Loa loa (African eye worm)
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Epidemiology
Pathology
- adult worms
- females 50-70 by 0.5 mm
- males 25-30 by 0.25 mm
- live in subcutaneous tissues
- sheath present
- microfilariae circulate in blood with a diurnal periodicity that peaks between 12 noon & 2 pm
- calabar swellings, localized angioedema & erythema, results from hypersensitivity to the adult worm (may result after initiation of treatment)
Clinical manifestations
- often asymptomatic in indigenous population
- calabar swellings, localized angioedema & erythema, generally on extremities
- subconjunctival migration of adult worm
- nephropathy, encephalopathy & cardiomyopathy are rare
Laboratory
- diagnosis is made by detection of microfilariae in peripheral blood or isolation of the adult worm from the eye or biopsy of subcutaneous tissues
- complete blood count (CBC)
- serology - antifilarial antibodies
- hypergammaglobulinemia
- elevated serum IgE
- Loa Loa DNA
Management
- diethylcarbamazine (DEC) 8-10 mg/kg/day for 21 days
- effective against both the adult worm & microfilaria
- multiple courses of treatment frequently necessary before infection completely resolves
- allergic or inflammatory reactions may take place during treatment including encephalitis & coma
- for heavy infection
- DEC 0.5 mg/kg/day, plus
- prednisone 40-60 mg PO QD
- if no adverse effects, rapidly taper prednisone & gradually increase dose of DEC to 8-10 mg/kg/day
- albendazole & ivermectin (not FDA approved) are effective in reducing microfilarial loads
- prophylaxis: DEC 300 mg weekly