Contribution of Asymptomatic Plasmodium Infections to the Transmission of Malaria in Kayin State, Myanmar

Abstract Background The objective of mass antimalarial drug administration (MDA) is to eliminate malaria rapidly by eliminating the asymptomatic malaria parasite reservoirs and interrupting transmission. In the Greater Mekong Subregion, where artemisinin-resistant Plasmodium falciparum is now widespread, MDA has been proposed as an elimination accelerator, but the contribution of asymptomatic infections to malaria transmission has been questioned. The impact of MDA on entomological indices has not been characterized previously. Methods MDA was conducted in 4 villages in Kayin State (Myanmar). Malaria mosquito vectors were captured 3 months before, during, and 3 months after MDA, and their Plasmodium infections were detected by polymerase chain reaction (PCR) analysis. The relationship between the entomological inoculation rate, the malaria prevalence in humans determined by ultrasensitive PCR, and MDA was characterized by generalized estimating equation regression. Results Asymptomatic P. falciparum and Plasmodium vivax infections were cleared by MDA. The P. vivax entomological inoculation rate was reduced by 12.5-fold (95% confidence interval [CI], 1.6–100-fold), but the reservoir of asymptomatic P. vivax infections was reconstituted within 3 months, presumably because of relapses. This was coincident with a 5.3-fold (95% CI, 4.8–6.0-fold) increase in the vector infection rate. Conclusion Asymptomatic infections are a major source of malaria transmission in Southeast Asia.

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Large Variations in Malaria Parasite Carriage by Afebrile School Children Living in Nearby Communities in the Central Region of Ghana

Journal of Tropical Medicine ◽

10.1155/2020/4125109 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10

Author(s):

Evans K. Obboh ◽

Ruth E. Okonu ◽

Linda E. Amoah

Keyword(s):

Malaria Transmission ◽

Central Region ◽

Malaria Control ◽

Filter Paper ◽

Malaria Parasite ◽

Molecular Evidence ◽

Asymptomatic Malaria ◽

Cape Coast ◽

Malaria Parasites ◽

Asymptomatic Infections

Background. Indicators of successful malaria control interventions include a reduction in the prevalence and densities of malaria parasites contained in both symptomatic and asymptomatic infections as well as a reduction in malaria transmission. Individuals harboring malaria parasites in asymptomatic infections serve as reservoirs for malaria transmission. This study determined the prevalence of asymptomatic malaria parasite carriage in afebrile children attending six different schools in two districts, the Cape Coast Metropolitan Assembly (CCMA) and the Komenda Edina Eguafo Abirem (KEEA) of the Central Region of Ghana. Methods. This cross sectional study recruited afebrile children aged between 3 and 15 years old from six randomly selected schools in the Central Region of Ghana. Finger-pricked blood was collected and used to prepare thick and thin blood smears as well as spot a strip of filter paper (Whatman #3). Nested PCR was used to identify Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale, and Plasmodium vivax in DNA extracted from the filter paper spots. The multiplicity of P. falciparum infection was determined using merozoite surface protein 2 genotyping. Results. Out of the 528 children sampled, PCR identified 27.1% to harbor Plasmodium parasites in asymptomatic infections, whilst microscopy identified malaria parasites in 10.6% of the children. The overall PCR estimated prevalence of P. falciparum and P. malariae was 26.6% and 1.3%, respectively, with no P. ovale or P. vivax identified by PCR or microscopy. The RDT positivity rate ranged from 55.8% in Simiw to 4.5% in Kuful. Children from the Simiw Basic School accounted for 87.5% of all the asymptomatic infections. The multiplicity of P. falciparum infection was predominantly monoclonal and biclonal. Conclusions. The low prevalence of asymptomatic malaria parasite carriage by the children living in the Cape Coast Metropolis suggests that the malaria control interventions in place in CCMA are highly effective and that additional malaria control interventions are required for the KEEA district to reduce the prevalence of asymptomatic malaria parasite carriers. No molecular evidence of P. ovale and P. vivax was identified in the afebrile children sampled from the selected schools.

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Evaluation of a single screen and treat strategy to detect asymptomatic malaria among pregnant women from selected health facilities in Lindi region, Tanzania

Malaria Journal ◽

10.1186/s12936-020-03513-0 ◽

2020 ◽

Vol 19 (1) ◽

Author(s):

Chonge Kitojo ◽

Frank Chacky ◽

Emmanuel S. Kigadye ◽

Joseph P. Mugasa ◽

Abdallah Lusasi ◽

...

Keyword(s):

Pregnant Women ◽

Intermittent Preventive Treatment ◽

First Trimester ◽

Asymptomatic Malaria ◽

Low Transmission ◽

The Past ◽

High Transmission ◽

History Of ◽

Asymptomatic Infections ◽

The Impact

Abstract Background In areas of high transmission, malaria in pregnancy (MiP) primarily causes asymptomatic infections; these infections nonetheless increase the risk of adverse maternal and fetal outcomes. In 2014, Tanzania initiated a single screening and treatment (SST) strategy for all pregnant women at their first antenatal care (ANC) visit using malaria rapid diagnostic tests (RDT) for surveillance purposes. However, there is paucity of data on the effectiveness of SST in the prevention of MiP. The objective of this study was to estimate the number of asymptomatic infections among pregnant women detected by SST, which would have been missed in the absence of the policy. Methods Data from pregnant women attending their first ANC visits between October 2017 and June 2018, including gestational age, history of fever, and RDT results, were abstracted from ANC registers in eight health centres in two randomly selected districts, Kilwa and Lindi, in Lindi Region. The proportion of symptomatic (with history of fever in the past 48 h) and asymptomatic pregnant women with positive RDTs were calculated and stratified by trimester (first, second and third). The study areas were categorized as low transmission with prevalence < 10% or moderate/high with ≥ 10%. Results Over the study period, 1,845 women attended their first ANC visits; 22.1% were in the first trimester (< 12 weeks gestation age). Overall 15.0% of the women had positive RDTs, and there was a trend towards higher malaria prevalence in the first (15.9%) and second (15.2%) trimesters, compared to the third (7.1%), although the differences were not statistically significant (p = 0.07). In total, 6.9% of women reported fever within the past 48 h and, of these, 96.1% were RDT positive. For every 100 pregnant women in the moderate/high and low transmission areas, SST identified 60 and 26 pregnant women, respectively, with asymptomatic infections that would have otherwise been missed. Among the 15.9% of women detected in the first trimester, 50.7% were asymptomatic. Conclusion In areas of moderate/high transmission, many infected women were asymptomatic, and would have been missed in the absence of SST. The benefits on maternal and fetal birth outcomes of identifying these infections depend heavily on the protection afforded by treatment, which is likely to be greatest for women presenting in the first trimester when intermittent preventive treatment (IPTp) with sulfadoxine-pyrimethamine (SP) is contraindicated, and in areas with high SP resistance, such as most parts of Tanzania. An evaluation of the impact and cost-effectiveness of SST across different transmission strata is warranted.

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Effects of conventional immunosuppressive therapy on functional and pathological features of CNS lupus in NZB/W mice

F1000Research ◽

10.12688/f1000research.6568.2 ◽

2018 ◽

Vol 4 ◽

pp. 163

Author(s):

Jessy Alexander ◽

Alexander Jacob ◽

Richard J. Quigg

Keyword(s):

Extracellular Matrix ◽

Lupus Erythematosus ◽

Extracellular Matrix Proteins ◽

Fold Increase ◽

Matrix Proteins ◽

Neurological Involvement ◽

Pcr Analysis ◽

Cns Lupus ◽

Disease Systemic Lupus Erythematosus ◽

The Impact

Neurological involvement is one of the most devastating complications of the disease, systemic lupus erythematosus (SLE). To understand the effect of the drugs, cyclophosphamide (CY) and prednisolone (PD) on CNS manifestations, the New Zealand Black/White (NZB/W) lupus mice, were given a cocktail of both drugs by intraperitoneal injections daily from 22 to 44 weeks of age. The treatment prolonged survival (10% of the treated 20 NZB/W mice died compared to 50% of the 30 NZB/W mice, with no mortality in the control NZW mice). Real-time PCR analysis showed a three- to fifteen-fold increase in the expression of GFAP, vimentin and syndecan4 in the cerebral cortex of 44 week NZB/W mice. These alterations were prevented by CY and PD treatment. Immunostaining revealed increased GFAP expression in NZB/W mice compared to congenic, nondiseased NZW mice, which was prevented by treatment. In addition, concomitant changes were observed in the expression of extracellular matrix proteins, collagen IV and fibronectin. To determine the impact of these alterations on the neurological manifestations of SLE, behavior was studied in these mice. The NZB/W mice were spontaneously less active in the open field and exhibited a decrease in distance traveled (58% of control, p<0.01) and ambulatory measurements (52% of control, p<0.01). They took more time (8.8+1.2min) to escape from the maze compared to the control NZW mice (2.6+0.8min). Even more striking was that the behavioral deficits were alleviated in these mice by CY and PD treatment. These results support the hypothesis that increased astrogliosis and altered extracellular matrix proteins may be two of the critical factors that mediate lupus brain disease.

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PO 8419 SPATIO-TEMPORAL MAPPING OF ASYMPTOMATIC AND CLINICAL MALARIA INFECTIONS REVEALS FOCI OF MALARIA TRANSMISSION FOR TARGETED CONTROL INTERVENTIONS

BMJ Global Health ◽

10.1136/bmjgh-2019-edc.91 ◽

2019 ◽

Vol 4 (Suppl 3) ◽

pp. A35.2-A35

Author(s):

Makhtar Niang ◽

Cheikh Talla ◽

Nafissatou Diagne ◽

Fatoutama Diene-Sarr ◽

Cheikh Sokhna

Keyword(s):

Malaria Transmission ◽

Malaria Incidence ◽

Clinical Malaria ◽

Asymptomatic Malaria ◽

Design Strategies ◽

Cross Sectional ◽

Asymptomatic Infections ◽

Spatio Temporal ◽

Malaria Episodes

BackgroundThe global decline of malaria incidence over the past decade has led to the thought that elimination could be achieved. This has resulted in an increased interest to design strategies to target the hidden reservoir of asymptomatic infections among populations and interrupt on-going residual local malaria transmission. This study explored the reservoir of asymptomatic Plasmodium infections and its relationship with subsequent clinical malaria infections in low-transmission areas in Senegal.MethodsCross-sectional surveys were carried out in 2013, 2014, 2015, and 2016 and combined with longitudinal follow-up to determine and geolocalise both asymptomatic and clinical malaria episodes in Dielmo and Ndiop, Senegal. The prevalence of asymptomatic Plasmodium carriage in the community was investigated by real-time PCR while clinical malaria attacks were identified at health facilities during the transmission season. All households were georeferenced to spatially map asymptomatic and clinical infections.ResultsThe study revealed substantial asymptomatic infections with average parasite carriage of 8.11% and 7% in Dielmo and Ndiop, respectively. P. falciparum accounted for most asymptomatic infections (more than 90%). In Dielmo, 95% of asymptomatic infections clustered within the same geographical areas while infections were disparate in Ndiop. Preliminary fine-scale mapping of asymptomatic and clinical malaria infections identified clusters of higher malaria incidence interpreted as foci of transmission across the four-year study period with 95%–98% of clinical infections occurring in households where an asymptomatic malaria infection existed.ConclusionThis study revealed substantial asymptomatic Plasmodium infections in both settings throughout the four-year study period and spatial clusters of malaria infections at the microepidemiological level. Together, these findings could offer a feasible approach for a rational targeting of malaria control interventions to achieve elimination.

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Evaluation of different deployment strategies for larviciding to control malaria: a simulation study

Malaria Journal ◽

10.1186/s12936-021-03854-4 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Manuela Runge ◽

Salum Mapua ◽

Ismail Nambunga ◽

Thomas A. Smith ◽

Nakul Chitnis ◽

...

Keyword(s):

Malaria Transmission ◽

Critical Role ◽

Indoor Residual Spraying ◽

Malaria Prevalence ◽

Transmission Model ◽

Malaria Vectors ◽

Relative Reduction ◽

Insecticide Treated Nets ◽

Host Seeking ◽

The Impact

Abstract Background Larviciding against malaria vectors in Africa has been limited to indoor residual spraying and insecticide-treated nets, but is increasingly being considered by some countries as a complementary strategy. However, despite progress towards improved larvicides and new tools for mapping or treating mosquito-breeding sites, little is known about the optimal deployment strategies for larviciding in different transmission and seasonality settings. Methods A malaria transmission model, OpenMalaria, was used to simulate varying larviciding strategies and their impact on host-seeking mosquito densities, entomological inoculation rate (EIR) and malaria prevalence. Variations in coverage, duration, frequency, and timing of larviciding were simulated for three transmission intensities and four transmission seasonality profiles. Malaria transmission was assumed to follow rainfall with a lag of one month. Theoretical sub-Saharan African settings with Anopheles gambiae as the dominant vector were chosen to explore impact. Relative reduction compared to no larviciding was predicted for each indicator during the simulated larviciding period. Results Larviciding immediately reduced the predicted host-seeking mosquito densities and EIRs to a maximum that approached or exceeded the simulated coverage. Reduction in prevalence was delayed by approximately one month. The relative reduction in prevalence was up to four times higher at low than high transmission. Reducing larviciding frequency (i.e., from every 5 to 10 days) resulted in substantial loss in effectiveness (54, 45 and 53% loss of impact for host-seeking mosquito densities, EIR and prevalence, respectively). In seasonal settings the most effective timing of larviciding was during or at the beginning of the rainy season and least impactful during the dry season, assuming larviciding deployment for four months. Conclusion The results highlight the critical role of deployment strategies on the impact of larviciding. Overall, larviciding would be more effective in settings with low and seasonal transmission, and at the beginning and during the peak densities of the target species populations. For maximum impact, implementers should consider the practical ranges of coverage, duration, frequency, and timing of larviciding in their respective contexts. More operational data and improved calibration would enable models to become a practical tool to support malaria control programmes in developing larviciding strategies that account for the diversity of contexts.

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The burden of submicroscopic and asymptomatic malaria in India revealed from epidemiology studies at three varied transmission sites in India

Scientific Reports ◽

10.1038/s41598-019-53386-w ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 4

Author(s):

Anna Maria van Eijk ◽

Patrick L. Sutton ◽

Lalitha Ramanathapuram ◽

Steven A. Sullivan ◽

Deena Kanagaraj ◽

...

Keyword(s):

Public Health ◽

Tamil Nadu ◽

Public Health Problem ◽

Malaria Prevalence ◽

Asymptomatic Malaria ◽

Community Surveys ◽

Blood Samples ◽

High Burden ◽

Asymptomatic Infections ◽

Epidemiology Studies

AbstractMalaria in India, while decreasing, remains a serious public health problem, and the contribution of submicroscopic and asymptomatic infections to its persistence is poorly understood. We conducted community surveys and clinic studies at three sites in India differing in their eco-epidemiologies: Chennai (Tamil Nadu), Nadiad (Gujarat), and Rourkela (Odisha), during 2012–2015. A total of 6,645 subject blood samples were collected for Plasmodium diagnosis by microscopy and PCR, and an extensive clinical questionnaire completed. Malaria prevalence ranged from 3–8% by PCR in community surveys (24 infections in Chennai, 56 in Nadiad, 101 in Rourkela), with Plasmodium vivax dominating in Chennai (70.8%) and Nadiad (67.9%), and Plasmodium falciparum in Rourkela (77.3%). A proportional high burden of asymptomatic and submicroscopic infections was detected in community surveys in Chennai (71% and 71%, respectively, 17 infections for both) and Rourkela (64% and 31%, 65 and 31 infections, respectively). In clinic studies, a proportional high burden of infections was identified as submicroscopic in Rourkela (45%, 42 infections) and Chennai (19%, 42 infections). In the community surveys, anemia and fever were significantly more common among microscopic than submicroscopic infections. Exploratory spatial analysis identified a number of potential malaria hotspots at all three sites. There is a considerable burden of submicroscopic and asymptomatic malaria in malarious regions in India, which may act as a reservoir with implications for malaria elimination strategies.

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Modelled and observed mean and seasonal relationships between climate, population density and malaria indicators in Cameroon

Malaria Journal ◽

10.1186/s12936-019-2991-8 ◽

2019 ◽

Vol 18 (1) ◽

Cited By ~ 1

Author(s):

Amelie D. Mbouna ◽

Adrian M. Tompkins ◽

Andre Lenouo ◽

Ernest O. Asare ◽

Edmund I. Yamba ◽

...

Keyword(s):

Population Density ◽

Malaria Transmission ◽

Disease Transmission ◽

Entomological Inoculation Rate ◽

Population Data ◽

Malaria Prevalence ◽

Housing Quality ◽

Population Movements ◽

Mitigation And Adaptation ◽

Malaria Model

Abstract Background A major health burden in Cameroon is malaria, a disease that is sensitive to climate, environment and socio-economic conditions, but whose precise relationship with these drivers is still uncertain. An improved understanding of the relationship between the disease and its drivers, and the ability to represent these relationships in dynamic disease models, would allow such models to contribute to health mitigation and adaptation planning. This work collects surveys of malaria parasite ratio and entomological inoculation rate and examines their relationship with temperature, rainfall, population density in Cameroon and uses this analysis to evaluate a climate sensitive mathematical model of malaria transmission. Methods Co-located, climate and population data is compared to the results of 103 surveys of parasite ratio (PR) covering 18,011 people in Cameroon. A limited set of campaigns which collected year-long field-surveys of the entomological inoculation rate (EIR) are examined to determine the seasonality of disease transmission, three of the study locations are close to the Sanaga and Mefou rivers while others are not close to any permanent water feature. Climate-driven simulations of the VECTRI malaria model are evaluated with this analysis. Results The analysis of the model results shows the PR peaking at temperatures of approximately 22 °C to 26 °C, in line with recent work that has suggested a cooler peak temperature relative to the established literature, and at precipitation rates at 7 mm day−1, somewhat higher than earlier estimates. The malaria model is able to reproduce this broad behaviour, although the peak occurs at slightly higher temperatures than observed, while the PR peaks at a much lower rainfall rate of 2 mm day−1. Transmission tends to be high in rural and peri-urban relative to urban centres in both model and observations, although the model is oversensitive to population which could be due to the neglect of population movements, and differences in hydrological conditions, housing quality and access to healthcare. The EIR follows the seasonal rainfall with a lag of 1 to 2 months, and is well reproduced by the model, while in three locations near permanent rivers the annual cycle of malaria transmission is out of phase with rainfall and the model fails. Conclusion Malaria prevalence is maximum at temperatures of 24 to 26 °C in Cameroon and rainfall rates of approximately 4 to 6 mm day−1. The broad relationships are reproduced in a malaria model although prevalence is highest at a lower rainfall maximum of 2 mm day−1. In locations far from water bodies malaria transmission seasonality closely follows that of rainfall with a lag of 1 to 2 months, also reproduced by the model, but in locations close to a seasonal river the seasonality of malaria transmission is reversed due to pooling in the transmission to the dry season, which the model fails to capture.

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Effects of conventional immunosuppressive therapy on functional and pathological features of CNS lupus in NZB/W mice

F1000Research ◽

10.12688/f1000research.6568.1 ◽

2015 ◽

Vol 4 ◽

pp. 163 ◽

Cited By ~ 1

Author(s):

Jessy Alexander ◽

Alexander Jacob ◽

Richard J. Quigg

Keyword(s):

Extracellular Matrix ◽

Lupus Erythematosus ◽

Extracellular Matrix Proteins ◽

Fold Increase ◽

Matrix Proteins ◽

Neurological Involvement ◽

Pcr Analysis ◽

Cns Lupus ◽

Disease Systemic Lupus Erythematosus ◽

The Impact

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Prevalence of Asymptomatic Malaria in Leaiten, Eritrea, 2017.

10.21203/rs.2.22330/v1 ◽

2020 ◽

Author(s):

Meron Berhe Tsegai ◽

Hermon Mekonen Gezae ◽

Tesfagabr Akalu Kifle ◽

Hosanna Ghenbot Liebe ◽

Aklilu Gebreyesus Gebrezgabiher ◽

...

Keyword(s):

Malaria Transmission ◽

Water Body ◽

Mosquito Control ◽

Open Water ◽

P Value ◽

Asymptomatic Malaria ◽

Or Education ◽

Closed Water ◽

Potential Factors ◽

The Impact

Abstract Background As much as malaria control interventions may be directed at restricting transmission through mosquito control and treatment of symptomatic cases, the effect of asymptomatic cases in the transmission of malaria has not been given too much attention. On the other hand, asymptomatic carriers do not seek treatment, becoming permanent reservoirs, and hence creating a real pose to the public health. Objective The purpose of the study was to determine the prevalence of asymptomatic malaria and its associated factors in Leaiten village, Eritrea. Methods 322 eligible participants were randomly selected and interviewed. Thin and thick blood films were collected and Giemsa-stained to determine blood parasitaemia and speciation using light microscopy. Multivariate Logistic Regression was used to assess relationship between the potential factors identified and asymptomatic malaria. Results The prevalence of asymptomatic malaria was 5.9%, with a predominantly higher proportion (P) of Plasmodium Falciparum (P= 94.7%, n=18) than Plasmodium Vivax (P= 5.3%, n=1). Most of the infections were low density and at their ring form (P = 94.7%, n = 18). Only one subject had medium density and a gametocyte stage infection (P = 5.3%). The odds of asymptomatic malaria by sex, age, occupation or education was not significantly different. Bed net usage in comparison to no usage was not a significant predictor of asymptomatic malaria (5.5% vs. 7.6, p-value = 0.519). Those with asymptomatic malaria who had previous malaria sickness (4.2%) was not significantly different to those who had never been sick (7.3%), (OR = 0.56, p-value = 0.248). People who lived near water body (8.5%) were equally likely to be asymptomatic to those who didn’t live near water body (4.9%), (OR = 1.82, p-value = 0.215), out of which, those who lived near open water body had no difference in acquiring asymptomatic malaria to those who lived near closed water body (OR = 2.26, p-value = 0.457). Conclusion This study indicated the hidden impact of asymptomatic malaria in perpetuating malaria transmission in the village. Further assessment of the impact of asymptomatic malaria, on malaria transmission, is needed based on a larger and more sensitive method.

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Novel Applications of Nanotechnology in Controlling HIV and HSV Infections

Current Drug Research Reviews ◽

10.2174/2589977512999201124121931 ◽

2020 ◽

Vol 12 ◽

Author(s):

Sai Akilesh M ◽

Ashish Wadhwani

Keyword(s):

Drug Delivery ◽

Viral Infections ◽

Polymeric Nanoparticles ◽

Volume Ratio ◽

Fold Increase ◽

Multi Drug Resistance ◽

Health Crisis ◽

Pharmaceutical Properties ◽

Simplex Virus ◽

The Impact

: Infectious diseases have been prevalent since many decades and viral pathogens have caused global health crisis and economic meltdown on a devastating scale. High occurrence of newer viral infections in the recent years, in spite of the progress achieved in the field of pharmaceutical sciences defines the critical need for newer and more effective antiviral therapies and diagnostics. The incidence of multi-drug resistance and adverse effects due to the prolonged use of anti-viral therapy is also a major concern. Nanotechnology offers a cutting edge platform for the development of novel compounds and formulations for biomedical applications. The unique properties of nano-based materials can be attributed to the multi-fold increase in the surface to volume ratio at the nano-scale, tunable surface properties of charge and chemical moieties. Idealistic pharmaceutical properties such as increased bioavailability and retention times, lower toxicity profiles, sustained release formulations, lower dosage forms and most importantly, targeted drug delivery can be achieved through the approach of nanotechnology. The extensively researched nano-based materials are metal and polymeric nanoparticles, dendrimers and micelles, nano-drug delivery vesicles, liposomes and lipid based nanoparticles. In this review article, the impact of nanotechnology on the treatment of Human Immunodeficiency Virus (HIV) and Herpes Simplex Virus (HSV) viral infections during the last decade are outlined.

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