Understanding transmission dynamics for malaria control and elimination in Peru

Despite the decline in its incidence in the past decade, malaria remains an important public health problem in Peru. A challenge faced by the National Malaria Control Programme (NMCP) is the ability to efficiently target and eliminate the remaining parasite reservoir in endemic areas, where malaria transmission is low, seasonal and increasingly focal. Two cross-sectional surveys that combined parasitological (PCR, microscopy) and serological metrics (seroprevalence, seroconversion rates) were conducted to characterize malaria transmission dynamics in low endemic areas of the Pacific northern coast and the Amazon region in Peru. Besides the serological evidence for high heterogeneity in malaria exposure, both to Plasmodium falciparum and Plasmodium vivax, at micro-geographical level and over time, PCR results confirmed that most malaria infections in the study areas were asymptomatic and sub-microscopic, and therefore unlikely to be detected by the routine passive case detection (PCD). Since the NMCP has recently introduced focal screening and treatment (FSAT) to overcome the limitations of PCD for detecting asymptomatic carriers, a modelling approach was developed to assess the potential impact of this strategy on the P. falciparum transmission in the Amazon region and to provide insights for the best criteria for its implementation. Although model predictions suggest that combined interventions enabled to reach elimination levels, the progression rates to those levels varied substantially according to different operational criteria (timing, duration, diagnostic tool) used for the intervention. The uncovered asymptomatic and sub-patent reservoir calls for an immediate shift in the malaria control policy in Peru from detecting and controlling clinical malaria to targeting and eliminating all malaria infections (both asymptomatic and symptomatic). The combination of molecular and serological tools have repeatedly proved their added value in accurately understanding the local malaria epidemiology, determining risk factors, describing spatial heterogeneity in transmission, detecting malaria hotpots for targeted interventions as FSAT, and identifying recent changes in malaria transmission in the study areas. (SP - Sciences de la santé publique) -- UCL, 2015