Conventional mosquito marking technology for mark-release-recapture (MRR) is quite limited in terms of information capacity and efficacy. To overcome both challenges, we have engineered, lab-tested, and field-evaluated a new class of marker particles, in which synthetic, short DNA oligonucleotides (DNA barcodes) are adsorbed and protected within tough, crosslinked porous protein microcrystals. Mosquitoes self-mark through ingestion of microcrystals in their larval habitat. Barcoded microcrystals persist transstadially through mosquito development if ingested by larvae, do not significantly affect adult mosquito survivorship, and individual barcoded mosquitoes are detectable in pools of up to at least 20 mosquitoes. We have also demonstrated crystal persistence following adult mosquito ingestion. Barcode sequences can be recovered by qPCR and next-generation sequencing (NGS) without detectable amplification of native mosquito DNA. These DNA-laden protein microcrystals have the potential to radically increase the amount of information obtained from future MRR studies compared to previous studies employing conventional mosquito marking materials.

ABSTRACT. Vector biologists have long sought the ability to accurately quantify the age of wild mosquito populations, a metric used to measure vector control efficiency. This has proven challenging due to the difficulties of working in the field and the biological complexities of wild mosquitoes. Ideal age grading techniques must overcome both challenges while also providing epidemiologically relevant age measurements. Given these requirements, the Detinova parity technique, which estimates age from the mosquito ovary and tracheole skein morphology, has been most often used for mosquito age grading despite significant limitations, including being based solely on the physiology of ovarian development. Here, we have developed a modernized version of the original mosquito aging method that evaluated wing wear, expanding it to estimate mosquito chronological age from wing scale loss. We conducted laboratory experiments using adult Anopheles gambiae held in insectary cages or mesocosms, the latter of which also featured ivermectin bloodmeal treatments to change the population age structure. Mosquitoes were age graded by parity assessments and both human- and computational-based wing evaluations. Although the Detinova technique was not able to detect differences in age population structure between treated and control mesocosms, significant differences were apparent using the wing scale technique. Analysis of wing images using averaged left- and right-wing pixel intensity scores predicted mosquito age at high accuracy (overall test accuracy: 83.4%, average training accuracy: 89.7%). This suggests that this technique could be an accurate and practical tool for mosquito age grading though further evaluation in wild mosquito populations is required.

Background The gains made against malaria have stagnated since 2015, threatened further by increasing resistance to insecticides and antimalarials. Improvement in malaria control necessitates a multipronged strategy, which includes the development of novel tools. One such tool is mass drug administration (MDA) with endectocides, primarily ivermectin, which has shown promise in reducing malaria transmission through lethal and sublethal impacts on the mosquito vector. Objective The primary objective of the study is to assess the impact of repeated ivermectin MDA on malaria incidence in children aged ≤10 years. Methods Repeat Ivermectin MDA for Malaria Control II is a double-blind, placebo-controlled, cluster-randomized, and parallel-group trial conducted in a setting with intense seasonal malaria transmission in Southwest Burkina Faso. The study included 14 discrete villages: 7 (50%) randomized to receive standard measures (seasonal malaria chemoprevention [SMC] and bed net use for children aged 3 to 59 months) and placebo, and 7 (50%) randomized to receive standard measures and monthly ivermectin MDA at 300 μg/kg for 3 consecutive days, provided under supervision to all eligible village inhabitants, over 2 successive rainy seasons. Nonpregnant individuals >90 cm in height were eligible for ivermectin MDA, and cotreatment with ivermectin and SMC was not permitted. The primary outcome is malaria incidence in children aged ≤10 years, as assessed by active case surveillance. The secondary safety outcome of repeated ivermectin MDA was assessed through active and passive adverse event monitoring. Results The trial intervention was conducted from July to November in 2019 and 2020, with additional sampling of humans and mosquitoes occurring through February 2022 to assess postintervention changes in transmission patterns. Additional human and entomological assessments were performed over the 2 years in a subset of households from 6 cross-sectional villages. A subset of individuals underwent additional sampling in 2020 to characterize ivermectin pharmacokinetics and pharmacodynamics. Analysis and unblinding will commence once the database has been completed, cleaned, and locked. Conclusions Our trial represents the first study to directly assess the impact of a novel approach for malaria control, ivermectin MDA as a mosquitocidal agent, layered into existing standard-of-care interventions. The study was designed to leverage the current SMC deployment infrastructure and will provide evidence regarding the additional benefit of ivermectin MDA in reducing malaria incidence in children. Trial Registrations ClinicalTrials.gov NCT03967054; https://clinicaltrials.gov/ct2/show/NCT03967054 and Pan African Clinical Trials Registry PACT201907479787308; https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=8219 International Registered Report Identifier (IRRID) DERR1-10.2196/41197

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BACKGROUND Malaria gains have stagnated since 2015, threatened further by increasing resistance to insecticides and antimalarials. Improvement in malaria control necessitates a multi-pronged strategy which includes the development of novel tools. One such tool is the mass drug administration (MDA) with endectocides, primarily ivermectin, which has shown promise in reducing malaria transmission through lethal and sublethal impacts on the mosquito vector. OBJECTIVE The primary objective of the study is to assess the impact of a combined approach of seasonal malaria chemoprevention (SMC) and bed net usage with or without repeated ivermectin MDA on malaria incidence in children age ≤ 10 years. METHODS Repeat ivermectin MDA for malaria control II (RIMDAMAL II) is a double-blind placebo-controlled cluster-randomized parallel-group trial conducted in a setting with intense seasonal malaria transmission in Southwest Burkina Faso. The study included 14 discrete villages: 7 randomized to receive standard measures (SMC for children ages 3 to 59 months and bed nets) plus placebo and 7 to receive standard measures plus ivermectin MDA over two successive rainy seasons. RESULTS The trial intervention (ivermectin MDA at 300 µg/kg for consecutive 3 days, provided under supervision to all eligible village inhabitants) was conducted from July to November in 2019 and 2020, with additional sampling of humans and mosquitoes occurring through February 2022 to assess for post-intervention changes in transmission patterns. Additional human and entomological assessments were performed over the two years in a subset of households from 6 cross-sectional villages. A subset of individuals underwent additional sampling in 2020 to characterize ivermectin pharmacokinetics/pharmacodynamics. CONCLUSIONS Our trial represents the first study to directly assess the impact of a novel approach to malaria control, ivermectin MDA as an endectocide, layered into existing standard of care interventions. The study was designed to leverage current SMC deployment infrastructure and will provide evidence as to the additional benefit of ivermectin MDA in reducing malaria incidence in children. CLINICALTRIAL ClinicalTrials.gov Identifier: NCT03967054; Pan African Clinical Trials Registry (PACTR): PACT201907479787308