Resistance to a key antimalarial drug called artemisinin has emerged in the malaria parasite in Southeast Asia, and it’s rapidly spreading. Now, according to new work published in Nature Communications this week, these drug-resistant parasites don’t just infect local mosquito species, they infect disease-transmitting bloodsuckers in Africa too. On that continent alone, malaria will kill an estimated 400,000 people this year, and the disease vector Anopheles coluzzii (formerly Anopheles gambiae M) will be largely responsible for those deaths.
Of the handful of known malaria parasites, Plasmodium falciparum is the deadliest species. Despite how fast it’s spreading, resistance to artemisinin was limited to just Southeast Asia, until now. To investigate the parasitic microorganism’s transmission potential, Rick Fairhurst from the U.S. National Institute of Allergy and Infectious Diseases infected various mosquito species from Southeast Asia and Africa with artemisinin-resistant parasites previously isolated from malaria patients in Cambodia.
Two Southeast Asian mosquito species – Anopheles dirus, collected from Pursat Province in western Cambodia, and Anopheles minimus, collected from Mae Sot in western Thailand – as well as the African Anopheles coluzzii were easily infected after feeding on blood containing any of six artemisinin-resistant or three artemisinin-sensitive parasite strains. The artemisinin-resistant isolates developed and produced spore-like sporozoites in both the local and non-native species; the team also found the parasites in the midguts and the salivary glands of almost all the mosquitoes after they were dissected – indicating that both drug-resistant and drug-sensitive Cambodian parasites are capable of infecting a variety of Anopheles species.
Using DNA extracted from white-blood-cell depleted blood, the researchers also discovered a shared genetic background among artemisinin-resistant parasites. Turns out, they’re able to infect a diversity of mosquito species by evading their immune systems.
It remains unclear, however, whether the infected mosquitoes are able to transmit the disease effectively to people or not. But drug-resistant parasites spreading across continents may compromise malaria eradication efforts worldwide. Next, the team plans to figure out which Cambodian Anopheles species can naturally transmit artemisinin-resistant parasites in the wild. For now, this threat exists only in lab settings.