According to the World Health Organization, malaria infection affects an estimated 200 million people and kills more than 400,000 people worldwide every year—most of them children. Plasmodium parasites cause the disease, and malaria spreads to people by the bite of infected Anopheles mosquitoes. While important information, the scientific community still has much to learn about malaria in order to limit its impact.
“We don’t know what is inside malaria infections,” explained Ian Cheeseman, PhD, Assistant Professor at Texas Biomedical Research Institute, which is home to the Southwest National Primate Research Center (SNPRC). “We don’t know how many different genetically distinct strains of parasites there are. We don’t know how related they are to each other. We don’t know how many mosquitoes they came from.”
To help answer these questions, Cheeseman and an international team of collaborators turned to a process called single cell genome sequencing. This technology allows for individual malaria parasite cells to be isolated and their genome amplified before being analyzed by a genome sequencer, which enables researchers to capture the genetic mutations present in a single cell. The process has been adopted by cancer researchers to understand how tumors evolve, but this study marked the first time the technology has been used to study malaria transmission.
The team examined single malaria-infected cells from patients in Malawi, a country heavily affected by the disease. Patients who donated malaria-infected blood samples used in this study reside in Chikhwawa, a region with a large mosquito population where people may be bitten by a malaria-infected mosquito every 48 hours.
The single cell sequencing approach applied in this study provides a new perspective on how often bites from an infected mosquito lead to a malaria infection. What researchers discovered went against conventional wisdom, as nearly all the infections they studied likely came from one mosquito bite each.
“We found that complex malaria infections are predominantly caused by a single mosquito bite transmitting many genetically diverse but related parasites into the bloodstream of a patient,” said Standwell Nkhoma, MSc, PhD, lead author on the study and a Malawian national.
Knowing this will enable scientists to design more effective interventions to block mosquitoes from spreading malaria and build better models to predict malaria transmission patterns and the spread of drug resistance. While a diagnosis of malaria is often treatable with drugs, the rise of antimalarial drug resistance is a major threat to malaria control across the world, as resistance to artemisinin and piperaquine, two common antimalarial drugs, continue to spread.
To learn more about how NPRC researchers are making progress toward controlling and eliminating infectious diseases worldwide, visit this link.
