Assessing malaria transmission in a low endemicity area of north-western Peru

Abstract

BackgroundWhere malaria endemicity is low, control programmes need increasingly sensitive tools for monitoring malaria transmission intensity (MTI) and to better define health priorities. A cross-sectional survey was conducted in a low endemicity area of the Peruvian north-western coast to assess the MTI using both molecular and serological tools.MethodsEpidemiological, parasitological and serological data were collected from 2,667 individuals in three settlements of Bellavista district, in May 2010. Parasite infection was detected using microscopy and polymerase chain reaction (PCR). Antibodies to Plasmodium vivax merozoite surface protein-119 (PvMSP119) and to Plasmodium falciparum glutamate-rich protein (PfGLURP) were detected by ELISA. Risk factors for exposure to malaria (seropositivity) were assessed by multivariate survey logistic regression models. Age-specific antibody prevalence of both P. falciparum and P. vivax were analysed using a previously published catalytic conversion model based on maximum likelihood for generating seroconversion rates (SCR).ResultsThe overall parasite prevalence by microscopy and PCR were extremely low: 0.3 and 0.9%, respectively for P. vivax, and 0 and 0.04%, respectively for P. falciparum, while seroprevalence was much higher, 13.6% for P. vivax and 9.8% for P. falciparum. Settlement, age and occupation as moto-taxi driver during previous year were significantly associated with P. falciparum exposure, while age and distance to the water drain were associated with P. vivax exposure. Likelihood ratio tests supported age seroprevalence curves with two SCR for both P. vivax and P. falciparum indicating significant changes in the MTI over time. The SCR for PfGLURP was 19-fold lower after 2002 as compared to before (λ1 = 0.022 versus λ2 = 0.431), and the SCR for PvMSP119 was four-fold higher after 2006 as compared to before (λ1 = 0.024 versus λ2 = 0.006).ConclusionCombining molecular and serological tools considerably enhanced the capacity of detecting current and past exposure to malaria infections and related risks factors in this very low endemicity area. This allowed for an improved characterization of the current human reservoir of infections, largely hidden and heterogeneous, as well as providing insights into recent changes in species specific MTIs. This approach will be of key importance for evaluating and monitoring future malaria elimination strategies.

Effect of Seasonal Malaria Chemoprevention (SMC) with SulfadoxinePyrimethamine (SP) and Amodiaquine (AQ) on the Acquisition of antiAMA1 and anti-MSP1_42 Antibodies among Children under 10 Years Living in the Southern part of Senegal (Velingara)

“…Antibody level increases with age and Pf carriage. Similar results were found previously [24][25][26][27]. Seroprevalence of anti-MSP1 _42 and anti-AMA1 antibodies increase with age.…”

Spatio-temporal analysis of malaria incidence in the Peruvian Amazon Region between 2002 and 2013

“…This emphasizes the need to sustain elimination efforts once they have been started. The rapid upsurge observed since 2011 could be partly explained by the large proportion of asymptomatic and sub-microscopic malaria infections in the Peruvian endemic areas22232425. These infections, undetected by routine PCD, are likely to sustain and even increase malaria transmission when ecological conditions are favourable and/or control efforts are relaxed2226.…”

Epidemiology of Plasmodium vivax Malaria in Peru

“…Test-and-treat strategies—PCD of symptomatic subjects with treatment only of confirmed malaria infections with ACT—together with implementation of community-based environmental management strategies to control the predominant vector Anopheles albimanus (such as the shift of rice cultivation patterns) probably contributed to the steady decline in malaria incidence observed in the northern coast from the early 2000s 8,42…”

“…Most affected people live in impoverished peri-urban and rural villages sparsely distributed along an extensive riverine network associated with tributaries feeding into the Amazon river 6,7. Intermittent epidemic malaria as well as sporadic cases take place in the Pacific northern coast,8 and transmission is low intensity in the high and central jungle,9 and the gold mining department of Madre de Dios,5 accounting together for about 5% of the total malaria cases reported in Peru 3…”