Filariasis is a tropical disease caused by parasitic roundworms transmitted through mosquito bites. The larvae can cause lymphatic obstruction and elephantiasis, a gross enlargement of body parts. Symptoms include fever, chills, and swelling of limbs or genitals. Diagnosis involves examining blood for parasite antibodies or microfilariae. Treatment uses medications to kill the parasites, though elephantiasis cannot be reversed. Prevention focuses on limiting mosquito bites by clothing, nets, and repellents.