Charles Patrick Davis, MD, PhD
Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
William C. Shiel Jr., MD, FACP, FACR
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
In this Article
- Tick facts
- What are ticks?
- What are tick bite symptoms and signs?
- What diseases do ticks transmit (act as vectors) to humans?
- How is a tick bite diagnosed?
- What are the symptoms and signs of diseases transmitted by ticks?
- What is the treatment for a tick bite?
- How is a tick removed from the skin?
- What is the prognosis (outlook) for people who get a tick bite?
- What are the risk factors for tick bites?
- How are bites from ticks prevented?
- Where can I find more information about ticks?
What diseases do ticks transmit (act as vectors) to humans?
Although most tick bites do not transmit pathogens, some bites do. It is not possible to determine if a tick is carrying pathogens visually. The following is a list of all of the major tick-borne diseases, the usual tick vector(s), and the pathogen(s) the tick transmits that may occur in the United States.
- Rocky Mountain spotted fever -- Dermacentor variabilis (American dog tick, see picture below) and Rocky Mountain wood tick (Dermacentor andersoni) (hard tick) are the primary vectors and occasionally the brown dog tick (Rhipicephalus sanguineus); Amblyomma cajennense (hard tick) is the vector in countries south of the U.S. -- vectors for Rickettsia bacteria.
- Lyme disease -- Ixodes species including deer ticks (hard ticks, see photo below) -- vectors for Borrelia species of bacteria
- Babesiosis -- Ixodes species (hard ticks) -- vectors for Babesia, a protozoan
- Ehrlichiosis -- Amblyomma americanum or lone star ticks; see photo below with "lone star" mark on the dorsal surface (hard ticks) -- vectors for Ehrlichia chaffeensis and Ehrlichia ewingii bacterial species
- Tick-borne relapsing fever -- Ornithodoros moubata or African tick; see illustration below (soft tick) -- vectors for Borrelia species of bacteria
- Tularemia -- Dermacentor variabilis (American dog tick; several species are also known as a wood tick) (hard tick) and Amblyomma americanum or lone star tick (hard tick) -- vectors for Francisella tularensis bacteria
- Anaplasmosis (human granulocytic anaplasmosis or HGA) -- Ixodes species (hard tick) -- vectors for Anaplasma phagocytophilum bacteria
- Colorado tick fever -- Dermacentor andersoni (hard tick) -- vectors for Coltivirus, a RNA virus
- Powassan encephalitis -- Ixodes species and Dermacentor andersoni (both hard ticks) -- vectors for Powassan encephalitis virus, an RNA arbovirus
- Q fever -- Rhipicephalus sanguineus, Dermacentor andersoni (see photo below), and Amblyomma americanum (all three are hard ticks) -- vectors for Coxiella burnetii, a bacterium
- Southern tick-associated rash illness (STARI) -- Amblyomma americanum or lone star tick (hard tick) -- infectious agent not yet identified according to U.S. Centers for Disease Control and Prevention (CDC)
This list shows that some ticks, for example, Ixodes, can transmit more than one type of pathogenic microbe (virus, bacteria, and protozoa). It is possible to transmit more than one pathogen in a single tick bite, although this rarely occurs. Outbreaks of tick-related illnesses follow seasonal patterns (about April to September in the U.S.) as ticks evolve from larvae to adults.
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