The causative agent of Lyme disease is:

Appeared in: NORCET 1 - 2020

Explanation

Borrelia burgdorferi is a species of spirochete bacterium that is the primary causative agent of Lyme disease in North America.
Lyme disease is a vector-borne illness, transmitted to humans by the bite of infected Ixodes ticks (commonly known as deer ticks).
The infection is characterized in its early stage by symptoms like fever, headache, fatigue, and a distinctive skin rash called erythema migrans (a bull's-eye rash).

Option A: Rickettsia prowazekii is a bacterium that causes epidemic (louse-borne) typhus, not Lyme disease.
Option B: Alphavirus is a genus of RNA viruses, not a bacterium. They are transmitted by mosquitoes and cause diseases such as Chikungunya and various forms of encephalitis.
Option D: Trypanosoma brucei gambiense is a protozoan parasite, not a bacterium. It is transmitted by the tsetse fly and is the causative agent of West African sleeping sickness (African trypanosomiasis).

Visual 1: Micrograph - A dark-field microscopy image showing the characteristic spiral shape of Borrelia burgdorferi spirochetes.
Visual 2: Infographic - The life cycle of the Ixodes tick, showing how it acquires and transmits Borrelia burgdorferi to humans and other hosts.
Visual 3: Clinical Image - A photograph of an erythema migrans rash, highlighting its typical 'bull's-eye' appearance, which is a key diagnostic sign of early Lyme disease.

Clinical Relevance

Nursing practice connection: Knowing Etiology of Infectious Diseases helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses play a crucial role in educating patients about preventing tick bites, which includes using insect repellent, wearing protective clothing in wooded areas, and performing tick checks after outdoor activities.
Early recognition of the erythema migrans rash is critical for prompt diagnosis and initiation of antibiotic therapy (typically doxycycline), which can prevent the progression to later, more severe stages of the disease.
A thorough patient history, including recent travel to endemic areas, is essential for diagnosis, as many patients may not recall a specific tick bite.

How to Approach the Question

First, identify the core of the question, which is asking for the specific 'causative agent' of 'Lyme disease'.
This is a factual recall question based on microbiology knowledge.
Access your knowledge base of common infectious diseases and their pathogens.
Evaluate each option: Borrelia burgdorferi is a well-known spirochete that causes Lyme disease.
Systematically rule out the distractors by identifying the diseases they cause: Rickettsia (typhus), Alphavirus (viral fevers like Chikungunya), and Trypanosoma (sleeping sickness).
Confirming the mismatch between the distractors and Lyme disease solidifies the correct choice.

Concept Tested & Keywords

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Practise the full NORCET 1 - 2020

Attempt every question from this paper in a timed mock, then review the full solution for each one.