Explain the pathogenicity of Wuchereria bancrofti, referring to lymphadenitis, lymphangitis and elephantiasis.

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The pathogenicity of Wuchereria bancrofti arises from the presence and activity of adult worms living and coiling within the host's lymphatic vessels and lymph nodes, which provokes a chronic inflammatory response and progressive mechanical obstruction of lymphatic drainage. In the earlier and more acute phase, this produces lymphadenitis — inflammation of the lymph nodes, which become visibly swollen, tender and painful — and lymphangitis, inflammation of the lymphatic vessels themselves, seen clinically as red, tender streaks running along the course of the affected lymphatics, frequently accompanied by fever during these episodes. If infection is repeated and lymphatic damage accumulates over years, the chronic, cumulative obstruction of lymph flow leads to progressive pooling of lymph fluid in the surrounding tissues of the affected part of the body — most commonly the legs, but also the external genitalia. Over time this produces the advanced, chronic condition called elephantiasis: gross, disfiguring swelling accompanied by thickening and hardening of the overlying skin, giving the limb an appearance said to resemble an elephant's leg. Because of the severe, lifelong d …

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CBSE 2018Set ANNUAL8 marks
$Q. Describe the life cycle of Wuchereria bancrofti with neat diagrams.$
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Wuchereria bancrofti, the filarial worm causing lymphatic filariasis (elephantiasis), completes its life cycle between a human definitive host (where adults live in lymphatics) and a Culex mosquito intermediate host/vector (where larval development occurs).

Life cycle of Wuchereria bancrofti:

Definitive host and adult location: Humans are the definitive host. Adult male and female worms (thread-like, creamy white) live coiled together in the lymphatic vessels and lymph nodes, especially of the lower limbs and genital region.

Production of microfilariae: After mating, the female worm is viviparous and releases large numbers of minute, sheathed larvae called microfilariae into the lymph, from where they enter the peripheral blood stream. These show nocturnal periodicity — they are most abundant in peripheral blood at night, coinciding with the biting activity of the Culex vector, and retreat to the deep blood vessels of the lungs during the day.

Transmission to the mosquito: When a female Culex mosquito bites an infected person at night, it ingests circulating microfilariae along with the blood meal.

Development within the mosquito: In the mosquito's gut, the microfilariae shed their sheath, penetrate the gut wall, and migrate to the thoracic (flight) muscles. There they develop through first-stage (L1) and second-stage (L2) larvae into the infective third-stage (L3) filariform larvae, which then migrate to the mosquito's proboscis, ready for transmission.

Transmission back to a human host: When the infected mosquito bites another person, the infective L3 larvae actively escape from the proboscis and enter the skin through the bite wound.

Maturation in the new human host: The larvae migrate into the lymphatic system, where they develop into adult worms over several months to years, and the cycle repeats as new adults mate and release microfilariae.

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Q.Explain the pathogenicity of Wuchereria bancrofti, referring to lymphadenitis, lymphangitis and elephantiasis.

Concept understanding — Wuchereria bancrofti and Filariasis

Q.Explain the pathogenicity of Wuchereria bancrofti, referring to lymphadenitis, lymphangitis and elephantiasis.

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