A Cambodian Anopheles mosquito - a strain that is spreading drug-resistant malaria in Southeast Asia.
Image credit: NIAID
The new study, published in Nature Communications, is the work of an international team that includes scientists from the National Institute of Allergy and Infectious Diseases (NIAID) - part of the National Institutes of Health.
Nearly 1 million people die of malaria every year, mostly babies, young children and pregnant women, the majority of whom are in Africa. Estimates suggest a child dies of malaria every 30 seconds.
Malaria typically spreads in human populations through the bite of female Anopheles mosquitoes carrying Plasmodium parasites.
The main drug for treating malaria, artemisinin, is becoming less and less effective in Southeast Asia due to the spread of resistant strains of Plasmodium falciparum - the deadliest of the malaria parasites.
Experts are concerned that these drug-resistant parasites will spread to Africa.
Drug-resistant malaria parasite easily infected African mosquitoes
- Each year, there are approximately 300-500 million cases of malaria worldwide
- Over 40% of the world's population live where there is a risk of malaria infection
- Malaria accounts for more than $12 billion in economic losses a year in Africa.
Currently, the drug-resistant parasites are spread by Anopheles mosquitoes that are confined to Southeast Asia, and before the new study, scientists had little idea of the risk of it spreading to Africa, where the major carrier of malaria is the Anopheles coluzzii mosquito, previously known as the Anopheles gambiae.
The researchers behind the new study decided one way to assess the risk was to establish whether resistant strains of P. falciparum can infect the African mosquitoes.
For their study, they infected various mosquito species from Southeast Asia and Africa with drug-resistant parasites from Cambodia in a laboratory setting.
Specifically, they produced gametocytes or germ cells from samples that displayed artemisinin resistance in patients and in lab cultures. Mature gametocytes are responsible for the spread of the parasite from infected people to mosquitoes.
They found that artemisinin-resistant P. falciparum easily infected the Southeast-Asian mosquito carriers A. dirus and A. minimus as well as the African A. coluzzii. They conclude:
"The ability of artemisinin-resistant parasites to infect such highly diverse Anopheles species, combined with their higher gametocyte prevalence in patients, may explain the rapid expansion of these parasites in Cambodia and neighboring countries, and further compromise efforts to prevent their global spread."
The researchers also discovered that drug-resistant parasites share a genetic feature that enables them to evade the mosquitoes' immune system and may explain how they manage to invade such a diverse range of species.
They now plan to investigate whether any other genetic traits help the parasites to infect mosquitoes, and also find out which Anopheles species from Cambodia are naturally transmitting artemisinin-resistant parasites in the wild.
Malaria parasites are also developing a new type of multidrug resistance, according to research published in the journal Emerging Infectious Diseases that Medical News Today learned of recently. The French researchers say they are very alarmed by the discovery, especially as the multidrug-resistant parasite is able to enter a quiescent state that cannot be detected by current tests for parasite resistance.