Loiasis B74.30

Infectious disease caused by Loa loa (migrating filiaria), filariae with typical subcutaneous swelling as a sign of a hypersensitivity reaction to the filariae migrating in the subcutaneous connective tissue.

Only indigenous to the West and Central African rainforest zone (Benin, Angola, Western Sudan).

Transmission of the approximately 0.2-0.3 cm large L3 larvae through the painful sting of the brake Chrysops demidiata. Chrysops demidiata is dependent on shady, humid biotopes of African rainforests. The larvae transferred during the sting grow into mature adults in 6-12 months (lifetime 15 years in subcutaneous fatty tissue). Microfilariae are cyclically released into the blood by the females, which can then be taken up again by horseflies.

Integument: The metabolic products of the migrating adult worm cause allergic reactions. Usually alternating, reddened, itchy swellings lasting about 3-4 days, depending on the location of the worm (5-7 cm long) in the skin.

Extracutaneous manifestation: Infestation of the conjunctiva of the eye (very painful when filariae are present; pathognomonic).

In rare cases, prolonged infestation with high eosinophilia can lead to chronic inflammatory processes with eosinophilic granulomas, especially on serous skins.

Late complications: endocarditis, renal damage and meningoencephalitis (adult worms can persist in the body for more than 10 years).

• Travel history
• Microfilariae detection in blood smear (usually possible 1-2 years after infection at the earliest). The blood sample should be taken during the day, preferably at midday. Detection of worms in skin or conjunctiva.
• Eosinophilia in the blood
• DEC provocation test
• Serological antibody detection against filarial crude antigen
• IgG4 serum antibody.

Diethylcarbamazine (e.g. Hetrazan): Start therapy gradually, as severe febrile reactions with risk of shock due to disintegration of filariae are possible. Capillary blockage by microfilariae in brain, meninges, retina and other sites may occur. Initial dosage: 0.5 mg/kg bw/day (avoidance of serious side effects), then increase to 8-10 mg/kg bw/day (max. 600 mg/day) distributed over 3 ED (taken after meals) for 3 weeks (total dose: max. 126 mg/kg bw). NW may include pruritus, fever, joint pain, dyspnoea, circulatory collapse, and others.

In severe cases, combination with betamethasone 3-5 mg/day i.v. 2 days before the 1st DEC dose and gradually reduce.

Alternative: In case of therapy failure, albendazole (400 mg/day for 3 weeks); an advantage is that no hyperergic reaction to microfilariae decay is to be expected with albendazole.

Alternative: There are also positive experience reports with ivermectin (Twum-Danso NA et al. 2003).

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