What is the causative agent for Lyme disease?

The causative agent for Lyme disease is Borrelia burgdorferi, a spirochete bacterium. It is transmitted to humans primarily through the bite of infected black-legged ticks, often referred to as deer ticks. When the tick bites into the skin to feed on blood, it can introduce the bacterium into the host’s bloodstream. The early symptoms of Lyme disease may include fever, headache, fatigue, and a characteristic skin rash known as erythema migrans, which can develop at the site of the tick bite.

Borrelia burgdorferi is unique among the choices provided, as it is the only bacterium associated specifically with Lyme disease. The other microorganisms listed, such as Rickettsia rickettsii (which causes Rocky Mountain spotted fever), Yersinia pestis (the causative agent of plague), and Brucella abortus (responsible for brucellosis), are associated with different diseases and transmission routes. This specificity makes Borrelia burgdorferi clearly identifiable as the causative agent of Lyme disease.