Towards the elimination of malaria in South Africa: a review of surveillance data in Mutale Municipality, Limpopo Province, 2005 to 2010

Design of a novel intelligent computing framework for predictive solutions of malaria propagation model

The paper presents an innovative computational framework for predictive solutions for simulating the spread of malaria. The structure incorporates sophisticated computing methods to improve the reliability of predicting malaria outbreaks. The study strives to provide a strong and effective tool for forecasting the propagation of malaria via the use of an AI-based recurrent neural network (RNN). The model is classified into two groups, consisting of humans and mosquitoes. To develop the model, the traditional Ross-Macdonald model is expanded upon, allowing for a more comprehensive analysis of the intricate dynamics at play. To gain a deeper understanding of the extended Ross model, we employ RNN, treating it as an initial value problem involving a system of first-order ordinary differential equations, each representing one of the seven profiles. This method enables us to obtain valuable insights and elucidate the complexities inherent in the propagation of malaria. Mosquitoes and humans constitute the two cohorts encompassed within the exposition of the mathematical dynamical model. Human dynamics are comprised of individuals who are susceptible, exposed, infectious, and in recovery. The mosquito population, on the other hand, is divided into three categories: susceptible, exposed, and infected. For RNN, we used the input of 0 to 300 days with an interval length of 3 days. The evaluation of the precision and accuracy of the methodology is conducted by superimposing the estimated solution onto the numerical solution. In addition, the outcomes obtained from the RNN are examined, including regression analysis, assessment of error autocorrelation, examination of time series response plots, mean square error, error histogram, and absolute error. A reduced mean square error signifies that the model's estimates are more accurate. The result is consistent with acquiring an approximate absolute error close to zero, revealing the efficacy of the suggested strategy. This research presents a novel approach to solving the malaria propagation model using recurrent neural networks. Additionally, it examines the behavior of various profiles under varying initial conditions of the malaria propagation model, which consists of a system of ordinary differential equations.

Towards malaria elimination: analysis of travel history and case forecasting using the SARIMA model in Limpopo Province

Despite various efforts and policy implementation aimed at controlling and eliminating malaria, imported malaria remains a major factor posing challenges in places that have made progress in malaria elimination. The persistence of malaria in Limpopo Province has largely been attributed to imported cases, thus reducing the pace of achieving the malaria-free target by 2025. Data from the Limpopo Malaria Surveillance Database System (2010-2020) was analyzed, and a seasonal auto-regressive integrated moving average (SARIMA) model was developed to forecast malaria incidence based on the incidence data's temporal autocorrelation. The study found that out of 57,288 people that were tested, 51,819 (90.5%) cases were local while 5469 (9.5%) cases were imported. Mozambique (44.9%), Zimbabwe (35.7%), and Ethiopia (8.5%) were the highest contributors of imported cases. The month of January recorded the highest incidence of cases while the least was in August. Analysis of the yearly figures showed an increasing trend and seasonal variation of recorded malaria cases. The SARIMA (3,1,1) X (3,1,0) [12] model used in predicting expected malaria case incidences for three consecutive years showed a decline in malaria incidences. The study demonstrated that imported malaria accounted for 9.5% of all cases. There is a need to re-focus on health education campaigns on malaria prevention methods and strengthening of indoor residual spray programs. Bodies collaborating toward malaria elimination in the Southern Africa region need to ensure a practical delivery of the objectives.

Household living conditions and individual behaviours associated with malaria risk: a community-based survey in the Limpopo River Valley, 2020, South Africa

BACKGROUND

Over the past decade, implementation of multiple malaria control strategies in most countries has largely contributed to advance the global malaria elimination agenda. Nevertheless, in some regions, seasonal epidemics may adversely affect the health of local populations. In South Africa, Plasmodium falciparum malaria is still present, with the Vhembe District experiencing an incidence rate of 3.79 cases/1000 person-years in 2018, particularly in the Limpopo River Valley, bordering Zimbabwe. To elucidate the complexity of the mechanisms involved in local regular malaria outbreaks, a community-based survey was implemented in 2020 that focused on the relationship between housing conditions and malaria risky behaviours.

METHODS

The community-based cross-sectional survey was conducted among the population of three study sites in the Vhembe District, which were selected based on malaria incidence rate, social and health characteristics of inhabitants. The household survey used a random sampling strategy, where data were collected through face-to-face questionnaires and field notes; to described the housing conditions (housing questionnaire), and focus on individual behaviours of household members. Statistical analyses were performed combining hierarchical classifications and logistic regressions.

RESULTS

In this study, 398 households were described, covering a population of 1681 inhabitants of all ages, and 439 adults who participated in community-based survey. The analysis of situations at risk of malaria showed that the influence of contextual factors, particularly those defined by the type of habitat, was significant. Housing conditions and poor living environments were factors of malaria exposure and history, regardless of site of investigation, individual preventive behaviours and personal characteristics of inhabitants. Multivariate models showed that, considering all personal characteristics or behaviours of inhabitants, housing conditions such as overcrowding pressures were significantly associated with individual malaria risk.

CONCLUSIONS

The results showed the overwhelming weight of social and contextual factors on risk situations. Considering the Fundamental Causes Theory, malaria control policies based on health behaviour prevention, should reinforce access to care or promoting health education actions. Overarching economic development interventions in targeted geographical areas and populations have to be implemented, so that malaria control and elimination strategies can be efficiently and effectively managed.

Measures of malaria transmission, infection, and disease in an area bordering two districts with and without sustained indoor residual spraying of insecticide in Uganda

Tororo District, in Eastern Uganda, experienced a dramatic decline in malaria burden starting in 2014 following the implementation of indoor residual spraying of insecticide (IRS) in the setting of repeated long-lasting insecticide treated nets (LLINs) distribution campaigns. However, in 2020 malaria began to resurge in Tororo following a change in the active ingredient used for IRS. In this study, epidemiological measures of malaria were compared shortly after the resurgence between two parishes in Tororo District (Kayoro and Osukuru) and one contiguous parish in Busia District (Buteba), where IRS has never been implemented. A cohort of 483 residents from 80 randomly selected households were followed from August 2020 to January 2021. Mosquitoes were collected every 2 weeks using CDC light traps in rooms where participants slept; parasitemia and gametoctyemia measured every 4 weeks by microscopy and PCR; and symptomatic malaria measured by passive surveillance. The annual entomological inoculation rate was significantly higher in Buteba (108.2 infective bites/person/year), compared to Osukuru (59.0, p = 0.001) and Kayoro (27.4, p<0.001). Overall, parasite prevalence was 19.5% by microscopy and 50.7% by PCR, with no significant differences between the three parishes. Among infected individuals, gametocyte prevalence by PCR was 45.5% and similar between sites. The incidence of malaria was significantly higher in Osukuru (2.46 episodes PPY) compared to Buteba (1.47, p = 0.005) and Kayoro (1.09, p<0.001). For participants over 15 years of age, the risk of symptomatic malaria if microscopic parasitemia was present was higher in Osukuru (relative risk [RR] = 2.99, p = 0.03) compared to Buteba. These findings highlight the complex relationships between measures of malaria transmission, infection, and disease, and the potential for excess disease burden, possibly due to waning immunity, in areas where vector control interventions begin to fail after a sustained period of highly effective control.

Cross-border malaria in Northern Brazil

BACKGROUND

Cross-border malaria is a major barrier to elimination efforts. Along the Venezuela-Brazil-Guyana border, intense human mobility fueled primarily by a humanitarian crisis and illegal gold mining activities has increased the occurrence of cross-border cases in Brazil. Roraima, a Brazilian state situated between Venezuela and Guyana, bears the greatest burden. This study analyses the current cross-border malaria epidemiology in Northern Brazil between the years 2007 and 2018.

METHODS

De-identified data on reported malaria cases in Brazil were obtained from the Malaria Epidemiological Surveillance Information System for the years 2007 to 2018. Pearson's Chi-Square test of differences was utilized to assess differences between characteristics of cross-border cases originating from Venezuela and Guyana, and between border and transnational cases. A logistic regression model was used to predict imported status of cases.

RESULTS

Cross-border cases from Venezuela and Guyana made up the majority of border and transnational cases since 2012, and Roraima remained the largest receiving state for cross-border cases over this period. There were significant differences in the profiles of border and transnational cases originating from Venezuela and Guyana, including type of movement and nationality of patients. Logistic regression results demonstrated Venezuelan and Guyanese nationals, Brazilian miners, males, and individuals of working age had heightened odds of being an imported case. Furthermore, Venezuelan citizens had heightened odds of seeking care in municipalities adjacent Venezuela, rather than transnational municipalities.

CONCLUSIONS

Cross-border malaria contributes to the malaria burden at the Venezuela-Guyana-Brazil border. The identification of distinct profiles of case importation provides evidence on the need to strengthen surveillance at border areas, and to deploy tailored strategies that recognize different mobility routes, such as the movement of refuge-seeking individuals and of Brazilians working in mining.

Parasite genetic diversity reflects continued residual malaria transmission in Vhembe District, a hotspot in the Limpopo Province of South Africa

BACKGROUND

South Africa aims to eliminate malaria transmission by 2023. However, despite sustained vector control efforts and case management interventions, the Vhembe District remains a malaria transmission hotspot. To better understand Plasmodium falciparum transmission dynamics in the area, this study characterized the genetic diversity of parasites circulating within the Vhembe District.

METHODS

A total of 1153 falciparum-positive rapid diagnostic tests (RDTs) were randomly collected from seven clinics within the district, over three consecutive years (2016, 2017 and 2018) during the wet and dry malaria transmission seasons. Using 26 neutral microsatellite markers, differences in genetic diversity were described using a multiparameter scale of multiplicity of infection (MOI), inbreeding metric (Fws), number of unique alleles (A), expected heterozygosity (He), multilocus linkage disequilibrium (LD) and genetic differentiation, and were associated with temporal and geospatial variances.

RESULTS

A total of 747 (65%) samples were successfully genotyped. Moderate to high genetic diversity (mean He = 0.74 ± 0.03) was observed in the parasite population. This was ascribed to high allelic richness (mean A = 12.2 ± 1.2). The majority of samples (99%) had unique multi-locus genotypes, indicating high genetic diversity in the sample set. Complex infections were observed in 66% of samples (mean MOI = 2.13 ± 0.04), with 33% of infections showing high within-host diversity as described by the Fws metric. Low, but significant LD (standardised index of association, ISA = 0.08, P < 0.001) was observed that indicates recombination of distinct clones. Limited impact of temporal (F_ST range - 0.00005 to 0.0003) and spatial (F_ST = - 0.028 to 0.023) variation on genetic diversity existed during the sampling timeframe and study sites respectively.

CONCLUSIONS

Consistent with the Vhembe District's classification as a 'high' transmission setting within South Africa, P. falciparum diversity in the area was moderate to high and complex. This study showed that genetic diversity within the parasite population reflects the continued residual transmission observed in the Vhembe District. This data can be used as a reference point for the assessment of the effectiveness of on-going interventions over time, the identification of imported cases and/or outbreaks, as well as monitoring for the potential spread of anti-malarial drug resistance.

Effective surveillance systems for vector-borne diseases in urban settings and translation of the data into action: a scoping review

Background

Vector-borne diseases (VBDs) continue to represent a global threat, with “old” diseases like malaria, and “emergent” or “re-emergent” ones like Zika, because of an increase in international trade, demographic growth, and rapid urbanization. In this era of globalization, surveillance is a key element in controlling VBDs in urban settings, but surveillance alone cannot solve the problem. A review of experiences is of interest to examine other solution elements. The objectives were to assess the different means of VBD surveillance in urban environments, to evaluate their potential for supporting public health actions, and to describe the tools used for public health actions, the constraints they face, and the research and health action gaps to be filled.

Main body

For this scoping review we searched peer-reviewed articles and grey literature published between 2000 and 2016. Various tools were used for data coding and extraction. A quality assessment was done for each study reviewed, and descriptive characteristics and data on implementation process and transferability were analyzed in all studies.

After screening 414 full-text articles, we retained a total of 79 articles for review. The main targets of the articles were arboviral diseases (65.8%) and malaria (16.5%). The positive aspects of many studies fit within the framework of integrated vector management. Public awareness is considered a key to successful vector control programs. Advocacy and legislation can reinforce both empowerment and capacity building. These can be achieved by collaboration within the health sector and with other sectors. Research is needed to develop well designed studies and new tools for surveillance and control.

Conclusions

The need for surveillance systems in urban settings in both developing and developed countries was highlighted. Countries face the same challenges relating to human, financial, and structural resources. These findings also constitute a wake-up call for governments, academia, funders, and World Health Organization to strengthen control programs and enhance VBD research in urban environments.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0473-9) contains supplementary material, which is available to authorized users.

Understanding human genetic factors influencing primaquine safety and efficacy to guide primaquine roll-out in a pre-elimination setting in southern Africa

Background

Primaquine (PQ) is recommended as an addition to standard malaria treatments in pre-elimination settings due to its pronounced activity against mature Plasmodium falciparum gametocytes, the parasite stage responsible for onward transmission to mosquitoes. However, PQ may trigger haemolysis in glucose-6-phosphate dehydrogenase (G6PD)-deficient individuals. Additional human genetic factors, including polymorphisms in the human cytochrome P450 2D6 (CYP2D6) complex, may negatively influence the efficacy of PQ. This study assessed the prevalence of G6PD deficiency and two important CYP2D6 variants in representative pre-elimination settings in South Africa, to inform malaria elimination strategies.

Methods

Volunteers (n = 248) attending six primary health care facilities in a malaria-endemic region of South Africa were enrolled between October and November 2015. G6PD status was determined phenotypically, using a CareStart™ G6PD rapid diagnostic test (RDT), and genotypically for two common African G6PD variants, namely A+ (A376G) and A− (G202A, A542T, G680T & T968C) by PCR, restriction fragment length polymorphisms (RFLP) and DNA sequencing. CYP2D6*4 and CYP2D6*17 variants were determined with PCR and RFLP.

Results

A prevalence of 13% (33/248) G6PD deficiency was observed in the cohort by G6PD RDT whilst by genotypic assessment, 32% (79/248) were A+ and 3.2% were A−, respectively. Among the male participants, 11% (6/55) were G6PD A− hemizygous; among females 1% (2/193) were G6PD A− homozygous and 16% (32/193) G6PD A− heterozygous. The strength of agreement between phenotyping and genotyping result was fair (Cohens Kappa κ = 0.310). The negative predictive value for the G6PD RDT for detecting hemizygous, homozygous and heterozygous individuals was 0.88 (95% CI 0.85–0.91), compared to the more sensitive genotyping. The CYP2D6*4 allele frequencies for CYP2D6*4 (inferred poor metabolizer phenotype) and CYP2D6*17 (inferred intermediate metabolizer phenotype) were 3.2 and 19.5%, respectively.

Conclusions

Phenotypic and genotypic analyses both detected low prevalence of G6PD deficiency and the CYP2D6*4 variants. These findings, combined with increasing data confirming safety of single low-dose PQ in individuals with African variants of G6PD deficiency, supports the deployment of single low-dose PQ as a gametocytocidal drug. PQ would pose minimal risks to the study populations and could be a useful elimination strategy in the study area.

Evaluating Efficacy of Landsat-Derived Environmental Covariates for Predicting Malaria Distribution in Rural Villages of Vhembe District, South Africa

Malaria in South Africa is still a problem despite existing efforts to eradicate the disease. In the Vhembe District Municipality, malaria prevalence is still high, with a mean incidence rate of 328.2 per 100,0000 persons/year. This study aimed at evaluating environmental covariates, such as vegetation moisture and vegetation greenness, associated with malaria vector distribution for better predictability towards rapid and efficient disease management and control. The 2005 malaria incidence data combined with Landsat 5 ETM were used in this study. A total of nine remotely sensed covariates were derived, while pseudo-absences in the ratio of 1:2 (presence/absence) were generated at buffer distances of 0.5-20 km from known presence locations. A stepwise logistic regression model was applied to analyse the spatial distribution of malaria in the area. A buffer distance of 10 km yielded the highest classification accuracy of 82% at a threshold of 0.9. This model was significant (ρ < 0.05) and yielded a deviance (D²) of 36%. The significantly positive relationship (ρ < 0.05) between the soil-adjusted vegetation index and malaria distribution at all buffer distances suggests that malaria vector (Anopheles arabiensis) prefer productive and greener vegetation. The significant negative relationship between water/moisture index (a₁ index) and malaria distribution in buffer distances of 0.5, 10, and 20 km suggest that malaria distribution increases with a decrease in shortwave reflectance signal. The study has shown that suitable habitats of malaria vectors are generally found within a radius of 10 km in semi-arid environments, and this insight can be useful to aid efforts aimed at putting in place evidence-based preventative measures against malaria infections. Furthermore, this result is important in understanding malaria dynamics under the current climate and environmental changes. The study has also demonstrated the use of Landsat data and the ability to extract environmental conditions which favour the distribution of malaria vector (An. arabiensis) such as the canopy moisture content in vegetation, which serves as a surrogate for rainfall.

Association of maternal KIR gene content polymorphisms with reduction in perinatal transmission of HIV-1

The role of killer cell immunoglobulin-like receptors (KIRs) in the transmission of HIV-1 has not been extensively studied. Here, we investigated the association of KIR gene content polymorphisms with perinatal HIV-1 transmission. The KIR gene family comprising 16 genes was genotyped in 313 HIV-1 positive Kenyan mothers paired with their infants. Gene content polymorphisms were presented as presence of individual KIR genes, haplotypes, genotypes and KIR gene concordance. The genetic data were analyzed for associations with perinatal transmission of HIV. There was no association of infant KIR genes with perinatal HIV-1 transmission. After adjustment for gravidity, viral load, and CD4 cell count, there was evidence of an association between reduction in perinatal HIV-1 transmission and the maternal individual KIR genes KIR2DL2 (adjusted OR = 0.50; 95% CI: 0.24–1.02, P = 0.06), KIR2DL5 (adjusted OR = 0.47; 95% CI: 0.23–0.95, P = 0.04) and KIR2DS5 (adjusted OR = 0.39; 95% CI: 0.18–0.80, P = 0.01). Furthermore, these maternal KIR genes were only significantly associated with reduction in perinatal HIV transmission in women with CD4 cell count ≥ 350 cells/ μl and viral load <10000 copies/ml. Concordance analysis showed that when both mother and child had KIR2DS2, there was less likelihood of perinatal HIV-1 transmission (adjusted OR = 0.44; 95% CI: 0.20–0.96, P = 0.039). In conclusion, the maternal KIR genes KIR2DL2, KIR2DL5, KIR2DS5, and KIR2DS2 were associated with reduction of HIV-1 transmission from mother to child. Furthermore, maternal immune status is an important factor in the association of KIR with perinatal HIV transmission.

Interactive Malaria Education Intervention and Its Effect on Community Participant Knowledge: The Malaria Awareness Program in Vhembe District, Limpopo, South Africa

Malaria is preventable and treatable, yet remains the most prevalent parasitic endemic disease in Africa. This article analyzes prospective observational data from the Malaria Awareness Program (MAP), an interactive malaria education initiative led by home-based care workers to improve participant knowledge of malaria as a precursor to increased uptake of malaria control interventions in the Vhembe District, Limpopo, South Africa. Between 2012 and 2016, 1,330 individuals participated in MAP. MAP's effectiveness was measured through pre- and post-participation surveys assessing knowledge in malaria transmission, symptoms, prevention, and treatment. The primary analysis assessed differences in knowledge between individuals who completed MAP ( n = 499) and individuals who did not complete MAP ( n = 399). The adjusted odds of correct malaria knowledge score versus partially correct or incorrect score among MAP completers was 3.3 and 2.8 times greater for transmission and prevention, respectively ( p values<.001). A subanalysis assessed knowledge improvement among participants who completed both pre- and post-MAP intervention surveys ( n = 266). There was a 21.4% and 10.5% increase in the proportion of participants who cited correct malaria transmission and prevention methods, respectively. Future research should assess behavioral changes toward malaria prevention and treatment as a result of an intervention and examine incidence changes in the region.

Genetic diversity and distribution of Mycobacterium tuberculosis genotypes in Limpopo, South Africa

BACKGROUND

Tuberculosis remains a major health problem and knowledge of the diversity of Mycobacterium tuberculosis strains in specific geographical regions can contribute to the control of the disease. This study describes the genetic profile of M. tuberculosis in five districts of Limpopo Province.

METHODS

A total 487 isolates were collected from the National Health Laboratory Services from all regions/districts of Limpopo Province. Only 215 isolates were confirmed to be M. tuberculosis by Bactec Mycobacterium Growth Indicator Tube 960® and Rhodamine-Auramine staining. Isolates were subcultured on Löwenstein-Jensen medium agar slants to validate purity. They were spoligotyped and data analysed using the international spoligotyping database 4 (SpolDB4).

RESULTS

Of the 215 isolates, 134 (62.3%) were genotyped into 21 genotype families while 81 (37.7%) were orphans. The 81 orphans were further subjected to resolution employing SpolDB3/RIM. Overall, the study revealed a high diversity of strains of 32 predominantly the non-Beijing lineages: the LAM- LAM3 (9.8%), LAM9 (4.7%) and LAM11- ZWE (3.3%), the T-T1(15.0%), T2 (0.9%), T2-T3 (1.4%), the CAS-CAS1-Delhi 5 (1.9%) and CAS1-KILI (1.4%) the MANU2 (1.4%), U (0.5%), X-X1(1.4%), X3 (1.9%), S (9.8%), CAS (1.4%), LAM7(0.9%), T3(0.5%), LAM8(4.7%), T4(1.4%), X2(0.4%), AI5(1.9%), LAM1(0.5%), FAMILY33 (1.9%), EAI4(1.4%), M. microti (1.9%). The Beijing and Beijing-like families were (14.9%) and (0.9%), respectively. A total of 28(13%) clusters and 77(36%) unique cases were identified. Beijing strain (SIT 1) formed the biggest cluster constituting 14%, followed by LAM3 (SIT 33), T1 (SIT 53) and LAM4 (SIT 811) with 7%, 5.1% and 2.8%, respectively. The Beijing family was the only genotype found in all the five districts and was predominant in Mopani (18.8%), Sekhukhune (23.7%) and Vhembe (23.3%). Dominant genotypes in Capricorn and Waterberg were LAM3 (11.9%) and T1 (13.3%), respectively.

CONCLUSION

A wide diversity of lineages was demonstrated at district level. A high number of clusters per district provided evidence of on-going transmission in this Province.

Could Malaria Control Programmes be Timed to Coincide with Onset of Rainfall?

Malaria cases in South Africa's Northern Province of Limpopo have surpassed known endemic KwaZulu Natal and Mpumalanga Provinces. This paper applies statistical methods: regression analysis and impulse response function to understand the timing of impact and the length that such impacts last. Climate data (rainfall and temperature) are obtained from South African Weather Services (SAWs); global data from the European Centre for Medium-Range Weather Forecasts (ECMWF), while clinical malaria data came from Malaria Control Centre in Tzaneen (Limpopo Province). Data collected span from January 1998 to July 2007. Signs of the coefficients are positive for rainfall and temperature and negative for their exponents. Three out of five independent variables consistently maintain a very high statistical level of significance. The coefficients for climate variables describe an inverted u-shape: parameters for the exponents of rainfall (-0.02, -0.01, -0.02, -0.00) and temperature (-46.61, -47.46, -48.14, -36.04) are both negative. A one standard deviation rise in rainfall (rainfall onset) increases malaria cases, and the effects become sustained for at least 3 months and conclude that onset of rainfall therefore triggers a 'malaria season'. Malaria control programme and early warning system should be intensified in the first 3 months following the onset of rainfall.

Serology reveals heterogeneity of Plasmodium falciparum transmission in northeastern South Africa: implications for malaria elimination

Background

It is widely acknowledged that modifications to existing control interventions are required if South Africa is to achieve malaria elimination. Targeting indoor residual spraying (IRS) to areas where cases have been detected is one strategy currently under investigation in northeastern South Africa. This seroprevalence baseline study, nested within a targeted IRS trial, was undertaken to provide insights into malaria transmission dynamics in South Africa and evaluate whether sero-epidemiological practices have the potential to be routinely incorporated into elimination programmes.

Methods

Filter-paper blood spots, demographic and household survey data were collected from 2710 randomly selected households in 56 study wards located in the municipalities of Ba-Phalaborwa and Bushbuckridge. Blood spots were assayed for Plasmodium falciparum apical membrane antigen-1 and merozoite surface protein-1₁₉ blood-stage antigens using an enzyme linked immunosorbent assay. Seroprevalence data were analysed using a reverse catalytic model to determine malaria seroconversion rates (SCR). Geospatial cluster analysis was used to investigate transmission heterogeneity while random effects logistic regression identified risk factors associated with malaria exposure.

Results

The overall SCR across the entire study site was 0.012 (95% CI 0.008–0.017) per year. Contrasting SCRs, corresponding to distinct geographical regions across the study site, ranging from <0.001 (95% CI <0.001–0.005) to 0.022 (95% CI 0.008–0.062) per annum revealed prominent transmission heterogeneity. Geospatial cluster analysis of household seroprevalence and age-adjusted antibody responses detected statistically significant (p < 0.05) spatial clusters of P. falciparum exposure. Formal secondary education was associated with lower malaria exposure in the sampled population (AOR 0.72, 95% CI 0.56–0.95, p = 0.018).

Conclusions

Although overall transmission intensity and exposure to malaria was low across both study sites, malaria transmission intensity was highly heterogeneous and associated with low socio-economic status in the region. Findings suggest focal targeting of interventions has the potential to be an appropriate strategy to deploy in South Africa. Furthermore, routinely incorporating sero-epidemiological practices into elimination programmes may prove useful in monitoring malaria transmission intensity in South Africa, and other countries striving for malaria elimination.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-017-1701-7) contains supplementary material, which is available to authorized users.

China's 1-3-7 surveillance and response strategy for malaria elimination: Is case reporting, investigation and foci response happening according to plan?

Background

The China’s 1-3-7 strategy was initiated and extensively adopted in different types of counties (geographic regions) for reporting of malaria cases within 1 day, their confirmation and investigation within 3 days, and the appropriate public health response to prevent further transmission within 7 days. Assessing the level of compliance to the 1-3-7 strategy at the county level is a first step towards determining whether the surveillance and response strategy is happening according to plan. This study assessed if the time-bound targets of the 1-3-7 strategy were being sustained over time. Such information would be useful to improve implementation of the 1-3-7 strategy in China.

Methods

This cross-sectional study involved country-wide programmatic data for the period January 1st 2013 to June 30th 2014. Data variables were extracted from the national malaria information system and included socio-demographic information, type of county, date of diagnosis, date of reporting, date of case investigation, case classification (indigenous, or imported, or unknown), focus investigation, date of reactive case detection (RACD), and date of indoor residual spraying (IRS). Summary statistics and proportions were used and comparisons between groups were assessed using the chi-square test. Level of significance was set at a P-value ≤ 0.05.

Results

Of a total of 5,688 malaria cases from 731 counties, there were 55 (1 %) indigenous cases (only in Type 1 and Type 2 counties) and 5,633 (99 %) imported cases from all types of counties. There was no delay in reporting malaria cases by type of county. In terms of case investigation, 97.5 % cases were investigated within 3 days with the proportion of delays (1.5 %) in type 2 counties, being significantly lower than type 1 counties (4.1 %). Regarding active foci, 96.4 % were treated by RACD and/or IRS.

Conclusions

The performance of 1-3-7 strategy was encouraging but identified some challenges that if addressed can further improve implementation.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-015-0089-2) contains supplementary material, which is available to authorized users.

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

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 reaction-positive participants, 46.4% (95% confidence interval [95% CI] = 42.6-50.2%) of participants had infections that were RDT-negative and asymptomatic, and 55.9% of those infections consisted of multiple parasite clones as assessed by merozoite surface protein-2 genotyping. Subpatent infections were more common in individuals reporting the use of non-artemisinin-based antimalarials in the 2 weeks preceding the survey (odds ratio = 2.49, 95% CI = 1.04-5.92) compared with individuals not reporting previous use of antimalarials. We observed a large and genetically complex pool of subpatent parasitemia in the Kenya highlands that must be considered in malaria interventions.

Communicating and monitoring surveillance and response activities for malaria elimination: China's "1-3-7" strategy

Qi Gao and colleagues describe China's 1-3-7 strategy for eliminating malaria: reporting of malaria cases within one day, their confirmation and investigation within three days, and the appropriate public health response to prevent further transmission within seven days.

Dynamics of malaria transmission and susceptibility to clinical malaria episodes following treatment of Plasmodium falciparum asymptomatic carriers: results of a cluster-randomized study of community-wide screening and treatment, and a parallel entomology study

Background

In malaria-endemic countries, large proportions of individuals infected with Plasmodium falciparum are asymptomatic and constitute a reservoir of parasites for infection of newly hatched mosquitoes.

Methods

Two studies were run in parallel in Burkina Faso to evaluate the impact of systematic identification and treatment of asymptomatic carriers of P. falciparum, detected by rapid diagnostic test, on disease transmission and susceptibility to clinical malaria episodes. A clinical study assessed the incidence of symptomatic malaria episodes with a parasite density >5,000/μL after three screening and treatment campaigns ~1 month apart before the rainy season; and an entomological study determined the effect of these campaigns on malaria transmission as measured by entomological inoculation rate.

Results

The intervention arm had lower prevalence of asymptomatic carriers of asexual parasites and lower prevalence of gametocyte carriers during campaigns 2 and 3 as compared to the control arm. During the entire follow-up period, out of 13,767 at-risk subjects, 2,516 subjects (intervention arm 1,332; control arm 1,184) had symptomatic malaria. Kaplan-Meier analysis of the incidence of first symptomatic malaria episode with a parasite density >5,000/μL showed that, in the total population, the two treatment arms were similar until Week 11–12 after campaign 3, corresponding with the beginning of the malaria transmission season, after which the probability of being free of symptomatic malaria was lower in the intervention arm (logrank p < 0.0001). Similar trends were observed in infants and children <5 years and in individuals ≥5 years of age. In infants and children <5 years old who experienced symptomatic malaria episodes, the geometric mean P. falciparum density was lower in the intervention arm than the control arm. This trend was not seen in those individuals aged ≥5 years. Over the year, monthly variation in mosquito density and entomological inoculation rate was comparable in both arms, with September peaks in both indices.

Conclusion

Community screening and targeted treatment of asymptomatic carriers of P. falciparum had no effect on the dynamics of malaria transmission, but seemed to be associated with an increase in the treated community’s susceptibility to symptomatic malaria episodes after the screening campaigns had finished. These results highlight the importance of further exploratory studies to better understand the dynamics of disease transmission in the context of malaria elimination.