Onchocerciasis, also known as river blindness, is caused by the parasitic worm Onchocerca volvulus and is transmitted to humans through the bites of infected blackflies. Laboratory diagnosis of onchocerciasis can involve several methods:
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Clinical Evaluation: Initially, the diagnosis may be suggested based on the clinical presentation, which includes symptoms such as skin rashes, itchiness, and ocular symptoms. A history of living in or visiting endemic areas is also a key factor.
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Skin Snips: One of the most commonly used laboratory methods is the skin snip technique. Small pieces of skin are removed from areas where the adult female worms are known to reside (often on the back and buttocks), and the sample is examined microscopically to identify Onchocerca microfilariae (larval forms).
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Nodule Aspiration: In some cases, nodules (hence called "onchocercomas") that form due to the presence of adult worms can be aspirated, and the aspirated material can be examined for the presence of microfilariae.
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Serological Tests: Various serological assays can be conducted to detect antibodies or antigens related to Onchocerca volvulus. These tests can aid in diagnosis, especially in cases where the skin snip does not yield conclusive results.
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Molecular Methods: Polymerase chain reaction (PCR) testing can be used to detect Onchocerca volvulus DNA in clinical specimens, providing a sensitive and specific means of diagnosis.
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Ocular Examination: In cases of suspected ocular involvement, ophthalmologists can perform exams and utilize specific imaging techniques to identify changes due to the infection.
While skin snips remain the gold standard for diagnosing onchocerciasis, the combination of clinical symptoms, history, and additional diagnostic methods can help confirm the presence of the infection.
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