Loa Loa

LOA LOA

Loiasis is a filarial disease of West Africa produced by the eye worm, Loa loa. The long-lived adults migrate continuously through the subcutaneous tissues of humans at a maximum rate of about 1 cm/hr. During migration, they produce localized areas of allergic inflammation termed Calabar swellings. These egg-sized lesions persist for 2 to 3 days and may be accom-panied by fever, itching, urticaria, and pain. At times, the adult worms may cross the eye sub-conjunctivally, producing intense tearing, pain, and alarm.

The female produces sheathed microfilariae, which are found in the bloodstream dur-ing daytime hours. Deer flies of the genus Chrysops serve as vectors.

The diagnosis is made by recovering the adult worm from the eye or by isolating the characteristic microfilariae from the blood or Calabar swellings. Eosinophilia is constant. DEC destroys both adults and microfilariae, but must be administered cautiously to avoid marked allergic reactions. Albendazole slowly decreases microfilarial levels without pro-ducing allergic reactions, possibly by preferential action on the adult worms.