Tick Bite

See Also

Types

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
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

Late spring through early fall presentation
Flu-like symptoms
1. Fever, Headache, malaise, myalgias are common presentations in tick-borne illness
2. However, nasal congestion or cough suggests alternative diagnosis (Upper Respiratory Infection)
Fever without obvious source
Focal neurologic deficit
Exotic travel or outdoor activities
Pet or livestock exposure
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

Viral-like syndrome (fever, Headache, malaise, myalgias) - Common Initial Presentation
1. Anaplasmosis
2. Ehrlichiosis
3. Rocky Mountain Spotted Fever
4. Colorado Tick Fever (high, biphasic fever)
5. Tickborne Relapsing Fever (high fever, Relapsing Fever)
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
  2. Starts on distal extremities (wrists, Forearms, ankles)
3. Alpha-Gal Reaction
  1. Urticarial (or Anaphylaxis) in response to red meat
4. Ehrlichiosis
  1. Rash occurs in one third of patients (esp. children)
5. Tularemia
  1. Scab at bite and painful regional adenopathy
Arthritis or Arthralgias
1. Lyme Disease
  1. Monoarthritis (esp. knee, hip) as early presentation; late presentation with Polyarthritis
Gastrointestinal or Hepatic Symptoms
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
Cardiac changes
1. Lyme Disease
  1. Pericarditis, Myocarditis or AV Nodal block
Malaria-like presentation
1. Babesiosis
  1. Fever, chills, myalgias, Headache, Dark Urine, Anorexia
  2. Possible Hepatosplenomegaly and Jaundice

Labs
General

Complete Blood Count
Serum Electrolytes
1. Hyponatremia
  1. Rocky Mountain Spotted Fever
Renal Function tests (BUN, Creatinine)
1. Decreased GFR to Acute Renal Failure
  1. Rocky Mountain Spotted Fever (late finding)
Liver Function Tests
1. Increased serum transaminases
2. Hyperbilirubinemia
  1. Rocky Mountain Spotted Fever

Labs
Diagnostic

Does not direct initial management
1. Most tests are delayed and may be initially normal
2. Start empiric Antibiotics without delay
Lyme Titer
1. ELISA with confirmatory Western Blot
Specific Serologic Tests (initial and repeated at 2-4 weeks)
Polymerase Chain Reaction (PCR)
Skin biopsy
1. Rocky Mountain Spotted Fever (immunohistochemical staining)
Peripheral Smear
1. Anaplasmosis
  1. Neutrophils with intracytoplasmic inclusions (morulae)
2. Babesiosis
  1. Maltese cross formation of RBC inclusions (appears similar to Malaria)
3. Tickborne Relapsing Fever
  1. Spirochetes under dark field microscopy and specific stains
Culture
1. Tularemia
  1. Culture is gold standard, but is a risk to lab staff (PCR or Serology is performed in most cases)
No tests available
1. Tick Paralysis
Experimental
1. Tick Borne Disease Serochip
  1. Tests for 8 tick borne infections in United States
  2. Tokarz (2018) Sci Rep 8(1):3158 [PubMed]

Diagnostics

Electrocardiogram
1. AV Nodal Block or Pericarditis (secondary or tertiary Lyme Disease)
Arthrocentesis of Monoarthritis
1. Increased Synovial Fluid WBCs (may be indistinguishable from Septic Joint)

Precautions

Lack of known bite or lack of secondary bite reaction do not exclude Tick Borne Illness
1. Patients often do not remember an initial Tick Bite
Prompt Tick Removal prevents pathogen transmission (e.g. Lyme Disease) and resolves Tick Paralysis
Keep high index of suspicion in non-localizing febrile illness (esp. summer fever, adults)
Coinfection with more than one tick-borne illness is common
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
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

Causes
Ticks - Eastern United States

Black-Legged Tick or Deer Tick (Ixodes Scapularis) - Eastern half of United States
1. Babesiosis
2. Human Granulocytic Anaplasmosis (Human Granulocytic Ehrlichiosis)
3. Lyme Disease
4. Borrelia Miyamotoi (emerging)
  1. Causes Relapsing Fever in endemic Lyme Disease regions
  2. Treated with same Antibiotics as Lyme Disease
American Dog Tick (Dermacentor variabilis) - East of Rocky Mountains and regions of Pacific Coast
Lone Star Tick (Amblyomma americanum, white spot on back) - Southeastern and eastern United States
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. Tularemia
5. Heartland Virus
6. Bourbon Virus
7. Southern Tick-Associated Rash Illness (STARI, Masters Disease)
  1. Rash similar to Erythema Migrans (Lyme Disease)
  2. Treated with Doxycycline
Woodchuck Tick or Groundhog Tick (Ixodes cookei) - Eastern half of United States
1. Powassan Encephalitis
  1. Rare Encephalitis cause in Northeastern and North Central States
  2. Cognitive Impairment in >50% of survivors, and 10-15% mortality
  3. Unknown treatment
Gulf Coast Tick (Amblyomma Maculatum) - Atlantic and Gulf Coasts
1. Rickettsia parkeri rickettsiosis (spotted fever)
Brown Dog Tick (Rhipicephalus snguineus) - Throughout United States
1. Q Fever
2. Rocky Mountain Spotted Fever

Causes
Ticks - Western United States

Rocky Mountain Wood Tick (Dermacentor andersoni) - Rocky Mountain States
1. Colorado Tick Fever
2. Q Fever (unproven association)
3. Powassan Encephalitis (unproven association)
4. Rocky Mountain Spotted Fever
5. Tick Paralysis
6. Tularemia
Western Black Legged Tick (Ixodes pacificus)
1. Same conditions as for Black-Legged Tick or Deer Tick above
2. Human Granulocytic Anaplasmosis (Human Granulocytic Ehrlichiosis)
3. Lyme Disease
Pacific Coast Tick (Dermacentor occidentalis)
1. Rickettsia phillipi (364D Rickettsiosis)
2. Rocky Mountain Spotted Fever
3. Tularemia
Soft Ticks (Ornithodoros)
1. Local pain, inflammation and in some cases necrosis
2. Relapsing Fever (Borrelia species)
Brown Dog Tick (Rhipicephalus snguineus) - Throughout United States
1. Q Fever
2. Rocky Mountain Spotted Fever

Associated Conditions
Tick-Borne Conditions by U.S. Frequency

Lyme Disease
1. Incidence: 30,000 cases per year in U.S.
2. Distribution: Primarily northeast U.S. and upper midwest (MN, WI)
Rocky Mountain Spotted Fever
1. Incidence: 6,000 cases per year in U.S.
2. Distribution: Primarily southeastern United States
Anaplasmosis
1. Incidence: 5000 cases per year in U.S.
2. Distribution: Primarily northeast U.S. and upper midwest (MN, WI)
Ehrlichiosis
1. Incidence: 1500 cases per year in U.S.
2. Distribution: Primarily southeastern U.S.
Babesiosis
1. Incidence: 1000-2000 cases per year in U.S.
2. Distribution: Primarily northeast U.S. and upper midwest (MN, WI)
Tularemia
1. Incidence: Hundreds of cases per year in U.S.
2. Distribution: Primarily southcentral U.S.
Colorado Tick Fever
1. Incidence: 200-300 cases per year in U.S.
2. Distribution: Rocky Mountains
Tickborne Relapsing Fever
1. Incidence: 20-30 cases per year in U.S.
2. Distribution: Rocky Mountains

Management
Antibiotic Selection

Background
1. Doxycycline is effective in most tick-borne illnesses (except Babesiosis and Tularemia)
Doxycycline
1. Avoided in age <8 years unless no alternative (due to dental effects)
  1. In many cases, including under age 8 years, Doxycycline is used
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 or pregnancy (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)
6. Tickborne Relapsing Fever
  1. Adults
Atovaquone with Azithromycin
1. Babesiosis
Clindamycin with Quinine
1. Babesiosis
  1. Alternative regimen
Amoxicillin
1. Lyme Disease
  1. Indicated in children <8 years old and those allergic to docycycline
Cefuroxime
1. Lyme Disease
  1. Indicated in children <8 years old with Penicillin Allergy or those allergic to docycycline
Erythromycin
1. Tickborne Relapsing Fever
  1. Pregnant women and children <8 years old
2. Lyme Disease
  1. Other agents are preferred due to lower Macrolide efficacy (use only if allergy to other agents)
Azithromycin
1. Lyme Disease
  1. Other agents are preferred due to lower Macrolide efficacy (use only if allergy to other agents)
2. Babesiosis
  1. Treat with combination of Azithromycin AND Atovaquone
Ceftriaxone
1. Lyme Disease
  1. Seconday or tertiary Lyme Disease
2. Tickborne Relapsing Fever
  1. Central Nervous System involvement
Chloramphenicol
1. Rocky Mountain Spotted Fever
  1. Indicated if Doxycycline is contraindicated
2. Anaplasmosis
  1. Indicated if Doxycycline is contraindicated
3. Ehrlichiosis
  1. Indicated if Doxycycline is contraindicated
Rifampin
1. Anaplasmosis
  1. Indicated if Doxycycline is contraindicated
2. Ehrlichiosis
  1. Indicated if Doxycycline is contraindicated
Streptomycin IM
1. Tularemia
Gentamicin IM
1. Tularemia
Supportive Care (No Antibiotics)
1. Colorado Tick Fever

Prevention

See Prevention of Tick-borne Infection
See Tick Removal

Resources

CDC Tickborne Diseases
1. http://www.cdc.gov/ticks/diseases/

References

Green and Millsap (2016) Crit Dec Emerg Med 30(1): 4
Pensa and Werner in Swadron (2022) EM:Rap 22(5): 8-12
Juckett (2013) Am Fam Physician 88(12): 841-7 [PubMed]
Pace (2020) Am Fam Physician 101(9): 530-40 [PubMed]