Tick-Borne Diseases

From a 2014 lecture by Dr William Lockwood (ID):
The most common:  RMSF and Lyme disease (most likely to be on the Boards).  But there are others!
ETIOLOGIC AGENTS:
Rickettsia:  RMSF, Ehrlichia, Anaplasma, others.
Borellia:  Lyme, relapsing fever, Stari.
Babesia:  B. microti
Bacteria:  F. tularensis, B. quintana
Viral:  tick-borne encephalitis (3 types in Europe), Powassan virus, Colorado tick fever
Chemical:  tick paralysis
RMSF:
– Rickettsia rickettsii
– central-south US – OK, MO, NC, SC, AR
– causes a vasculitis
– young males most often
– incubation: 2-14 days
Symptoms:
   – Early symptoms:  fever, HA, myalgias, abd, N/V (latter two esp children)
   – Later symptoms:  petechial rash around day 3-5, 10% no rash; wrist, ankles, palms, soles
   – Late symptoms:  coma, seizures, gangrene of extremities
Diagnosis:
   – WBC variable, platelets typically low, LFTs typically elevated, CSF moderate pleocytosis
   – Best test:  skin biopsy of the rash lesions:  DFA, immunoenzyme  (biopsy doesn’t have to be a petechial lesion, but extremity best location)
   – Serology is often positive too late!
Treatment:
   –  Doxycycline 100mg PO q 12h
   –  This is the ONE time to use doxycycline in children!
   –  In pregnancy, use chloramphenicol (if you can find it).
Other rickettsial diseases:
Rash (plus fever, HA) – Mediterranean spotted fever
or
Eschar (plus fever, HA) – African tick bite fever
Tx for all:  doxycycline as above.
TICK BORNE RELAPSING FEVER:
– Borrelia species
– Biphasic symptoms:  fever x 1-3 days, then okay for 4-14 days, then fever.
– occasional neuro sxs
– Dx:  thick/thin smears, PCR; antibody testing not helpful.
– Tx:  tetracycline/doxycycline, or erythro/PCN
TICK BORNE ENCEPHALITIS
– Europe only
– Incubation 7-14 days
– Biphasic illness
– fever, HA, malaise
– encephalitis, paralysis
– 8-10% mortality, only supportive care available
POWASSAN VIRUS
– NE, N central US, Canada, Russia
– Dx PCR, Ab testing
– no tx, no vaccine
EHRLICHIA AND ANAPLASMA
– infects monocytes (Anaplasma infects granulocytes)
– mid-Atlantic states through OK area
– Sxs:  fever, HA, myalgias, rash in only 30% for Ehrlichia, 1% for anaplasma (“Rocky Mountain spotless fever”)
– Dx – PCR, serology
– Tx – amox in children, tetracycline
TICK PARALYSIS (looks a lot like G-B syndrome!)
– reaction to chemical in tick saliva
– weakness, fatigue
– ascending paralysis in 1-2 days, no fever, normal sensorium
– usually normal WBC, normal CSF
– Tx is removal of tick, symptoms self-limited
COLORADO TICK FEVER
– from 4K – 10K feet elevation
– spring to summer
– fever, HA, myalgias, conjunctivitis
– mildly low WBC, platelets
– Dx serology
– Tx none, self-limited up to 6 weeks.
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