How is the diagnosis of blood filariasis confirmed?

Patient Question: Drug Name: glucose, cephalocyte fire (drip). Instructions for use: daily drip glucose 500ML, head cell 100ML. 15 days of continuous drip, no obvious effect. At the onset of fever, chills all over the body, right calf red, hot, swollen, distended and painful in the local city hospital, could not confirm the diagnosis, I would like to ask, how can I confirm that it is blood filariasis, which hospitals can confirm the diagnosis and treatment of this disease? Doctor’s reply: Blood filariasis is relatively rare at present. In addition, in your current case, testing is recommended to rule out vasculitis and vascular embolic lesions (angiography of the right lower limb).