Mass drug administration of ivermectin and dihydroartemisinin-piperaquine against malaria in settings with high coverage of standard control interventions: a cluster-randomised controlled trial in The Gambia

Advancing adoptability and sustainability of digital prediction tools for climate-sensitive infectious disease prevention and control

Few forecasting models have been translated into digital prediction tools for prevention and control of climate-sensitive infectious diseases. We propose a 3-U (useful, usable, and used) research framework for advancing the adoptability and sustainability of these tools. We make recommendations for 1) developing a tool with a high level of accuracy and sufficient lead time to permit effective proactive interventions (useful); 2) conducting a needs assessment to ensure that a tool meets the needs of end-users (usable); and 3) demonstrating the efficacy and cost-effectiveness of a tool to secure its adoption into routine surveillance and response systems (used).

Safety and efficacy of repeat ivermectin mass drug administrations for malaria control (RIMDAMAL II): a phase 3, double-blind, placebo-controlled, cluster-randomised, parallel-group trial

BACKGROUND

The success of crucial vector control efforts in Africa (eg, long-lasting insecticide-treated nets [ITNs] and indoor residual spraying) are threatened by widespread insecticide resistance and insufficient effect on outdoor mosquito biting. Studies have shown that ivermectin, used for the treatment of parasitic diseases, can kill malaria vectors that feed on the blood of treated people and thus might be an effective complementary vector control tool if administered widely to communities in malaria endemic regions. We aimed to test the safety of repeated, high-dose ivermectin mass drug administration (MDA) and its efficacy for reducing malaria incidence among children when integrated with seasonal malaria chemoprevention (SMC) delivery.

METHODS

We conducted a phase 3, double-blind, placebo-controlled, cluster-randomised, parallel-group trial in southwest Burkina Faso over two consecutive rainy seasons (2019-20). 14 villages or village sectors (clusters) were randomly assigned (1:1) to ivermectin or placebo MDA by random draw, and study-eligible participants (those who regularly lived in the cluster and provided written informed consent) from all households were enrolled in July, 2019 and July, 2020. Participants were eligible for MDA if they were 90 cm in height or taller and not excluded for other safety reasons (eg, pregnancy or taking SMC drugs). There were no age restrictions for participants. Each rainy season (July to October), eligible participants from the intervention group clusters received monthly high-dose oral ivermectin MDA (three daily doses, approximately 300 μg/kg dosed by height bands) and those from the control group received monthly oral placebo MDA for up to eight treatment rounds. MDA was performed by study staff alongside community health worker administration of monthly SMC to children aged 3-59 months in both groups. All participants and study personnel, apart from the pharmacist, were masked to group assignment. The primary outcome was weekly malaria incidence in children aged 10 years and younger, as assessed by weekly active case detection until week 16 of year 2, by intention to treat. Adverse events were monitored in all MDA participants through active and passive surveillance. Blood was sampled for secondary parasitological outcomes, including analysis of parasite species distribution among malaria cases. Mosquitoes were sampled from pre-selected households in three clusters per group for secondary entomological outcomes, including analysis of blood-fed mosquito survivorship, mosquito biting rates, and entomological inoculation rates. Changes in haemoglobin pre-intervention and post-intervention in children aged 10 years and younger were assessed in 2020. The trial is registered with ClinicalTrials.gov (NCT03967054) and the Pan African Clinical Trials Registry (PACT201907479787308) and is completed.

FINDINGS

The study took place from July 13, 2019, to Nov 8, 2020, with seven villages assigned to the control group and seven to the intervention group. Participants were enrolled from households in both groups in July, 2019, and July, 2020. In the intervention group, 1928 participants in 2019 and 2163 participants in 2020 were followed up, and 703 children in 2019 and 686 children in 2020 were analysed. In the control group, 1604 participants in 2019 and 1921 participants in 2020 were followed up, and 605 children in 2019 and 641 children in 2020 were analysed. MDA coverage (receiving ≥1 dose) in the enrolled population (including those who were ineligible) varied over the intervention period (68-74%), with 86-95% of participants who were eligible receiving ivermectin or placebo over the study period. 288 (47·2%) of 610 children in the control group and 312 (44·2%) of 706 children in the ivermectin group received SMC, and all clusters received new dual-chemistry Interceptor G2 ITNs containing chlorfenapyr and α-cypermethrin by government authorities in October, 2019. The average estimated weekly malaria incidence rate per 100 person-weeks among children in the intervention group was 1·78 (95% CI 1·24-2·53) and 1·84 (1·29-2·64) in the control group, and the incidence rate ratio was 0·96 (95% CI 0·58-1·59; p=0·8723). The risk of adverse events among eligible participants in the intervention group was lower than in the control group (risk ratio 0·63, 95% CI 0·46-0·87; p=0·0049). The distribution of Plasmodium spp detected in children with clinical malaria was unexpectedly diverse with non-Plasmodium falciparum species detected in 56 (11%) of 505 symptomatic children; however, species distribution did not differ between groups (p=0·15). Blood-fed Anopheles gambiae species complex mosquitoes captured in intervention group clusters the week after MDA in 2019 had decreased survival relative to those captured from control group clusters (p<0·0001), but this effect was not seen in mosquitoes captured 3 weeks after MDA. Overall entomological inoculation rates (EIRs; infectious bites per person per night) did not differ between groups (intervention EIR 0·010; control EIR 0·011; between-group ratio 0·91, 95% CI 0·56-1·30; p=0·45). In 2020, children aged 10 years and younger in the intervention group had a significantly higher increase in haemoglobin pre-intervention versus post-intervention than children in the control group (p=0·007).

INTERPRETATION

Repeated high-dose ivermectin MDA integrated with SMC distributions at the study site did not reduce malaria incidence among children relative to placebo MDA, despite evidence that, compared with the control group, mosquito survivorship in the first year was reduced in the intervention group the week following MDA and overall improvements in haemoglobin were greater in children in the intervention group. Confounding factors, including unexpectedly low malaria incidence over the trial period, possibly due to government distribution of dual-chemistry ITNs to all trial clusters in the middle of the intervention period, overdispersion of the primary incidence outcome between clusters, and high parasite and mosquito species diversity, might have influenced the primary outcome.

FUNDING

National Institute of Allergy and Infectious Diseases.

Effect of mass drug administration on malaria incidence in southeast Senegal during 2020-22: a two-arm, open-label, cluster-randomised controlled trial

BACKGROUND

In Africa, the scale-up of malaria-control interventions has reduced malaria burden, but progress towards elimination has stalled. Mass drug administration (MDA) is promising as a transmission-reducing strategy, but evidence from low-to-moderate transmission settings is needed. We aimed to assess the safety, coverage, and effect of three cycles of MDA with dihydroartemisinin-piperaquine plus single, low-dose primaquine on Plasmodium falciparum incidence and prevalence in southeast Senegal.

METHODS

We conducted a two-arm, open-label, cluster-randomised controlled trial in villages in the Tambacounda health district of southeast Senegal. Eligible villages had a population size of 200-800, were within a health-post catchment area with an annual malaria incidence of 60-160 cases per 1000 people, and had an established or planned Prise en Charge à Domicile Plus model. We randomly assigned villages (1:1) using a stratified, constrained randomisation approach to receive either three cycles of MDA with oral dihydroartemisinin-piperaquine plus single, low-dose primaquine administered at 6-week intervals (intervention) or to standard of care, which included three cycles of seasonal malaria chemoprevention (SMC) with oral sulfadoxine-pyrimethamine plus amodiaquine administered at 4-week intervals (control). Participants, the field team, and all investigators, including those who assessed outcomes and analysed data, were unmasked to allocation assignment. Laboratory technicians were masked to intervention assignment. The primary outcome was village-level, P falciparum-confirmed malaria incidence in the post-intervention year (ie, July to December, 2022). Secondary outcomes included malaria incidence during the intervention year (ie, July to December, 2021), coverage and safety of MDA, and adverse events. We conducted analyses using an intention-to-treat approach. The trial is registered with ClinicalTrials.gov (NCT04864444) and is completed.

FINDINGS

Between Sept 1 and Oct 25, 2020, 523 villages were geolocated and screened for eligibility; 111 met the inclusion criteria. Of these, 60 villages were randomly selected and assigned to the intervention arm or control arm. Distribution coverage of all three doses of dihydroartemisinin-piperaquine was 6057 (73·6%) of 8229 participants in the first cycle, 6836 (78·8%) of 8673 participants in the second cycle, and 7065 (81·3%) of 8690 participants in the third cycle. Distribution coverage of single, low-dose primaquine was 6286 (78·6%) of 7999 participants in the first cycle, 6949 (82·1%) of 8462 participants in the second cycle, and 7199 (84·0%) of 8575 participants in the third cycle. Distribution coverage of all three doses of SMC was 3187 (92·2%) of 3457 children aged 3-120 months in the first cycle, 3158 (91·8%) of 3442 children aged 3-120 months in the second cycle, and 3139 (91·4%) of 3434 children aged 3-120 months in the third cycle. In the intervention year (ie, July to December, 2021), the adjusted effect of MDA was 55% (95% CI 28 to 71). In the post-intervention year (ie, July to December 2022), the adjusted MDA effect was 26% (-17 to 53). Malaria incidence during the transmission season of the post-intervention year was 126 cases per 1000 population in the intervention arm and 146 cases per 1000 population in the control arm. No serious adverse events were reported.

INTERPRETATION

In southeast Senegal, a low-to-moderate transmission setting where malaria-control measures have been scaled up, three cycles of MDA with dihydroartemisinin-piperaquine plus single, low-dose primaquine was safe and reduced malaria burden during the intervention year. However, its sustained effect was weak and continuation of MDA or another transmission-reducing strategy could be required.

FUNDING

US President's Malaria Initiative.

Adjunctive ivermectin mass drug administration for malaria control on the Bijagos Archipelago of Guinea-Bissau (MATAMAL): a quadruple-blinded, cluster-randomised, placebo-controlled trial

BACKGROUND

Arthropod vectors feeding on the blood of individuals treated with ivermectin have substantially increased mortality. Whether this effect will translate into a useful tool for reducing malaria burden at scale is not clear. Our trial aimed to assess whether using ivermectin as an adjunct to mass drug administration (MDA) with dihydroartemisinin-piperaquine would further reduce malaria prevalence.

METHODS

MATAMAL was a quadruple-blinded, cluster-randomised, placebo-controlled trial, conducted on the Bijagos Archipelago, Guinea-Bissau, an area of seasonal malaria transmission. All residents were invited to participate, with exclusions for drug safety. 24 clusters were randomised in a 1:1 ratio, using restriction randomisation, to either MDA with three daily oral doses of dihydroartemisinin-piperaquine and ivermectin (300 μg/kg per day) in three sequential months during the transmission season in 2021 and 2022, or MDA with dihydroartemisinin-piperaquine and placebo in the same schedule. The primary outcome was quantitative PCR prevalence of Plasmodium falciparum parasitaemia in all age groups, during peak transmission, after the second year of intervention. The primary entomological outcome was anopheline parity rate. The trial is registered with ClinicalTrials.gov (NCT04844905).

FINDINGS

Participants were recruited between June 7, 2021 and Sept 21, 2022. The baseline population was 25 882 (12 634 [50·6%] were female individuals and 12 317 [49·4%] were male individuals): 13 832 were in the intervention group and 12 050 in the control group. Cluster-level coverage for dihydroartemisinin-piperaquine ranged from 60·4% to 78·7%, and for ivermectin or ivermectin-placebo from 58·1 to 77·1%. Following the intervention, the prevalence of P falciparum infection was 118 (5·05%) of 2300 in the control group and 141 (6·64%) of 2083 in the intervention group. The adjusted risk difference was 1·67% (95% CI -1·44 to 4·78; p=0·28). There were 124 adverse events in the control group (1·0% of participants) and 267 in the intervention group (1·9% of participants). Two serious adverse events were reported, neither related to the intervention, and no treatment-related deaths. The anopheline parity rate was 1679 (67·8%) of 2475 in control clusters and 1740 (72·3%) of 2414 in intervention clusters. The adjusted risk difference was -1·32 (95% CI -14·77 to 12·12; p=0·84).

INTERPRETATION

Adding ivermectin to dihydroartemisinin-piperaquine MDA had no additional effect on reducing malaria prevalence or vector parity in this setting. The intervention was well tolerated. To our knowledge, this trial is the first to be designed to assess whether ivermectin has an additive effect on malaria when coadministered with dihydroartemisinin-piperaquine MDA.

FUNDING

The National Institute for Health and Care Research, Medical Research Council, Wellcome, and Foreign, Commonwealth & Development Office.

Mosquitocidal efficacy and pharmacokinetics of single-dose ivermectin versus three-day dose regimen for malaria vector control compared with albendazole and no treatment: An open-label randomized controlled trial

OBJECTIVES

When malaria vectors consume ivermectin in a blood meal, their survival probability decreases, potentially reducing malaria transmission during mass drug administrations. However, questions remain regarding the optimal dosing. This study aimed to compare the mosquitocidal effect and pharmacokinetics of two-dose regimens of ivermectin for malaria vector control.

DESIGN

We conducted an open-label randomized control trial in Kenya, staggered in blocks with sequential intervention groups and parallel controls. Participants were randomly assigned (2:1:1:1) using computer random-sequence generation, unstratified, with one block of six pharmacokinetics-only participants (single-dose ivermectin) and six blocks of four participants (3:1 intervention vs control), to receive single-dose ivermectin (400 mcg/kg, n = 12), three daily doses (3-day regimen 300 mcg/kg, n = 6), albendazole (400 mg, n = 6), or no treatment (negative control, n = 6). Our primary outcome was Anopheles gambiae survival (time-to-event [days]) after blood feeding up to 10 days after drug administration. We also evaluated pharmacokinetics (peak plasma and capillary blood concentration, areas under the plasma and capillary blood concentration-time curve from time of last administration to time of last observation, time to reach peak plasma and capillary blood concentration, terminal elimination half-life) up to 7 days after treatment.

RESULTS

A total of 36 healthy volunteers aged 21-32 years were recruited into the study and followed up to completion, with two participants not attending the visit on day 28. All drug regimens were well-tolerated. Both regimens showed significant mosquitocidal effect in the first 7 days. At 10 days after treatment, the single dose presented superior longevity of effect (adjusted hazard ratio = 3.91; 95% confidence interval = 1.93-7.93; P <0.001) compared with the triple dose (adjusted hazard ratio = 1.79; 95% confidence interval = 0.88-3.62; P = 0.0.11). Albendazole had, overall, no mosquitocidal effect.

CONCLUSIONS

It is unclear why a single dose led to increased bio-efficacy compared with a triple dose. We recommend trials investigating ivermectin mass drug administrations for malaria control to consider single-dose ivermectin. A single-dose regimen is also expected to present additional operational advantages compared with a 3-day regimen, leading to improved programmatic suitability.

Microheterogeneity of Transmission Shapes Submicroscopic Malaria Carriage in Coastal Tanzania

BACKGROUND

Asymptomatic carriage of malaria parasites persists even as malaria transmission declines. Low-density infections are often submicroscopic, not detected with rapid diagnostic tests (RDTs) or microscopy but detectable by polymerase chain reaction (PCR).

METHODS

To characterize submicroscopic Plasmodium falciparum carriage in an area of declining malaria transmission, asymptomatic persons >5 years of age in rural Bagamoyo District, Tanzania, were screened using RDT, microscopy, and PCR. We investigated the size of the submicroscopic reservoir of infection across villages, determined factors associated with submicroscopic carriage, and assessed the natural history of submicroscopic malaria over 4 weeks.

RESULTS

Among 6076 participants, P. falciparum prevalences by RDT, microscopy, and PCR were 9%, 9%, and 28%, respectively, with roughly two-thirds of PCR-positive individuals harboring submicroscopic infection. Adult status, female sex, dry season months, screened windows, and bed net use were associated with submicroscopic carriage. Among 15 villages encompassing 80% of participants, the proportion of submicroscopic carriers increased with decreasing village-level malaria prevalence. Over 4 weeks, 23% of submicroscopic carriers (61 of 266) became RDT positive, with half exhibiting symptoms, while half (133 of 266) were no longer parasitemic at the end of 4 weeks. Progression to RDT-positive patent malaria occurred more frequently in villages with higher malaria prevalence.

CONCLUSIONS

Microheterogeneity in transmission observed at the village level appears to affect both the size of the submicroscopic reservoir and the likelihood of submicroscopic carriers developing patent malaria in coastal Tanzania.

Mass drug administration to reduce malaria incidence in a low-to-moderate endemic setting: short-term impact results from a cluster randomised controlled trial in Senegal

Background

In Africa, the scale-up of malaria control interventions, including seasonal malaria chemoprevention (SMC), has dramatically reduced malaria burden, but progress toward malaria elimination has stalled. We evaluated mass drug administration (MDA) as a strategy to accelerate reductions in malaria incidence in Senegal.

Methods

We conducted an open-label, cluster-randomised controlled trial in a low-to-moderate transmission setting of Tambacounda, Senegal. Eligible villages had a population size between 200-800. All villages received pyrethroid-piperonyl butoxide bednets and proactive community case management of malaria at baseline. Sixty villages were randomised 1:1 to either three cycles of MDA with dihydroartemisinin-piperaquine+single-low dose primaquine administered to individuals aged ≥3 months, six-weeks apart starting the third week of June (intervention), or standard-of-care, which included three monthly cycles of SMC with sulfadoxine-pyrimethamine+amodiaquine administered to children aged 3-120 months starting end of July (control). MDA and SMC were delivered door-to-door. The primary outcome was clinical malaria incidence in all ages assessed during the peak transmission season (July-December), the year after intervention. Here, we report safety, coverage, and impact outcomes during the intervention year. The trial is registered at ClinicalTrials.Gov (NCT04864444).

Findings

Between June 21, 2021 and October 3, 2021, 6505, 7125, and 7250 participants were administered MDA and 3202, 3174, and 3146 participants were administered SMC across cycles. Coverage of ≥1 dose of MDA drugs was 79%, 82%, and 83% across cycles. During the transmission season of the intervention year, MDA was associated with a 55% [95% CI: 28%-72%] lower incidence of malaria compared to control (MDA: 93 cases/1000 population; control: 173 cases/1000 population). No serious adverse events were reported in either arm.

Interpretation

In low-to-moderate malaria transmission settings with scaled-up malaria control interventions, MDA with dihydroartemisinin-piperaquine+single-low dose primaquine is effective and well-tolerated for reducing malaria incidence. Further analyses will focus on the sustainability of this reduction.

Funding

United States President's Malaria Initiative.

HM, Antoshechkin I, Marshall JM, Akbari OS. Eliminating malaria vectors with precision-guided sterile males

Controlling the principal African malaria vector, the mosquito Anopheles gambiae, is considered essential to curtail malaria transmission. However, existing vector control technologies rely on insecticides, which are becoming increasingly ineffective. Sterile insect technique (SIT) is a powerful suppression approach that has successfully eradicated a number of insect pests, yet the A. gambiae toolkit lacks the requisite technologies for its implementation. SIT relies on iterative mass releases of nonbiting, nondriving, sterile males which seek out and mate with monandrous wild females. Once mated, females are permanently sterilized due to mating-induced refractoriness, which results in population suppression of the subsequent generation. However, sterilization by traditional methods renders males unfit, making the creation of precise genetic sterilization methods imperative. Here, we introduce a vector control technology termed precision-guided sterile insect technique (pgSIT), in A. gambiae for inducible, programmed male sterilization and female elimination for wide-scale use in SIT campaigns. Using a binary CRISPR strategy, we cross separate engineered Cas9 and gRNA strains to disrupt male-fertility and female-essential genes, yielding >99.5% male sterility and >99.9% female lethality in hybrid progeny. We demonstrate that these genetically sterilized males have good longevity, are able to induce sustained population suppression in cage trials, and are predicted to eliminate wild A. gambiae populations using mathematical models, making them ideal candidates for release. This work provides a valuable addition to the malaria genetic biocontrol toolkit, enabling scalable SIT-like confinable, species-specific, and safe suppression in the species.

In vitro interaction of naphthoquine with ivermectin, atovaquone, curcumin, and ketotifen in the asexual blood stage of Plasmodium falciparum 3D7

Naphthoquine is a promising candidate for antimalarial combination therapy. Its combination with artemisinin has demonstrated excellent efficacy in clinical trials conducted across various malaria-endemic areas. A co-formulated combination of naphthoquine and azithromycin has also shown high clinical efficacy for malaria prophylaxis in Southeast Asia. Developing new combination therapies using naphthoquine will provide additional arsenal responses to the growing threat of artemisinin resistance. Furthermore, due to its long half-life, the possible interaction of naphthoquine with other drugs also needs attention. However, studies on its pharmacodynamic interactions with other drugs are still limited. In this study, the in vitro interactions of naphthoquine with ivermectin, atovaquone, curcumin, and ketotifen were evaluated in the asexual stage of Plasmodium falciparum 3D7. By using the combination index analysis and the SYBR Green I-based fluorescence assay, different interaction patterns of selected drugs with naphthoquine were revealed. Curcumin showed a slight but significant synergistic interaction with naphthoquine at lower effect levels, and no antagonism was observed across the full range of effect levels for all tested ratios. Atovaquone showed a potency decline when combined with naphthoquine. For ivermectin, a significant antagonism with naphthoquine was observed at a broad range of effect levels below 75% inhibition, although no significant interaction was observed at higher effect levels. Ketotifen interacted with naphthoquine similar to ivermectin, but significant antagonism was observed for only one tested ratio. These findings should be helpful to the development of new naphthoquine-based combination therapy and the clinically reasonable application of naphthoquine-containing therapies.

IMPORTANCE

Pharmacodynamic interaction between antimalarials is not only crucial for the development of new antimalarial combination therapies but also important for the appropriate clinical use of antimalarials. The significant synergism between curcumin and naphthoquine observed in this study suggests the potential value for further development of new antimalarial combination therapy. The finding of a decline in atovaquone potency in the presence of naphthoquine alerts to a possible risk of treatment or prophylaxis failure for atovaquone-proguanil following naphthoquine-containing therapies. The observation of antagonism between naphthoquine and ivermectin raised a need for concern about the applicability of naphthoquine-containing therapy in malaria-endemic areas with ivermectin mass drug administration deployed. Considering the role of atovaquone-proguanil as a major alternative when first-line artemisinin-based combination therapy is ineffective and the wide implementation of ivermectin mass drug administration in malaria-endemic countries, the above findings will be important for the appropriate clinical application of antimalarials involving naphthoquine-containing therapies.

Safety, pharmacokinetics, and potential neurological interactions of ivermectin, tafenoquine, and chloroquine in Rhesus macaques

Ivermectin (IVM) could be used for malaria control as treated individuals are lethal to blood-feeding Anopheles, resulting in reduced transmission. Tafenoquine (TQ) is used to clear the liver reservoir of Plasmodium vivax and as a prophylactic treatment in high-risk populations. It has been suggested to use ivermectin and tafenoquine in combination, but the safety of these drugs in combination has not been evaluated. Early derivatives of 8-aminoquinolones (8-AQ) were neurotoxic, and ivermectin is an inhibitor of the P-glycoprotein (P-gp) blood brain barrier (BBB) transporter. Thus, there is concern that co-administration of these drugs could be neurotoxic. This study aimed to evaluate the safety and pharmacokinetic interaction of tafenoquine, ivermectin, and chloroquine (CQ) in Rhesus macaques. No clinical, biochemistry, or hematological outcomes of concern were observed. The Cambridge Neuropsychological Test Automated Battery (CANTAB) was employed to assess potential neurological deficits following drug administration. Some impairment was observed with tafenoquine alone and in the same monkeys with subsequent co-administrations. Co-administration of chloroquine and tafenoquine resulted in increased plasma exposure to tafenoquine. Urine concentrations of the 5,6 orthoquinone TQ metabolite were increased with co-administration of tafenoquine and ivermectin. There was an increase in ivermectin plasma exposure when co-administered with chloroquine. No interaction of tafenoquine on ivermectin was observed in vitro. Chloroquine and trace levels of ivermectin, but not tafenoquine, were observed in the cerebrospinal fluid. The 3''-O-demethyl ivermectin metabolite was observed in macaque plasma but not in urine or cerebrospinal fluid. Overall, the combination of ivermectin, tafenoquine, and chloroquine did not have clinical, neurological, or pharmacological interactions of concern in macaques; therefore, this combination could be considered for evaluation in human trials.

Mosquitocidal effect of ivermectin-treated nettings and sprayed walls on Anopheles gambiae s.s

Ivermectin (IVM) has been proposed as a new tool for malaria control as it is toxic on vectors feeding on treated humans or cattle. Nevertheless, IVM may have a direct mosquitocidal effect when applied on bed nets or sprayed walls. The potential for IVM application as a new insecticide for long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) was tested in this proof-of-concept study in a laboratory and semi-field environment. Laboratory-reared, insecticide-susceptible Kisumu Anopheles gambiae were exposed to IVM on impregnated netting materials and sprayed plastered- and mud walls using cone bioassays. The results showed a direct mosquitocidal effect of IVM on this mosquito strain as all mosquitoes died by 24 h after exposure to IVM. The effect was slower on the IVM-sprayed walls compared to the treated nettings. Further work to evaluate possibility of IVM as a new insecticide formulation in LLINs and IRS will be required.

Risk factors for non-participation in ivermectin and dihydroartemisinin-piperaquine mass drug administration for malaria control in the MASSIV trial

BACKGROUND

Mass Drug Administration (MDA) has become a mainstay for the control of several diseases over the last two decades. Successful implementation of MDA programmes requires community participation and can be threatened by systematic non-participation. Such concerns are particularly pertinent for MDA programmes against malaria, as they require multi-day treatment over several consecutive months. Factors associated with non-participation to the MDA campaign with ivermectin (IVM) and dihydroartemisinin-piperaquine (DHP) implemented within the MASSIV cluster randomized trial were determined.

METHODS

Coverage data was extracted from the MASSIV trial study database, with every datapoint being a directly observed therapy (DOT). A complete month of MDA was classified as receiving all three daily doses of treatment. For both ivermectin and DHP, ordinal logistic regression was used to identify individual and household level variables associated with non-participation.

RESULTS

For ivermectin, 51.5% of eligible participants received all 3 months of treatment while 30.7% received either one or two complete months. For DHP, 56.7% of eligible participants received all 3 months of treatment and 30.5% received either one or two complete months. Children aged 5-15 years and adults aged more than 50 years were more likely to receive at least one complete month of MDA than working age adults, both for ivermectin (aOR 4.3, 95% CI 3.51-5.28 and aOR of 2.26, 95% CI 1.75-2.95) and DHP (aOR 2.47, 95%CI 2.02-3.02 and aOR 1.33, 95%CI 1.01-1.35), respectively. Members of households where the head received a complete month of MDA were more likely to themselves have received a complete month of MDA, both for ivermectin (aOR 1.71, 95%CI 1.35-2.14) and for DHP (aOR 1.64, 95%CI 1.33-2.04).

CONCLUSION

Personal and household-level variables were associated with participation in the MDA programme for malaria control. Specific strategies to (increase participation amongst some groups may be important to ensure maximum impact of MDA strategies in achieving malaria elimination.

TRIAL REGISTRATION

The MASSIV trial is registered under NCT03576313.

Efficacy and safety of ivermectin for the treatment of Plasmodium falciparum infections in asymptomatic male and female Gabonese adults - a pilot randomized, double-blind, placebo-controlled single-centre phase Ib/IIa clinical trial

BACKGROUND

Ivermectin's mosquitocidal effect and in vitro activity against Plasmodium falciparum asexual stages are known. Its in vivo blood-schizonticidal efficacy is unknown. Ivermectin's tolerability and efficacy against P. falciparum infections in Gabonese adults were assessed.

METHODS

The study consisted of a multiple dose stage and a randomized, double-blind, placebo-controlled stage. Adults with asymptomatic P. falciparum parasitaemia (200-5000 parasites/μl) were enrolled. First, three groups of five participants received 200 μg/kg ivermectin once daily for one, two, and three days, respectively, and then 34 participants were randomized to 300 μg/kg ivermectin or placebo once daily for 3 days. Primary efficacy outcome was time to 90% parasite reduction. Primary safety outcomes were drug-related serious and severe adverse events (Trial registration: PACTR201908520097051).

FINDINGS

Between June 2019 and October 2020, 49 participants were enrolled. Out of the 34 randomized participants, 29 (85%) completed the trial as per protocol. No severe or serious adverse events were observed. The median time to 90% parasite reduction was 24.1 vs. 32.0 h in the ivermectin and placebo groups, respectively (HR 1.38 [95% CI 0.64 to 2.97]).

INTERPRETATION

Ivermectin was well tolerated in doses up to 300 μg/kg once daily for three days and asymptomatic P. falciparum asexual parasitaemia was reduced similarly with this dose of ivermectin compared to placebo. Further studies are needed to evaluate plasmodicidal effect of ivermectin at higher doses and in larger samples.

FUNDING

This study was funded by the Centre de Recherches Médicales de Lambaréné and the Centre for Tropical Medicine of the Bernhard Nocht Institute for Tropical Medicine.

A field bioassay for assessing ivermectin bio-efficacy in wild malaria vectors

BACKGROUND

Ivermectin (IVM) mass drug administration is a candidate complementary malaria vector control tool. Ingestion of blood from IVM treated hosts results in reduced survival in mosquitoes. Estimating bio-efficacy of IVM on wild-caught mosquitoes requires they ingest the drug in a blood meal either through a membrane or direct feeding on a treated host. The latter, has ethical implications, and the former results in low feeding rates. Therefore, there is a need to develop a safe and effective method for IVM bio-efficacy monitoring in wild mosquitoes.

METHODS

Insectary-reared Anopheles gambiae s.s. were exposed to four IVM doses: 85, 64, 43, 21 ng/ml, and control group (0 ng/ml) in three different solutions: (i) blood, (ii) 10% glucose, (iii) four ratios (1:1, 1:2, 1:4, 1:8) of blood in 10% glucose, and fed through filter paper. Wild-caught An. gambiae s.l. were exposed to 85, 43 and 21 ng/ml IVM in blood and 1:4 ratio of blood-10% glucose mixture. Survival was monitored for 28 days and a pool of mosquitoes from each cohort sacrificed immediately after feeding and weighed to determine mean weight of each meal type.

RESULTS

When administered in glucose solution, mosquitocidal effect of IVM was not comparable to the observed effects when similar concentrations were administered in blood. Equal concentrations of IVM administered in blood resulted in pronounced reductions in mosquito survival compared to glucose solution only. However, by adding small amounts of blood to glucose solution, mosquito mortality rates increased resulting in similar effects to what was observed during blood feeding.

CONCLUSION

Bio-efficacy of ivermectin is strongly dependent on mode of drug delivery to the mosquito and likely influenced by digestive processes. The assay developed in this study is a good candidate for field-based bio-efficacy monitoring: wild mosquitoes readily feed on the solution, the assay can be standardized using pre-selected concentrations and by not involving treated blood hosts (human or animal) variation in individual pharmacokinetic profiles as well as ethical issues are bypassed. Meal volumes did not explain the difference in the lethality of IVM across the different meal types necessitating further research on the underlying mechanisms.

Micro-heterogeneity of transmission shapes the submicroscopic malaria reservoir in coastal Tanzania

Background

Asymptomatic malaria may be patent (visible by microscopy) and detectable by rapid malaria diagnostic tests (RDTs), or it may be submicroscopic and only detectable by polymerase chain reaction (PCR).

Methods

To characterize the submicroscopic reservoir in an area of declining malaria transmission, asymptomatic persons >5 years of age in Bagamoyo District, Tanzania, were screened using RDT, microscopy, and PCR. We investigated the size of the submicroscopic reservoir across villages, determined factors associated with submicroscopic parasitemia, and assessed the natural history of submicroscopic malaria over four weeks.

Results

Among 6,076 participants, Plasmodium falciparum prevalence by RDT, microscopy, and PCR was 9%, 9%, and 28%, respectively, with roughly two-thirds of PCR-positive individuals harboring submicroscopic infection. Adult status, female gender, dry season months, screened windows, and bednet use were associated with submicroscopic carriage. Among 15 villages encompassing 80% of participants, the proportion of submicroscopic carriers increased with decreasing village-level malaria prevalence. Over four weeks, 23% (61/266) of submicroscopic carriers became RDT-positive and were treated, with half exhibiting symptoms. This occurred more frequently in villages with higher malaria prevalence.

Conclusions

Micro-heterogeneity in transmission impacts the size of the submicroscopic reservoir and the likelihood of submicroscopic carriers developing patent malaria in coastal Tanzania.

Ivermectin as a novel malaria control tool: Getting ahead of the resistance curse

Reduction in malaria clinical cases is strongly dependent on the ability to prevent Anopheles infectious bites. Vector control strategies using long-lasting insecticidal nets and indoor residual spraying with insecticides have contributed to significantly reduce the incidence of malaria in many endemic countries, especially in the Sub-Saharan region. However, global progress in reducing malaria cases has plateaued since 2015 mostly due to the increased insecticide resistance and behavioral changes in Anopheles vectors. Additional control strategies are thus required to further reduce the burden of malaria and contain the spread of resistant and invasive Anopheles vectors. The use of endectocides such as ivermectin as an additional malaria control tool is now receiving increased attention, driven by its different mode of action compared to insecticides used so far and its excellent safety record for humans. In this opinion article, we discuss the advantages and disadvantages of using ivermectin for malaria control with a focus on the risk of selecting ivermectin resistance in malaria vectors. We also highlight the importance of understanding how ivermectin resistance could develop in mosquitoes and what its underlying mechanisms and associated molecular markers are, and propose a research agenda to manage this phenomenon.

Effects of larval exposure to sublethal doses of ivermectin on adult fitness and susceptibility to ivermectin in Anopheles gambiae s.s

BACKGROUND

The effects of ivermectin (endectocide) on mosquito survival make it a potential new malaria vector control tool. The drug can be administered to mosquito disease vectors through blood hosts that include humans and livestock. Its increased use may cause contamination of larval habitats, either directly through livestock excreta or indirectly through leaching or run-off from contaminated soil, albeit in sublethal doses. However, the effects of such exposure on immature stages and the subsequent adults that emerge are poorly understood. This study was undertaken to evaluate the impact of ivermectin exposure on Anopheles gambiae s.s. larvae and its effects on fitness and susceptibility to ivermectin in the emerging adults.

METHODS

Laboratory-reared An. gambiae s.s. (Kilifi strain) larvae were exposed to five different ivermectin concentrations; 0, 0.00001, 0.0001, 0.001, and 0.01 ppm, and larval survival was monitored to determine the appropriate sub-lethal dose. Concentrations with survival > 50% (0.00001 and 0.0001 ppm) were selected and used as the sub-lethal doses. The fecundity, fertility, and susceptibility to ivermectin of adults emerging after larval exposure to the sub-lethal doses were examined.

RESULTS

Overall, exposure of An. gambiae s.s. aquatic stages to ivermectin caused a dose-dependent reduction in larval survival irrespective of the stage at which the larvae were exposed. Exposure to ivermectin in the larval stage did not have an effect on either the number of eggs laid or the hatch rate. However, exposure of first/second-instar larvae to 0.0001 ppm and third/fourth-instar larvae to 0.001 ppm of ivermectin reduced the time taken to oviposition. Additionally, exposure to ivermectin in the larval stage did not affect susceptibility of the emerging adults to the drug.

CONCLUSIONS

This study shows that contamination of larval habitats with ivermectin affects An. gambiae s.s. larval survival and could potentially have an impact on public health. However, there are no carry-over effects on the fecundity, fertility, and susceptibility of the emerging adults to ivermectin. In addition, this study shows that environmental exposure to ivermectin in the larval habitats is unlikely to compromise the efficacy of ivermectin in the emerging adults.

HM, Antoshechkin I, Marshall JM, Akbari OS. Eliminating Malaria Vectors with Precision Guided Sterile Males

Controlling the principal African malaria vector, the mosquito Anopheles gambiae, is considered essential to curtail malaria transmission. However existing vector control technologies rely on insecticides, which are becoming increasingly ineffective. Sterile insect technique (SIT) is a powerful suppression approach that has successfully eradicated a number of insect pests, yet the A. gambiae toolkit lacks the requisite technologies for its implementation. SIT relies on iterative mass-releases of non-biting, non-driving, sterile males which seek out and mate with monandrous wild females. Once mated, females are permanently sterilized due to mating-induced refractoriness, which results in population suppression of the subsequent generation. However, sterilization by traditional methods renders males unfit, making the creation of precise genetic sterilization methods imperative. Here we develop precision guided Sterile Insect Technique (pgSIT) in the mosquito A. gambiae for inducible, programmed male-sterilization and female-elimination for wide scale use in SIT campaigns. Using a binary CRISPR strategy, we cross separate engineered Cas9 and gRNA strains to disrupt male-fertility and female-essential genes, yielding >99.5% male-sterility and >99.9% female-lethality in hybrid progeny. We demonstrate that these genetically sterilized males have good longevity, are able to induce population suppression in cage trials, and are predicted to eliminate wild A. gambiae populations using mathematical models, making them ideal candidates for release. This work provides a valuable addition to the malaria genetic biocontrol toolkit, for the first time enabling scalable SIT-like confinable suppression in the species.

Activity of Ivermectin and Its Metabolites against Asexual Blood Stage Plasmodium falciparum and Its Interactions with Antimalarial Drugs

Ivermectin is an endectocide used widely to treat a variety of internal and external parasites. Field trials of ivermectin mass drug administration for malaria transmission control have demonstrated a reduction of Anopheles mosquito survival and human malaria incidence. Ivermectin will mostly be deployed together with artemisinin-based combination therapies (ACT), the first-line treatment of falciparum malaria. It has not been well established if ivermectin has activity against asexual stage Plasmodium falciparum or if it interacts with the parasiticidal activity of other antimalarial drugs. This study evaluated antimalarial activity of ivermectin and its metabolites in artemisinin-sensitive and artemisinin-resistant P. falciparum isolates and assessed in vitro drug-drug interaction with artemisinins and its partner drugs. The concentration of ivermectin causing half of the maximum inhibitory activity (IC50) on parasite survival was 0.81 μM with no significant difference between artemisinin-sensitive and artemisinin-resistant isolates (P = 0.574). The ivermectin metabolites were 2-fold to 4-fold less active than the ivermectin parent compound (P < 0.001). Potential pharmacodynamic drug-drug interactions of ivermectin with artemisinins, ACT-partner drugs, and atovaquone were studied in vitro using mixture assays providing isobolograms and derived fractional inhibitory concentrations. There were no synergistic or antagonistic pharmacodynamic interactions when combining ivermectin and antimalarial drugs. In conclusion, ivermectin does not have clinically relevant activity against the asexual blood stages of P. falciparum. It also does not affect the in vitro antimalarial activity of artemisinins or ACT-partner drugs against asexual blood stages of P. falciparum.

Protocol for a cluster randomised placebo-controlled trial of adjunctive ivermectin mass drug administration for malaria control on the Bijagós Archipelago of Guinea-Bissau: the MATAMAL trial

INTRODUCTION

As malaria declines, innovative tools are required to further reduce transmission and achieve elimination. Mass drug administration (MDA) of artemisinin-based combination therapy (ACT) is capable of reducing malaria transmission where coverage of control interventions is already high, though the impact is short-lived. Combining ACT with ivermectin, an oral endectocide shown to reduce vector survival, may increase its impact, while also treating ivermectin-sensitive co-endemic diseases and minimising the potential impact of ACT resistance in this context.

METHODS AND ANALYSIS

MATAMAL is a cluster-randomised placebo-controlled trial. The trial is being conducted in 24 clusters on the Bijagós Archipelago, Guinea-Bissau, where the peak prevalence of Plasmodium falciparum (Pf) parasitaemia is approximately 15%. Clusters have been randomly allocated to receive MDA with dihydroartemisinin-piperaquine and either ivermectin or placebo. The primary objective is to determine whether the addition of ivermectin MDA is more effective than dihydroartemisinin-piperaquine MDA alone in reducing the prevalence of P. falciparum parasitaemia, measured during peak transmission season after 2 years of seasonal MDA. Secondary objectives include assessing prevalence after 1 year of MDA; malaria incidence monitored through active and passive surveillance; age-adjusted prevalence of serological markers indicating exposure to P. falciparum and anopheline mosquitoes; vector parous rates, species composition, population density and sporozoite rates; prevalence of vector pyrethroid resistance; prevalence of artemisinin resistance in P. falciparum using genomic markers; ivermectin's impact on co-endemic diseases; coverage estimates; and the safety of combined MDA.

ETHICS AND DISSEMINATION

The trial has been approved by the London School of Hygiene and Tropical Medicine's Ethics Committee (UK) (19156) and the Comite Nacional de Eticas de Saude (Guinea-Bissau) (084/CNES/INASA/2020). Results will be disseminated in peer-reviewed publications and in discussion with the Bissau-Guinean Ministry of Public Health and participating communities.

TRIAL REGISTRATION NUMBER

NCT04844905.

Unexpected Loa loa Finding in an Asymptomatic Patient From The Gambia: A Case Report

A 17-year-old asymptomatic male from The Gambia presented for a routine health examination after migration to Spain. Laboratory diagnosis confirmed the presence of Loa loa microfilariae. This unusual finding emphasizes the importance of screening in newly arrived migrants and the need of an extended anamnesis including migratory route and previous travels.

Pharmacokinetics of ivermectin metabolites and their activity against Anopheles stephensi mosquitoes

BACKGROUND

Ivermectin (22,23-dihydroavermectin B_1a: H₂B_1a) is an endectocide used to treat worm infections and ectoparasites including lice and scabies mites. Furthermore, survival of malaria transmitting Anopheles mosquitoes is strongly decreased after feeding on humans recently treated with ivermectin. Currently, mass drug administration of ivermectin is under investigation as a potential novel malaria vector control tool to reduce Plasmodium transmission by mosquitoes. A "post-ivermectin effect" has also been reported, in which the survival of mosquitoes remains reduced even after ivermectin is no longer detectable in blood meals. In the present study, existing material from human clinical trials was analysed to understand the pharmacokinetics of ivermectin metabolites and feeding experiments were performed in Anopheles stephensi mosquitoes to assess whether ivermectin metabolites contribute to the mosquitocidal action of ivermectin and whether they may be responsible for the post-ivermectin effect.

METHODS

Ivermectin was incubated in the presence of recombinant human cytochrome P₄₅₀ 3A4/5 (CYP 3A4/5) to produce ivermectin metabolites. In total, nine metabolites were purified by semi-preparative high-pressure liquid chromatography. The pharmacokinetics of the metabolites were assessed over three days in twelve healthy volunteers who received a single oral dose of 12 mg ivermectin. Blank whole blood was spiked with the isolated metabolites at levels matching the maximal blood concentration (C_max) observed in pharmacokinetics study samples. These samples were fed to An. stephensi mosquitoes, and their survival and vitality was recorded daily over 3 days.

RESULTS

Human CYP3A4 metabolised ivermectin more rapidly than CYP3A5. Ivermectin metabolites M1-M8 were predominantly formed by CYP3A4, whereas metabolite M9 (hydroxy-H₂B_1a) was mainly produced by CYP3A5. Both desmethyl-H₂B_1a (M1) and hydroxy-H₂B_1a (M2) killed all mosquitoes within three days post-feeding, while administration of desmethyl, hydroxy-H₂B_1a (M4) reduced survival to 35% over an observation period of 3 days. Ivermectin metabolites that underwent deglycosylation or hydroxylation at spiroketal moiety were not active against An. stephensi at C_max levels. Interestingly, half-lives of M1 (54.2 ± 4.7 h) and M4 (57.5 ± 13.2 h) were considerably longer than that of the parent compound ivermectin (38.9 ± 20.8 h).

CONCLUSION

In conclusion, the ivermectin metabolites M1 and M2 contribute to the activity of ivermectin against An. stephensi mosquitoes and could be responsible for the "post-ivermectin effect".

Repeat Ivermectin Mass Drug Administrations for Malaria Control II: Protocol for a Double-blind, Cluster-Randomized, Placebo-Controlled Trial for the Integrated Control of Malaria

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.

A campaign of mass drug administration with artemisinin-piperaquine to antimalaria in Trobriand Islands

We conducted a study on the Trobriand Islands of Papua New Guinea (PNG) in 2018 to verify the safety and efficacy of the artemisinin-piperaquine (AP) mass drug administration (MDA) campaign in regions with moderate to high mixed malaria transmission. Based on the natural topography of the Trobriand Islands, 44,855 residents from 92 villages on the islands were enrolled and divided into the main and outer islands. Three rounds of MDA were conducted using grid-based management. The primary endpoint was the coverage rate. Adverse reactions, parasitemia, and malaria morbidity were the secondary endpoints. There were 36,716 people living in 75 villages on the main island, and the MDA coverage rate was 92.58-95.68%. Furthermore, 8,139 people living in 17 villages on the outer islands had a coverage rate of 94.93-96.11%. The adverse reactions were mild in both groups, and parasitemia decreased by 87.2% after one year of surveillance. The average annual malaria morbidity has decreased by 89.3% after the program for four years. High compliance and mild adverse reactions indicated that the MDA campaign with AP was safe. The short-term effect is relatively ideal, but the evidence for long-term effect evaluation is insufficient.

Effects of ivermectin mass drug administration for malaria vector control on ectoparasites and soil-transmitted helminths: a cluster randomized trial

OBJECTIVES

Ivermectin, used to control several neglected tropical diseases, may also reduce malaria transmission. Mass drug administration (MDA) for malaria control therefore might have off-target impacts on neglected tropical diseases.

METHODS

In The Gambia, nested in a trial of ivermectin MDA, cross-sectional surveys measuring ectoparasites and soil-transmitted helminths in children aged 3 to 14 years took place in June and November 2019 and in November 2021.

RESULTS

After MDA, scabies prevalence was 41.2% (237/576) in the control and 38.2% (182/476) in the intervention arm (odds ratio [OR] 0.89 (95% confidence interval [CI] 0 67-1.2), P-value = 0.471) but by 2021, had rebounded to 38.8% (180/464) in the control and 53.2% (245/458) in the intervention arm. After MDA, prevalence of Strongyloides stercoralis was 16.8% (87/518) in the control and 9.1% (40/440) in the intervention arm (OR 0.4 (95% CI 0.16-0.94), P-value = 0.039). In 2021, it was 9.2% (38/413) in the control and 11.3% (45/399) in the intervention arm (OR 1.31 (95% CI 0.74-2.28), P-value = 0.35).

CONCLUSION

Scabies prevalence was similar between the two study arms. S. stercoralis prevalence was reduced. However, this effect did not last long: the prevalence 2 years after MDA was similar between study arms.

Entomological impact of mass administration of ivermectin and dihydroartemisinin-piperaquine in The Gambia: a cluster-randomized controlled trial

BACKGROUND

Vector control interventions in sub-Saharan Africa rely on insecticide-treated nets and indoor residual spraying. Insecticide resistance, poor coverage of interventions, poor quality nets and changes in vector behavior threaten the effectiveness of these interventions and, consequently, alternative tools are needed. Mosquitoes die after feeding on humans or animals treated with ivermectin (IVM). Mass drug administration (MDA) with IVM could reduce vector survival and decrease malaria transmission. The entomological impact of MDA of combined IVM and dihydroartemisinin-piperaquine was assessed in a community-based, cluster-randomized trial.

METHODS

A cluster-randomized trial was implemented in 2018 and 2019 in 32 villages in the Upper River Region, The Gambia. The with the inhabitants of 16 intervention villages eligible to receive three monthly rounds of MDA at the beginning of the malaria transmission season. Entomological surveillance with light traps and human landing catches (HLC) was carried out during a 7- to 14-day period after each round of MDA, and then monthly until the end of the year. The mosquitocidal effect of IVM was determined by direct membrane feeding assays.

RESULTS

Of the 15,017 mosquitoes collected during the study period, 99.65% (n = 14,965) were Anopheles gambiae sensu lato (An. gambiae s.l.), comprising Anopheles arabiensis (56.2%), Anopheles coluzzii (24.5%), Anopheles gambiae sensu stricto (An. gembiae s.s.; 16.0%) and Anopheles funestus sensu lato (An. funestus s.l.; 0.35%). No effect of the intervention on vector parity was observed. Vector density determined on light trap collections was significantly lower in the intervention villages in 2019 (adjusted incidence rate ratio: 0.39; 95% confidence interval [CI]: 0.20, 0.74; P = 0.005) but not in 2018. However, vector density determined in HLC collections was similar in both the intervention and control villages. The entomological inoculation rate was significantly lower in the intervention villages than in the control villages (odds ratio: 0.36, 95% CI: 0.19, 0.70; P  = 0·003). Mosquito mortality was significantly higher when blood fed on IVM-treated individuals up to 21 days post-treatment, particularly in adults and individuals with a higher body mass index.

CONCLUSION

Mass drug administration with IVM decreased vector density and the entomological inoculation rate while the effect on vector parity was less clear. Survival of mosquitoes fed on blood collected from IVM-treated individuals was significantly lower than that in mosquitoes which fed on controls. The influence of host characteristics on mosquito survivorship indicated that dose optimization could improve IVM efficacy. Future detailed entomological evaluation trials in which IVM is administered as stand-alone intervention may elucidate the contribution of this drug to the observed reduction in transmission.

Quercetin and Luteolin may be the New Effective Drugs for Radiation Pneumonitis: Based on a Systems Pharmacology

Background: The occurrence of radiation pneumonia not only affects the efficacy of radiotherapy, but also seriously threatens the health of patients undergoing radiotherapy for lung cancer. Studies have suggested that a feining granule is a potentially effective drug for the treatment of radiation pneumonitis, but its mechanism and main components are still unclear. Our study used bioinformatics methods to analyze the main drug Aster tataricus L. f. in feining granules and aims to gain the main mechanism in the treatment of radiation pneumonitis. Methods: Analyzed the effective drug components and targets of A tataricus through the Traditional Chinese Medicine Systems Pharmacology website. And obtained gene targets related to radiation pneumonia through the website of OMIM, Genecard, and Disgenet. Protein–protein interaction (PPI), gene ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of the obtained drugs and gene-related targets were conducted. Verify the effects of small molecule drugs on corresponding targets by conducting molecular docking experiments. Results: In total, 193 targets were identified for 13 molecules of A tataricus, and 897 genes were identified to be related to radiation pneumonia. Finally, we obtained 111 genes by crossing drug and disease-related target genes. Using PPI, GO, and KEGG analysis, we found TP53, HSP90AA1, RELA, JUN, AKT1, mitogen-activated protein kinase 1 ( MAPK1), tumor necrosis factor ( TNF), and interleukin-6 ( IL-6) are the most critical genes, which were mainly focused on the GOs of DNA-binding transcription factor, RNA polymerase II-specific DNA-binding transcription factor and protein serine/threonine kinase activity, and the pathways of lipids and atherosclerosis, advanced glycation end products and their receptors, and IL-17. Conclusion: Through molecular docking experiments, it was found that the small molecules of quercetin and luteolin bind tightly to RELA and JUN proteins. We reveal the mechanism of action of A tataricus in the treatment of radiation pneumonia. Quercetin and luteolin may be effective small molecules for radiation pneumonitis.

Vector control: agents of selection on malaria parasites?

Insect vectors are responsible for spreading many infectious diseases, yet interactions between pathogens/parasites and insect vectors remain poorly understood. Filling this knowledge gap matters because vectors are evolving in response to the deployment of vector control tools (VCTs). Yet, whilst the evolutionary responses of vectors to VCTs are being carefully monitored, the knock-on consequences for parasite evolution have been overlooked. By examining how mosquito responses to VCTs impact upon malaria parasite ecology, we derive a framework for predicting parasite responses. Understanding how VCTs affect the selection pressures imposed on parasites could help to mitigate against parasite evolution that leads to unfavourable epidemiological outcomes. Furthermore, anticipating parasite evolution will inform monitoring strategies for VCT programmes as well as uncovering novel VCT strategies.