Scrub typhus is caused by:

ESIC Nursing Officer -2019 (Shift -1)

Applied Microbiology & Infection control

Easy

Appeared in: ESIC Nursing Officer -2019 (Shift -1)

Explanation

Scrub typhus is an acute, febrile illness caused by the bacterium Orientia tsutsugamushi.
This organism is an obligate intracellular gram-negative bacterium, which was formerly classified under the genus Rickettsia but is now recognized as distinct.
The disease is transmitted to humans by the bite of infected larval mites (chiggers) of the family Trombiculidae.
A characteristic sign in about half of the patients is the formation of a black, necrotic lesion called an eschar at the site of the bite.

Option A: Rickettsia prowazekii is the causative agent of epidemic typhus, also known as louse-borne typhus.
Option B: Rickettsia akari is the bacterium that causes rickettsialpox, a relatively mild disease.
Option D: Rickettsia typhi is the causative agent of murine typhus, also known as endemic or flea-borne typhus.

Visual 1: Infographic - A table comparing different rickettsial diseases, their causative agents, vectors, and key clinical features. This helps in differentiating between Scrub typhus, Epidemic typhus, Murine typhus, and Rickettsialpox.
Visual 2: Image - A close-up photograph of the characteristic eschar of scrub typhus. The image should show a dark, crusted, painless ulcer, which is a key diagnostic sign.
Visual 3: Diagram - The life cycle of the Trombiculid mite (chigger), illustrating how Orientia tsutsugamushi is maintained in the mite population (transovarial transmission) and transmitted to humans.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Etiology of Scrub Typhus as background academic context rather than a clinical decision trigger.
A key nursing role is obtaining a thorough patient history, including recent travel to endemic areas (like rural or forested regions of Southeast Asia, India, and Northern Australia) and outdoor activities that could lead to chigger bites.
Nurses must perform a meticulous skin assessment to look for the eschar, as its presence is a strong clue for scrub typhus and can guide early diagnosis, even before lab results are available.
Patient education is vital. Nurses should instruct patients on preventive measures, such as using insect repellent (DEET), wearing protective clothing, and avoiding sitting or lying on bare ground in endemic areas.

How to Approach the Question

This is a factual recall question that tests your knowledge of microbiology and infectious diseases.
First, identify the specific disease mentioned in the question stem: 'Scrub typhus'.
Next, scan the options provided. You will notice they are all names of bacteria, mostly from the Rickettsia genus.
The task is to correctly match the disease with its specific causative organism.
Recall that while scrub typhus is a rickettsial disease, its causative agent, Orientia tsutsugamushi, is genetically distinct from the Rickettsia genus. This distinction is key to selecting the correct answer and eliminating the other options which cause different types of typhus.

Concept Tested & Keywords

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