Tick-Borne Diseases Flashcards
What are the causative agent and vector for Lyme disease?
agent = Borrelia burgdorferi vector = deer tick (Ixodides scapularis)
How long must the tick be attached to transmit Lyme disease?
36-48 hours
What is the geography of Lyme disease?
Northeast and upper Midwest
What are the 3 stages of Lyme disease?
(1) localized infection, (2) early disseminated infection, (3) late disseminated infection
What are the characteristic findings of localized infection in Lyme disease?
Erythema migrans - dark-pale-dark spreading, painless rash (pathognomonic - target or bull’s eye lesion), flu-like symptoms in the summer (fever, headache, myalgia)
What are the characteristic findings of early disseminated infection in Lyme disease?
carditis (pericarditis, myocarditis, AV block) and neurological findings (meningitis, encephalitis, radiculopathy, cranial nerve palsy)
What are the characteristic findings of late disseminated infection in Lyme disease?
migratory arthralgia or arthritis (large joints)
What type of cranial nerve palsy is common in Lyme disease?
Bell’s palsy (7th cranial nerve/peripheral nerve)
What are the characteristics of Bell’s palsy?
inability to wrinkle brow, drooping eyelid (inability to close eye), inability to puff cheeks (no muscle tone), droopy mouth (inability to smile or pucker)
What distinguishes Bell’s palsy from a stroke?
Bell’s palsy is due to dysfunction of cranial nerve VII (peripheral nerve) - motor nerve that affects both upper and lower parts of the face => stroke is due to an upper motor neuron (enervates both hemispheres) so forehead is spared (“upper spares upper”)
What is the initial test for Lyme disease?
clinical diagnosis - if erythema migrans is present, you don’t need anything else to make the diagnosis => blood cultures are the “gold standard” but rarely positive
When do you need serology for diagnosing Lyme disease?
for late manifestations - if PT presents with S and S of Lyme after many years (fatigue/myalgia):
=> if never treated - IgG and Abx
=> if previously treated - Tx is not recommended
What is the Tx for symptomatic Lyme disease?
=> Erythema migrans, Bell’s palsy, arthritis (all peripheral lesions) - doxycycline or amoxicillin for 14 days
=> carditis, meningitis, encephalitis, AV block (all central or severe lesions) - Ceftriaxone (Rocephin) 2g/d IV for 14 days
If a deer tick has been attached < 36 hours, what should you do?
remove the tick - Abx Tx not necessary
What is the Tx for asymptomatic Lyme disease?
a single dose (PO) of doxycycline (200 mg) only if:
=> endemic region
=> tick was attached for > 36 hours
=> within 72 hours of tick removal
What PT education should be provided for Lyme disease?
wear long sleeved shirts, long pants, and light colors; perform a nightly tick check; use insect repellant (containing DEET)
What are the causative agent and vector for Rocky Mountain Spotted Fever?
agent = Rickettsia rickettsii (Gram- bacteria) vector = dog tick (Dermacenter variabilis)/wood tick
What is the geography of Rocky Mountain Spotted Fever?
Southeastern and South Central U.S. (Appalachian fever)
What is the effect of R. rickettsii biologically?
invades endothelial cells leading to vasculitis (infection of vascular wall - bleeding and clotting/microinfarcts) and vascular permeability (edema) => hemorrhagic petechiae can affect all organs
What are the clinical manifestations of Rocky Mountain Spotted Fever?
acute onset of high fever (>= 102 degrees F), severe headache, arthralgia, petechial (not blanchable and pinpoint) rash begins on the extremities and spreads to the trunk (centripedal - 5 days after symptoms begin) => PTs are usually seen before the rash appears
What are the hallmarks of Rocky Mountain Spotted Fever?
flu-like symptoms following camping or hiking in endemic areas during the summer months
What are the meningeal signs typically seen with Rocky Mountain Spotted Fever?
Kernig = passively lift PT's knee - PT will feel pain in the back as meninges are stretched Brudzinski = passive lift PT's head to chest - knees flex
What are the late manifestations of Rocky Mountain Spotted Fever?
meningitis and encephalitis
What’s the best initial diagnostic test for Rocky Mountain Spotted Fever?
clinical diagnosis based on Hx and S and S but have to perform lumbar puncture first to rule out bacterial meningitis
What distinguishes the rash from Rocky Mountain Spotted Fever from measles (Rubeola)?
measles rash starts at the face and moves down the trunk to the extremities
How do you interpret WBC findings from CSF analysis (lumbar puncture) in the diagnosis of Rocky Mountain Spotted Fever?
WBCs:
=> < 5 = normal
=> 5 to 1,000 (with 50% lymphocyctes) = viral, TB, Lyme, Rocky Mountain Spotted Fever, fungal
=> > 1,000 (with 80% neutrophils) = bacterial meningitis
When do you do a CT scan of the brain prior to lumbar puncture?
CT scan w/out contrast if suspect focal lesion/deficit (e.g., weakness on one side) or if PT is uncooperative (e.g., unconscious or confused)
What is the Tx for Rocky Mountain Spotted Fever?
doxycycline 200 mg BID (IV initially then switch to PO) for 7 to 10 days => for everyone - no other Abx has been shown to successfully treat RMSF
When should you start Tx for Rocky Mountain Spotted Fever?
start empiric therapy based on clinical grounds (fever, headache/flu-like symptoms in the summer months, +/- camping/hiking in endemic areas, +/- tick bite) => do NOT wait for rash or antibody to appear (5-10% mortality rate if untreated)
