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Long-lasting insecticide-treated nets (LLINs) play a crucial role in preventing malaria transmission. LLINs should remain effective for at least three years, even after repeated washings. Currently, monitoring insecticides in LLINs is cumbersome, costly, and requires specialized equipment and hazardous solvents. Our aim was to develop a simple, high-throughput and low-resource method for measuring insecticides in LLINs. To extract insecticides, polyethylene-LLIN samples were heated at 85 °C for 45 min in a non-hazardous solvent mix containing dicyclohexylphthalate as an internal standard. The extraction solvent was reduced from 50 to 5 ml using a 0.2 g sample, 90% smaller than the recommended sample size. By optimizing HPLC chromatography, we simultaneously detected pyrethroid and pyriproxyfen insecticides with high sensitivity in LLIN's extract. The method can quantify levels ≥ 0.0015% permethrin, 0.00045% alpha-cypermethrin and 0.00025% pyriproxyfen (w/w) in polyethylene, allowing for insecticide tracking before and after the use of LLINs. This method can be used to assess LLINs with 1% pyriproxyfen (pyriproxyfen-LLIN) or 2% permethrin (Olyset® Net), 1% pyriproxyfen and 2% permethrin (Olyset® Duo), or 0.55% pyriproxyfen and 0.55% alpha-cypermethrin (Royal Gaurd®). One can run 120 samples (40 nets) simultaneously with high precision and accuracy, improving throughput and reducing labour, costs, and environmental impact.

Objective\ud Failure to control domestic Triatoma infestans in the Chaco is attributed to vulnerable adobe construction, which provides vector refuges and diminishes insecticide contact. We conducted a pilot to test the impact of housing improvement plus indoor residual spraying (IRS) on house infestation and vector abundance in a rural community in the Bolivian Chaco. \ud \ud Methods\ud The intervention included three arms: housing improvement + IRS [HI], assisted IRS [AS] in which the team helped to clear the house pre-IRS and routine IRS [RS]. HI used locally available materials, traditional construction techniques and community participation. Vector parameters were assessed by Timed Manual Capture for 2 person-hours per house at baseline and medians of 114, 173, 314, 389 and 445 days post-IRS-1. A second IRS round was applied at a median of 314 days post-IRS-1.\ud \ud Results\ud Post-intervention infestation indices and abundance fell in all three arms. The mean odds of infestation was 0.29 (95% CL 0.124, 0.684) in the HI relative to the RS arm. No difference was observed between AS and RS. Vector abundance was reduced by a mean 44% (24.8, 58.0) in HI compared to RS, with no difference between AS and RS. Median delivered insecticide concentrations per house were lower than the target of 50 mg/m2 in >90% of houses in all arms. \ud \ud Conclusion\ud Housing improvement using local materials and community participation is a promising strategy to improve IRS effectiveness in the Bolivian Chaco. A larger trial is needed to quantify the impact on reinfestation over time.

Additional file 2. Median alpha-cypermethrin a.i. concentrations on filter papers fitted to houses at different wall heights (n = 158 at 0.2 m; n = 157 at 1.2 m; n = 165 at 2 m). The horizontal lines represent the alpha-cypermethrin a.i. target concentration range (50 mg �� 20% a.i./m2). Error bars represents the lower and upper adjacent values to the median; points represent the outside values.

Additional file 5. (A) Median spray rates (m2/min) in IRS-treated houses with (+ F.P.) and without (��� F.P.) filter papers fitted to the walls pre-spraying, stratified by the level of householder compliance with the request to empty their houses in preparation for IRS application (n = 55 houses); (B) Median insecticide a.i. concentrations (mg/m2) delivered to houses stratified by householder compliance (n = 25 houses).

Additional file 1. Protocol of laboratory assays.

Additional file 4. Variation in the spray rates by individual health workers (A) median observed spray rates (m2/min); and (B) observed/expected spray rate ratio where the expected ratio is 19 m2/min for the spraying equipment calibration.

Additional file 3. Frequency distribution of the observed/expected spray rates in IRS-treated houses (n = 80 houses).

Background: Quality control of indoor residual spraying (IRS) is necessary to ensure that spray operators (SOs)\ud deposit the correct concentration of insecticide on sprayed structures, while also confrming that spray records are not being falsifed.\ud Methods: Using high-performance liquid chromatography (HPLC), this study conducted quality control of the organophosphate insecticide pirimiphos-methyl (Actellic 300CS), during the 2018 IRS round on Bioko Island, Equatorial Guinea. Approximately 60 SOs sprayed a total of 67,721 structures in 16,653 houses during the round. Houses that were reportedly sprayed were randomly selected for quality control testing. The SOs were monitored twice in 2018,\ud an initial screening in March followed by sharing of results with the IRS management team and identifcation of SOs to be re-trained, and a second screening in June to monitor the efectiveness of training. Insecticide samples were adhesive-lifted from wooden and cement structures and analysed using HPLC.\ud Results: The study suggests that with adequate quality control measures and refresher training, suboptimal spraying was curtailed, with a signifcant increased concentration delivered to the bedroom (diference=0.36, P

Additional file 1: Table 1. Comparison of primiphos-methyl recovery by Bostik adhesive glue dots from rough tile surface treated with various concentrations (0.25–3 g/m2) of Actellic 300CS® formulation.

Primaquine (PQ) is an essential antimalarial drug but despite being developed over 70 years ago, its mode of action is unclear. Here, we demonstrate that hydroxylated-PQ metabolites (OH-PQm) are responsible for efficacy against liver and sexual transmission stages of Plasmodium falciparum. The antimalarial activity of PQ against liver stages depends on host CYP2D6 status, whilst OH-PQm display direct, CYP2D6-independent, activity. PQ requires hepatic metabolism to exert activity against gametocyte stages. OH-PQm exert modest antimalarial efficacy against parasite gametocytes; however, potency is enhanced ca.1000 fold in the presence of cytochrome P450 NADPH:oxidoreductase (CPR) from the liver and bone marrow. Enhancement of OH-PQm efficacy is due to the direct reduction of quinoneimine metabolites by CPR with the concomitant and excessive generation of H2O2, leading to parasite killing. This detailed understanding of the mechanism paves the way to rationally re-designed 8-aminoquinolines with improved pharmacological profiles.