Occurrence of histidine-rich protein 2/3 gene deletions among plasmodium falciparum isolates from newly arrived refugees in Uganda: Implications for malaria control strategies

Abstract

The WHO declared Histidine Rich Protein 2/3 gene deletions a rising global health threat. This is because they cause false negative results with HRP2-based RDTs hence affecting effective disease management. HRP2-based RDTs are used to conduct 90% of all malaria RDT tests in Uganda. The aim of this study was to determine the occurrence of hrp2/3 gene deletions among newly arrived refugees in Uganda across four refugee transit centers. Using RDT and microscopy results from 752 newly arrived (< 7 days of stay in Uganda) refugees aged 6 months to 10 years old from November 2023 to April 2024, dried blood spot (DBS) samples of study participants with RDT-negative/microscopy-positive results were retrieved from cold storage (-20°C). 6 out of 752 samples were RDT-negative/microscopy-positive and their DNA was extracted from DBS. Parasitemia of the samples was determined using qPCR. Four samples had parasitemia above 1 parasite/µL. These were then analyzed using nano-plate digital PCR to assess for hrp2/3 gene deletions. Nano plate digital PCR found no hrp2/3 gene deletions in any of the four samples. Based on these findings, the discordance in the RDT-negative/microscopy-positive results of the samples was not as a result of hrp2/3 gene deletions. It could however be due to very low parasitemia as determined by qPCR and mixed infections with non-P. falciparum parasites which could reduce the sensitivity of RDTs. However, since the countries of origin of the newly arrived refugees including DRC, South Sudan, Ethiopia, Eritrea and Rwanda have reported occurrences of hrp2/3 gene deletions, the study cannot rule out occurrence of these gene deletions in P. falciparum among newly arrived refugees since the sample collection period was small (6 months) and the sample size (n=752) is only a small fraction of population of the countries of origin. Continuous monitoring for hrp2/3 gene deletions in this study population is hence recommended as they are still a significant rising threat to malaria control globally.