NETHERLANDS – Mosquitoes are usually associated with serious diseases, such as malaria, dengue fever and yellow fever. However, researchers from Leiden University Medical Center (LUMC) and Radboud University in the Netherlands may have found a valuable new role for the insects: as vaccine distributors. Their scientists say they have successfully engineered mosquitoes to deliver vaccines that could potentially provide significantly enhanced immunity against malaria. The World Health Organization’s most recent World Malaria Report revealed that an estimated 597,000 people died of malaria globally in 2023 with African countries bearing the brunt of the death toll – accounting for 95 percent of malaria fatalities. Scientists estimated that more than 240 million malaria cases occur annually worldwide. Children and expectant mothers are the most vulnerable to the disease.
The vaccine employs a weakened strain of Plasmodium falciparum (P falciparum), the parasite that causes the deadliest form of malaria in humans. “We have removed an important gene in the malaria parasite, still allowing the parasite to infect people but not making them sick,” explained vaccinologist Meta Roestenberg, professor of vaccinology and clinical head of the Controlled Human Infection Center at LUMC.
Typically, the malaria parasite is transferred to humans by a bite. The mosquito uses its long, needle-like mouth (called a proboscis) to pierce the skin, injecting its saliva into the bloodstream before sucking blood. Parasites in the saliva travel directly to the liver, where they rapidly reproduce, before leaving the liver to infect red blood cells with malaria. This leads to symptoms such as fever, chills and sweating. In the clinical trial, the research team used mosquitoes carrying the modified parasite to deliver the vaccine via bites, mirroring the natural transmission of malaria. The goal: creating a strong immune response in the liver and protection from a malaria infection.
“Because the gene [is] turned off, this parasite cannot complete its development in the liver, cannot enter the bloodstream and thus cannot cause disease symptoms,” Roestenberg said. “At least that was the theory.” (Aljazeera)

Photo: A laboratory technician holds a mosquito at the World Mosquito Program factory in Medellin, Colombia. (AFP)