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Loa loa (African eye worm)
Epidemiology:
1) rain forests of West & Central Africa
2) transmitted by Chrysops (deerflies)
Pathology:
1) adult worms
a) females 50-70 by 0.5 mm
b) males 25-30 by 0.25 mm
c) live in subcutaneous tissues
d) sheath present
2) microfilariae circulate in blood with a diurnal periodicity that peaks between 12 noon & 2 pm
3) calabar swellings, localized angioedema & erythema, results from hypersensitivity to the adult worm (may result after initiation of treatment)
Clinical manifestations:
1) often asymptomatic in indigenous population
2) calabar swellings, localized angioedema & erythema, generally on extremities
3) subconjunctival migration of adult worm
4) nephropathy, encephalopathy & cardiomyopathy are rare
Laboratory:
1) diagnosis is made by detection of microfilariae in peripheral blood or isolation of the adult worm from the eye or biopsy of subcutaneous tissues
2) complete blood count (CBC)
a) eosinophilia
b) leukocytosis
3) serology - antifilarial antibodies
4) hypergammaglobulinemia
5) elevated serum IgE
6) Loa Loa DNA
Management:
1) diethylcarbamazine (DEC) 8-10 mg/kg/day for 21 days
a) effective against both the adult worm & microfilaria
b) multiple courses of treatment frequently necessary before infection completely resolves
2) allergic or inflammatory reactions may take place during treatment including encephalitis & coma
3) for heavy infection
a) DEC 0.5 mg/kg/day, plus
b) prednisone 40-60 mg PO QD
c) if no adverse effects, rapidly taper prednisone & gradually increase dose of DEC to 8-10 mg/kg/day
4) albendazole & ivermectin (not FDA approved) are effective in reducing microfilarial loads
5) prophylaxis: DEC 300 mg weekly
Related
fly/gnat-borne infection
General
Loa
Properties
KINGDOM: animal
PHYLUM: helminth
References
- Harrison's Principles of Internal Medicine, 14th ed.
Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 1215
- Harrison's Principles of Internal Medicine, 13th ed.
Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 920, 923