Prevalence of afebrile parasitaemia due to Plasmodium falciparum & P. vivax in district Balaghat (Madhya Pradesh): Implication for malaria control

Asymptomatic Malaria Reservoirs in Honduras: A Challenge for Elimination

BACKGROUND

Efforts on a global scale for combating malaria have achieved substantial progress over the past twenty years. Two Central American nations have accomplished their goal of eliminating malaria: El Salvador and Belize. Honduras has decreased the incidence of malaria and now reports fewer than 4000 malaria cases annually, aspiring to reach elimination by 2030. To accomplish this goal, it is essential to assess the existing strategies employed for malaria control and to address the task of incorporating novel intervention strategies to identify asymptomatic reservoirs.

METHODS

A survey for detecting asymptomatic cases was carried out in the community of Kaukira, in Gracias a Dios, Honduras, focusing on malaria transmission during 2023. Asymptomatic community members were recruited as participants, malaria screening was performed through a rapid diagnostic test in situ, and a blood sample was collected on filter paper. Highly sensitive molecular assays based on photo-induced electron transfer PCR (PET-PCR) were performed to detect the two species of Plasmodium circulating in Honduras: Plasmodium vivax and Plasmodium falciparum. In addition, the identification of the parasite species was verified by amplifying three genetic markers (Pvmsp3α, Pvmsp3ß, and Pfmsp1).

RESULTS

A total of 138 participants were recruited, mostly adult women. All individuals tested negative on the rapid diagnostic test. Positive results for malaria were detected by PET-PCR in 17 samples (12.3%). Most samples (12 out of 17) were amplified with a Ct value between 37 and 42, indicating very low parasitemias. Out of the 17 samples, 16 of them also showed amplification in the species assays. There were nine cases of P. falciparum infections and seven cases of P. vivax infections that were further confirmed by nested PCR (nPCR) of Pvmsp3 and Pfmsp1. Parasitemias ranged from 100 p/μL to less than 0.25 p/μL. One sample showed mixed infection.

CONCLUSIONS

The existence of asymptomatic malaria reservoirs in Honduras can contribute to disease transmission and pose a challenge that may hinder elimination efforts, requiring public health authorities to modify surveillance strategies to identify the disease and treat this population accordingly.

Mass Testing and Treatment to Accelerate Malaria Elimination: A Systematic Review and Meta-Analysis

In regions where malaria transmission persists, the implementation of approaches aimed at eliminating parasites from the population can effectively decrease both burden of disease and transmission of infection. Thus, mass strategies that target symptomatic and asymptomatic infections at the same time may help countries to reduce transmission. This systematic review assessed the potential benefits and harms of mass testing and treatment (MTaT) to reduce malaria transmission. Searches were conducted in March 2021 and updated in April 2022 and included cluster-randomized controlled trials (cRCTs) as well as nonrandomized studies (NRSs) using malaria infection incidence, clinical malaria incidence, or prevalence as outcomes. The risk of bias was assessed with Cochrane's risk of bias (RoB2) tool and Risk of Bias Tool in Nonrandomized Studies - of Interventions (ROBINS-I), and the certainty of evidence (CoE) was graded for each outcome. Of 4,462 citations identified, seven studies (four cRCTs and three NRSs) contributed outcome data. The analysis revealed that MTaT did not reduce the incidence (risk ratio [RR]: 0.95, 95% CI: 0.87-1.04; 1,181 participants; moderate CoE) or prevalence (RR: 0.83, 95% CI: 0.67-1.01; 7,522 participants; moderate CoE) of malaria infection but resulted in a small reduction in clinical malaria (RR: 0.82; 95% CI: 0.70-0.95; 334,944 participants; moderate CoE). Three studies contributing data on contextual factors concluded that MTaT is an acceptable, feasible, and cost-effective intervention. Mathematical modeling analyses (n = 10) suggested that MTaT effectiveness depends on the baseline transmission level, diagnostic test performance, number of rounds, and other co-interventions. Based on the limited evidence available, MTaT has little to no impact on reducing malaria transmission.

Burden of malaria during pregnancy in perennial transmission settings of two densely forested and remote blocks (Baihar and Birsa) of district Balaghat, Madhya Pradesh, central India

Background Malaria in pregnancy (MIP) is a major public health problem due to the vulnerability of pregnant women to infections, resulting in adverse maternal/foetal outcomes in endemic areas. Methods We did a field-based study to assess the burden of MIP (prevalence at the time of enrolment and follow-up) and to identify risk factors for MIP in the Birsa and Baihar blocks of district Balaghat in Madhya Pradesh, which have perennial malaria transmission. Malaria screening (during 2015-2017) was done by microscopy and bivalent rapid diagnostic test (SD Bioline RDT, malaria antigen Plasmodium falciparum/Plasmodium vivax Pf/Pv). Dried blood spots were used for haemoglobin estimation. Sociodemographic details with past and present pregnancy status were obtained. A subset of pregnant women were followed up for malaria during pregnancy. Women were also screened for malaria post delivery. Malaria treatment was given as per the National Guidelines of 2013. Multivariate analysis was done to assess independent risk factors for malaria. Results A total of 1728 pregnant women were screened, of which 1651 were included in the final analysis. Malaria prevalence at first screening was 23.4% (Pf 88%). Prevalence and Pf parasitaemia both were significantly higher among primigravid (G1) compared to multigravid (G>2; p value 0.012 and 0.019, respectively). Pregnant women of the Baiga ethnic group were more likely to have malaria compared to those belonging to the Gond group (OR [95% CI]; 2.4 [1.7-3.4]; p<0.00001) and non-indigenous group (OR [95% CI]; 8.3 [3.9-19.7]; p<0.00001). Primigravid status of women, first and second trimester of pregnancy, women belonging to indigenous ethnic tribal group and cash crop insufficiency for whole year (a socioeconomic indicator) in the family were the independent risk factors for malaria. Conclusion MIP is a major public health problem in forested tribal settlements of Birsa and Baihar blocks of Balaghat district in Madhya Pradesh and requires immediate intervention.

Mass screening and treatment (MSaT) for identifying and treating asymptomatic cases of malaria-malaria elimination demonstration project (MEDP), Mandla, Madhya Pradesh

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.

Significance of nested PCR testing for the detection of low-density malaria infection amongst febrile patients from the Malaria Elimination Demonstration Project in Mandla, Madhya Pradesh, India

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.

Heterogeneity in prevalence of subclinical Plasmodium falciparum and Plasmodium vivax infections but no parasite genomic clustering in the Chittagong Hill Tracts, Bangladesh

BACKGROUND

Malaria remains endemic in Bangladesh, with the majority of cases occurring in forested, mountainous region in the Chittagong Hill Tracts (CHT). This area is home to Bengali and diverse groups of indigenous people (Pahari) residing largely in mono-ethnic villages.

METHODS

1002 individuals of the 9 most prominent Pahari and the Bengali population were randomly selected and screened by RDT and qPCR. Parasites were genotyped by msp2 and deep sequencing of 5 amplicons (ama1-D3, cpmp, cpp, csp, and msp7) for Plasmodium falciparum (n = 20), and by microsatellite (MS) typing of ten loci and amplicon sequencing of msp1 for Plasmodium vivax (n = 21). Population structure was analysed using STRUCTURE software. Identity-by-state (IBS) was calculated as a measure of parasite relatedness and used to generate relatedness networks.

RESULTS

The prevalence of P. falciparum and P. vivax infection was 0.7% by RDT (P. falciparum 6/1002; P. vivax 0/1002, mixed: 1/1002) and 4% by qPCR (P. falciparum 21/1002; P. vivax 16/1002, mixed: 5/1002). Infections were highly clustered, with 64% (27/42) of infections occurring in only two Pahari groups, the Khumi and Mro. Diversity was high; expected heterozygosity was 0.93 for P. falciparum and 0.81 for P. vivax. 85.7% (18/21) of P. vivax and 25% (5/20) of P. falciparum infections were polyclonal. No population structure was evident for either species, suggesting high transmission and gene flow among Pahari groups.

CONCLUSIONS

High subclinical infection prevalence and genetic diversity mirror ongoing transmission. Control activities should be specifically directed to Pahari groups at greatest risk.

The prevalence of tuberculosis and malaria in minority indigenous populations of South- East Asia and the Western Pacific Region: a systematic review and meta-analysis

Infectious diseases have been shown to disproportionately affect indigenous populations. Tuberculosis (TB) and malaria continue to impose a significant burden on humanity and are among the infectious diseases targeted within the 2030 Agenda for Sustainable Development. A systematic review and meta-analyses were undertaken to evaluate the prevalence of TB and malaria infections within minority indigenous populations of the South-East Asia and Western Pacific Regions. The review was undertaken in accordance with The Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines following a published protocol. A random effects meta-analysis was used to calculate the pooled prevalence of TB and malaria. A meta-regression analysis was applied to quantify associations with study covariates and a sub-group analysis undertaken where studies provided comparative data between minority indigenous and other population groups. From the 3,275 unique publications identified, 24 on TB, and 39 on malaria were included in the final analysis. The pooled prevalence of TB was 2.3% (95% CI: 1.7, 2.9) and the pooled prevalence of malaria was 19.9% (95% CI: 15.9, 24.2). There was significant (p = 0.000) heterogeneity (I2) between studies. Significant difference was not observed in TB and malaria prevalence between minority indigenous and other population groups, although the odds ratio of malaria infection in minority indigenous populations was 1.15 (95% CI 0.99, 1.34: p-value 0.06) compared to other population groups. The review identified a paucity of data on TB and malaria in minority indigenous populations despite the significant prevalence and burden of these diseases within these regions.

Dry Post Wintertime Mass Surveillance Unearths a Huge Burden of P. vivax, and Mixed Infection with P. vivax P. falciparum, a Threat to Malaria Elimination, in Dhalai, Tripura, India

With India aiming to achieve malaria elimination by 2030, several strategies have been put in place. With that aim, mass surveillance is now being conducted in some malaria-endemic pockets. As dry season mass surveillance has been shown to have its importance in targeting the reservoir, a study was undertaken to assess the parasite load by a sensitive molecular method during one of the mass surveys conducted in the dry winter period. It was executed in two malaria-endemic villages of Dhalai District, Tripura, in northeast India, also reported as P. falciparum predominated area. The present study found an enormous burden of Rapid Diagnostic Test negative malaria cases with P. vivax along with P. vivax and P. falciparum mixed infections during the mass surveillance from febrile and afebrile cases in dry winter months (February 2021–March 2021). Of the total 150 samples tested, 72 (48%) were positive and 78 (52%) negative for malaria by PCR. Out of the 72 positives, 6 (8.33%) were P. falciparum, 40 (55.55%) P. vivax, and 26 (36.11%) mixed infections. Out of 78 malaria negative samples, 6 (7.7%) were with symptoms, while among the total malaria positive, 72 cases 7 (9.8%) were with symptoms, and 65 (90.2%) were asymptomatic. Out of 114 samples tested by both microscopy and PCR, 42 samples turned out to be submicroscopic with 4 P. falciparum, 23 P. vivax, and 15 mixed infections. Although all P. vivax submicroscopic infections were asymptomatic, three P. falciparum cases were found to be febrile. Evidence of malaria transmission was also found in the vectors in the winter month. The study ascertained the use of molecular diagnostic techniques in detecting the actual burden of malaria, especially of P. vivax, in mass surveys. As Jhum cultivators in Tripura are at high risk, screening for the malarial reservoirs in pre-Jhum months can help with malaria control and elimination.

Demonstration of indigenous malaria elimination through Track-Test-Treat-Track (T4) strategy in a Malaria Elimination Demonstration Project in Mandla, Madhya Pradesh

BACKGROUND

Many malaria endemic countries are heading towards malaria elimination through the use of case management and vector control strategies, which employ surveillance, improving access to early diagnosis, prompt treatment., and integrated vector control measures. There is a consensus that elimination of malaria is feasible when rapid detection and prompt treatment is combined with mosquito-human contact interruption in an efficient and sustainable manner at community levels. This paper describes results of an integrated case management and vector control strategy for reducing malaria cases in 1233 villages over 3 years in district Mandla, Madhya Pradesh, India.

METHODS

The project enrolled the entire population (1,143,126) of Mandla district for fever surveillance followed by testing of febrile cases and treatment of positive subjects using T4 strategy, which is Track (by fever), Test (by RDTs), Treat (by ACT) and Track (for completion of treatment). In addition to the active and passive surveillance for detection and treatment of febrile cases, the project conducted mass screening and treatment to clear the asymptomatic reservoirs of infection. Febrile cases were also tested in the out-patient department of the District Hospital from June 2018 to September, 2018 and in a community-based medical camp from November 7 to 14, 2019. The project also used vector control measures for interrupting human-mosquito contact, and information, education and communication (IEC) campaigns to increase demand for malaria services at community level.

RESULTS

This project has revealed about 91% reduction of indigenous cases of malaria during the period from June 2017 to May 2020, through case management and vector control strategies. A total 357,143 febrile cases were screened, out of which 0.19% were found positive for the presence of malaria parasites, with Plasmodium falciparum and Plasmodium vivax ratio of 62:38. The prevalence of malaria was higher in individuals > 15 years of age (69% cases). The positivity rate was 0.33% in 2017-18, 0.13% in 2018-19, and 0.06% in 2019-20. In all of the 3 years of the project, the peak transmission correlated with rains. Mass screening revealed 0.18% positivity in Sep-Oct 2018, followed by 0.06% in June 2019, and 0.03% in December 2019, and these were mostly asymptomatic cases in the community. Imported cases into the district were mostly contributed by the distant state of Telangana (51.13%). Fever patients tested for malaria parasites in the District Hospital and medical camp revealed zero cases.

CONCLUSION

Using the current intervention and prevention tools along with optimum utilization of human resources, a 91% reduction in indigenous cases of malaria was seen in the district in 3 years. The reduction was similar in the three high prevalence blocks of the district. These results reveal that malaria elimination is achievable in India within a stipulated time frame. The reduction of malaria at the community level was further validated when zero malaria cases were diagnosed during hospital and community-based studies in Mandla. Prompt detection and treatment of imported/migratory cases may have prevented outbreaks in the district. This project has demonstrated that field programmes backed by adequate technical, management, operational, and financial controls with robust monitoring are needed for achieving malaria elimination.