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This man has lymphatic filariasis, also called elephantiasis due to the resemblance of the limbs of those affected to an elephant's. The enlargement of the limbs is caused by an infestation of filarial worms, which are round worms passed from person to person though mosquitoes. These worms live in the lymphatic system and block the normal flow of fluid throughout the body. Due to this blockage and the subsequent damage to the tissue, fluid collects in the tissue and causes the swelling. As you might expect, the first from of treatment is to kill the worms. However, the swelling is often seen in people who no longer have active infections. Another possible side effect of an infestation is something known as hydrocele: swelling of the scrotum.
The biggest way to prevent the disease to to not be bitten by mosquitoes. This includes using replant, wearing clothing that covers as much skin as possible, and sleeping under mosquito netting. There are current efforts being put in place to eliminate this unfortunate, disfiguring disease.