Assessment and Treatment of Loiasis With Positive Microfilaremia

Loiasis is a vector-borne filariasis endemic in the forested areas in Central Africa whose incidence and morbi-mortality are poorly understood. Estimated prevalence is around 10 millions cases for a population around 30 million people. Considered to be a benign pathology, it has recently been associated with excess mortality, mainly in cases with major microfilaremia (\> 8000 mf/ml). Transmission is related to a mostly diurnal vector from the Chrysops genus. Adult worms are located in skin and subcutaneous tissues of infected patients. Females worms produce microfilariae which join bloodstream. Infected patients are mainly asymptomatic. Nevertheless, adult worms migration can lead to transient oedema (" œdème de Calabar ") ; adult worm can also be observed during subcunjonctival migration. Hypereosinophilia is also frequently encountered. Microfilariae presence in the bloodstream is asymptomatic, even in individuals with major microfilaremia. Treatment differs according to the initial microfilaremia. There are three drugs available : diethylcarbamazine (DEC) ; albendazole (ALB) and ivermectin (IVM) each with different macrofilaricidal and microfiliaricidal activities. Several treatment guidelines based on the initial microfilaremia and drug activities have been proposed, on the basis of limited data. DEC is suggested for patients with microfilaremia \ 30000 mf/ml, initial treatment with ALB or apheresis is suggested to reduce blood microfilaremia, followed by DEC. All these guidelines are associated with major adverse events, mainly life-threatening encephalopathies. These adverse events are mostly encountered in patients with major blood microfilarem