Extensive low-density Plasmodium falciparum reservoir in the island of Príncipe, an isolated malaria pre-elimination setting

• Published in: International journal of infectious diseases Vol. 147; p. 107220
• Main Authors: de Sousa, Taís Nóbrega, Machado, Patricia Carneiro, Lopes, Inês, Das Neves, Edvaldo, Narciso, Alda, Pires, Anastácio, Santos, Adalberto, Trovoada, Maria Jesus, Gil, José Pedro, Lopes, Dinora
• Format: Journal Article
• Language: English
• Published: Canada Elsevier Ltd 01.10.2024; Elsevier
• Subjects: Elimination; Malaria; Medicin och hälsovetenskap; Parasite reservoir; Plasmodium falciparum; Parasite reservoir; Plasmodium falciparum; Malaria; Elimination
• ISSN: 1201-9712; 1878-3511; 1878-3511
• DOI: 10.1016/j.ijid.2024.107220

•Quantitative polymerase chain reaction unveiled 70% of low-density Plasmodium falciparum infections.•Prevalences were even higher in reactive case detection surveys.•Parasite reservoirs contribute to sporadic cases hindering malaria elimination. The isolated Príncipe is at the malaria pre-elimination stage. Autochthonous clinical cases have been reported sporadically on the island, signaling the possibility of a sizable subpatent (i.e., rapid diagnostic test- and microscopy-negative and polymerase chain reaction [PCR]-positive) parasite reservoir. Asymptomatic low-density infections were detected by quantitative PCR (qPCR) targeting Plasmodium falciparum multicopy genes (pfr364 and varATS). Positivity rates were assayed for samples surveyed by active case detection (n = 112) and reactive case detection (n = 221) in 2022. qPCR unveiled 70% of low parasitemia carriers, reaching >90% in reactive case detection. The high P. falciparum prevalence was confirmed by the two high-sensitivity qPCR protocols. Higher positivity rates were observed in the localities where most malaria cases were reported in 2022. Most parasitemias were very low (<2 Pf /µl). These findings suggest that pre-elimination surveillance can benefit from the routine application of highly sensitive tools to unveil otherwise invisible but potentially relevant parasite populations.