RESUMEN
OBJECTIVES: In low malaria transmission areas, the elimination of the disease has been hampered partly by the existence of a reservoir of subpatent Plasmodium falciparum infections within communities. This reservoir, often undetected, serves as a source of parasites and contributes to ongoing transmission and clinical malaria cases. METHODS: This study, spanning a period of 9 years from June 2014 to December 2022, examined individual variations and long-term subpatent P. falciparum carriage in two matched cohorts of 44 individuals each living in Dielmo village in the Sudanian area of Senegal. Biannual blood samples, collected in June/July and December of each year, underwent P. falciparum diagnosis by quantitative polymerase chain reaction. QGIS and R analytical tools were used to map infections, assess the occurrence and clustering of subpatent and clinical P. falciparum infections, and determine the risk of infection in the vicinity of asymptomatic P. falciparum carriers. RESULTS: The point frequency and long-term P. falciparum carriage were significantly higher among the quantitative polymerase chain reaction (qPCR) positive cohort compared to the negative cohort across the 16 cross-sectional surveys analyzed in this study (19.76% vs 10.99%, P-value <0.001). Asymptomatic carriage events in qPCR-positive group were 18.86 ± 1.72% and significantly greater (P-value = 0.001) than in the qPCR-negative group (11.32 ± 1.32%). The relative risk of P. falciparum infection or clinical malaria calculated with a 95% confidence interval significantly increased in the vicinity of infected individuals and was 1.44 (P-value = 0.53) and 2.64 (P-value = 0.04) when at least one individual in the direct (household) or indirect (block of households) vicinity is infected, respectively. The risk increased to 3.64 (P-value <0.001) if at least 1/5 of individuals in the indirect vicinity were P. falciparum-infected. CONCLUSIONS: The study provides a detailed qualitative and quantitative analysis of the asymptomatic P. falciparum reservoir and its temporal and spatial dynamics within two subgroups of P. falciparum-infected and non-infected individuals in Dielmo village. It identified high-risk populations known as "hotpops" and hotspots that could be targeted by innovative interventions to accelerate the elimination of malaria in Dielmo village.
RESUMEN
The necessity of the human hippocampus and surrounding medial temporal lobe structures to semantic memory remains contentious. Impaired semantic memory following hippocampal lesions could arise either due to partially intertwined episodic memories and/or retrograde/anterograde effects. In this study, we tested amnesic individuals with lesions in hippocampus and surrounding medial temporal lobe (n = 7) and age-matched controls (n = 14) on their ability to precisely recall the dates of famous public events that occurred either before (i.e., pre-lifetime) or after participants' birth date (lifetime). We show that deficits in dating precision are greatest for recent lifetime events, consistent with the notion that recent event memory may be particularly intertwined with episodic memory. At the same time, individuals with medial temporal lobe lesions showed more subtle impairments in their ability to date pre-birth and remote lifetime events precisely. Together, these findings suggest that the hippocampus and surrounding medial temporal lobe structures are important for representational precision of semantic memories regardless of their remoteness.