Understanding Tick-Borne Fever: Bacteria, Viruses & Parasites

Tick-Borne Pathogens by Microbial Class

Class	Organism	Disease	Vector (US)	Key Features
Bacteria	Borrelia burgdorferi (spirochete)	Lyme disease	Ixodes scapularis (NE/MW), I. pacificus (West)	EM rash, arthritis, neuroborreliosis; treat doxycycline
	Anaplasma phagocytophilum (coccus)	Human Granulocytic Anaplasmosis (HGA)	Ixodes spp.	Fever, leukopenia, thrombocytopenia; treat doxycycline
	Ehrlichia chaffeensis (coccus)	Human Monocytic Ehrlichiosis (HME)	Amblyomma americanum (Lone Star)	Fever, transaminitis; treat doxycycline
	Rickettsia rickettsii (coccobacillus)	Rocky Mountain Spotted Fever (RMSF)	Dermacentor variabilis, D. andersoni	Fever, rash (palms/soles), vasculitis; treat doxycycline URGENT
Francisella tularensis (coccobacillus)	Tularemia	Dermacentor, Amblyomma	Ulceroglandular, typhoidal; treat aminoglycoside/doxy
Viruses	Powassan virus (Flavivirus)	Powassan encephalitis	Ixodes, Dermacentor	Rapid neuroinvasion; no specific Rx; 10% fatal
	Heartland virus (Phlebovirus)	Heartland virus disease	Amblyomma americanum	Fever, leukopenia, thrombocytopenia; supportive
	Bourbon virus (Thogotovirus)	Bourbon virus disease	Amblyomma americanum	Rare; similar to Heartland
Parasites	Babesia microti (protozoan)	Babesiosis	Ixodes scapularis	Malaria-like; hemolysis; treat atovaquone+azithro or clinda+quinine
	Babesia duncani (WA/CA)	Babesiosis (West Coast)	Ixodes pacificus	Similar

Coinfections

Single tick bite can transmit multiple pathogens (e.g., Lyme + Anaplasma + Babesia). Test for coinfections if atypical presentation or poor response.

Prevention

• Permethrin-treated clothing (0.5%).
• DEET / picaridin / IR3535 on skin.
• Tick checks within 2 hrs; shower.
• Remove attached ticks with fine-tipped tweezers; pull straight.
• Prophylactic doxycycline 200 mg single dose within 72 hrs for high-risk tick bite in Lyme-endemic area (IDSA).