![]() There can be non-painful swelling of lymph glands, but this is not common. But many people do have symptoms, which include itchy skin rashes, nodules under the skin, and vision changes. volvulus, as the larvae can migrate through the human body without provoking a response from the immune system. Some people do not experience symptoms while infected with O. The adult worms can live approximately 10–15 years inside the human body, and their larvae have a lifespan of approximately 12–15 months. The larvae become detectable in the skin 12–18 months after the initial infection. As adults, female worms produce thousands of new larvae daily. Inside the nodules the worms are relatively safe from the human immune response. Nodules form around the worms as part of the interaction between the parasite and its human host. Adult male worms are usually found near the female worms. Most adult female worms live in fibrous nodules under the skin and sometimes near muscles and joints. Once inside the human body, the larvae mature into adults in approximately 12–18 months. Humans become infected when blackflies deposit Onchocerca infective larvae into the skin when biting to extract blood. They migrate to the biting parts of the fly where they can be transmitted back to humans when it bites again. The larvae develop inside the blackfly and become infective for humans in about one week. ![]() If a blackfly bites an infected person, onchocerciasis larvae can be ingested by the blackfly after which they migrate to the flight muscles. Some species of blackflies may also feed on certain animals as well. Female blackflies need to ingest blood for ovulation, so they feed on humans. ![]() ![]() The blackflies that transmit the parasite bite during the day. Blackflies are the vector for onchocerciasis. ![]()
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