High levels of asymptomatic and subpatent Plasmodium falciparum parasite carriage at health facilities in an area of heterogeneous malaria transmission intensity in the Kenyan highlands.
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ABSTRACT:
SUBMITTER: Stresman GH
PROVIDER: S-EPMC4257630 | biostudies-literature | 2014 Dec
REPOSITORIES: biostudies-literature
Publications
High levels of asymptomatic and subpatent Plasmodium falciparum parasite carriage at health facilities in an area of heterogeneous malaria transmission intensity in the Kenyan highlands.
Stresman Gillian H GH Stevenson Jennifer C JC Ngwu Nnenna N Marube Elizabeth E Owaga Chrispin C Drakeley Chris C Bousema Teun T Cox Jonathan J
The American journal of tropical medicine and hygiene 20141020 6
In endemic settings, health facility surveys provide a convenient approach to estimating malaria transmission intensity. Typically, testing for malaria at facilities is performed on symptomatic attendees, but asymptomatic infections comprise a considerable proportion of the parasite reservoir. We sampled individuals attending five health facilities in the western Kenyan highlands. Malaria prevalence by rapid diagnostic test (RDT) was 8.6-32.9% in the health facilities. Of all polymerase chain re ...[more]
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Project description:Malaria represents a major public health problem in Africa [1]. In the East African highlands, even in high-altitude areas previously considered too cold to support vector population and parasite transmission [2], frequent malaria epidemics have been reported since the 1980’s [3]. Plasmodium falciparum infections have been detected in areas as high as 1,600-2,400m above sea level in Africa [4], albeit there is a marked gradient of parasite prevalence along the altitude transect [5-7]. Both the historical absence of malaria in the African highlands and now the intensive malaria control efforts put in place after the recent outbreaks have reduced malaria prevalence and incidence [8], rendering the East African highlands particularly prone to epidemic malaria due to the lack of the protective immunity, and causing significant human mortality amongst all age groups [9]. Therefore, malaria transmission monitoring in the East African highlands becomes a particularly important public health issue.Despite the overall lower immunity of the population in these historically malaria-free areas, the many successive outbreaks since the 1980’s may have generated some level of immunity against P. falciparum amongst highland residents. The antibody response to Plasmodium is cumulative and long lasting, developing after repeated exposures to the parasite and persisting for months or years after infection was resolved. The antibody response to Plasmodium varies amongst individuals of different age groups (i.e. toddlers, children and adults) as well as amongst individuals of same age groups from areas of different parasite prevalence [10]. The repertoire of targets of the antibody response also expands after multiple infections, with the number of recognized antigens being correlated to parasite prevalence, age and immunity to clinical malaria [11,12]. Serological studies bring forth indirect evidence of human exposure to the parasite, and can reliably assess its prevalence and transmission intensity in an endemic area [13-15]. However, the vast majority of serological studies of malaria have been, hereto, limited to a small number of the parasite’s antigens. The work we present here is an expansion of the study published by Badu et al. [16], in which the antibody response to the 19kDa fragment of merozoite surface protein 1 (MSP-119) was examined in populations from two endemic areas in the western Kenyan highlands. There, the tremendous variations of malaria transmission intensity in a small spatial scale are caused by substantial differences in altitude, topography and other environmental conditions [6,7,17,18]. We now expand our antibody profiling survey to include 854 P. falciparum proteins by using high-throughput proteomic microarray technology. Protein microarrays have been used to explore the humoral response to P. falciparum in other African settings [19-24], but this is the broadest characterization of the antibody responses of the population of western Kenyan highlands to date. In the present study we: i) determined the serological reactivity against P. falciparum (Pf) in subjects residing in a low transmission area, and detected hotspots of transmission; ii) examined the dynamics of antibody response to hundreds of Pf proteins generated by sera from toddlers, older children and adults residing in two endemic areas differing in transmission intensities, during two distinct malaria seasons, and compared the intensity, breadth and antigenic targets of these responses; and iii) identified candidate Pf antigenic markers that could provide more sensitive serological surveillance to detect micro-geographic variations in malaria transmission levels and differentiate hotspots of infection in low endemic areas. (references provided in the 'readme.txt')
2013-06-20 | GSE48089 | GEO
Project description:Malaria represents a major public health problem in Africa [1]. In the East African highlands, even in high-altitude areas previously considered too cold to support vector population and parasite transmission [2], frequent malaria epidemics have been reported since the 1980M-bM-^@M-^Ys [3]. Plasmodium falciparum infections have been detected in areas as high as 1,600-2,400m above sea level in Africa [4], albeit there is a marked gradient of parasite prevalence along the altitude transect [5-7]. Both the historical absence of malaria in the African highlands and now the intensive malaria control efforts put in place after the recent outbreaks have reduced malaria prevalence and incidence [8], rendering the East African highlands particularly prone to epidemic malaria due to the lack of the protective immunity, and causing significant human mortality amongst all age groups [9]. Therefore, malaria transmission monitoring in the East African highlands becomes a particularly important public health issue.Despite the overall lower immunity of the population in these historically malaria-free areas, the many successive outbreaks since the 1980M-bM-^@M-^Ys may have generated some level of immunity against P. falciparum amongst highland residents. The antibody response to Plasmodium is cumulative and long lasting, developing after repeated exposures to the parasite and persisting for months or years after infection was resolved. The antibody response to Plasmodium varies amongst individuals of different age groups (i.e. toddlers, children and adults) as well as amongst individuals of same age groups from areas of different parasite prevalence [10]. The repertoire of targets of the antibody response also expands after multiple infections, with the number of recognized antigens being correlated to parasite prevalence, age and immunity to clinical malaria [11,12]. Serological studies bring forth indirect evidence of human exposure to the parasite, and can reliably assess its prevalence and transmission intensity in an endemic area [13-15]. However, the vast majority of serological studies of malaria have been, hereto, limited to a small number of the parasiteM-bM-^@M-^Ys antigens. The work we present here is an expansion of the study published by Badu et al. [16], in which the antibody response to the 19kDa fragment of merozoite surface protein 1 (MSP-119) was examined in populations from two endemic areas in the western Kenyan highlands. There, the tremendous variations of malaria transmission intensity in a small spatial scale are caused by substantial differences in altitude, topography and other environmental conditions [6,7,17,18]. We now expand our antibody profiling survey to include 854 P. falciparum proteins by using high-throughput proteomic microarray technology. Protein microarrays have been used to explore the humoral response to P. falciparum in other African settings [19-24], but this is the broadest characterization of the antibody responses of the population of western Kenyan highlands to date. In the present study we: i) determined the serological reactivity against P. falciparum (Pf) in subjects residing in a low transmission area, and detected hotspots of transmission; ii) examined the dynamics of antibody response to hundreds of Pf proteins generated by sera from toddlers, older children and adults residing in two endemic areas differing in transmission intensities, during two distinct malaria seasons, and compared the intensity, breadth and antigenic targets of these responses; and iii) identified candidate Pf antigenic markers that could provide more sensitive serological surveillance to detect micro-geographic variations in malaria transmission levels and differentiate hotspots of infection in low endemic areas. (references provided in the 'readme.txt') Antibody profiling was performed on sera from residents of western Kenyan highlands against Plasmodium falciparum. One-hundred and ten age-stratified serum samples collected during the dry and the wet seasons, from residents of two locations with differing parasite transmission levels (uphill and valley bottom), and 10 unexposed USA controls were probed on a protein microarray displaying 854 unique proteins of P. falciparum.
2013-06-20 | E-GEOD-48089 | biostudies-arrayexpress
Project description:Heterogeneity in malaria exposure is most readily recognized in areas with low-transmission patterns. By comparison, little research has been done on spatial patterns in malaria exposure in high-endemic settings. We determined the spatial clustering of clinical malaria incidence, asymptomatic parasite carriage, and Anopheles density in two villages in Mali exposed to low- and mesoendemic-malaria transmission. In the two study areas that were < 1 km(2) in size, we observed evidence for spatial clustering of Anopheles densities or malaria parasite carriage during the dry season. Anopheles density and malaria prevalence appeared associated in some of our detected hotspots. However, many households with high parasite prevalence or high Anopheles densities were located outside the identified hotspots. Our findings indicate that within small villages exposed to low- or mesoendemic-malaria transmission, spatial patterns in mosquito densities and parasite carriage are best detected in the dry season. Considering the high prevalence of parasite carriage outside detected hotspots, the suitability of the area for targeting control efforts to households or areas of more intense malaria transmission may be limited.
| S-EPMC4596601 | biostudies-literature
Project description:Background: We employed DNA microarray technology to investigate the host response to Streptococcus pneumoniae in a mouse model of asymptomatic carriage. Over a period of six weeks, we profiled transcript abundance and complexity in the Nasal Associated Lymphoid Tissue (NALT) to identify genes whose expression differed between pneumococcal-colonized and uncolonized states. Results: Colonization with S. pneumoniae altered the expression of hundreds of genes over the course of the study, demonstrating that carriage is a dynamic process characterized by increased expression of a set of early inflammatory responses, including induction of a Type 1 Interferon response, and the production of several antimicrobial factors. Subsequent to this initial inflammatory response, we observed increases in transcripts associated with T cell development and activation, as well as wounding, basement membrane remodeling, and cell proliferation. Our analysis suggests that microbial colonization induced expression of genes encoding components critical for controlling JAK/STAT signaling, including stat1, stat2, socs3, and mapk1, as well as induction of several Type 1 Interferon-inducible genes and other antimicrobial factors at the earliest stages of colonization. Conclusions: Examining multiple time points over six weeks of colonization demonstrated that asymptomatic carriage stimulates a dynamic host response characterized by temporal waves with distinct biological programs. Our data suggest that the usual response to the presence of the pneumocccus is an initial controlled inflammatory response followed by activation of host physiological processes such as response to wounding, basement membrane remodeling, and increasing cellular numbers that ultimately allow the host to maintain an intact epithelium and eventually mount a preventive adaptive immune response. A disease state experiment design type is where the state of some disease such as infection, pathology, syndrome, etc is studied.
2009-08-31 | GSE16803 | GEO
Project description:BackgroundMalaria transmission in African highland areas can be prone to epidemics, with minor fluctuations in temperature or altitude resulting in highly heterogeneous transmission. In the Kenyan Highlands, where malaria prevalence has been increasing, characterising malaria incidence and identifying risk factors for infection is complicated by asymptomatic infection.MethodsThis all-age cohort study, one element of the Malaria Transmission Consortium, involved monthly follow-up of 3155 residents of the Kisii and Rachuonyo South districts during June 2009-June 2010. Participants were tested for malaria using rapid diagnostic testing at every visit, regardless of symptoms.ResultsThe incidence of Plasmodium falciparum infection was 0.2 cases per person, although infections were clustered within individuals and over time, with the majority of infections detected in the last month of the cohort study. Overall, incidence was higher in the Rachuonyo district and infections were detected most frequently in 5-10-year-olds. The majority of infections were asymptomatic (58%). Travel away from the study area was a notable risk factor for infection.ConclusionsIdentifying risk factors for malaria infection can help to guide targeting of interventions to populations most likely to be exposed to malaria.
| S-EPMC6391934 | biostudies-literature
Project description:Malaria infections occurring below the limit of detection of standard diagnostics are common in all endemic settings. However, key questions remain surrounding their contribution to sustaining transmission and whether they need to be detected and targeted to achieve malaria elimination. In this study we analyse a range of malaria datasets to quantify the density, detectability, course of infection and infectiousness of subpatent infections. Asymptomatically infected individuals have lower parasite densities on average in low transmission settings compared to individuals in higher transmission settings. In cohort studies, subpatent infections are found to be predictive of future periods of patent infection and in membrane feeding studies, individuals infected with subpatent asexual parasite densities are found to be approximately a third as infectious to mosquitoes as individuals with patent (asexual parasite) infection. These results indicate that subpatent infections contribute to the infectious reservoir, may be long lasting, and require more sensitive diagnostics to detect them in lower transmission settings.
| S-EPMC6440965 | biostudies-literature
Project description:BackgroundMalaria epidemiology in Madagascar is classified into four different areas, ranging from unstable seasonal transmission in the highlands to hyperendemic perennial transmission areas in the costal level. Most malaria studies in Madagascar are focused on symptomatic children. However, because of the low transmission in some areas with correspondingly low level of semi-immunity, adults are also at risk, in particular pregnant women. The objective of this study was to gain information on the genetic epidemiology of malarial infections in pregnant women in order to provide information for malaria control and elimination programmes in Madagascar.MethodsBetween May and August 2010, we carried out cross-sectional surveys targeting healthy pregnant women in six locations, three in the coastal area and three in the highlands at 850-1300 m. 1244 blood samples were screened for anti-Plasmodium falciparum antibodies by immunofluorescence test and for malarial infection by realtime-PCR. The prevalence of chloroquine and sulphadoxine-pyrimethamine resistance markers was also determined in all Plasmodium falciparum samples by PCR-RFLP as well as the multiplicity of infection through genotyping six neutral microsatellites.ResultsIn the highlands, 67.4% of the women presented antibodies against Plasmodium falciparum and 9.2% were carrying parasites, at the coast 95.6% and 14.8%, respectively. In the mean, 1.2 clones were detected in infected pregnant woman in the highlands and 1.5 at the coast. A higher level of monoclonal infections was found in the highlands (85.4%) compared to the coast (61.8%). Resistance markers for sulphadoxine-pyrimethamine were present only in two sites.ConclusionImmunity is triggered in Malagasy highland populations when they are infected with malaria parasites, but these populations could also serve as a reservoir for epidemics.
| S-EPMC4432997 | biostudies-literature
Project description:This study aimed to estimate the prevalence of asymptomatic and subpatent P. falciparum infections in the city of Bouaké, Central Côte d'Ivoire, to compare the performance of three tests, and to investigate potential P. falciparum histidine-rich protein 2 (pfhrp2) gene deletions. A cross-sectional survey was conducted in nine neighborhoods in Bouaké in 2016. Matched light microscopy (LM), rapid diagnostic test (RDT), and quantitative PCR (qPCR) data were used to determine the prevalence of P. falciparum infection and compare the performance of the three diagnostic tests. Pfhrp2/3 deletions were genotyped by digital PCR. Among 2313 individuals, 97.2% were asymptomatic and 2.8% were symptomatic. P. falciparum prevalence among symptomatic individuals was 25.8%, 30.3%, and 40.9% by LM, RDT, and varATS qPCR, respectively, and among asymptomatic individuals, it was 10.3%, 12.5%, and 34.9%. Asymptomatic infections comprised 96.4% of all malaria infections, with 58.2% detectable only by varATS qPCR. Although the prevalence of asymptomatic P. falciparum infections was higher in school-age children (5-14 years: 42.0%) compared to < 5 years (17.3%) and ≥ 15 years (35.9%), subpatent infections were more likely in ≥ 15 years (70.4%) than in < 5 years (39.7%) and school-age children (41.2%). LM and RDTs were reliable only at parasite densities > 10,000 parasites/µL. Individuals who were positive according to all three tests had significantly greater parasite density (856.8 parasites/µL; 95% CI 707.3-1,038) than did those who were positive by varATS qPCR only (13.7 parasites/µL; 95% CI 11.4-16.3) (p < 0.0001). No pfhrp2 deletions were observed. The high prevalence of asymptomatic and subpatent infections highlights the need for targeted strategies to reduce malaria in urban Côte d'Ivoire.
| S-EPMC11330520 | biostudies-literature
Project description:BackgroundAsymptomatic malaria infections can serve as potential reservoirs for malaria transmission. The density of parasites contained in these infections range from microscopic to submicroscopic densities, making the accurate detection of asymptomatic parasite carriage highly dependent on the sensitivity of the tools used for the diagnosis. This study sought to evaluate the sensitivities of a variety of molecular and serological diagnostic tools at determining the prevalence of asymptomatic Plasmodium falciparum parasite infections in two communities with varying malaria parasite prevalence.MethodsWhole blood was collected from 194 afebrile participants aged between 6 and 70 years old living in a high (Obom) and a low (Asutsuare) malaria transmission setting of Ghana. Thick and thin blood smears, HRP2 based malaria rapid diagnostic test (RDT) and filter paper dried blood spots (DBS) were prepared from each blood sample. Genomic DNA was extracted from the remaining blood and used in Plasmodium specific photo-induced electron transfer polymerase chain reaction (PET-PCR) and Nested PCR, whilst the HRP2 antigen content of the DBS was estimated using a bead immunoassay. A comparison of malaria parasite prevalence as determined by each method was performed.ResultsParasite prevalence in the high transmission site of Obom was estimated at 71.4%, 61.9%, 60%, 37.8% and 19.1% by Nested PCR, the HRP2 bead assay, PET-PCR, HRP2-RDT and microscopy respectively. Parasite prevalence in the low transmission site of Asutsuare was estimated at 50.1%, 11.2%, 5.6%, 0% and 2.2% by Nested PCR, the HRP2 bead assay, PET-PCR, RDT and microscopy, respectively. The diagnostic performance of Nested PCR, PET-PCR and the HRP2 bead assay was similar in Obom but in Asutsuare, Nested PCR had a significantly higher sensitivity than PET-PCR and the HRP2 bead assay, which had similar sensitivity.ConclusionsNested PCR exhibited the highest sensitivity by identifying the highest prevalence of asymptomatic P. falciparum in both the high and low parasite prevalence settings. However, parasite prevalence estimated by the HRP2 bead assay and PET-PCR had the highest level of inter-rater agreement relative to all the other tools tested and have the advantage of requiring fewer processing steps relative to Nested PCR and producing quantitative results.
| S-EPMC8858553 | biostudies-literature
Project description:BackgroundThe ABO and the Rhesus blood group systems, as well as various abnormal haemoglobin (Hb) variants (haemoglobinopathies) are known to influence malaria parasite carriage and disease severity in individuals living in malaria endemic areas. This study identified the blood group and Hb variant distribution and Plasmodium falciparum infection status of afebrile individuals living in southern Ghana.MethodsAfebrile participants were recruited from Obom (358) in the Greater Accra Region and Ewim (100) and Simiw (329) in the Central Region of Ghana. Venous blood (1 ml) was collected into EDTA vacutainer tubes. Three 20 μl drops of blood were used for blood group analysis using the tile method. Another 500 μl aliquot was used for the qualitative sickling test using sodium metabisulphite and haemoglobin electrophoresis. Genomic DNA was extracted from 100 μl of whole blood and used in P. falciparum species-specific PCR.ResultsThe most abundant blood group and abnormal haemoglobin variant in both sites was blood group O + (47.4%) and HbAS (15.8%). A total of 13 (1.7%) of the participants had full haemoglobinopathies (SS, SC and CC), whilst 196 (25.4%) were carriers (AS and AC). Although there was a significantly higher prevalence of sickling positive participants from the Central Region, genotyping identified a similar prevalence of each of the abnormal haemoglobin genes in both sites. Asymptomatic parasite carriage estimated by PCR was 40.9% in the Central Region and 41.8% in the Greater Accra Region.ConclusionsAsymptomatic carriage of P. falciparum parasite in the study population was not associated with any particular blood group variant or haemoglobin genotype.
| S-EPMC7310487 | biostudies-literature