**Question:** True about B. recurrentis:

A. It is a causative agent of epidemic relapsing fever
B. It is harmless to humans
C. It is the only known human pathogen of the Borrelia group
D. It is found only in camels and camel meat

**Correct Answer:** B. It is harmless to humans

**Core Concept:**
B. recurrentis is a species of the Borrelia genus, known to cause epidemic relapsing fever. This disease is characterized by recurrent episodes of fever, chills, and constitutional symptoms. Borrelia species are generally known for causing Lyme disease, but B. recurrentis stands out as the only known human pathogen within the Borrelia group.

**Why the Correct Answer is Right:**
B. recurrentis is considered harmless to humans as it primarily infects and causes disease in humans, rather than causing disease in its reservoir hosts like other Borrelia species. The disease it causes, epidemic relapsing fever, is transmitted via the bites of the argasid ticks, also known as sandflies. These ticks are not known to carry other Borrelia species, thereby limiting the risk of cross-infection.

**Why Each Wrong Option is Incorrect:**
A. Although B. recurrentis is a causative agent of epidemic relapsing fever, it is not true that it is harmless to humans. It is responsible for causing disease in humans, albeit rarely.
C. While B. recurrentis is the only known human pathogen of the Borrelia group, it is not harmless to humans. It can cause epidemic relapsing fever, a severe illness.
D. B. recurrentis is not found only in camels and camel meat. It is transmitted via sandfly bites, not associated with camels or camel meat consumption.

**Clinical Pearl:**
Borrelia species are not typically considered harmless to humans, as they can cause various diseases including Lyme disease, relapsing fever, and others. However, the correct statement regarding B. recurrentis is that it is the only known human pathogen within the Borrelia group, and it causes epidemic relapsing fever. This disease is transmitted via sandfly bites, not directly associated with camels or camel meat consumption.