What tick species causes tick-borne illness?

Tick Species Causing Tick-Borne Illnesses

Multiple tick species are responsible for transmitting different tick-borne illnesses, with the primary vectors being Ixodes scapularis (blacklegged tick), Ixodes pacificus (western blacklegged tick), Amblyomma americanum (lone star tick), and Rhipicephalus sanguineus (brown dog tick). 1

Major Tick Vectors and Associated Diseases

Ixodes Species (Blacklegged Ticks)

• Ixodes scapularis (blacklegged tick or deer tick):

  • Primary vector in northeastern and Midwestern United States 1
  • Transmits:
    • Borrelia burgdorferi (Lyme disease)
    • Anaplasma phagocytophilum (anaplasmosis)
    • Babesia microti (babesiosis)
    • Borrelia miyamotoi (tick-borne relapsing fever)
    • Powassan virus (tick-borne encephalitis) 1, 2

• Ixodes pacificus (western blacklegged tick):

  • Principal vector along the West Coast 1
  • Transmits similar pathogens as I. scapularis, including Anaplasma phagocytophilum 1

Amblyomma americanum (Lone Star Tick)

• Most commonly encountered tick in southeastern United States 1
• Transmits:
  • Ehrlichia chaffeensis (human monocytic ehrlichiosis)
  • Ehrlichia ewingii (ehrlichiosis)
  • Associated with Southern tick-associated rash illness (STARI) 1, 3

Rhipicephalus sanguineus (Brown Dog Tick)

• Vector for Rocky Mountain spotted fever in parts of Arizona 1
• Associated with unusually high incidence and case-fatality rates, particularly among children 1

Geographic Distribution and Seasonality

• Ixodes scapularis is prevalent in northeastern and upper Midwestern states 1, 2
• Ixodes pacificus is found primarily along the West Coast, especially northern California 1
• Amblyomma americanum is common in southeastern and South Central United States, with range extensions into New England states 1
• Most tick-borne illnesses occur during spring and summer months, corresponding with the feeding periods of ticks 1
• Anaplasmosis shows a bimodal seasonality with peaks in June-July and October 1

Clinical Implications

• Recognizing the tick species can help predict potential pathogens and associated diseases 4
• Co-infections are possible when the same tick species transmits multiple pathogens 1, 5
• For example, patients in endemic areas may be co-infected with Borrelia burgdorferi, Anaplasma phagocytophilum, or Babesia microti since they are all transmitted by Ixodes ticks 5

Important Considerations for Diagnosis and Treatment

• Early diagnosis is crucial to decrease morbidity and mortality 6
• Doxycycline is the drug of choice for most tick-borne rickettsial diseases 4
• Treatment should be initiated based on clinical suspicion without waiting for laboratory confirmation 4
• Transmission of Borrelia burgdorferi typically requires 24-48 hours of tick attachment 7

Prevention

• Avoid tick-infested areas when possible
• Use tick repellents containing DEET
• Wear protective clothing
• Perform thorough tick checks after potential exposure
• Remove attached ticks promptly 4

Understanding which tick species transmit specific pathogens is essential for risk assessment, diagnosis, and appropriate management of tick-borne diseases, which can significantly impact morbidity and mortality if not promptly identified and treated.