Brown dog tick (Rhipicephalus sanguineus)
The brown dog tick (Rhipicephalus sanguineus) is a plain reddish-brown tick that favors dogs. It is found across the United States. Unlike most ticks, it can complete its whole life cycle indoors. So it can infest homes, dog kennels, and yards, even in cold places where other ticks cannot survive winter outside. Dogs are its strongly preferred host at every life stage, and it bites people far less often. But it can and does bite people. It matters most to public health as a carrier of Rocky Mountain spotted fever in the US Southwest. There, year-round outbreaks are tied to heavy infestations on free-roaming dogs. This page is for learning and is not medical advice.
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How to identify it
- Even reddish-brown color, with a long, narrow oval body. It has no pale markings or patterns on the back.
- Six-sided (hexagonal) base plate where the mouthparts attach (basis capituli). This is the classic feature that sets it apart from nearly all other US ticks. It is best seen with a magnifier.
- Adult male: the hard shield (scutum) covers the whole back. Adult female: the shield covers only the front part, leaving the rear free to swell as she feeds.
- Fully fed (engorged) females balloon into a gray to blue-gray, raisin-like blob many times their unfed size.
- Context is a clue: look on dogs and indoors. It is most often found along baseboards, in wall cracks, and up kennel walls, rather than in tall grass, leaf litter, or deep woods.
Size by life stage
Larvae are about 0.5 mm and nymphs about 1.1–1.3 mm. Unfed adults are about 1/8 inch (2.3–3.2 mm long). A fully fed female can grow about a hundredfold, to about 1/2 inch (up to ~12 mm), the size of a raisin. Males take only small blood meals and change little in size.
Where it lives and when
Found throughout the continental United States and around the world. It is thought to be the most widespread tick species on Earth. Because it can live and breed indoors, it settles into homes and kennels even in colder areas where outdoor ticks cannot survive winter. The Rocky Mountain spotted fever it spreads to people is centered in the US Southwest. This is notably in tribal communities in Arizona and in areas along the US–Mexico border. Cases there happen year-round and are linked to heavy tick infestations on free-roaming dogs. Elsewhere in the country it is a common dog and household pest, but a much smaller human disease concern.
Season
Because it can live indoors, the brown dog tick can be active all year. In the parts of the Southwest where RMSF is common, human cases happen throughout the year, not just in a warm-weather peak. So stay alert in every season, not only in summer.
Where it waits
- Homes, dog kennels, and yards (closely tied to domestic dogs)
- Indoor cracks and gaps: along baseboards, behind furniture, around window and door frames, and up walls or kennel sides
- Fenced yards and resting spots dogs use, rather than tall grass, leaf litter, or wooded trails
Diseases it can carry
Tick presence is not the same as personal disease risk. Not every bite transmits a pathogen.
Look-alikes
Its plain reddish-brown back, with no pattern, can be confused with other brown ticks. The American dog tick, the other main US RMSF carrier, is a useful contrast. American dog tick adults have a patterned, mottled off-white shield, while the brown dog tick is evenly reddish-brown. The best single clue is the six-sided base of the mouthparts (basis capituli), best seen with a magnifier. Fully fed females of many species look alike as gray blobs, so context helps. A tick found on a dog or indoors is very often a brown dog tick. Note that in the US, "Rhipicephalus sanguineus" is a group of closely related species (sensu lato). Sure identification down to the species may need an expert.
Compare all tick speciesCommon questions
Do brown dog ticks bite people?
Yes, but much less often than dogs. Dogs are the strongly preferred host at every life stage. Still, brown dog ticks can and do bite humans. In parts of the US Southwest, those bites can spread Rocky Mountain spotted fever, which is a medical emergency if it develops.
Can brown dog ticks infest my house?
Yes. Unlike most ticks, this species can complete its whole life cycle indoors. A dog can bring ticks home that then breed in cracks, along baseboards, and in kennels. Infestations can build up in homes and kennels even in cold climates. Control usually means treating the dog, the home, and the yard together. This is often done with help from a vet and a pest-control expert.
Does the brown dog tick carry Lyme disease?
No. Blacklegged (deer) ticks spread Lyme disease, not the brown dog tick. In the US, its main human disease concern is Rocky Mountain spotted fever. This is especially true in tribal communities in Arizona and other parts of the Southwest.
How is it different from the American dog tick?
They look and behave differently, though both can spread RMSF. American dog ticks have a patterned, mottled shield and live in grassy, brushy places outdoors. Brown dog ticks are plain reddish-brown with a six-sided mouthpart base. They stay close to dogs, homes, and kennels.
Sources
- 1.Rocky Mountain Spotted Fever (RMSF) (opens in a new tab) · CDC
Spread by American dog, Rocky Mountain wood, and brown dog ticks. Most US cases are in South-Central states; can be fatal without prompt doxycycline.
- 2.Where Ticks Live (opens in a new tab) · CDC
The Lone Star tick is widely distributed in the Northeast, South, and Midwest U.S.
- 3.TickEncounter Resource Center (opens in a new tab) · University of Rhode Island
Tick identification, prevention, and reporting resources.
- 4.
Educational information only, not medical advice. If you were bitten, use the tick bite tool and contact a licensed clinician if symptoms develop. Read our sources and disclaimer.