Filariasis is a parasitic disease caused by roundworms. Depending on the area occupied by the parasites, the disease is divided into two types: Lymphatic and Non Lymphatic. Lymphatic Filariasis is targeted at the lymph nodes and lymph vessels in the body. Non Lymphatic Filariasis is targeted at the subcutaneous skin and fat layers of legs and genital areas. The body's immune system produces antibodies when any such harmful foreign body enters. This makes it easier to identify a particular parasite, by identifying the antibody associated with it. Filariasis induces an excess of IgG4 antibodies in the blood stream. If the patient shows symptoms of the disease, the doctor usually orders a blood test to detect presence of IgG4 in the blood.