The American Dog Tick, Dermacentor variabilis, is one of the most widespread ticks across the United States, primarily found east of the Rocky Mountains. This organism is a vector, meaning it can transmit pathogens between hosts, including humans. Understanding the risks associated with this tick’s bite is important for anyone who spends time outdoors in grassy fields, along trails, or in wooded areas. The American Dog Tick is associated with several serious diseases, making awareness and prevention important for outdoor safety.
Identifying the American Dog Tick
The physical characteristics of the American Dog Tick help distinguish it from other local tick species. Adult ticks are relatively large, measuring about five millimeters before feeding, with reddish-brown bodies. A distinct ornate pattern on the dorsal shield, or scutum, aids identification. Females have a large off-white or grayish pattern behind the head, while the pattern covers most of the male’s back. After feeding, females can swell significantly, reaching up to 15 millimeters in length.
These ticks prefer habitats with little tree cover, making them common in grassy fields, scrublands, and along trails and roadsides. They engage in “questing,” climbing onto low vegetation, waving their front legs, and waiting for a host to brush by. This species is resilient and can survive for up to two years if a suitable host is not found.
Diseases Transmitted by the Tick
The American Dog Tick is a confirmed vector for two bacterial diseases that can affect humans, as well as a unique neurological condition.
Rocky Mountain Spotted Fever (RMSF)
Rocky Mountain Spotted Fever is caused by the bacterium Rickettsia rickettsii. Symptoms typically begin abruptly two to fourteen days after a bite, starting with a high fever, severe headache, and muscle pain. A rash often appears two to five days after the fever begins, usually starting on the wrists and ankles before spreading to the rest of the body. Early antibiotic treatment is necessary, as untreated RMSF can lead to serious complications involving the central nervous system, heart, lungs, and kidneys.
Tularemia
Tularemia is caused by the bacterium Francisella tularensis, which the American Dog Tick can transmit from small animals. The most common form following a tick bite is ulceroglandular tularemia, where a skin ulcer develops at the bite site. This presentation is accompanied by fever, chills, and painful swelling of the lymph glands nearest to the wound, often in the armpit or groin. Symptoms usually appear three to five days after exposure, though the incubation period can range from one to twenty-one days.
Tick Paralysis
Tick Paralysis is a rare, non-infectious condition caused by a neurotoxin released in the tick’s saliva. The toxin leads to an ascending flaccid paralysis, typically starting with weakness and unsteadiness in the legs. The weakness progresses upward toward the trunk and arms, and in severe cases, it can affect the muscles necessary for breathing. Recovery is usually rapid and complete once the attached tick is found and removed.
The Mechanism of Disease Transmission
Ticks must attach to a host and begin the feeding process to transmit a pathogen. They insert their mouthparts into the skin and secrete saliva containing compounds that prevent blood clotting and suppress the host’s immune response. Pathogens residing in the tick’s body must migrate to the salivary glands before being transferred to the host.
Pathogen transfer is not immediate upon attachment, meaning the duration of feeding is a factor in disease risk. For Rocky Mountain Spotted Fever, transmission can occur relatively quickly, sometimes requiring only six to ten hours of attachment. The risk of transmission for both RMSF and Tularemia increases significantly the longer the tick remains attached, especially if it feeds for more than twenty-four hours. This delayed mechanism emphasizes the importance of performing thorough and timely tick checks after outdoor exposure.
Prevention and Safe Removal Techniques
Reducing exposure involves proactive measures, particularly when entering high-risk areas like tall grass or dense brush.
- Wear light-colored clothing to spot ticks easily, and tuck long pants into socks to create a physical barrier.
- Apply repellents containing DEET to exposed skin, or Permethrin to clothing, for chemical protection.
- Perform a full-body “tick check” immediately after coming indoors.
- Showering within two hours can help wash off unattached ticks and locate those that have begun to feed.
If an attached tick is found, safe removal is necessary to minimize the risk of infection. Use fine-tipped tweezers to grasp the tick as close to the skin’s surface as possible. Pull upward with a steady, even pressure without twisting or jerking, as this can cause the mouthparts to break off and remain embedded. After removal, the bite area and hands should be thoroughly cleaned with rubbing alcohol or soap and water.