Ivermectin for causal malaria prophylaxis: a randomised controlled human infection trial

Area of Science:

• Parasitology
• Tropical Medicine
• Pharmacology

Background:

• Ivermectin is a safe antiparasitic drug effective against helminths and arthropods.
• Mass drug administration of ivermectin is being explored by the WHO as a malaria control strategy.
• Preclinical data suggest ivermectin may target the liver stages of Plasmodium falciparum.

Purpose of the Study:

• To evaluate the prophylactic efficacy of ivermectin against Plasmodium falciparum in a controlled human malaria infection model.
• To assess the impact of ivermectin on the pre-erythrocytic stages of the malaria parasite.

Main Methods:

• A randomized controlled trial involving 12 volunteers (8 ivermectin, 4 placebo).
• Volunteers received a single oral dose of ivermectin (0.4 mg/kg) or placebo 2 hours before experimental infection with P. falciparum sporozoites.
• Parasitemia was monitored by thick blood smear and RT-qPCR.

Main Results:

• All but one volunteer in the ivermectin group and all placebo volunteers became parasitemic.
• Parasitemia onset occurred between day 11 and day 12 post-infection.
• Ivermectin did not significantly alter the time to parasitemia detection.

Conclusions:

• Ivermectin, at the tested dosage, demonstrated no clinically relevant activity against the pre-erythrocytic stages of Plasmodium falciparum.
• The findings do not support the use of ivermectin as a prophylactic agent for malaria in this context.