Which organism is the causative agent of Lyme disease?

Borrelia burgdorferi is recognized as the primary causative agent of Lyme disease, a tick-borne illness that affects humans and animals. This spirochete bacterium is typically transmitted to humans through the bite of infected Ixodes ticks, commonly known as black-legged ticks or deer ticks.

Upon entering the host, Borrelia burgdorferi can invade various tissues and elicit an immune response that results in the characteristic symptoms of Lyme disease, which often include erythema migrans (a distinctive bull's-eye rash), fever, fatigue, and joint pain. If left untreated, the infection can lead to more serious complications affecting the heart, nervous system, and joints.

The other organisms listed do not cause Lyme disease. Rickettsia rickettsii is responsible for Rocky Mountain spotted fever, Francisella tularensis is known for tularemia, and Clostridium botulinum produces the toxin that leads to botulism. Understanding the specific pathogen involved in each disease is crucial for proper diagnosis and treatment.