Assessment of the efficacy and safety of two albendazole regimens for the treatment of hypermicrofilaraemic loiasis in adults in Woleu-Ntem Province, Gabon: A phase IIb single-blind randomised controlled trial.

BACKGROUND: Loa (L.) loa hypermicrofilaraemia (≥ 8,000 mf/mL) increases the risk of severe adverse events during mass ivermectin administration for onchocerciasis control. Albendazole has been proposed as a potential alternative for reducing microfilaraemia prior to ivermectin administration. METHODOLOGY AND PRINCIPAL FINDINGS: This prospective study was conducted in northern Gabon from November 2021 to April 2022. Individuals infected with L. loa were screened and allocated to three groups: two treatment arms receiving 400 mg or 800 mg of albendazole daily for 30 days among hypermicrofilaraemic participants, and a group with microfilaraemia < 8,000 mf/mL. Clinical symptoms and parasitological data were collected on Days 0, 2, 7, 14, and 30. A total of 70 participants were enrolled: 16 in the 400 mg group, 16 in the 800 mg group, and 38 in the group with microfilaraemia below 8,000 mf/mL. Itching was the most frequently reported adverse event. By Day 30, no participants in the group with microfilaraemia below 8,000 mf/mL presented with clinical symptoms. Microfilaraemia significantly decreased in all groups (p < 0.01). After 30 days, over 70.0% of patients treated with albendazole had microfilaraemia < 8,000 mf/mL. There was no significant difference in efficacy between the two albendazole regimens. CONCLUSIONS/SIGNIFICANCE: Daily administration of 400 mg albendazole for 30 days effectively reduces microfilarial loads in patients with L. loa hypermicrofilaraemia and is well tolerated and safe. This pre-treatment regimen may reduce the risk of adverse events associated with ivermectin administration. Further research is needed to evaluate the long-term persistence of microfilarial suppression.