Why do certain regions and populations differ in transmission of the same species of human and non-human primate malaria parasites?

Due to various restrictions such as travel restrictions and research activity guidelines at the institutions to which the principal investigator, co-researchers, and research collaborators belong due to the spread of the new coronavirus, as well as circumstances in the partner country, sufficient on-site surveys have not been conducted. For this reason, the analysis was focused on various materials that were carried over, although incomplete, in the fiscal year.

a) Regarding the status of malaria infection in Sabah, Malaysia, which is one of the study areas, human blood samples collected in Ranau district of Sabah were examined. The Ranau district is inland, at an altitude of 1,000 meters, and has a population of approximately 100,000 people, many of whom are farmers. As a result of the investigation and sample analysis, following results were obtained

• The number of people infected with Plasmodium knowlesi (Pk) has been increasing year by year. 
• Most of the Pk-infected people were males over the age of 13 and were agricultural workers.
• The Pk-infected person had memories of being bitten by vector mosquitoes in farmland around the forest, so it was assumed that the area around the forest was where the infection occurred.
• Due to movement restrictions due to the spread of COVID-19 infection, a decrease in malaria patients was observed. 
• There were no patients with human malaria infection, only patients with Pk monoinfection.

b)The comparison site was Lai Chau Province in northern Vietnam, which has a similar natural environment to Ranau. We also analyzed human peripheral blood samples taken just before travel to Vietnam. In Lai Chau Province, there were no malaria cases before 2017, but several cases of P. vivax malaria were confirmed in 2017 and 2018. However, when analyzing the 2019 samples, they found 56 cases of P. vivax malaria. Of particular note, one case of falciparum malaria was found that had not been previously detected in the 2021 samples. However, no other malaria infections, including Pk, were observed.

Project details

Epidemiology
Measurement of Transmission
Social Science

Apr 2020 — Mar 2023

$108,561

Malaysia
Vietnam

Plasmodium knowlesi