infectious diseases
Loiasis
Diagnosis of Loiasis
Observation of an adult worm subconjunctivally crossing the eye Identification of an adult worm removed from the eye or skin Identification and quantification of microfilariae in blood by microscopy or quantitative polymerase chain reaction (PCR) Loiasis should be suspected in immigrants or travelers who have a history of exposure in an endemic area and who present with eye worms, Calabar swellings, or unexplained peripheral eosinophilia. Occasionally, the diagnosis of loiasis is confirmed by observing an adult worm migrating under the conjunctiva or by identifying a worm after it is removed from the eye or skin. Microscopic detection of microfilariae in peripheral blood establishes the diagnosis; the number of microfilariae per milliliter of blood should be quantified. Blood samples should be drawn between 10 AM and 2 PM, when microfilaremia levels are the highest. Many serologic tests for antibodies do not differentiateLoa loafrom other filarial nematode infections.Loa-specific antibody tests have been developed, but they are not widely available in the United States. Also, a positive serologic test does not distinguish between past and current infection. A quantitative real-time PCR (qPCR) to confirm the diagnosis and quantify the microfilarial burden is available at the Laboratory of Parasitic Diseases, National Institutes of Health. People from endemic regions of Africa should be checked forLoa loabefore they are treated with diethylcarbamazine orivermectinfor other disorders because these drugs can have substantial adverse effects in people with loiasis. If treated with diethylcarbamazine orivermectin, people with ≥ 8000Loa loamicrofilariae/mL blood are at risk of potentially fatal encephalopathy, caused by the release of antigens from dying microfilariae. 