**Question:** A 25-year-old male university student gave history of multiple tick bites when he was at a camp 45 days ago. Ever since, he has episodes of high grade fever accompanied by headache, myalgias, arthralgias, nausea, and occasional vomiting. After 6-7 days, his symptoms would subside. Such episodes occurred thrice with a symptom free interval of 9-10 days. O/E, his temperature was 98°F, and his pulse was 72 beats per minute. His physical examination was completely within normal limits except some mild splenomegaly and skin lesions. Wright stain of this patient's peripheral blood smear was done. What is the first oral drug of choice in the above patient: -

A. Doxycycline
B. Clarithromycin
C. Chloroquine
D. Pyrimethamine

**Correct Answer:**

**Core Concept:** The patient presents with a clinical picture consistent with early stage Lyme disease, caused by the bacterium **Borrelia burgdorferi**. Lyme disease is transmitted to humans through the bite of infected black-legged ticks (Ixodes ticks) which are common in the United States, Europe, and parts of Asia.

**Why the Correct Answer is Right:**

The correct drug choice for Lyme disease treatment is **Doxycycline** due to the following reasons:

1. **Doxycycline** is a broad-spectrum antibiotic belonging to the tetracycline group. It is effective against various bacteria including **Borrelia burgdorferi**, the causative agent of Lyme disease.
2. The disease follows three phases: early local (erythema migrans), early disseminated (generalized symptoms), and late stage (neurological, cardiac, and joint involvement). Doxycycline is effective against all three phases, unlike the other options.

**Why Other Options are Incorrect:**

1. **Clarithromycin** (Option B) is a macrolide antibiotic, effective against a few bacterial pathogens but not against **Borrelia burgdorferi**. It is not the first choice for Lyme disease treatment.
2. **Chloroquine** (Option C) is an antimalarial drug prescribed for malaria and is ineffective against **Borrelia burgdorferi**, the causative agent of Lyme disease.
3. **Pyrimethamine** (Option D) is a drug used in the treatment of malaria and toxoplasmosis, but it is not effective against **Borrelia burgdorferi**, the causative agent of Lyme disease.

**Clinical Pearl:**

Lyme disease is a tick-borne infection caused by **Borrelia burgdorferi** and is distributed in the United States, Europe, and parts of Asia. Early diagnosis and treatment are crucial to prevent complications related to the disease, as it can lead to severe neurological, cardiac, and joint symptoms if left untreated. Doxycycline is the first-line antibiotic for Lyme disease treatment due to its effectiveness against the causative agent,