Filariasis is a tropical parasitic disease. It is caused by any of a variety of thread-like filarial nematodes (roundworms) in the family Filarioidea. Mosquites transmit filarial parasites to humans. Once inside the human body, the worms migrate to the lymphatic system and develop into adult worms. Filariasis can cause a range of illnesses, the most notable being lymphatic filariasis, which can lead to the condition known as elephantiasis. This is characterized by severe swelling in the arms, legs, or genitals, and is a result of the worms causing a blockage in the lymphatic system. Another form of filariasis is onchocerciasis. Also known as river blindness, it is caused by Onchocerca volvulus and can lead to severe itching and visual impairment. Treatment and control of filariasis focus on mass drug administration to reduce the spread of the infection and manage symptoms. Public health efforts are also essential in preventing the disease, primarily through controlling the mosquito populations that transmit the parasites.