Treatment of Loiasis (Loa loa infection)

Diethylcarbamazine (DEC)

• has activity against both L. loa microfilariae and adult worms, so a sustained decrease in microfilarial intensity occurs following treatment.
• its use can lead to encephalitis and/or shock in patients with high levels of circulating microfilariae due to rapid microfilariae killing. Therefore, reduction of microfilariae with apheresis (if available) or albendazole should be pursued prior to DEC treatment in the management of patients with symptomatic loiasis and >2500 microfilariae per mL of blood. 
• patients with any detectable microfilariae should be monitored in a hospital setting during the first three days of treatment. Antihistamines and/or corticosteroids have been used to limit posttreatment reactions, including Calabar swellings and urticaria, but do not prevent serious side effects, including encephalopathy.
• In patients with high levels of microfilariae, the risks and benefits of treatment need to be considered. In general, treatment should be reserved for symptomatic patients, patients with marked elevations in the peripheral eosinophil count, and/or patients with concomitant onchocerciasis or lymphatic filariasis (who require therapy to prevent morbidity and mortality due to these infections).
• Treatment with albendazole, has been shown to significantly decrease Loa microfilarial levels in a randomized trial (dosed 200 mg twice daily for three weeks). Shorter higher dose regimens have not been effective.
• Treatment for patients without evidence of microfilaremia consists of DEC 9 mg/kg/day orally in three divided doses for 21 days.

DEC Dosing

• Treatment for patients with microfilaremia consists of a graded dosing schedule for DEC as follows:

• Day 1: 50 mg (1 mg/kg)
• Day 2: 50 mg (1 mg/kg) three times a day
• Day 3: 100 mg (1 to 2 mg/kg) three times a day
• Day 4 to 21: 9 mg/kg/day in three divided doses

• A single 21-day course of DEC is curative in approximately 50 percent of patients. There are no data available on shorter course therapy. 
• Long-term follow-up is needed after therapy, and retreatment should be considered if symptoms recur. DEC should be avoided in pregnancy.

Albendazole 

• alternative agent for treatment of loiasis.
• has macrofilaricidal activity, causing sterilization or death of adult L. loa worms.
• Unlike DEC, does not have significant microfilaricidal activity. 
• Consequently, fewer adverse effects are observed compared with DEC, since there is no massive antigen release associated with dying microfilariae.
• Use against the adult worm leads to a gradual decline in microfilariae levels over several months. 
• Although cure rates following albendazole treatment of loiasis have not been studied directly, the fact that microfilariae are not completely eliminated in most patients suggests that albendazole is less effective than DEC as initial therapy.
• has also been used as an alternative agent in individuals with L. loa infection that is refractory to multiple courses of DEC. A dose of 200 mg twice daily for three weeks has been used.

Ivermectin 

• has L. loa microfilaricidal activity
• unlike DEC, has no effect on adult worms and is not curative in L. loa infection.
• not a preferred therapeutic agent for treatment of loiasis. It has microfilaricidal activity against L. loa but is not active against adult worms.
• As with DEC, the rapid microfilaricidal effect of ivermectin can result in severe adverse events (encephalitis and/or shock), particularly in individuals with high-level microfilaremic infections.
• Patients with concomitant loiasis and onchocerciasis should receive ivermectin treatment prior to definitive therapy with DEC or a regimen that does not contain DEC.

*Endosymbiotic Wolbachia have not been identified in L. loa, precluding the use of doxycycline or other antibacterial agents for the treatment of loiasis.

Reference  

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