Abstract:With the paradigm shift from the reduction of morbidity and mortality to the interruption of transmission, the focus of malaria control broadens from symptomatic infections in children ≤ 5 years of age to include asymptomatic infections in older children and adults. In addition, as control efforts intensify and the number of interventions increases, there will be decreases in prevalence, incidence and transmission with additional decreases in morbidity and mortality. Expected secondary consequences of these ch… Show more
“…The use of ITNs reduces the contact between host and vector and as shown in this study, children sleeping under ITNs were significantly less at risk of PI. There is evidence in the literature of the positive impact of their use on reduction of disease [ 15 , 57 - 59 ], but, paradoxically, the protection of ITNs brings the fear of shifting vulnerability to malaria onto school-aged children: on the one hand, schoolchildren may use ITNs less, and on the other hand, an impaired acquisition of immunity to malaria due to diminished contact with Plasmodium at younger age [ 58 , 60 - 64 ]. ITNs were efficient in preventing parasitaemia only when PD was ≥2,000/μl, which might explain the decrease of mortality due to malaria by the use of ITNs [ 65 ], as patients with symptomatic PI tend to have a higher PD than asymptomatic subjects [ 66 ].…”
Section: Discussionmentioning
confidence: 99%
“…In addition, all suspected cases of symptomatic Plasmodium infection (PI) should be biologically confirmed prior to treatment [ 9 - 14 ]. Thus, by definition, diagnosis and treatment are focused on symptomatic individuals while asymptomatic ones also play a role in the sustainability of the transmission, acting as a reservoir for the disease [ 15 - 19 ]. Furthermore, asymptomatic PI may have an impact on the morbidity of the disease in terms of anaemia, nutritional status and even cognitive development of children [ 2 , 4 - 7 , 20 , 21 ].…”
BackgroundMalaria is preventable and treatable when recommended interventions are properly implemented. Thus, diagnosis and treatment focus on symptomatic individuals while asymptomatic Plasmodium infection (PI) plays a role in the sustainability of the transmission and may also have an impact on the morbidity of the disease in terms of anaemia, nutritional status and even cognitive development of children. The objective of this study was to assess PI prevalence and its relationship with known morbidity factors in a vulnerable but asymptomatic stratum of the population.MethodsA simple random sample, household survey in asymptomatic children under the age of five was conducted from April to September 2012 in two health areas of the health zone of Mont Ngafula 1, Kinshasa, Democratic Republic of Congo.ResultsThe PI prevalence were 30.9% (95% CI: 26.5-35.9) and 14.3% (95% CI: 10.5-18.1) in Cité Pumbu and Kindele health areas, respectively, (OR: 2.7; p <0.001). All were Plasmodium falciparum infected and 4% were co-infected with Plasmodium malariae. In Cité Pumbu and Kindele, the prevalence of anaemia (haemoglobin <11 g/dL) was 61.6% (95% CI: 56.6-66.5) and 39.3% (95% CI: 34.0-44.6), respectively, (OR: 2.5; p <0.001). The health area of Cité Pumbu had 32% (95% CI: 27.5-37.0) of chronic malnutrition (HAZ score ≤ −2SD) compared to 5.1% (95% CI: 2.8-7.6) in Kindele. PI was predictor factor for anaemia (aOR: 3.5, p =0.01) and within infected children, there was an inverse relationship between parasite density and haemoglobin level (β = −5*10−5, p <0.001). Age older than 12 months (aOR: 3.8, p = 0.01), presence of anaemia (aOR: 3.4, p =0.001), chronic malnutrition (aOR: 1.8, p = 0.01), having a single parent/guardian (aOR: 1.6, p =0.04), and the non-use of insecticide-treated nets (aOR: 1.7, p = 0.04) were all predictors for PI in the overall population.ConclusionPI in asymptomatic children was correlated with anaemia and chronic malnutrition and was thus a harmful condition in the study population. Malaria control initiatives should not only focus on treatment of symptomatic infections but also take into consideration asymptomatic but infected children.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-015-0595-5) contains supplementary material, which is available to authorized users.
“…The use of ITNs reduces the contact between host and vector and as shown in this study, children sleeping under ITNs were significantly less at risk of PI. There is evidence in the literature of the positive impact of their use on reduction of disease [ 15 , 57 - 59 ], but, paradoxically, the protection of ITNs brings the fear of shifting vulnerability to malaria onto school-aged children: on the one hand, schoolchildren may use ITNs less, and on the other hand, an impaired acquisition of immunity to malaria due to diminished contact with Plasmodium at younger age [ 58 , 60 - 64 ]. ITNs were efficient in preventing parasitaemia only when PD was ≥2,000/μl, which might explain the decrease of mortality due to malaria by the use of ITNs [ 65 ], as patients with symptomatic PI tend to have a higher PD than asymptomatic subjects [ 66 ].…”
Section: Discussionmentioning
confidence: 99%
“…In addition, all suspected cases of symptomatic Plasmodium infection (PI) should be biologically confirmed prior to treatment [ 9 - 14 ]. Thus, by definition, diagnosis and treatment are focused on symptomatic individuals while asymptomatic ones also play a role in the sustainability of the transmission, acting as a reservoir for the disease [ 15 - 19 ]. Furthermore, asymptomatic PI may have an impact on the morbidity of the disease in terms of anaemia, nutritional status and even cognitive development of children [ 2 , 4 - 7 , 20 , 21 ].…”
BackgroundMalaria is preventable and treatable when recommended interventions are properly implemented. Thus, diagnosis and treatment focus on symptomatic individuals while asymptomatic Plasmodium infection (PI) plays a role in the sustainability of the transmission and may also have an impact on the morbidity of the disease in terms of anaemia, nutritional status and even cognitive development of children. The objective of this study was to assess PI prevalence and its relationship with known morbidity factors in a vulnerable but asymptomatic stratum of the population.MethodsA simple random sample, household survey in asymptomatic children under the age of five was conducted from April to September 2012 in two health areas of the health zone of Mont Ngafula 1, Kinshasa, Democratic Republic of Congo.ResultsThe PI prevalence were 30.9% (95% CI: 26.5-35.9) and 14.3% (95% CI: 10.5-18.1) in Cité Pumbu and Kindele health areas, respectively, (OR: 2.7; p <0.001). All were Plasmodium falciparum infected and 4% were co-infected with Plasmodium malariae. In Cité Pumbu and Kindele, the prevalence of anaemia (haemoglobin <11 g/dL) was 61.6% (95% CI: 56.6-66.5) and 39.3% (95% CI: 34.0-44.6), respectively, (OR: 2.5; p <0.001). The health area of Cité Pumbu had 32% (95% CI: 27.5-37.0) of chronic malnutrition (HAZ score ≤ −2SD) compared to 5.1% (95% CI: 2.8-7.6) in Kindele. PI was predictor factor for anaemia (aOR: 3.5, p =0.01) and within infected children, there was an inverse relationship between parasite density and haemoglobin level (β = −5*10−5, p <0.001). Age older than 12 months (aOR: 3.8, p = 0.01), presence of anaemia (aOR: 3.4, p =0.001), chronic malnutrition (aOR: 1.8, p = 0.01), having a single parent/guardian (aOR: 1.6, p =0.04), and the non-use of insecticide-treated nets (aOR: 1.7, p = 0.04) were all predictors for PI in the overall population.ConclusionPI in asymptomatic children was correlated with anaemia and chronic malnutrition and was thus a harmful condition in the study population. Malaria control initiatives should not only focus on treatment of symptomatic infections but also take into consideration asymptomatic but infected children.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-015-0595-5) contains supplementary material, which is available to authorized users.
“…The epidemiology of asymptomatic malaria in different transmission settings is attracting increasing attention, because asymptomatic individuals are still able to produce gametocytes and therefore provide the reservoir for transmission [14,15]. The majority of malariological studies are carried out in areas of high and stable transmission and less is known about settings with marked seasonal transmission [16].…”
BackgroundMalaria transmission was reported to have declined in some East African countries. However, a comparable trend has not been confirmed for West Africa. This study aims to assess the dynamics of parasite prevalence and malaria species distribution over time in an area of highly seasonal transmission in Burkina Faso. The aim was also to compare frequency of asymptomatic parasitaemia between wet and dry season by parasite density status and age group.MethodsDuring the years 2009–2012, six cross-sectional studies were performed in the rural village Bourasso in the Nouna Health District in north-west Burkina Faso. In subsequent rainy and dry seasons blood samples were collected to assess the parasite prevalence, species, density and clinical parameters. In total, 1,767 children and adults were examined and compared to a baseline collected in 2000.ResultsThe microscopical parasite prevalence (mainly P. falciparum) measured over the rainy seasons decreased significantly from 78.9% (2000) to 58.4%, 55.9% and 49.3%, respectively (2009–2011; p <0.001). The frequency of Plasmodium malariae infections (mono- and co-infections) decreased parallel to the overall parasite prevalence from 13.4% in 2000 to 2.1%, 4.1% and 4.7% in 2009–2011 (p <0.001). Comparing parasite-positive subjects from the rainy season versus dry season, the risk of fever was significantly reduced in the dry season adjusting for parasite density (grouped) and age group.ConclusionsThe results of this study suggest a decline of malaria transmission over the rainy seasons between 2000 and 2009–2011 in the region of Nouna, Burkina Faso. The decreased transmission intensity was associated with lower prevalence of P. malariae infections (both mono-infections and co-infections). Asymptomatic parasitaemia was more frequent in the dry season even adjusting for parasite density and age group in a multivariate regression. Possible reasons for this observation include the existence of less pathogenic Plasmodium falciparum genotypes prevailing in the dry season, or the effect of a reduced incidence density during the dry season.
“…The premise of this paper is that developing a DCMS for study sites in Mali, Senegal and The Gambia (Fig. 1) was a critically important outcome of the West African ICEMR [14, 15]. Fig.…”
BackgroundDeveloping and sustaining a data collection and management system (DCMS) is difficult in malaria-endemic countries because of limitations in internet bandwidth, computer resources and numbers of trained personnel. The premise of this paper is that development of a DCMS in West Africa was a critically important outcome of the West African International Centers of Excellence for Malaria Research. The purposes of this paper are to make that information available to other investigators and to encourage the linkage of DCMSs to international research and Ministry of Health data systems and repositories.MethodsWe designed and implemented a DCMS to link study sites in Mali, Senegal and The Gambia. This system was based on case report forms for epidemiologic, entomologic, clinical and laboratory aspects of plasmodial infection and malarial disease for a longitudinal cohort study and included on-site training for Principal Investigators and Data Managers. Based on this experience, we propose guidelines for the design and sustainability of DCMSs in environments with limited resources and personnel.ResultsFrom 2012 to 2017, we performed biannual thick smear surveys for plasmodial infection, mosquito collections for anopheline biting rates and sporozoite rates and year-round passive case detection for malarial disease in four longitudinal cohorts with 7708 individuals and 918 households in Senegal, The Gambia and Mali. Major challenges included the development of uniform definitions and reporting, assessment of data entry error rates, unstable and limited internet access and software and technology maintenance. Strengths included entomologic collections linked to longitudinal cohort studies, on-site data centres and a cloud-based data repository.ConclusionsAt a time when research on diseases of poverty in low and middle-income countries is a global priority, the resources available to ensure accurate data collection and the electronic availability of those data remain severely limited. Based on our experience, we suggest the development of a regional DCMS. This approach is more economical than separate data centres and has the potential to improve data quality by encouraging shared case definitions, data validation strategies and analytic approaches including the molecular analysis of treatment successes and failures.Electronic supplementary materialThe online version of this article (10.1186/s40249-018-0494-4) contains supplementary material, which is available to authorized users.
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