Tick-Borne Diseases

Question 1

What are the causative agent and vector for Lyme disease?

Answer 1

agent = Borrelia burgdorferi
vector = deer tick (Ixodides scapularis)

Question 2

How long must the tick be attached to transmit Lyme disease?

Answer 2

36-48 hours

Question 3

What is the geography of Lyme disease?

Answer 3

Northeast and upper Midwest

Question 4

What are the 3 stages of Lyme disease?

Answer 4

(1) localized infection, (2) early disseminated infection, (3) late disseminated infection

Question 5

What are the characteristic findings of localized infection in Lyme disease?

Answer 5

Erythema migrans - dark-pale-dark spreading, painless rash (pathognomonic - target or bull’s eye lesion), flu-like symptoms in the summer (fever, headache, myalgia)

Question 6

What are the characteristic findings of early disseminated infection in Lyme disease?

Answer 6

carditis (pericarditis, myocarditis, AV block) and neurological findings (meningitis, encephalitis, radiculopathy, cranial nerve palsy)

Question 7

What are the characteristic findings of late disseminated infection in Lyme disease?

Answer 7

migratory arthralgia or arthritis (large joints)

Question 8

What type of cranial nerve palsy is common in Lyme disease?

Answer 8

Bell’s palsy (7th cranial nerve/peripheral nerve)

Question 9

What are the characteristics of Bell’s palsy?

Answer 9

inability to wrinkle brow, drooping eyelid (inability to close eye), inability to puff cheeks (no muscle tone), droopy mouth (inability to smile or pucker)

Question 10

What distinguishes Bell’s palsy from a stroke?

Answer 10

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”)

Question 11

What is the initial test for Lyme disease?

Answer 11

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

Question 12

When do you need serology for diagnosing Lyme disease?

Answer 12

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

Question 13

What is the Tx for symptomatic Lyme disease?

Answer 13

=> 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

Question 14

If a deer tick has been attached < 36 hours, what should you do?

Answer 14

remove the tick - Abx Tx not necessary

Question 15

What is the Tx for asymptomatic Lyme disease?

Answer 15

a single dose (PO) of doxycycline (200 mg) only if:
=> endemic region
=> tick was attached for > 36 hours
=> within 72 hours of tick removal

Question 16

What PT education should be provided for Lyme disease?

Answer 16

wear long sleeved shirts, long pants, and light colors; perform a nightly tick check; use insect repellant (containing DEET)

Question 17

What are the causative agent and vector for Rocky Mountain Spotted Fever?

Answer 17

agent = Rickettsia rickettsii (Gram- bacteria)
vector = dog tick (Dermacenter variabilis)/wood tick

Question 18

What is the geography of Rocky Mountain Spotted Fever?

Answer 18

Southeastern and South Central U.S. (Appalachian fever)

Question 19

What is the effect of R. rickettsii biologically?

Answer 19

invades endothelial cells leading to vasculitis (infection of vascular wall - bleeding and clotting/microinfarcts) and vascular permeability (edema) => hemorrhagic petechiae can affect all organs

Question 20

What are the clinical manifestations of Rocky Mountain Spotted Fever?

Answer 20

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

Question 21

What are the hallmarks of Rocky Mountain Spotted Fever?

Answer 21

flu-like symptoms following camping or hiking in endemic areas during the summer months

Question 22

What are the meningeal signs typically seen with Rocky Mountain Spotted Fever?

Answer 22

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

Question 23

What are the late manifestations of Rocky Mountain Spotted Fever?

Answer 23

meningitis and encephalitis

Question 24

What’s the best initial diagnostic test for Rocky Mountain Spotted Fever?

Answer 24

clinical diagnosis based on Hx and S and S but have to perform lumbar puncture first to rule out bacterial meningitis

Question 25

What distinguishes the rash from Rocky Mountain Spotted Fever from measles (Rubeola)?

Answer 25

measles rash starts at the face and moves down the trunk to the extremities

Question 26

How do you interpret WBC findings from CSF analysis (lumbar puncture) in the diagnosis of Rocky Mountain Spotted Fever?

Answer 26

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

Question 27

When do you do a CT scan of the brain prior to lumbar puncture?

Answer 27

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)

Question 28

What is the Tx for Rocky Mountain Spotted Fever?

Answer 28

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

Question 29

When should you start Tx for Rocky Mountain Spotted Fever?

Answer 29

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)