infectious diseases
Loiasis
Key Points
Humans are the only known natural reservoir forLoa loa,which is transmitted by day-biting tabanid flies. Most infected people are asymptomatic, but some have areas of angioedema (Calabar swellings), which occur mainly on the extremities, or report worms moving across their eyes. Diagnose by microscopic examination of peripheral blood drawn between 10 AM and 2 PM, when microfilaremia levels are the highest; confirm and measure the concentration of microfilariae by quantitative polymerase chain reaction (qPCR). Occasionally, diagnosis of loiasis is confirmed by observing an adult worm migrating under the conjunctiva or by identifying a worm after it is surgically removed from the eye or skin. Diethylcarbamazine, which should not be administered to patients concurrently infected withOnchocerca volvulus, is the only drug that kills microfilariae and adult worms; in the United States, it is available only from the Centers for Disease Control and Prevention. Seek expert assistance in measuring the number of microfilariae and determining the severity of the infection, and seek expert advice before initiating treatment. In patients with heavy infection, pretreatment with apheresis oralbendazoleis recommended because in these patients, the filarial antigens released as diethylcarbamazine kills microfilariae may trigger encephalopathy, leading to coma and death. 