Q.Assertion (A) : In humans, filariasis is characteried by inflammation in the lower limbs. Reason (R) : Filarial worm usually lives in the lymphatic vessels of the lower limbs.
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Start your 14-day free trial to unlock the full solution →Filariasis causes inflammation in the lower limbs because the filarial worm lives and breeds in the lymphatic vessels of those limbs, blocking them and leading to swelling.
Filariasis, also known as elephantiasis, is a parasitic disease that has plagued tropical regions for centuries. The condition is caused by thread-like nematodes (roundworms) of the family Filariidae, most commonly Wuchereria bancrofti. To understand why the disease manifests so dramatically in the legs, you have to follow the worm's life cycle and its preferred habitat inside the human body.
The adult filarial worms are long, slender parasites that take up residence in the lymphatic system. The lymphatic vessels are a network of thin tubes that run throughout the body, much like blood vessels, but their job is to drain excess fluid from tissues and return it to the bloodstream. They also play a crucial role in immune defence. The filarial worm has a strong preference for the lymphatic vessels of the lower limbs — the legs and feet. This is not a random choice; the slower flow of lymph in the legs, combined with gravity, makes them an ideal breeding ground for the worms.
Once inside these vessels, the adult worms mate and produce millions of microscopic larvae called microfilariae. These larvae circulate in the blood, usually at night, waiting to be picked up by a mosquito vector. The real trouble, however, is caused by the adult worms themselves. As they grow, coil, and die, they physically block the lymphatic channels. The body's immune system also reacts to the presence of the worms and their waste products, causing chronic inflammation.
The inflammation is not just from the worm's presence. Repeated bacterial and fungal infections of the skin are common in affected limbs because the damaged lymphatic system can no longer fight off minor infections effectively. This secondary infection adds to the swelling and tissue damage. …
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