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The International Journal of the Royal Society of Thailand
Volume XI - 2019

gametocytes and as mass ACT administrations. The Faculty of Tropical Medicine
has conducted studies for the improvement of malaria prophylaxis and effective
blockade of malaria transmission. Selected here are studies describing mosquito-

cidal effects of ivermectin, the safety and immunogenicity of the RTS,S vaccine
when administered in combination with ACTs, and a mass drug administration
(MDA) in Lao PDR.

Ivermectin mosquito-cidal effect

Ivermectin was discovered in 1981 by William C. Campbell and Satoshi
Ōmura, who shared the 2015 Nobel Prize in Physiology or Medicine. Ivermectin has
been widely used to control onchocerciasis (river blindness), lymphatic filariasis,
and to treat certain types of endo-and ecto-parasites in humans and in veterinary
medicine. The drug is effective against some ectoparasite infestations by flea, mite,
and lice and is lethal to mosquitos. The mosquito-killing effect of ivermectin was
discovered in 2012 when the mosquitoes were fed with blood obtained from
people who took this drug. Ivermectin was used in conjunction with the MDA for
malaria control in many Africa countries (Chotivanich & Hanboonkunupakarn,
2018). As a candidate for blocking malaria transmission, more clinical and
pharmacokinetic data of ivermectin are essential.

The Faculty of Tropical Medicine, in collaboration with the Armed Forces
Research Institute of Medical Sciences (AFRIMS), conducted a clinical trial to
evaluated ivermectin in combinations with the common antimalarial drug used
for MDA, dihydroartemisinin-piperaquine, and primaquine. The study was in
healthy volunteers to evaluate safety, tolerability, pharmacokinetics, and mosquito-
cidal effects of ivermectin (Kobylinski et al, 2019). The co-administration with
dihydroartemisinin-piperaquine resulted in increased blood concentrations and

mosquito-cidal effect of ivermectin across all subjects. The mortality of Anopheles
dirus and Anopheles minimus increased up to 35-fold when feeding on volunteer
blood after ivermectin administration compared with control human blood
prepared by direct mixing of ivermectin compound. The mosquito-cidal effect
lasted for 10 days after the drug administration perhaps suggesting the presence
of more slowly eliminated metabolites with mosquito‐cidal effects (Figure 5). This
combined approach is a promising prototype for accelerating malaria elimination
and warrants further studies in endemic areas.

18 Precision Tools for Malaria Control and Mahidol University’s
Research on the Malaria Elimination

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