A cluster randomized trial comparing deltamethrin and bendiocarb as insecticides for indoor residual spraying to control malaria on Bioko Island, Equatorial Guinea.

BACKGROUND: Indoor residual spraying (IRS) has been used on Bioko for malaria control since 2004. In 2013 the insecticide was changed from bendiocarb to deltamethrin. Shortly after this change, there was a marked increase in malaria prevalence on the island. This trial was carried out to compare the effectiveness of bendiocarb and deltamethrin for use in IRS on Bioko. METHODS: Twenty-four clusters of houses were randomized to receive IRS with either bendiocarb or deltamethrin. Approximately 3 months after the intervention, the prevalence of malaria and levels of haemoglobin were measured in children aged 2-14 years in each cluster. RESULTS: Prevalence of malaria in 2-14 year olds was lower in the bendiocarb arm (16.8, 95 % CI 11.1-24.7, N = 1374) than in the deltamethrin arm (23.2, 95 % CI 16.0-32.3, N = 1330) but this difference was not significant (p = 0.390), even after adjusting for covariates (p = 0.119). Mean haemoglobin in children was marginally higher in the bendiocarb clusters (11.6 g/dl, 95 % CI 11.5-11.8, N = 1326) than in the deltamethrin clusters (11.5 g/dl, 95 % CI 11.3-11.7, N = 1329). This difference was borderline significant after adjusting for covariates (p = 0.049). CONCLUSIONS: The results are suggestive of bendiocarb being more effective at preventing malaria on Bioko although evidence for this was weak. The results are likely due to the fact that local vectors remain fully susceptible to bendiocarb whereas subsequent tests have shown resistance to deltamethrin

Infection importation: a key challenge to malaria elimination on Bioko Island, Equatorial Guinea.

BACKGROUND: The impact of importation of falciparum malaria from mainland Equatorial Guinea on malaria infection in non-travellers and travellers on Bioko Island was examined. METHODS: Malaria indicator surveys were conducted in 2013 and 2014 to assess the association between malaria infection and travel to the mainland. Infection in non-travellers was compared in neighbourhoods of high travel and neighbourhoods of low travel. Boat passengers leaving from and arriving on the island were tested for infection. RESULTS: Children who had travelled to the mainland in the previous eight weeks were at greater risk of infection than those who had not travelled (56 vs 26% in 2013; 42 vs 18% in 2014). Children who had not travelled, living in localities with the highest proportion of travellers, were significantly more likely to be infected compared to those in localities with the smallest proportion of travellers (adjusted odds ratios 7.7 (95% CI 2.3-25) and 5.3 (95% CI 2.5-11) in 2013 and 2014, respectively). Infection in arriving boat passengers was substantially higher than in those departing (70 vs 38%, p = 0.017). DISCUSSION: Malaria importation by travellers poses a serious public health challenge affecting non-travellers as well as travellers

Outdoor biting by Anopheles mosquitoes on Bioko Island does not currently impact on malaria control.

BACKGROUND: There have been many recent reports that the rate of outdoor biting by malaria vectors has increased. This study examined the impact this might have on malaria transmission by assessing the association between exposure to outdoor bites and malaria infection on Bioko Island, Equatorial Guinea. METHODS: Responses to questions about time spent outside the previous night from a malaria indicator survey were combined with human landing catch measurements of hourly rates of outdoor and indoor biting for the whole island to estimate the number of outdoor and indoor bites received by each survey respondent. The association between RDT measured malaria infection status of individuals and outdoor bites received was investigated. RESULTS: The average number of bites received per person per night was estimated as 3.51 in total, of which 0.69 (19.7%) would occur outdoors. Malaria infection was not significantly higher in individuals who reported spending time outside between 7 pm and 6 am the previous night compared to those not spending time outside in both adults (18.9% vs 17.4%, p = 0.20) and children (29.2% vs 27.1%, p = 0.20). Malaria infection in neither adults (p = 0.56) nor in children (p = 0.12) was associated with exposure to outdoor bites, even after adjusting for confounders. CONCLUSIONS: Malaria vector mosquitoes in Bioko do bite humans outdoors, and this has the potential to reduce the effectiveness of vector control. However, outdoor biting is currently not a major factor influencing the malaria burden, mainly because more than 95% of the population are indoors during the middle of the night, which is the peak biting period for malaria vector mosquitoes. The majority of resources should remain with control measures that target indoor biting and resting such as LLINs and IRS

Prevalence of substandard and falsified artemisinin-based combination antimalarial medicines on Bioko Island, Equatorial Guinea.

INTRODUCTION: Poor-quality artemisinin-containing antimalarials (ACAs), including falsified and substandard formulations, pose serious health concerns in malaria endemic countries. They can harm patients, contribute to the rise in drug resistance and increase the public's mistrust of health systems. Systematic assessment of drug quality is needed to gain knowledge on the prevalence of the problem, to provide Ministries of Health with evidence on which local regulators can take action. METHODS: We used three sampling approaches to purchase 677 ACAs from 278 outlets on Bioko Island, Equatorial Guinea as follows: convenience survey using mystery client (n=16 outlets, 31 samples), full island-wide survey using mystery client (n=174 outlets, 368 samples) and randomised survey using an overt sampling approach (n=88 outlets, 278 samples). The stated active pharmaceutical ingredients (SAPIs) were assessed using high-performance liquid chromatography and confirmed by mass spectrometry at three independent laboratories. RESULTS: Content analysis showed 91.0% of ACAs were of acceptable quality, 1.6% were substandard and 7.4% falsified. No degraded medicines were detected. The prevalence of medicines without the SAPIs was higher for ACAs purchased in the convenience survey compared with the estimates obtained using the full island-wide survey-mystery client and randomised-overt sampling approaches. Comparable results were obtained for full island survey-mystery client and randomised overt. However, the availability of purchased artesunate monotherapies differed substantially according to the sampling approach used (convenience, 45.2%; full island-wide survey-mystery client, 32.6%; random-overt sampling approach, 21.9%). Of concern is that 37.1% (n=62) of these were falsified. CONCLUSION: Falsified ACAs were found on Bioko Island, with the prevalence ranging between 6.1% and 16.1%, depending on the sampling method used. These findings underscore the vital need for national authorities to track the scale of ineffective medicines that jeopardise treatment of life-threatening diseases and value of a representative sampling approach to obtain/measure the true prevalence of poor-quality medicines

Mapping and enumerating houses and households to support malaria control interventions on Bioko Island.

BACKGROUND: Housing mapping and household enumeration are essential for the planning, implementation, targeting, and monitoring of malaria control interventions. In many malaria endemic countries, control efforts are hindered by incomplete or non-existent housing cartography and household enumeration. This paper describes the development of a comprehensive mapping and enumeration system to support the Bioko Island Malaria Control Project (BIMCP). RESULTS: A highly detailed database was developed to include every housing unit on Bioko Island and uniquely enumerate the associated households residing in these houses. First, the island was divided into a virtual, geo-dereferenced grid of 1 × 1 km sequentially numbered map-areas, each of which was in turn subdivided into one hundred, 100 × 100 m sequentially numbered map-sectors. Second, high-resolution satellite imagery was used to sequentially and uniquely identify all housing units within each map-sector. Third, where satellite imagery was not available, global positioning systems (GPS) were used as the basis for uniquely identifying and mapping housing units in a sequential manner. A total of 97,048 housing units were mapped by 2018, 56% of which were concentrated in just 5.2% of Bioko Island's total mapped area. Of these housing units, 70.7% were occupied, thus representing uniquely identified households. CONCLUSIONS: The housing unit mapping and household enumeration system developed for Bioko Island enabled the BIMCP to more effectively plan, implement, target, and monitor malaria control interventions. Since 2014, the BIMCP has used the unique household identifiers to monitor all household-level interventions, including indoor residual spraying, long-lasting insecticide-treated nets distribution, and annual malaria indicator surveys. The coding system used to create the unique housing unit and household identifiers is highly intuitive and allows quick location of any house within the grid without a GPS. Its flexibility has permitted the BIMCP to easily take into account the rapid and substantial changes in housing infrastructure. Importantly, by utilizing this coding system, an unprecedented quantity and diversity of detailed, geo-referenced demographic and health data have been assembled that have proved highly relevant for informing decision-making both for malaria control and potentially for the wider public health agenda on Bioko Island

Advancing global health through development and clinical trials partnerships: a randomized, placebo-controlled, double-blind assessment of safety, tolerability, and Immunogenicity of Plasmodium falciparum sporozoites vaccine for malaria in healthy Equatoguinean men

Equatorial Guinea (EG) has implemented a successful malaria control program on Bioko Island. A highly effective vaccine would be an ideal complement to this effort and could lead to halting transmission and eliminating malaria. Sanaria® PfSPZ Vaccine (Plasmodium falciparum sporozoite Vaccine) is being developed for this purpose. To begin the process of establishing the efficacy of and implementing a PfSPZ Vaccine mass vaccination program in EG, we decided to conduct a series of clinical trials of PfSPZ Vaccine on Bioko Island. Because no clinical trial had ever been conducted in EG, we first successfully established the ethical, regulatory, quality, and clinical foundation for conducting trials. We now report the safety, tolerability, and immunogenicity results of the first clinical trial in the history of the country. Thirty adult males were randomized in the ratio 2:1 to receive three doses of 2.7 × 105 PfSPZ of PfSPZ Vaccine (N = 20) or normal saline placebo (N = 10) by direct venous inoculation at 8-week intervals. The vaccine was safe and well tolerated. Seventy percent, 65%, and 45% of vaccinees developed antibodies to Plasmodium falciparum (Pf) circumsporozoite protein (PfCSP) by enzyme-linked immunosorbent assay, PfSPZ by automated immunofluorescence assay, and PfSPZ by inhibition of sporozoite invasion assay, respectively. Antibody responses were significantly lower than responses in U.S. adults who received the same dosage regimen, but not significantly different than responses in young adult Malians. Based on these results, a clinical trial enrolling 135 subjects aged 6 months to 65 years has been initiated in EG; it includes PfSPZ Vaccine and first assessment in Africa of PfSPZ-CVac. ClinicalTrials.gov identifier: NCT02418962

Elucidating barriers to malaria elimination: An analysis of the role of low-density and imported Plasmodium falciparum infections to onward malaria transmission

Thesis (Ph.D.)--University of Washington, 2022Despite yearly investments of more than US $4.1 billion dollars and extensive efforts, malaria continues to be one of the greatest contributors to morbidity and mortality in endemic areas. To continue to reduce the malaria burden, new control strategies, therapeutics, and vaccines are needed. While the malaria burden has declined since the last decade, the rate of change has plateaued in recent years, calling for new and innovative strategies to continue to drive malaria elimination. To prioritize resource allocation, accurately assess the effectiveness of candidate vaccines and therapeutics, and develop effective control strategies, it is essential to better understand the drivers of Plasmodium transmission, identify malaria hotspots, and develop new methodologies that allow for a more in-depth understanding of the true burden of disease. There are several threats to malaria elimination efforts. Among these include a large reservoir of low-density Plasmodium infections in endemic areas and importation of cases. Low-density infections are highly prevalent in endemic areas and can contribute to onward transmission. However, since at low densities, they do not cause immediate clinical illness and are below the limit of detection (LoD) of standard field diagnostics, there is a paucity of data on their natural history of infection, which limits our understanding of the necessity of targeting these types of infections. Imported Plasmodium infections, which can be further transmitted, and introduce new strains or lines of resistance, are of rising concern, especially with increasing human mobility. This dissertation utilizes advanced epidemiologic methods and novel laboratory techniques to study low-density and imported Plasmodium infections. In the first analysis, household clustering of subpatent infections around rapid diagnostic test (RDT) positive infections on Bioko Island, Equatorial Guinea was analyzed. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) for Plasmodium 18S rRNA was used to identify Plasmodium falciparum (Pf) parasite infections that were not detected by RDT (referred to as subpatent infections) on a subset of household samples from the 2015 Malaria Indicator Survey (MIS). The association between living in a household with an RDT(+) individual and having a subpatent infection was evaluated using multivariate hierarchical logistic regression models with inverse probability weights for selection. To evaluate possible modification of the association by potential importation of the RDT(+) case, the analysis was repeated among strata of matched sets based on the reported eight-week travel history of the RDT(+) individual(s). The adjusted prevalence odds of subpatent infection were 2.59-fold greater (95% CI: 1.31, 5.09) for those in a household with an RDT(+) individual compared to individuals in a household without RDT(+) individuals. When stratifying by travel history of the RDT(+) individual, the association between subpatent infections and RDT(+) infections was stronger in the strata in which the RDT(+) individual(s) had not recently travelled (adjusted Prevalence Odds Ratio (aPOR) 2.95; 95% CI:1.17, 7.41), and attenuated in the strata in which recent travel was reported (aPOR 1.76; 95% CI: 0.54, 5.67). In the second analysis, data collected before and after a travel moratorium imposed in response to COVID-19 was leveraged to estimate the impact of imported Plasmodium infections on prevalence in areas of historically high travel prevalence on Bioko Island. A difference in differences approach was used to estimate the change in odds of Pf infection for individuals living in historically high travel areas following the travel moratorium relative to those living in historically low travel areas. A survey generalized linear model with robust standard errors and a logit link function was fit with an interaction term between travel area and year to estimate the impact of the travel moratorium on risk of Plasmodium infection. Comparing the change from 2019 to 2020 in high travel areas to low travel areas, the adjusted odds of infection were 39% lower in high travel areas (aOR: 0.61; 95% CI: 0.43, 0.88) than would have been expected in the absence of a travel moratorium. Finally, in a third study, the feasibility of using daily at-home dried blood spot (DBS) collection as a method to study the natural history of asymptomatic, low-density infections was assessed in a small pilot study in Katakwi district, Uganda. One hundred and two adults and 29 children who were RDT-negative and asymptomatic for malaria at screening were invited to self-collect DBS daily for 28 days. Venous blood samples and clinic-collected DBS were taken at enrollment and at four weekly clinic visits as well. Participant opinions about the DBS collection process were solicited through daily Diary Cards and a 5-point Likert scale survey on acceptability administered at the final clinic visit. The DBS and venous blood were analyzed by qRT-PCR. The number of participants completing the study, the total number of DBS collected, and the opinions of the process and any reported pain were analyzed to determine compliance and acceptability of the study procedure. The human internal control mRNA and Plasmodium 18S rRNA were evaluated for the at-home versus clinic-collected DBS and venous blood to assess quality of the at-home collected samples and evaluate the accuracy of DBS as a parasite detection tool. At-home DBS collection was found to be a feasible approach to studying low-density infections. Almost all participants (92%) completed the study, and only three individuals withdrew due to pain or inconvenience of the study procedure. Overall, 97% of participants collected ≥ 16 of 24 home DBS, and 87% of all spots had ≥ 40 µL of blood. The procedure was well tolerated and viewed favorably by participants. At-home collected DBS were acceptable for qRT-PCR and showed only slightly lower concentrations of human control mRNA compared to clinic-collected DBS (human internal control TBP mRNA cycle threshold 0.8 cycles earlier for clinic-collected DBS; 95%CI: 0.65, 0.98), though this latter difference was not clinically impactful. Correlation between Pf 18S rRNA from paired whole blood and DBS samples was high (R=0.93) Conclusions: The results of these studies provide new evidence on the contribution and characteristics of low-density and imported Plasmodium carriage to malaria transmission. In addition, a new method for studying Plasmodium infections over time that is particularly well suited for the study of low-density infections has been validated. At-home DBS collection should be widely implemented for epidemiological surveillance, clinical trial baseline surveys and parasite monitoring, as well as for in-depth analyses of parasite dynamics, immune responses, and genetics. The increased understanding of low-density infections that will come from the utilization of this evaluation strategy will improve control strategies and development of new therapeutics and vaccines to combat malaria

Study Protocol: Feasibility of daily dried blood spot sampling to evaluate the natural history of low-density Plasmodium infections

This document is the IRB-approved clinical trial protocol for a field study conducted in 2021 in Uganda. The findings of this study have been published (PMID: 35836179 and additional manuscripts in review).U.S. National Institutes of Healt

Trends in parasite prevalence following 13 years of malaria interventions on Bioko island, Equatorial Guinea: 2004–2016

Abstract Background Whilst there have been substantial reductions in malaria transmission over the past decade, in many countries in West and Central Africa the malaria burden remains high. Monitoring and evaluation of malaria transmission trends and intervention strategies are key elements for malaria control programmes. This study uses a time series of annual malaria indicator surveys to track the progress of malaria control in Bioko Island, Equatorial Guinea, over a 13 year period of intensive interventions. Malaria infection and haemoglobin were measured annually in children (1 to 14 years) in cross-sectional household surveys from 2004 to 2016 in 18 sentinel sites across the island. Trends in transmission patterns were assessed and the impact of the vector control interventions (net use and spray coverage) was evaluated. Results Between 2004 and 2016 approximately 106,500 individual tests for parasitaemia were conducted using rapid diagnostic tests. Although spray coverage remained relatively high (> 70%) over the time period, reported net usage was generally below 40%. Parasite prevalence reduced from 43.3 to 10.5% between 2004 and 2016. The prevalence of moderate to severe anaemia in children aged 1–5 years reduced from 14.9 to 1.6%. Impact in individual sites ranged from 57 to 100% reductions in parasite prevalence between 2004 and 2016. Sleeping under a net and living in a house that had been sprayed in the past 12 months were independently protective against infection (OR = 0.69 [95%CI 0.61–0.80] and OR = 0.87 [95% CI 0.78–0.97], respectively), whilst recent travel to the mainland increased the odds of infection nearly fourfold (OR = 3.94 [95%CI 2.79–5.56]). Conclusion Island-wide interventions have resulted in a substantial reduction in malaria transmission on Bioko Island. This unique time series of 13 consecutive annual malaria indicator surveys clearly demonstrates the long-term effectiveness of the sustained use of two vector control interventions, indoor residual spraying and LLINs, and the value of comprehensive and sustained surveillance. Despite considerable success in reducing the burden on the island, malaria is still endemic, with populations in some areas remaining at high risk of infection

Dataset: Assessing the daily natural history of asymptomatic Plasmodium infections in adults and older children in Katakwi, Uganda: a longitudinal cohort study

Data fields: Column 1: Row identifier Column 2: id (subject identifier) Column 3: sex (male/female) Column 4: age_category (adult or older child) Column 5: study_day (by day) Colum 6: Pf_parasites_per_mL_va (P. falciparum parasites/mL of blood by 18S rRNA RT-PCR) Column 7: Pan_parasites_per_mL_va (pan-Plasmodium parasites/mL of blood by 18S rRNA RT-PCR) Column 8: infection_type (category of infection: Negative, Pf, Pan, or Mixed)This is the dataset accompanying Hergott et al. publications related to this field study conducted in Katakwi District, Uganda in March-May 2021. This dataset contains line listings of sample-by-sample data for Plasmodium RT-PCR results by subject.U.S. National Institutes of Health (R21AI146763) Bill and Melinda Gates Foundation INV-00931