Which tick species can bite people?
The phrase “human-biting ticks” doesn’t have the same meaning for everyone who uses it. In many public health settings in North America, “human-biting ticks” refers to a set of about four to ten species that are thought to bite people most frequently. But in reality, the diversity of tick species we might encounter is much more varied, and each species can pose a risk of exposure to different pathogens.
How many species of ticks are found in the world?
First, a note on taxonomy. In everyday conversation, when most people say “tick,” they are probably referring to members of the hard tick (Ixodidae) family such as the black-legged or “deer” tick, the American dog tick, the Lone star tick, the Pacific Coast tick, or several others. Unless otherwise noted, we use “tick” as shorthand for hard ticks throughout this blog post and across our website. “Soft ticks” (Argasidae) and a few unique outliers are also part of the Ixodida order, but do tend to bite people less frequently, at least in most parts of North America.
The hard tick family includes over 700 individual species worldwide, and nearly 100 of these species are found in North America. Most hard ticks in the U.S. and Canada belong to one of the following genera:
Ixodes
Dermacentor
Amblyomma
Rhipicephalus
Haemaphysalis
How do WE at MedZu labs define “human-biting ticks?”
This one’s easy—any tick submitted to our testing lab that is reported as having bitten a person is a human-biting tick in our book. From 2006 to mid-2023, we have tested 101,275 ticks that passed our molecular quality controls and had an identifiable species. 97.3% of those belong to one of just four species (in order of frequency: Ixodes scapularis, Dermacentor variabilis, Amblyomma americanum, and Ixodes pacificus), but more than 45 species of ticks were identified in total! So, the public-health focus on a small set of the most common human biters is certainly true to an extent, but it’s important to remember that ticks are (generally) opportunistic feeders. Many species have a strong preference for one type of host over others, but won’t turn down a free meal if a person stumbles through their habitat. This is especially true for hunters, wilderness hikers, and other people who spend significant time off-trail; less-maintained ground and proximity to animals that generally avoid humans can bring us in contact with ticks that don’t thrive in yards and human-adjacent areas. People who care for pets or other animals may also have increased exposure to diverse ticks as those animals nose around and lie down in brush where we wouldn’t typically go. One good example to consider is exposure to the “Rabbit tick” (Haemaphysalis leporispalustris): in their adult stage these ticks seem to show a strong preference for rabbit hosts, and human bites are quite rare (our lab has only received two Rabbit ticks that had bitten people), but people who raise outdoor rabbits or hunt rabbits may transfer these ticks to themselves while handling the rabbits.
Which species of tick bite humans most frequently?
Across North America in general, the most common human biters—accounting for just over 91% of submissions to the TickReport testing lab are:
Ixodes scapularis: “black-legged tick” or “deer tick.”
Dermacentor variabilis: “American dog tick.”
Amblyomma americanum: “Lone star tick.”
Ixodes pacificus: “Western black-legged tick.”
The next most common species are found in the Western part of North America from the Pacific Coast through the Rocky Mountains.
Dermacentor occidentalis: “Pacific Coast Tick.” Distributed throughout the Western U.S. and parts of Northern Mexico.
Dermacentor andersoni: “Rocky Mountain Wood Tick.” Typically found at high elevations in the Rocky Mountains, Cascade mountains, or (less frequently) Sierra Nevada mountains.
Ixodes spinipalpis: this species does not have a common name or “nickname.” It traditionally parasitizes rodents, but we have received over 100 samples that bit people or dogs. Earlier research, including infection data, can be found in a publication on TickReport submissions from the Western U.S..
Other regional species include:
Amblyomma maculatum: “Gulf Coast Tick.” These ticks are expanding their range from along the Gulf of Mexico and Atlantic Ocean to stretch across a large part of the Eastern U.S.. These ticks are now regularly found as far west as Oklahoma and as far north as Illinois, Michigan, or even Wisconsin.
Amblyomma cajennense: “Cayenne tick.” These ticks are most common in Texas, but can appear in any state bordering the Gulf of Mexico or in Southern California. They are widely distributed throughout Central and South America.
Ixodes cookei: “Woodchuck tick” or “Groundhog tick.” These can be found in pockets throughout much of North America, but are most common in New England, New York state, around the Great Lakes, and in parts of Southern and Eastern Canada. They are the third most common human biter from the Ixodes genus in North America after Ixodes scapularis and Ixodes pacificus, and are a vector of Powassan virus.
Notice that to this point, even when we consider different regional patterns, the most common human-biting ticks still fall into the top three genera of Ixodes, Dermacentor, and Amblyomma ticks. As we move down the list to consider tick species that are only represented by a few dozen samples in our collection, we observe both the continued diversity of those genera as well as a few new genera.
Haemaphysalis longicornis: “Asian Longhorned Tick.”
Rhipicephalus sanguineus: “Brown dog tick.”
Ixodes angustus: no widely-accepted common name
Ixodes dentatus: no widely-accepted common name
Ixodes marxi: “Squirrel tick.”
Ixodes muris: “Mouse tick.”
Dermacentor albipictus: “Winter Tick” or “Moose Tick.”
Haemaphysalis leporispalustris: “Rabbit Tick.”
Does identifying the exact tick species matter?
Absolutely. Knowing the exact species of tick—which very often can only be determined by a trained expert through careful examination under a microscope—goes a long way in determining the risk of pathogen exposure from a bite. Ixodes cookei is typically going to be less likely to carry Borrelia burgdorferi, Borrelia miyamotoi, Anaplasma phagocytophilum, or Babesia microti than an Ixodes scapularis tick from the same region. Dermacentor andersoni ticks are more likely to carry Colorado Tick Fever (CTF) virus or cause “tick paralysis” than the much more common Dermacentor variabilis tick.
From a surveillance standpoint, it’s also important to identify ticks exactly so we can trace when and how their ranges expand. Encounters between ticks and humans can surprise us sometimes, and it’s easy for less-typical human biters to get lumped together with the star species from their genus. This is one of the reasons we introduced molecular species assays to TickReport testing. We identify and photograph every tick we test under a microscope, then confirm that identification through DNA and RNA testing. Molecular ID is part of an overlapping series of quality controls in our testing process that helps us assess the condition of the tick sample (and by extension, confidence in the pathogen results we report to users) and safeguards against inaccurate identification, especially of engorged or damaged samples.
What species of tick bit you? Find out by testing your tick at TickReport.com.
Bonus material: more “exotic” tick species
Other tick species we have tested in very small numbers or that were known to originate outside the U.S. include those listed below. All were reported as biting a human host.
Amblyomma parvum
Amblyomma coelebs
Amblyomma sabanerae
Amblyomma tapirellum
Amblyomma tuberculatum
Dermacentor marginatus
Ixodes holocyclus
Rhipicephalus pulchellus
Amblyomma testudinarium
Ixodes affinis
Amblyomma variegatum
Amblyomma hebraeum
Amblyomma tholloni
Dermacentor auratus
Dermacentor hunteri
Dermacentor reticulatus
Haemaphysalis spinigera
Hyalomma aegyptium
Hyalomma truncatum
Ixodes pilosus
Rhipicephalus turanicus