Which organ is primarily affected by Brugia malayi?

Brugia malayi primarily affects the lymphatic system, making it the correct answer. This parasite is a type of filarial worm and is the causative agent of lymphatic filariasis, a condition characterized by severe swelling and the accumulation of lymphatic fluid in various body parts, commonly the legs and genitals. The lifecycle of Brugia malayi involves vectors like mosquitoes, which transmit the larval forms into human hosts, leading to chronic inflammation and obstruction of lymphatic vessels.

The involvement of the lymphatic system is crucial as it disrupts the normal flow of lymph, resulting in the characteristic symptoms associated with the infection, such as lymphedema and hydrocele. This specific targeting of the lymphatic system distinguishes Brugia malayi from conditions that primarily affect other organs, such as the intestines or liver.