced
- WBC usually normal
- LFTs and CPK and ESR elevated
- DIC may be present
Also positive serology: IFA and ELISA
(PCR actually has low sensitivity here)
What should be in the differential with RMSF?
meningococcemia with petechial rash
measles/rubella
typhoid
ehrlichiosis or anaplasmosis
other rickettsioses
What is the drug of choice for RMSF? Others?
Doxycycline
Tetracycline
Chloramphenicol
RIfampin
What causes babesiosis?
It’s a hemato-parasite called Babesiosis microti (in US at least)
What isthe tick bector for babesiosis?
What are the mammal reservoirs?
Ixodes scapularis again - deer tick
mouse and white tailed deer again
What is the incubation perios for babesiosis?
1-6 weeks
Does babesiosis require treatment? Who would we be worried about?
In otherwise healthy hosts, babesiosis will resolve on its own without treatement and is hardly ever fatal
However, in people who are s/p splenectomy or are immunocompromise, the fatality rate is 40%!
What is a very common way babesiosis is transmitted other than via tick bites?
it’s the most common transfusion related infection in the US
Describe the clinical presentation of babesiosis.
- gradual onset
of non-specific flu-like symptoms with fever, headache, myalgia,s malaise, weakness, nausea - NO diganostic rash or eschar at bite site
- maybe hepatosplenomegaly
- occasional jaundice
What lab results would there be with babesiosis?
- variable/non-specific CBC changes
- maybe increase in billirubin and ALT
- ESR increased
- positive blood smear
- positive IFA for IgG
What will you see on a blood smear in a babesia microti infection?
trophozoite rings in RBCs
What are the two options for treatment of Babesiosis?
- combo quinine and clindamycin (for more severe cases)
- combo atovaquone and azithromycin
doxycycline WILL NOT work
chloroquine will provide symptomatic improvement, but won’t reduce the parasitemia
What microorganism causes tularemia?
Franciscella tularensis
What are the vectors for franciscella tularensis?
Reservoir hosts?
vectors - ticks, deer flies, mosqitoes
reservoirs - rabbits and other rodents, deer
WHat is the incubation period for tularemia?
1 day to 3 weeks
Describe the clinical presentation of tularemia.
- abrupt onset fever andchills, headache, myalgias sore throat
- bite site ulcerates and forms balck eschar with nonhealing ulcer
- regional lymphadenopathy, nause,a and vomitting common
Note: can have a pneuonic form when inhaled
Typhoideal form highest mortality
Where will you get the most lymphadenopathy in tularemia?
depends on how you got it -
inguinal from tick bite
axilla from rabbits (cuts on hands)
What are some lab findings in tularemia?
- WBC, LFTs, and ESR elevated
- thombocytopenia seen occasionally
- positive blood culture
- Positive PCR (high specificity)
What is the preferred therapy for tularemia? Alternatives?
antibiotics: streptomycin, gentamicin, doxycycline
alternative: cirpofloxacin, moxifloxacin, chloramphenicol
Describe the bacteria that cause ehrlichia and anaplasma.
both gram negative bacteria
obligate intracellular organism
What do ehrlichia and anaplsma bacteria have tropism for? WHat do they form in these cells?
WBCs
they grow to form an intracytoplasmis morulae (cluster of bacteria)
Which ehrlichia causes human monocytic ehrlichiosis?
Which one causes huan granulocytic ewingii ehrlichiosis?
Which one causes human anaplasmosis?
HME = E. chaffeensis
HGE = E. ewingii
HGA = A. phagocytophilum
What is the vector for ehrlichiosis/anaplasmosis?
Reservoir?
tick vector
reservoir: mice and deer
What is the incubaton period for ehrlichiosis and anaplasmosis?
2-14 days
In ehrlichiosis and anaplasmosis, what are hte most frequent complaints?
Less common complaitns?
Rare complaints?
frequent: fever, chills, headache, myalgia
less common: arthralgias, nausea, cough, confusion
uncommon: rash
What are some lab results that will occur with ehrlichiosis and anaplasmosis?
- CBC with nonspecific changes
- may observe leukopenia, relative granulocytosis with marked left shift, lymphopenia
- thromobyctopenia
- mild icnrease in AST and ALT
- Elevated ESR and CRP
- Normal billirubin, creatinine, and CPK
Which are you more likely to see the morulae on a blood smear in, HME or HGA?
HGA - in 20 to 60 % of cases you’ll see it
only 5 % in HME
What is the treatment for ehrliciosis /anaplasmosis?
doxycycine, tetracycline, rifamycins
NOT chloramphenicol
