Tick Bite


Tick Bite, Tick-Borne Disease, Tick Borne Illness, Alpha-gal Reaction

  • Types
  1. Hard Ticks (Ixodidae)
    1. Hard body casing
    2. Head visible when viewed from above
    3. Responsible for most Tick-Borne Disease (due to ability to adhere to skin for days)
    4. Habitat: Tall grass and brush
  2. Soft Ticks (Argasidae)
    1. Soft, leathery body casing
    2. Head not visible when viewed from above
    3. Habitat: Animal nests
  • History
  • Presentations suggestive of tick-borne illness
  1. Late spring through early fall presentation
  2. Flu-like symptoms
  3. Fever without obvious source
  4. Focal neurologic deficit
  5. Exotic travel or outdoor activities
  6. Pet or livestock exposure
  7. New severe, sudden, Allergic Reaction (Urticaria, Anaphylaxis) to red meat (Alpha-gal Reaction)
    1. Sensitization to galactose-alpha-1,3-galactose (alpha-gal)
    2. Alpha-gal is present in both ticks and red meat (lamb, pork, beef)
    3. Commins (2011) J Allergy Clin Immunol 127(5): 1286-93 [PubMed]
  • Findings
  1. Rash
    1. Lyme Disease (Erythema Migrans)
      1. Develops days 3-21 after Tick Bite
      2. Target or erythematous Plaque >5 cm centered at bite site and gradually increasing to >10-20 cm
    2. Rocky Mountain Spotted Fever
      1. Erythematous Macules (day 6) that transition to Petechiae
    3. Alpha-gal Reaction
      1. Urticarial (or Anaphylaxis) in response to red meat
  2. Arthritis or Arthralgias
    1. Lyme Disease
      1. Monoarthritis (esp. knee, hip) as early presentation; late presentation with Polyarthritis
  3. Neurologic changes
    1. Lyme Disease
      1. Cranial Nerve dysfunction (esp. Bells Palsy), Meningitis, Sudden Hearing Loss, polyradiculoneuritis
    2. Tick Paralysis
      1. Ascending paralysis starting with leg weakness, areflexia, then upper extremity and head weakness
  4. Cardiac changes
    1. Lyme Disease
      1. Pericarditis, Myocarditis or AV Nodal block
  5. Viral-like syndrome (fever, Headache, malaise, Nausea, Vomiting, cough)
    1. Anaplasmosis
    2. Ehrlichiosis
    3. Rocky Mountain Spotted Fever
  6. Malaria-like presentation
    1. Babesiosis
      1. Fever, chills, myalgias, Headache, Dark Urine, Anorexia (and possible Hepatosplenomegaly and Jaundice)
  1. Complete Blood Count
    1. Thrombocytopenia
    2. Leukopenia
  2. Serum Electrolytes
    1. Hyponatremia
  3. Renal Function tests (BUN, Creatinine)
    1. Decreased GFR
  4. Liver Function Tests
    1. Increased serum transaminases
  • Labs
  • Diagnostic
  1. Does not direct initial management
    1. Most tests are delayed and may be initially normal
  2. Lyme Titer
    1. ELISA with confirmatory western blot
  3. Specific serologic tests (initial and repeated at 2-4 weeks)
    1. Anaplasmosis
    2. Ehrlichiosis
    3. Rocky Mountain Spotted Fever
  4. Polymerase Chain Reaction (PCR)
    1. Babesiosis
  5. Skin biopsy
    1. Rocky Mountain Spotted Fever (immunohistochemical staining)
  6. Peripheral Smear
    1. Anaplasmosis
      1. Neutrophils with intracytoplasmic inclusions (morulae)
    2. Babesiosis
      1. Maltese cross formation of RBC inclusions (appears similar to Malaria)
  7. No tests available
    1. Tick Paralysis
  • Diagnostics
  1. Electrocardiogram
    1. AV Nodal Block or Pericarditis (secondary or tertiary Lyme Disease)
  2. Arthrocentesis of Monoarthritis
    1. Increased Synovial Fluid WBCs (may be indistinguishable from Septic Joint)
  • Precautions
  1. Lack of known bite or lack of secondary bite reaction do not exclude Tick Borne Illness
  2. Prompt Tick Removal prevents pathogen transmission (e.g. Lyme Disease) and resolves Tick Paralysis
  3. Start empiric antibiotics immediately if Tick Borne Illness is suspected
    1. Untreated Rocky Mountain Spotted Feveray be lethal by day 8 after Tick Bite
    2. Untreated Lyme Disease may progress to AV Block, Pericarditis, Myocarditis, Polyarthritis, Meningitis, Bells Palsy
    3. Untreated Babesiosis may progress to DIC, Renal Failure and death
  4. Admit patients with significant complications of tick-borne illness
    1. Lyme Disease with Cardiac involvement (e.g. AV nodal block, Pericarditis, Myocarditis)
    2. Lyme Disease with CNS involvement (e.g. Meningitis)
    3. Rocky Mountain Spotted Fever (unless diagnosed early, before day 5 and before rash appears)
    4. Immunocompromised patients or significant complication of other tick-borne illness (Anaplasmosis, Ehrlichiosis)
    5. Babesiosis beyond early phase
  • Management
  • Antibiotic Selection
  1. Doxycycline
    1. Avoided in age <8 years unless no alternative (due to dental effects)
    2. Lyme Disease
      1. Indicated in adults, children >8 years old, Penicillin allergic children at any age
    3. Rocky Mountain Spotted Fever
      1. Adults and children regardless of age (despite dental adverse effects)
      2. Do not delay treatment
    4. Anaplasmosis
      1. Adults and children regardless of age (despite dental adverse effects)
    5. Ehrlichiosis
      1. Adults and children regardless of age (despite dental adverse effects)
  2. Atovaquone with Azithromycin
    1. Babesiosis
  3. Clindamycin with Quinine
    1. Babesiosis
      1. Alternative regimen
  4. Amoxicillin
    1. Lyme Disease
      1. Indicated in children <8 years old and those allergic to docycycline
  5. Cefuroxime
    1. Lyme Disease
      1. Indicated in children <8 years old with Penicillin Allergy or those allergic to docycycline
  6. Ceftriaxone
    1. Lyme Disease
      1. Seconday or tertiary Lyme Disease
  • Associated Conditions
  1. See Tick-Borne Disease
  2. American Dog Tick (Dermacentor variabilis)
    1. Q Fever
    2. Rocky Mountain Spotted Fever
    3. Tick Paralysis
    4. Tularemia
  3. Black-Legged Tick or Deer Tick (Ixodes Scapularis)
    1. Babesiosis
    2. Human Granulocytic Anaplasmosis (Human Granulocytic Ehrlichiosis)
    3. Lyme Disease
  4. Western Black Legged Tick (Ixodes pacificus)
    1. Same conditions as for Black-Legged Tick or Deer Tick above
  5. Brown Dog Tick (Rhipicephalus snguineus)
    1. Q Fever
    2. Rocky Mountain Spotted Fever
  6. Lone Star Tick (Amblyomma americanum, white spot on back)
    1. Alpha-gal Sensitivity (IgE Antibody to galactose-alpha 1,3-galactose)
      1. Anaphylaxis to red meat (beef, pork, lamb) as well as cetuximab (Erbitux)
    2. Human Monocytic Ehrlichiosis
    3. Q Fever
    4. Southern Tick-Associated Rash Illness (Masters Disease)
    5. Tularemia
  7. Pacific Coast Tick (Dermacentor occidentalis)
    1. Rickettsia phillipi (364D Rickettsiosis)
    2. Rocky Mountain Spotted Fever
    3. Tularemia
  8. Rocky Mountain Wood Tick (Dermacentor andersoni)
    1. Colorado Tick Fever
    2. Q Fever (unproven association)
    3. Powassan Encephalitis (unproven association)
    4. Rocky Mountain Spotted Fever
    5. Tick Paralysis
    6. Tularemia
  9. Soft Ticks (Ornithodoros)
    1. Local pain, inflammation and in some cases necrosis
    2. Relapsing Fever (Borrelia species)
  10. Woodchuck Tick (Ixodes cookei)
    1. Powassan Encephalitis
  • Resources
  1. CDC Tickborne Diseases
  • References
  1. Green and Millsap (2016) Crit Dec Emerg Med 30(1): 4
  2. Juckett (2013) Am Fam Physician 88(12): 841-7 [PubMed]