All of the following are the diseases commonly transmitted by lice, EXCEPT:

DSSSB 14 August 2024

Microbiology

Medium

Appeared in: DSSSB 14 August 2024

Explanation

Giardiasis is an intestinal infection caused by the protozoan parasite Giardia lamblia.
Its primary mode of transmission is the fecal-oral route, which occurs through the ingestion of cysts in contaminated food or water.
Unlike the other options, giardiasis is not transmitted by any insect vector, including lice.

Option A: Epidemic typhus, caused by Rickettsia prowazekii, is a classic louse-borne disease. The bacteria are transmitted when infected louse feces are rubbed into a bite or other skin abrasion.
Option C: Louse-borne relapsing fever is caused by the spirochete Borrelia recurrentis. Humans are infected when the louse is crushed, and the bacteria enter the body through the skin.
Option D: Trench fever, caused by Bartonella quintana, is also transmitted by the body louse. The bacteria are excreted in the louse's feces and infect humans through skin abrasions.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Modes of transmission for infectious diseases, specifically differentiating between vector-borne (louse-borne) and water-borne illnesses as background academic context rather than a clinical decision trigger.
Understanding the mode of transmission is critical for diagnosis and prevention. A patient presenting with fever and a rash who has lived in crowded, unhygienic conditions might be suspected of a louse-borne disease.
In contrast, a patient with diarrhea and abdominal cramps after a camping trip where they drank from a stream would point towards giardiasis.
Public health interventions differ based on transmission. Louse-borne diseases require vector control (delousing, improving hygiene), while giardiasis prevention focuses on water purification and food safety.

How to Approach the Question

First, identify the keyword "EXCEPT". This tells you that three of the options are similar in some way, and one is the outlier.
The question's theme is "diseases commonly transmitted by lice". This means you are looking for the one disease on the list that is NOT transmitted by lice.
Review each option. Recall or deduce the transmission method for each disease.
Epidemic typhus, relapsing fever, and trench fever are historically associated with poor hygiene and crowding, conditions that favor louse infestations.
Giardiasis is widely known as a cause of gastroenteritis (diarrhea) linked to drinking contaminated water ('beaver fever').
Conclude that giardiasis is the exception because its transmission route (fecal-oral) is different from the others (louse-borne).

Concept Tested & Keywords

Concept Tested: Modes of transmission for infectious diseases, specifically differentiating between vector-borne (louse-borne) and water-borne illnesses.
Stem keywords: diseases, transmitted by lice
Lead-in keywords: EXCEPT
Negative lead-in flag: The question asks to identify the option that does NOT fit the described category (transmitted by lice).

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