Onchocerca volvulus is a parasitic worm that causes river blindness, also known as onchocerciasis. It is transmitted to humans through the bites of infected blackflies, primarily found near fast-flowing rivers in tropical regions. The adult worms live in the human body, forming nodules under the skin and releasing larvae into the bloodstream. The larvae can migrate to the eyes, leading to severe inflammation and potential blindness. Efforts to control onchocerciasis include mass drug administration of ivermectin, which helps reduce the number of larvae and prevent transmission. Public health initiatives aim to eliminate the disease in affected areas.