The Pacific Coast Tick, Dermacentor occidentalis, is a common arthropod found along the Pacific Coast of North America. This species holds public health significance due to its ability to transmit various pathogens to humans and animals. Understanding this tick’s characteristics, preferred habitats, and the health concerns associated with its bites is important for public safety.
Identifying the Pacific Coast Tick and its Habitat
Pacific Coast Ticks, Dermacentor occidentalis, are generally brown with off-white mottling. Adult females have a mottled off-white dorsal shield, while males appear more mottled. They are flat and oval-shaped, ranging from 3 mm to 15 mm depending on engorgement.
This tick is widely distributed along the Pacific Coast of North America, from Oregon to northern Baja California and parts of Mexico. While it is the most common tick throughout much of California, it is less prevalent in the arid central valley and southeastern desert regions. Pacific Coast Ticks prefer habitats such as shrublands, chaparral, grassy areas, and hiking trails.
Adult Pacific Coast Ticks are active year-round in California, with peak activity in spring, especially April and May. Immature nymphal stages are most abundant during spring and summer. Adults feed on large mammals like deer, cattle, horses, and humans, while nymphs primarily feed on rodents, particularly squirrels.
Health Risks from Pacific Coast Ticks
The Pacific Coast Tick can transmit several pathogens. One primary disease is Pacific Coast Tick Fever (PCTF), caused by Rickettsia philipii. Symptoms of PCTF often include a dark scab at the bite site, known as an eschar, which can be about a quarter-inch in size. Fever and headache are also common, with onset typically occurring a few days to a week after the bite.
The Pacific Coast Tick can also transmit Rocky Mountain Spotted Fever (RMSF), caused by Rickettsia rickettsii. RMSF symptoms include sudden onset of moderate to high fever, severe headache, muscle pain, chills, and sometimes a rash that spreads to the palms and soles. Both PCTF and RMSF are part of spotted fever rickettsioses, and their symptoms can sometimes be difficult to distinguish.
Beyond rickettsial infections, the Pacific Coast Tick can transmit tularemia, caused by Francisella tularensis. It has also been implicated in cases of tick paralysis in animals like cattle, deer, and ponies. Seek medical attention if any symptoms develop after a tick bite, as early diagnosis and treatment with antibiotics like doxycycline are recommended for spotted fever rickettsioses.
Preventing Bites and Safe Tick Removal
Preventing Pacific Coast Tick bites involves several practical strategies when spending time outdoors. Wearing protective clothing, such as long-sleeved shirts and long pants tucked into socks, can help create a barrier against ticks. Using EPA-registered insect repellents on exposed skin is also recommended. Avoiding high-risk vegetated areas like dense shrublands, tall grasses, and along hiking trails can further reduce exposure. After outdoor activities, conducting thorough tick checks on yourself and your pets is an important preventive measure.
Should a tick become attached, safe and effective removal is important. Use clean, fine-tipped tweezers to grasp the tick as close to the skin’s surface as possible. Pull the tick upward with steady, even pressure, avoiding twisting or jerking, which could cause the mouthparts to break off. If mouthparts remain, the body will typically expel them over time, or they can be removed with tweezers if easily accessible.
After removing the tick, clean the bite area and your hands thoroughly with soap and water or rubbing alcohol. Dispose of the live tick by placing it in a sealed container, wrapping it tightly in tape, or flushing it down the toilet. Do not crush the tick with your fingers. Monitor the bite site for any signs of rash or infection in the days and weeks following the bite, and seek medical attention if you experience a rash, fever, or other concerning symptoms.