Elephantiasis disease in man is caused by

Concept

Diseases are classified according to their causative agent: a virus is a sub-microscopic infectious particle, bacteria are single-celled organisms, parasitic worms (helminths) are multicellular organisms that live in or on a host, and insects are commonly vectors — carriers that transmit a pathogen between hosts rather than being the pathogen themselves.

Application

Elephantiasis, medically called lymphatic filariasis, is caused by infection with thread-like filarial worms — chiefly Wuchereria bancrofti, and less commonly Brugia malayi or Brugia timori. These parasitic worms lodge in the lymphatic vessels and lymph nodes, blocking normal lymph drainage and producing the massive swelling of the limbs and other body parts that gives the disease its name.

Cross-check

• Virus: causes diseases such as dengue or influenza; no virus is involved in this condition.

• Bacteria: cause diseases such as tuberculosis or cholera; this condition does not have a bacterial origin.

• Insect (mosquito): certain mosquito species (Culex, Anopheles, Aedes) transmit the infective larvae from person to person, acting only as the vector; the insect itself is not the organism responsible for the disease.

Since the swelling arises directly from worm infestation of the lymphatic system, the causative agent of elephantiasis is a parasitic worm.