Between 2000 and 2015, the world’s fight against malaria made remarkable progress, with millions of lives saved through better prevention, diagnosis, and treatment. Of late, however, that momentum has slowed. In 2023 alone, malaria claimed nearly 6 lakh lives, with 95% of those deaths occurring in the African region.
India has made dramatic progress too, with malaria cases dropping by over 80% in the last decade, especially in urban and semi-urban areas. However, some districts in Odisha, Chhattisgarh, Jharkhand, and the Northeastern States continue to struggle with persistent transmission.
This lingering threat has drawn renewed attention to the mass drug administration (MDA) of endectocides, systemic insecticides that work from inside the human body, as a promising tool to reduce malaria transmission. Among these, ivermectin reportedly stands out as the most promising candidate.
From worms to mosquitoes
Ivermectin has been around since the 1970s. Originally developed to treat parasitic worms, it has been safely given to more than four billion people and is a cornerstone of global campaigns against river blindness and lymphatic filariasis. Dubbed a “wonder drug,” it earned its discoverers the Nobel Prize.
However, a surprising discovery later expanded its potential: mosquitoes that bit people recently treated with ivermectin often died or didn’t live long enough to spread malaria.
This finding sparked renewed interest in using ivermectin as a vector control tool in malaria-endemic regions. Subsequent modelling and pilot studies suggested that mass drug administration with ivermectin, especially when timed to seasonal transmission peaks, could help bring down infection rates by shrinking the mosquito population.
In malaria control, mass drug administration aims to eliminate the parasite from both symptomatic and asymptomatic individuals, reducing the human reservoir and interrupting transmission.
The BOHEMIA trial
To test this idea in the real world, scientists launched the BOHEMIA trial in Kenya and Mozambique and the findings were published on July 23 in The New England Journal of Medicine.
In Kenya, the trial was conducted in Kwale County, a coastal region with year-round malaria transmission despite 85% bed net coverage. The villagers were randomly given either ivermectin or albendazole (an anti-parasitic drug that doesn’t affect mosquitoes) once a month for more than three months, starting in October 2023. Children aged 5 to 15, who are among the most vulnerable, were then monitored for six months.
The result: malaria cases dropped by 26% in the ivermectin group. This figure exceeded the World Health Organisation’s threshold of a 20% reduction to be considered a valuable public health tool. Notably, children living farther from untreated areas had even greater protection, suggesting a strong community-level impact.
More than 56,000 doses were administered during the study and the participants reported no serious side effects. However, the trial excluded pregnant women and children under 15 kg of body weight, which may limit the drug’s broader applicability.
The Mozambique trial could not yield conclusive results as the research term’s operations were severely disrupted by Cyclone Gombe and a subsequent cholera outbreak.
The MATAMAL trial
In November 2024, a study in Guinea-Bissau called the MATAMAL trial involved more than 25,000 people in 24 villages. It tested whether adding the drug ivermectin to an already strong malaria treatment program — which used the drug dihydroartemisinin–piperaquine, or DP — could make the program work better.
Contrary to expectations, there was no significant difference in malaria prevalence between villages that received ivermectin and those that received a placebo. In fact, there were slightly more malaria cases in the ivermectin group, with no clear impact on mosquito survival or infection rates.
Researchers concluded that the timing and dosing used in this trial may not have been sufficient to add value to existing interventions.
Ivermectin still matters
Despite mixed results, both trials reaffirmed ivermectin’s safety in large-scale campaigns. Side effects were mild and temporary, mostly headaches and dizziness, with no serious adverse events reported.
Ivermectin also offered a distinct advantage over traditional malaria control tools. Bed nets, indoor spraying, and larvicides target mosquitoes that bite indoors and at night. But mosquitoes evolve: some now bite earlier, outdoors or even feed on livestock. This makes it harder to keep them at bay with conventional tools.
On the other hand, ivermectin kills mosquitoes from the inside after they bite humans, regardless of time or location. It can also be delivered through existing deworming or parasitic disease campaigns, making it a practical dual-use tool, particularly in remote or underserved areas.
The BOHEMIA team also found significant collateral benefits. In Mozambique, people who took ivermectin had fewer skin problems like scabies and head lice. In Kenya, many noticed a dramatic drop in bed bugs.
Resistance concern
As with all widespread interventions, resistance is a looming concern. A 2024 review in Parasitology Research highlighted the growing resistance to ivermectin in ectoparasites like ticks, lice, and scabies mites, mostly due to overuse in veterinary medicine.
While resistance among human parasites is still rare, there’s little data on its impact on Anopheles mosquitoes. Only two out of 18 reviewed studies examined ivermectin’s impact on mosquito populations, highlighting a critical gap in surveillance.
Should resistance emerge, the drug’s value as a malaria control tool could diminish rapidly. And the drug’s widespread use for scabies, lice, and livestock parasites may make resistance develop faster.
Researchers have also warned that as ivermectin’s mass drug administration expands, resistance in non-target organisms must be closely monitored as this risk is often overlooked. Ivermectin affects many parasites, so targeting one species may accelerate resistance in others. In regions with multiple parasites, the chosen doses might favour the target but harm broader control efforts.
To stay ahead, researchers are exploring longer-lasting formulations, higher doses, and combining ivermectin with malaria vaccines or genetically modified mosquitoes. Upcoming trial data and resistance tracking will shape its future role in malaria control programs.
Manjeera Gowravaram has a PhD in RNA biochemistry and works as a freelance science writer.
Published – September 28, 2025 05:30 am IST