America's most common ticks and how to identify them

- Scientific name: Amblyomma americanum
- Where it's found: Widely distributed in the eastern United States, but more common in the South.
- Diseases it transmits: Ehrlichia chaffeensis and E. ewingii (which cause human ehrlichiosis), Francisella tularensis (tularemia), Heartland virus (Heartland virus disease), Bourbon virus (Bourbon virus disease), and Southern tick-associated rash illness (STARI).

The lone star tick is named for the white dot or “lone star” on its back, which distinguishes an adult female; adult females and nymphs most often bite humans. In recent years, changing weather patterns and bird migration patterns have helped the lone star tick move northward from the southern United States and Mexico: During summer 2019, it was found as far north as Wisconsin. This range expansion is bad news for northerners—this tick, described as “very aggressive” by the CDC, is a major carrier for ehrlichiosis, a potentially fatal disease which causes fever, headache, muscle pains, and rashes. Also, some victims of lone star tick bites have developed allergies to red (mammalian) meat; scientists are currently researching this association.

- Scientific name: Dermacentor andersoni
- Where it's found: Rocky Mountain states.
- Diseases it transmits: Rickettsia rickettsii (Rocky Mountain spotted fever), Colorado tick fever virus (Colorado tick fever), and Francisella tularensis (tularemia).

Readers living in Colorado, Idaho, Montana, or Wyoming should beware of the Rocky Mountain wood tick, commonly found in shrublands, open grasslands, and along trails at lower elevations. Adults of this species love to eat large mammals, and their bites can carry Rocky Mountain spotted fever (RMSF)—a disease which can be rapidly become fatal if it's not treated within the first five days. Early symptoms for RMSF include high fever, severe headache, lack of appetite, and swelling on the eyes and on the backs of hands; late symptoms (after five days) include comas and cerebral swelling, respiratory compromise, and organ failure.

- Scientific name: Amblyomma maculatum
- Where it's found: Southeastern and mid-Atlantic states and southern Arizona.
- Diseases it transmits: R. parkeri (R. parkeri rickettsiosis), a form of spotted fever.

Gulf Coast ticks may be identified by the patterns on their backs: Adult females have dark brown backs with silvery-white ornamentation near their heads; adult males have silver lines all across their backs. These ticks transmit a form of spotted fever similar to Rocky Mountain spotted fever (RMSF) but less severe; symptoms include fever, headache, and a maculopapular rash. The best way to distinguish R. parkeri from RMSF is to look for an eschar, a small circle of dead tissue left at the site where the tick bit—an R. parkeri bite leaves an eschar while an RMSF bite typically does not.

- Scientific name: Ixodes pacificus
- Where it's found: In the Pacific Coast states.
- Diseases it transmits: Anaplasma phagocytophilum (anaplasmosis), B. burgdorferi (Lyme disease), and likely B. miyamotoi (Borrelia miyamotoi disease, a form of relapsing fever).

Western blacklegged ticks transmit the infamous Lyme disease, which can cut your summer short by a month if it's not treated early. A characteristic early symptom of Lyme disease is erythema migrans, or EM rash: a red ring-like or homogenous rash which expands slowly over the course of a few days (see example photos from the CDC here). While all life stages of the western blacklegged tick bite humans, nymphs and adult females are more common culprits; both have black and reddish-orange patterns on their backs.

- Scientific name: Rhipicephalus sanguineus
- Where it's found: Worldwide.
- Diseases it transmits: Rickettsia rickettsii (Rocky Mountain spotted fever). Primary vector for R. rickettsii transmission in the southwestern United States and along the U.S.-Mexico border.

It's not enough to check your own limbs for ticks after a hike through the woods—you should be sure to check your dog, too, especially if you live in the southern or southwestern U.S. Brown dog ticks at all life stages can transmit the dangerous Rocky Mountain spotted fever (RMSF) to humans and dogs, and if your pooch becomes infested, it can take several months to treat your pet and sanitize your home. To tick check your dog, comb through its hair with your fingers, or a small brush or flea comb.

- Scientific name: Dermacentor variabilis
- Where it's found: Widely distributed east of the Rocky Mountains. Also occurs in limited areas on the Pacific Coast.
- Diseases it transmits: Francisella tularensis (tularemia) and Rickettsia rickettsii (Rocky Mountain spotted fever).

American dog ticks, despite their name, commonly attack humans, as well as other medium-sized mammals, including skunks, opossums, coyotes, and domestic dogs and cats. These ticks are commonly found in areas with little tree cover and are most active during the spring and summer. The adult females, which are most likely to bite humans, can be distinguished by the large white spots on the backs of their dark brown bodies. American dog ticks may carry RMTS or tularemia, a disease which can cause fever, headache, fatigue, anorexia, chest discomfort, sore throat, and other symptoms.

- Scientific name: Ixodes scapularis
- Where it's found: Widely distributed across the eastern United States.
- Diseases it transmits: Borrelia burgdorferi and B. mayonii (which cause Lyme disease), Anaplasma phagocytophilum (anaplasmosis), B. miyamotoi disease (a form of relapsing fever), Ehrlichia muris eauclairensis (ehrlichiosis), Babesia microti (babesiosis), and Powassan virus (Powassan virus disease).

As carriers of Lyme and several other diseases, blacklegged ticks are the scourge of the East Coast. Watch out for their reddish-brown bodies, long, thin mouthparts, and dark patches on their backs. While both adult females and nymphs feed on humans, nymphs are more likely to spread disease because their small size often allows them to go undetected for a long time. Nymphs are most active in the spring and summer, and adults are most active in the fall; however, adult ticks may still be active in the winter, as long as the temperature is above freezing.

- Scientific name: Ixodes cookei
- Where it's found: Throughout the eastern half of the United States.
- Diseases it transmits: Powassan virus (Powassan virus disease).

Groundhog ticks are fairly small: adult females are approximately 1/8th of an inch in length, or about the size of a sesame seed, and are colored tan to reddish with a darker shield on their backs. These ticks rarely attack humans; they prefer to bite smaller animals, including skunks, squirrels, rabbits, raccoons, foxes, and groundhogs, hence their name. However, humans should still be wary of these ticks, as they are common carriers of Powassan virus disease, a potentially deadly disease with symptoms including fever, headache, vomiting, and progression to inflation of the brain.

- Scientific name: Ornithodoros spp.
- Where it's found: Throughout the western half of the United States, including Texas.
- Diseases it transmits: Borrelia hermsii, B. turicatae (tick-borne relapsing fever [TBRF]).

The CDC warns that soft ticks most commonly pose a danger to people staying in rustic cabins or caves. These ticks come out at night and bite while people are sleeping, leaving most victims unaware that they have been bitten. This phenomenon is most common in the summer, but it can also occur in the winter when fires started by visitors to warm their cabins wake up ticks hibernating in the walls. Soft tick bites may carry tick-borne relapsing fever (TBRF); symptoms include headache, muscle pain, joint pain, chills, nausea, and febrile episodes, seizures associated with high body temperature.

- Scientific name: Haemaphysalis longicornis
- Where it's found: First reported in the U.S. in 2017; as of June 2019, longhorned ticks have been found in Arkansas, Connecticut, Kentucky, Maryland, North Carolina, New Jersey, New York, Pennsylvania, Tennessee, Virginia, and West Virginia.
- Diseases it transmits: In other countries, bites from these ticks can make people and animals seriously ill. As of June 2019, no harmful germs that can infect people have been found in the ticks collected in the United States. Research is ongoing.

Asian longhorned ticks are newcomers to the U.S.: the first individual was discovered on a New Jersey sheep in September 2017. Since then, over 50 longhorned ticks have been found in eleven states, primarily on domestic animals but also on wildlife and two humans. The presence of these ticks is particularly concerning for the CDC because singular females of the species can lay up to 2,000 eggs at a time without mating—meaning they can rapidly spread disease—and because they are commonly found on lawns and other domesticated areas, where people are not traditionally taught to take precautions against ticks. In Asia, Australia, and New Zealand, longhorned ticks have transmitted Lyme disease, Heartland virus, Powassan virus, Japanese spotted fever, and other severe fevers. This past June, a man in Westchester County, N.Y. was bitten by a longhorn tick after only going outside on his and other lawns; he has not shown any signs of disease because of the bite, but scientists are closely monitoring his case and other instances of longhorned ticks to learn more about the species' presence in America.