EM may be preceded or accompanied by flu like symptoms. These symptoms may persist, change disappear and reappear intermittently for several weeks. Less frequently, irregularities of the hear rhythm occur. The spirochete causing Lyme disease was first isolated from this tick in 1984. Adults feed on large mammals, including deer, dogs, and humans.
All stages feed by imbedding their mouthparts into the skin of a host and taking a blood meal.
Studies indicate that wood rats serve as the primary reservoir host, and together with another nonhumanbiting lxodes tick, maintain the agent of Lyme disease in nature. Approximately 24 to 72 hours of attachment is necessary for transmission of the Lyme disease spirochete to occur. In California a low percentage of the ticks are infected with the Lyme disease spirochete. Both are teardrop shaped. The western black-legged tick has been reported from 55 of the 58 California counties, but is most common in the humid coastal areas and on the western slopes of the Sierra Nevada range.