Effect of Two or Six Doses 800 mg of Albendazole Every Two Months on Loa loa Microfilaraemia: A Double Blind, Randomized, Placebo-Controlled Trial

Background: Loiasis is a parasitic infection endemic in the African rain forest caused by the filarial nematode Loa loa. Loiasis can be co-endemic with onchocerciasis and/or lymphatic filariasis. Ivermectin, the drug used in the control of these diseases, can induce serious adverse reactions in patients with high L loa microfilaraemia (LLM). A drug is needed which can lower LLM below the level that represents a risk so that ivermectin mass treatment to support onchocerciasis and lymphatic filariasis elimination can be implemented safely. Methodology: Sixty men and women from a loiasis endemic area in Cameroon were randomized after stratification by screening LLM (≤30000, 30001–50000, >50000) to three treatment arms: two doses albendazole followed by 4 doses matching placebo (n = 20), six doses albendazole (n = 20) albendazole or 6 doses matching placebo (n = 20) administered every two months. LLM was measured before each treatment and 14, 18, 21 and 24 months after the first treatment. Monitoring for adverse events occurred three and seven days as well as 2 months after each treatment. Principal Findings: None of the adverse events recorded were considered treatment related. The percentages of participants with ≥ 50% decrease in LLM from pre-treatment for ≥ 4 months were 53%, 17% and 11% in the 6-dose, 2-dose and placebo treatment arms, respectively. The difference between the 6-dose and the placebo arm was significant (p = 0.01). The percentages of participants with LLM 30 000 microfilariae/ml blood) can develop severe and serious adverse reactions to ivermectin. In rare cases, these have been fatal. A way of preventing these reactions could be to administer a treatment that decreases the microfilareamia in all subjects below the risk level before mass treatment with ivermectin. Building on results of previous studies, this randomised placebo-controlled trial evaluated the efficacy and safety of two or six doses of albendazole administered every two months on the microfilaraemia of Loa loa. Six doses led to a decrease in microfilaraemia by at least 50% for at least four months in 53% of participants. However, it did not reduce the microfilaraemia below the risk level in all participants. Therefore, this regimen has not sufficient efficacy to prevent severe adverse reactions to ivermectin.