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Background & objectives:
Submicroscopic malaria infections with low parasite density serve as a silent reservoir for maintaining residual transmission in the population. These infections should be identified and targeted to be eliminated for sustained malaria control. The conventional methods of diagnosis such as light microscopy and rapid diagnos...
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... from 9 districts allocated equal in high, medium and low API stratum. Thus, the total sample size of the study population was about 9 lakhs for the purpose of active and passive surveillance for estimation of malaria disease burden, however, only part of the samples were used for the present study. The location of nine study districts is shown in Fig. ...
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Background: Due to the low prevalence of clinical malaria of 1-2 % among pregnant women in Myanmar, little is known about its impact on mothers and newborns. Helminth and HIV co-infections may cause anaemia and other adverse health outcomes for both mother and child. This study assessed the prevalence of subclinical malaria and co-infections among...
Citations
... The emergence of P. falciparum clusters in the newer regions requires targeted interventions to disrupt further transmission. As the elimination process is progressing to be malaria-free by 2027 and to eliminate the disease by 2030, the road ahead is bumpy and beset with many challenges, including the emergence of a set of new asymptomatic or sub-microscopic malaria parasitaemia [39][40][41][42], the emergence of artemisinin and multidrugresistant malaria [43,44]. Likewise, eliminating malaria fever incidence and measuring transmission requires a robust monitoring system that facilitates early infection detection and quick, efficient action. ...
Background
Malaria, a prominent vector borne disease causing over a million annual cases worldwide, predominantly affects vulnerable populations in the least developed regions. Despite their preventable and treatable nature, malaria remains a global public health concern. In the last decade, India has faced a significant decline in malaria morbidity and mortality. As India pledged to eliminate malaria by 2030, this study examined a decade of surveillance data to uncover space–time clustering and seasonal trends of Plasmodium vivax and Plasmodium falciparum malaria cases in West Bengal.
Methods
Seasonal and trend decomposition using Loess (STL) was applied to detect seasonal trend and anomaly of the time series. Univariate and multivariate space–time cluster analysis of both malaria cases were performed at block level using Kulldorff’s space–time scan statistics from April 2011 to March 2021 to detect statistically significant space–time clusters.
Results
From the time series decomposition, a clear seasonal pattern is visible for both malaria cases. Statistical analysis indicated considerable high-risk P. vivax clusters, particularly in the northern, central, and lower Gangetic areas. Whereas, P. falciparum was concentrated in the western region with a significant recent transmission towards the lower Gangetic plain. From the multivariate space–time scan statistics, the co-occurrence of both cases were detected with four significant clusters, which signifies the regions experiencing a greater burden of malaria cases.
Conclusions
Seasonal trends from the time series decomposition analysis show a gradual decline for both P. vivax and P. falciparum cases in West Bengal. The space–time scan statistics identified high-risk blocks for P. vivax and P. falciparum malaria and its co-occurrence. Both malaria types exhibit significant spatiotemporal variations over the study area. Identifying emerging high-risk areas of P. falciparum malaria over the Gangetic belt indicates the need for more research for its spatial shifting. Addressing the drivers of malaria transmission in these diverse clusters demands regional cooperation and strategic strategies, crucial steps towards overcoming the final obstacles in malaria eradication.
... Our study confirmed the declining trend of malaria infections in Chhattisgarh, but did not attempt to ascertain the impact of the MSaT strategy on reducing malaria prevalence. However, a study in a moderate malaria-burden area in Madhya Pradesh showed the effectiveness of MSaT in reducing the prevalence [39][40][41][42][43][44][45]. Further research is recommended to assess the effectiveness of the MSaT strategy in reducing the prevalence of malaria in high-burden areas. ...
... A number of techniques are available for detecting afebrile malaria, including some that are suitable for field conditions [38][39][40][41][42][43][44][45]; however, this study used only one method, RDT. ...
A key obstacle in the fight against malaria is afebrile malaria. It remains undiagnosed and, therefore, is invisible to the health system. Apart from being a serious illness, it contributes to increased transmission. Existing studies in India have not adequately reported afebrile malaria and its determinants, including the use of long-lasting insecticide-treated nets (LLINs). This study used six waves of mass screening, which were conducted by the state government in the high-malaria-burden region of Chhattisgarh, a state in India, in 2020, 2021, and 2022. Each round of data collection included more than 15000 individuals. Descriptive statistics were used to analyse key indicators of malaria prevalence and LLIN use. Multivariate analyses were performed to identify the determinants of afebrile malaria and LLIN use. Malaria prevalence in the afebrile population varied from 0.6% to 1.4% across the different waves of mass screening. In comparison, malaria positivity among febrile individuals was greater than 33% in each wave. Afebrile malaria contributed to 19.6% to 47.2% of the overall malaria burden in the region. Indigenous communities (scheduled tribes) were more susceptible to malaria, including afebrile malaria. Individuals using LLINs were less likely to be affected by afebrile malaria. Overall, 77% of the individuals used LLINs in early monsoon season, and in winter the rate was lower at 55%. LLIN use was significantly associated with the number of LLINs the households received from the government. Although fever continues to be a primary symptom of malaria, afebrile malaria remains a significant contributor to the malaria burden in the region. The free distribution of LLINs should be expanded to include high-burden populations. Global policies must include strategies for surveillance and control of afebrile malaria in high-burden areas.
... En el estado de Punjab, se encontró una diferencia de 23,4% de casos detectados por PCR y aquellos detectados por microscopía o pruebas de diagnóstico rápido. Estas parasitemias submicroscópicas sirven como reservorio silencioso para perpetuar la transmisión de la malaria en las regiones (Kaura et al., 2019) Aunque la presencia de malaria asintomática ha sido reportada frecuentemente en áreas de transmisión alta e intermedia, se han informado casos en zonas de baja endemicidad en la región amazónica de Brasil, Perú, Venezuela y Colombia . En Colombia, para el año 2015, se encontró una prevalencia de 0,3% de malaria submicroscópica en zonas endémicas, diagnosticada por gota gruesa mientras que por PCR fue de 9,7% (Vallejo et al., 2015). ...
... Prevalence of submicroscopic malaria in low transmission state of Punjab: A potential threat to malaria elimination. Kaura T et al. 2019 India Journal Vector Borne Disease La aplicación de herramientas de diagnóstico más sensibles como la PCR puede ser mucho más útil en la detección de parasitemias de baja densidad, particularmente en entornos de baja transmisión. ...
Introducción: A pesar de ser una enfermedad prevenible y curable, la malaria continúa siendo un problema para la salud pública. Objetivo: Identificar las barreras y facilitadores para la eliminación de la malaria. Material y Método: Entre 2019 y 2020 se revisó literatura disponible en las bases de datos Pubmed y LILACS; se realizó una matriz para la organización y posterior análisis de la información. Resultados: En total, 57 artículos fueron seleccionados evidenciando como barreras, la falta de recurso humano, técnico y económico, la resistencia del vector al manejo farmacológico, la diversidad parasitaria y de vectores y la movilidad humana entre en regiones endémicas. Estrategias como el manejo integrado de vectores, la estratificación dinámica de la enfermedad, la detección y manejo oportuno y la adecuada vigilancia epidemiológica, fueron repetidamente enunciadas como facilitadores. Conclusión: Es necesario identificar la realidad social, epidemiológica y política en el nivel regional y así poder personalizar y sostener las estrategias de eliminación.
... However, India still accounted for 83% of malaria cases and 82% of malaria fatalities in the region [2]. Some of the challenges towards malaria elimination in India include diverse climate, diverse vector population, complex epidemiology, emerging drug and insecticide resistance, asymptomatic malaria, low-density infections and various operational limitations [3][4][5][6][7][8]. ...
Background
Mass screening and treatment (MSaT) aims at reducing the spread of malaria in communities by identifying and treating infected persons regardless of the symptoms. This study was conducted to identify and treat asymptomatic cases using MSaT approaches in the community.
Methods
Three rounds of MSaT using cluster combination approaches were carried out during September 2018 to December 2019 to identify and treat asymptomatic malaria cases in the community. All individuals who were present in the household were screened using RDT irrespective of malaria related symptoms. Simultaneously thick and thin blood smear and blood spot were collected for further analysis using microscopy and diagnostic PCR done in a subset of the samples.
Results
Logistic regression analysis revealed that asymptomatic malaria cases significantly less among the older age groups compared with < 5 years children (OR ranged between 0.52 and 0.61; p < 0.05), lowest in cluster 4 (OR = 0.01; p < 0.0001); during third round of MSaT survey (OR = 0.11; p < 0.0001) and significantly higher in moderate to high endemic areas (OR = 88.30; p < 0.0001).
Conclusion
Over the three rounds of MSaT, the number of asymptomatic cases were significantly less in the older age groups, and during third round. Similarly, the asymptomatic cases were significantly less in the low endemic area with API < 1 (cluster four). Therefore, the malaria elimination programme may consider the MSaT strategy to identify asymptomatic cases that would be otherwise missed by routine fever based surveillance. This MSaT strategy would help accomplish the malaria elimination goal in an expedited manner.
... In India, the sub-microscopic malaria burden has been previously reported [9][10][11][12][13][14][15][16][17][18][19]. Studies conducted so far using various molecular methods in different transmission settings, have reported the prevalence of sub-microscopic P. falciparum from 5 to 50% [20]. ...
Background
Low-density malaria infections (LDMI) are defined as infections that are missed by the rapid diagnostic test (RDT) and/or microscopy which can lead to continued transmission and poses a challenge in malaria elimination efforts. This study was conducted to investigate the prevalence of LDMI in febrile cases using species-specific nested Polymerase Chain Reaction (PCR) tests in the Malaria Elimination Demonstration Project, where routine diagnosis was conducted using RDT.
Methods
Every 10th fever case from a cross-sectional community based fever surveillance was tested with RDT, microscopy and nested PCR. Parasite DNA was isolated from the filter paper using Chelex based method. Molecular diagnosis by nested PCR was performed targeting 18SrRNA gene for Plasmodium species.
Results
The prevalence of malaria was 2.50% (436/17405) diagnosed by PCR, 1.13% (196/17405) by RDT, and 0.68% (118/ 17,405) by microscopy. Amongst 17,405 febrile samples, the prevalence of LDMI was 1.51% (263/17405) (95% CI 1.33–1.70), which were missed by conventional methods. Logistic regression analysis revealed that illness during summer season [OR = 1.90 (p < 0.05)] and cases screened within three days of febrile illness [OR = 5.27 (p < 0.001)] were the statistically significant predictors of LDMI.
Conclusion
The prevalence of malaria among febrile cases using PCR was 2.50% (436/17405) as compared to 1.13% (196/17405) by RDT. Higher number of the LDMI cases were found in subjects with ≤ 3 days mean duration of reported fever, which was statistically significant (p < 0.001). This observation suggests that an early detection of malaria with a more sensitive diagnostic method or repeat testing of the all negative cases may be useful for curtailing malaria transmission. Therefore, malaria elimination programme would benefit from using more sensitive and specific diagnostic methods, such as PCR.
... Submicroscopic malaria infections are hidden parasite reservoirs as infected individuals were not identified and treated with antimalarial drugs. They can serve as the source of infection and contribute to transmission in the community and/or other malaria-free areas (33)(34)(35), thereby hindering malaria control and elimination. The present study showed that submicroscopic infections were high among malaria suspected febrile patients in the southwestern part of Ethiopia. ...
The identification and management of low parasitemia infections have become increasingly challenging for malaria control and elimination. Submicroscopic Plasmodium infections and G6PD deficiency among febrile patients require more sensitive diagnostic methods to improve detection and careful treatment regime of these infections. In Ethiopia, information on the low density submicroscopic malarial infections and frequency of G6PD deficiency (G6PDd) is scarce. In this study, 297 malaria suspected febrile patient samples were collected from health facilities of Bonga town in southwestern Ethiopia. The positivity rates of Plasmodium infection were determined by microscopy and quantitative PCR. G6PD activity level was determined by careSTART™ G6PD biosensor and the frequency of three common variants: G6PD*A (A376G), G6PD*A− (G202A) and Mediterranean (C563T) were investigated. G6PD gene sequencing was performed to detect mutations in exons 2-11 for both G6PD normal and deficient samples based on the phenotypic assay. More than twice Plasmodium infected samples was detected by qPCR (52/297; 17.4%) than microscopy (21/297; 7.0%). About 31 (10%) of the infections were submicroscopic. Bednet usage and age had a significant association with Plasmodium infection. Of the 271 participants who were tested for G6PD phenotype, 19 (7.0%) had low G6PD level. No mutations were observed in A376G, G202A, and C563T in the G6PDd samples, but three novel non-synonymous mutations in exon 2 including a C to T transition at position ChrX:6504 (Arg to Thr), G to T at ChrX:6369 (Ser to IIe), and G to C at ChrX:6664 (Gln to His) were detected. A high number of submicroscopic Plasmodium infections observed in this study pose a challenge for accurate and Frontiers in Tropical Diseases
... Ninety-seven percent of the infected individuals had asymptomatic, sub-microscopic infection, which could only be detected through molecular (PCR-based) methods. A high prevalence of sub-microscopic infections was previously reported from malaria-endemic areas in India [22][23][24] and elsewhere [25][26][27]. As sub-microscopic carriers may contribute to sustained transmission of Plasmodium infection [28], the use of molecular diagnostic tools for detection of low-density infections has been recommended for malaria surveillance in low-endemic settings [29]. ...
Background
A detailed analysis of household and individual level Plasmodium infection patterns in two low-endemic districts of Meghalaya was undertaken to better understand the epidemiology of malaria in northeast India.
Methods
Socio-demographic and behavioural information from residents (aged 1–69 years) of households were collected through pre-tested, questionnaire conducted in 2018 and 2019. Blood samples collected from participants were tested for Plasmodium falciparum and/or Plasmodium vivax infection using rapid diagnostic test, microscopy and PCR. Plasma samples from a subset of participants were analysed for antibodies against thirteen P. falciparum and four P. vivax antigens. Associations between household and individual level risk factors, and Plasmodium infections were evaluated using multilevel logistic regression models.
Results
A total of 2753 individuals from 827 households were enrolled in 2018, and 834 individuals from 222 households were enrolled in 2019. Of them, 33 (1.2%) were positive by PCR for P. falciparum in 2018 and none were positive for P. vivax. In 2019, no PCR-positive individuals were detected. All, but one, infections were asymptomatic; all 33 infections were sub-microscopic. Reported history of malaria in the past 12 months (OR = 8.84) and history of travel in the past 14 days (OR = 10.06) were significantly associated with Plasmodium infection. A significant trend of increased seropositivity with age was noted for all 17 antigens. Although adults (≥ 18 years) consistently had the highest seropositivity rates, a sizeable proportion of under-five children were also found to be seropositive. Almost all individuals (99.4%) reported sleeping under an insecticide-treated bed-net, and household indoor residual spray coverage in the 12 months preceding the survey was low (23%). Most participants correctly identified common signs and symptoms of malaria, i.e., fever (96.4%), headache (71.2%), chills (83.2%) and body-ache (61.8%). Almost all participants (94.3%) used government-provided services for treatment of malaria.
Conclusion
This study explored the epidemiology of malaria in two communities in Meghalaya, India, in the context of declining transmission. The presence of widespread asymptomatic infections and seropositivity among under-five children suggest that low-level Plasmodium transmission persists in this region. Implications of the study findings for malaria elimination efforts in low-transmission settings are discussed.
... Malaria epidemiological studies often generate a very large number of samples [2,26,27], and as the prevalence of infection decreases, more samples need to be tested to identify infected persons. As such, laboratory testing for pooled samples is appealing since pooling could potentially lower reagent costs, reduce labour, and accelerate results by reducing laboratory test counts [28,29]. ...
Background
Plasmodium 18S rRNA is a sensitive biomarker for detecting Plasmodium infection in human blood. Dried blood spots (DBS) are a practical sample type for malaria field studies to collect, store, and transport large quantities of blood samples for diagnostic testing. Pooled testing is a common way to reduce reagent costs and labour. This study examined performance of the Plasmodium 18S rRNA biomarker assay for DBS, improved assay sensitivity for pooled samples, and created graphical user interface (GUI) programmes for facilitating optimal pooling.
Methods
DBS samples of varied parasite densities from clinical specimens, Plasmodium falciparum in vitro culture, and P. falciparum Armored RNA® were tested using the Plasmodium 18S rRNA quantitative triplex reverse transcription polymerase chain reaction (qRT-PCR) assay and a simplified duplex assay. DBS sample precision, linearity, limit of detection (LoD) and stability at varied storage temperatures were evaluated. Novel GUIs were created to model two-stage hierarchy, square matrix, and three-stage hierarchy pooling strategies with samples of varying positivity rates and estimated test counts. Seventy-eight DBS samples from persons residing in endemic regions with sub-patent infections were tested in pools and deconvoluted to identify positive cases.
Results
Assay performance showed linearity for DBS from 4 × 10 ⁷ to 5 × 10 ² parasites/mL with strong correlation to liquid blood samples (r ² > 0.96). There was a minor quantitative reduction in DBS rRNA copies/mL compared to liquid blood samples. Analytical sensitivity for DBS was estimated 5.3 log copies 18S rRNA/mL blood (28 estimated parasites/mL). Properly preserved DBS demonstrated minimal degradation of 18S rRNA when stored at ambient temperatures for one month. A simplified duplex qRT-PCR assay omitting the human mRNA target showed improved analytical sensitivity, 1 parasite/mL blood, and was optimized for pooling. Optimal pooling sizes varied depending on prevalence. A pilot DBS study of the two-stage hierarchy pooling scheme corroborated results previously determined by testing individual DBS.
Conclusions
The Plasmodium 18S rRNA biomarker assay can be applied to DBS collected in field studies. The simplified Plasmodium qRT-PCR assay and GUIs have been established to provide efficient means to test large quantities of DBS samples.
... Indeed, remote tribal areas and low resource settings are more inclined towards using RDTs in comparison to microscopy, due to its user-friendly operations, quick results and no requirements of any equipment, electricity or technical speciality whatsoever (McMorrow et al. 2011). Recent evidence suggests the presence of sub-microscopic infections (van Eijk et al. 2019), low-density Plasmodium infection and asymptomatic parasitaemia in Indian community (van Eijk et al. 2020;Shankar et al. 2021), even in low transmission settings (Kaura et al. 2019). The presence of such hidden reservoir of infectiousness may pose a challenge to the malaria elimination programme and therefore must be curtailed to achieve the elimination goal. ...
An early and accurate diagnosis followed by prompt treatment is pre-requisite for the management of any disease. Malaria diagnosis is routinely performed by microscopy and rapid diagnostic tests (RDTs) in the field settings; however, their performance may vary across regions, age and asymptomatic status. Owing to this, we assessed the diagnostic performance of conventional and advanced molecular tools for malaria detection in low and high malaria-endemic settings. We performed mass blood surveys in low and high endemic regions of two North-Eastern districts from the states of Assam and Meghalaya. A total of 3322 individuals were screened for malaria using RDT, microscopy and PCR and measures of diagnostic accuracy were estimated. Out of 3322 individuals, 649 (19.5%) were detected with malaria parasite. Asymptomatic were 86.4% (2872/3322), of which 19.4% (557/2872) had Plasmodium infection. The sensitivity and specificity of microscopy were 42.7% and 99.3%, and RDT showed 49.9% and 90.4%, respectively, considering PCR as standard. RDT (AUC: 0.65 vs 0.74; p = 0.001) and microscopy (AUC: 0.64 vs 0.76; p < 0.0001) performances were significantly lower in low compared to high endemic areas. True positive rate was lower in asymptomatics but true negative rate was found similar to symptomatic individuals. The conventional diagnostic tools (RDT and microscopy) had detected malaria in children with nearly twofold greater sensitivity than in the adults (p < 0.05). To conclude, asymptomatics, adults and low malaria-endemic regions require major attention due to mediocre performance of conventional diagnostic tools in malaria detection.
... 27,28 Another challenge for continued transmission is the existence of submicroscopic parasitaemias in the community, which serve as a silent reservoir for maintaining transmission in the population. The presence of submicroscopic parasitaemia has been reported in the Punjab state, 29 thus future studies should be undertaken to estimate the burden of malaria using highly sensitive molecular techniques to predict low density infection in the population, thereby facilitating malaria elimination. ...
Background:
The state of Punjab in India qualifies for malaria elimination because the number of cases reported through routine surveillance is in decline. However, surveillance system prevalence mainly provides malaria trends. Therefore, a prospective epidemiological study was designed to estimate the malaria burden in the state.
Methods:
District-wise annual parasite incidence (API) was used for identification of three strata, representing high, moderate and low API zones. A total of 0.9 million people from nine districts was under malaria surveillance for 1 y. The weighted estimates of API for the three regions was calculated and combined to give an estimate of API for the total population of the state.
Results:
Based upon the primary data generated, malaria cases from high, moderate and low malaria-endemic areas were estimated to be 3727, 904 and 106, respectively. Further, the total number of malaria cases in the state was estimated to be 4737 (95% CI 4006 to 5469) cases per annum.
Conclusion:
Actual burden of malaria in the state of Punjab, India, is about seven to eight times higher than that reported by routine surveillance activities. However, the state still qualifies for malaria elimination but needs vigorous efforts to strengthen the active surveillance and reporting system along with implementation of effective control strategies to achieve malaria elimination.
