Dog ticks carry several serious diseases, including Rocky Mountain spotted fever, tularemia, and ehrlichiosis. Two species go by the common name “dog tick” in the United States: the American dog tick, found widely east of the Rocky Mountains with limited populations to the west, and the brown dog tick, which lives throughout the country and is the only tick species that can complete its entire life cycle indoors. Both can transmit potentially life-threatening infections to humans and pets.
Rocky Mountain Spotted Fever
Rocky Mountain spotted fever (RMSF) is the most dangerous disease associated with dog ticks. Both the American dog tick and the brown dog tick can transmit the bacterium that causes it, though brown dog tick transmission has been documented primarily in the southwestern U.S. and Mexico.
Early symptoms appear within the first few days of infection and look a lot like the flu: fever, headache, nausea, vomiting, and muscle pain. A rash typically shows up two to four days after the fever starts, beginning as small, flat, pink spots on the wrists, forearms, and ankles before spreading to the trunk and sometimes the palms and soles. By day five or six, the rash can become petechial, meaning tiny bleeding spots under the skin, which signals severe disease.
Left untreated, RMSF can escalate quickly. Complications include swelling in the brain, respiratory failure, kidney damage, and loss of blood flow to the extremities severe enough to require amputation. This is not a wait-and-see illness. Treatment needs to begin based on symptoms alone, before blood test results come back, because confirmation requires comparing antibody levels from two blood draws taken weeks apart.
Tularemia
The American dog tick is a known carrier of the bacterium that causes tularemia, sometimes called “rabbit fever.” When transmitted through a tick bite, tularemia usually takes an ulceroglandular form: a skin ulcer develops at the bite site, and nearby lymph nodes swell painfully. Not every case produces a visible ulcer, so unexplained swollen lymph nodes after time spent outdoors should raise concern. Tularemia is treatable with antibiotics, but it can become serious if the infection spreads to the lungs or bloodstream.
Ehrlichiosis
The brown dog tick transmits several species of Ehrlichia bacteria. In dogs, these cause canine monocytic ehrlichiosis and canine granulocytic ehrlichiosis, both of which can produce fever, lethargy, weight loss, and bleeding disorders. For pet owners, this is one of the most common tick-borne threats to be aware of, especially if your dog picks up brown dog ticks frequently.
Humans are not off the hook. The brown dog tick has been reported to transmit the pathogen responsible for human monocytic ehrlichiosis. Symptoms in people include fever, headache, fatigue, and muscle aches, often appearing one to two weeks after a bite. Like RMSF, ehrlichiosis is diagnosed through paired blood samples and is treated with antibiotics. It can become severe in people with weakened immune systems or in older adults.
Tick Paralysis
Dog ticks also cause a condition that isn’t an infection at all. Tick paralysis happens when a female American dog tick attaches and feeds for several days, releasing a neurotoxin into the host’s body. The result is an ascending paralysis that starts in the legs and moves upward, causing an unsteady gait, difficulty standing, loss of reflexes, and eventually trouble breathing. It can be mistaken for serious neurological conditions like Guillain-Barré syndrome or botulism.
The good news is that recovery is remarkably fast once the tick is found and removed. In one documented case, breathing difficulties and absent reflexes began improving within seven hours of tick removal. The key is finding the tick, which can be hidden in the scalp or behind the ears. Tick paralysis is most commonly reported in children, likely because their smaller body weight means the toxin reaches effective levels more quickly.
Diseases in Dogs vs. Humans
The risks aren’t identical for you and your pet. Dogs are particularly vulnerable to ehrlichiosis from brown dog ticks, and heavy infestations can build up indoors since brown dog ticks thrive in kennels, homes, and cracks in walls. A single unnoticed female brown dog tick can lay thousands of eggs inside your house.
Humans face the greatest risk from RMSF and tularemia, both carried by the American dog tick picked up in grassy, brushy, or wooded areas. The American dog tick is most active in spring and summer, and adults actively seek larger hosts like dogs and people. Unlike deer ticks, which are tiny, American dog ticks are relatively large and easier to spot during a tick check, giving you a better chance of removing them before disease transmission occurs.
Reducing Your Risk
Tick repellents registered by the EPA are proven to reduce tick bites. Products containing DEET are effective, with protection time increasing at higher concentrations up to about 50%, beyond which there’s no meaningful additional benefit. Products with less than 10% active ingredient typically offer only one to two hours of protection, which may not be enough for a full day outdoors. Picaridin is another effective option.
For dogs, year-round tick prevention products (oral or topical) are the most reliable way to reduce brown dog tick infestations in your home. After spending time outside, check yourself and your dog thoroughly. On your body, pay special attention to the scalp, behind the ears, underarms, and the waistband area. On your dog, check around the ears, between the toes, and under the collar. Removing a tick within the first several hours of attachment significantly lowers the chance of disease transmission for most pathogens, though tick paralysis requires finding the tick before symptoms will resolve.