By Julien Chongwang
Experts have broadly welcomed a study that found repeated mass administration of the drug ivermectin could reduce malaria cases in children under five by a fifth, but caution that more analysis is needed.
The study, published in The Lancet science journal, says the drug makes the patient’s blood deadly for the biting mosquito. The insect dies after the bite and cannot bite another person to transmit the disease.
According to the World Health Organisation (WHO) there were 219 million cases of malaria globally in 2017, resulting in 435,000 deaths, with children being the most vulnerable to the disease. In Africa, about 285 000 children died before their fifth birthdays in 2016.
“It provides encouraging results for research and discovery of slow-release formulations which could have a potential role in future in reducing residual malaria transmission,”
Andrea Bosman, malaria prevention, diagnosis and treatment coordinator, WHO
Researchers from the United States and Burkina Faso conducted the first randomized trial of its kind using a sample of 2,700 people, including 590 children from eight villages in Burkina Faso, in 2015.
During the rainy season when malaria transmission is high, the entire population of the eight villages received a single dose of ivermectin, plus an anti-worm medication.
The residents of four of the villages – the intervention group – then received five further three-weekly doses of ivermectin, while those from the other four villages – the control group – did not. Children aged five and under were tested for malaria every two weeks.
‘No obvious harm’
Malaria episodes per child were reduced by 20 per cent in the intervention group, compared to the control group, with “no obvious drug-related harms”, according to the study, released March 13.
Andrea Bosman, of the WHO’s malaria programme, said the results were “encouraging” but required “additional analysis”.
The study was led by Professor Brian Foy of the department of microbiology, immunology and pathology at Colorado State University, in the United States, alongside research institutions in Burkina Faso.
“I’ve been interested for a long time in ways one might inhibit vector-borne disease transmission by targeting mosquitoes with an anti-vector vaccine approach,” Foy told SciDev.Net.
He recalled that by the end of the 1980s researchers had already discovered that malaria vectors were sensitive to “surprisingly” low concentrations of ivermectin in the blood of people who had used the drug to treat the tropical diseases onchocerciasis and lymphatic filariasis.
He said the drug, better known in Africa under its brand name Mectizan, was already widely used to combat these diseases and “could be a useful tool in disease reduction if further trials show similar results”.
Chris Drakeley, professor of infection and immunity at the London School of Hygiene and Tropical Medicine, welcomed the study, which he said showed “a new methodology for controlling and eliminating malaria, giving drugs to humans to target mosquitoes.”
He cautioned, however, that it was only “relatively small scale” and that there would be “a number of logistical hurdles to investigate before this approach could be implemented.”
Bosman, WHO’s malaria prevention, diagnosis and treatment coordinator, said the study confirmed that even in areas with very high malaria transmission mass administration of ivermectin had a “time-limited impact” on malaria incidence.
“It provides encouraging results for research and discovery of slow-release formulations which could have a potential role in future in reducing residual malaria transmission,” he said, while warning that the study lacked detail on drug safety monitoring.
“It would have been good to perform additional analysis to show that higher use of bed nets in the intervention villages did not impact on malaria incidence,” he added.
Pharmaceutical company Merck, which makes ivermectin, said in a statement to SciDev.Net: “We appreciate the efforts of the medical community to better understand how to better treat parasitic diseases, including the potential use of ivermectin for malaria control.”
A Merck spokeswoman said the drug was currently marketed in 10 countries for onchocerciasis, lymphatic filariasis, intestinal strongyloidiasis, human sarcoptic scabies, and crusted scabies.
Researchers are poised to continue their work with larger clinical trials and other control tools, as growing antimalarial drug resistance challenges scientists to find new ways to fight the disease.