DR P. MARAZZI / SCIENCE PHOTO LIBRARY DR P. MARAZZI / SCIENCE PHOTO LIBRARY
Swelling due to parasitic worm. Swollen wrist (bottom) of a 24-year-old female voluntary worker in West Africa, caused by a parasitic nematode worm (Loa loa). This worm lives under human skin, causing a disease called loiasis (a form of filariasis). The worms are spread by bloodsucking Chrysops flies in tropical Africa, and reach 3-7cm when mature. The symptoms of loiasis are swollen, painful areas of skin called calabar swellings, which are probably allergic reactions to the worms' waste products. The swelling can be accompanied by fever and itching. Diagnosis may be made by taking a blood sample and the worms can be destroyed by the drug diethylcarbamazine.
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