Onchocerciasis causes?

DSSSB - 29 August 2019 (Shift-2)

Pathology & Genetics (E5)

Easy

Appeared in: DSSSB - 29 August 2019 (Shift-2)

Explanation

Onchocerciasis is a parasitic disease caused by the filarial worm Onchocerca volvulus.
It is transmitted by the bite of infected blackflies (Simulium species) that breed in fast-flowing rivers, leading to its common name, 'river blindness'.
The most severe manifestation is blindness, which occurs due to inflammatory reactions to microfilariae (larvae) dying in the eyes, causing corneal scarring and optic nerve damage.
Onchocerciasis is the world's second-leading infectious cause of blindness.

Option A: Acute respiratory tract infections are typically caused by viral or bacterial pathogens, not by the parasitic filarial worm responsible for onchocerciasis.
Option B: Malaria is a distinct parasitic disease caused by a protozoan (Plasmodium species) and is transmitted by Anopheles mosquitoes, not blackflies.
Option D: Poliomyelitis is a viral disease caused by the poliovirus. It affects the nervous system and has no etiological link to the parasitic worm that causes onchocerciasis.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Disease manifestation of Onchocerciasis as background academic context rather than a clinical decision trigger.
Nurses must be aware of vector-borne diseases endemic to certain regions to provide appropriate patient education on prevention, such as using insect repellent and wearing protective clothing.
Early recognition of symptoms like severe skin itching (pruritus) and subcutaneous nodules in a patient with a history of travel to an endemic area is crucial for timely referral and treatment to prevent irreversible blindness.
What if? If a patient presents with eye lesions and skin changes but has never traveled to an area with blackflies, the differential diagnosis would shift away from onchocerciasis towards other causes of uveitis or dermatitis, such as autoimmune conditions or other infections.

How to Approach the Question

First, identify the key term in the question: 'Onchocerciasis'. This is a specific medical term for a disease.
The question asks what this disease 'causes'. This is a direct factual recall question linking a disease to its primary outcome or common name.
Evaluate the options. 'River blindness' is a common name for a disease. The other options are distinct, well-known diseases.
Try to recall the association between Onchocerciasis and its common name or major complication. The name 'river blindness' is directly linked to the vector's habitat (rivers) and the disease's most severe outcome (blindness).
If you don't know the direct link, use elimination. You may know that malaria is from mosquitoes, polio is a virus, and respiratory infections are from germs. This makes 'river blindness' the most likely answer for a less common parasitic disease.

Concept Tested & Keywords

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E6 Nelson Textbook of Pediatrics(2024) — Volume 1 p. 2213-2215

E6 Medicine Harrison 22e Part 1 p. 1864-1866