CDC light traps underestimate the protective efficacy of an indoor spatial repellent against bites from wild Anopheles arabiensis mosquitoes in Tanzania

BACKGROUND: Methods for evaluating efficacy of core malaria interventions in experimental and operational settings are well established but gaps exist for spatial repellents (SR). The objective of this study was to compare three different techniques: (1) collection of blood-fed mosquitoes (feeding), (2) human landing catch (HLC), and (3) CDC light trap (CDC-LT) collections for measuring the indoor protective efficacy (PE) of the volatile pyrethroid SR product Mosquito Shield() METHODS: The PE of Mosquito Shield() against a wild population of pyrethroid-resistant Anopheles arabiensis mosquitoes was determined via feeding, HLC, or CDC-LT using four simultaneous 3 by 3 Latin squares (LS) run using 12 experimental huts in Tanzania. On any given night each technique was assigned to two huts with control and two huts with treatment. The LS were run twice over 18 nights to give a sample size of 72 replicates for each technique. Data were analysed by negative binomial regression. RESULTS: The PE of Mosquito Shield() measured as feeding inhibition was 84% (95% confidence interval (CI) 58-94% [Incidence Rate Ratio (IRR) 0.16 (0.06-0.42), p < 0.001]; landing inhibition 77% [64-86%, (IRR 0.23 (0.14-0.36) p < 0.001]; and reduction in numbers collected by CDC-LT 30% (0-56%) [IRR 0.70 (0.44-1.0) p = 0.160]. Analysis of the agreement of the PE measured by each technique relative to HLC indicated no statistical difference in PE measured by feeding inhibition and landing inhibition [IRR 0.73 (0.25-2.12) p = 0.568], but a significant difference in PE measured by CDC-LT and landing inhibition [IRR 3.13 (1.57-6.26) p = 0.001]. CONCLUSION: HLC gave a similar estimate of PE of Mosquito Shield() against An. arabiensis mosquitoes when compared to measuring blood-feeding directly, while CDC-LT underestimated PE relative to the other techniques. The results of this study indicate that CDC-LT could not effectively estimate PE of the indoor spatial repellent in this setting. It is critical to first evaluate the use of CDC-LT (and other tools) in local settings prior to their use in entomological studies when evaluating the impact of indoor SR to ensure that they reflect the true PE of the intervention

A household-based community health worker programme for non-communicable disease, malnutrition, tuberculosis, HIV and maternal health: a stepped-wedge cluster randomised controlled trial in Neno District, Malawi

BACKGROUND: Community health worker (CHW) programmes are a valuable component of primary care in resource-poor settings. The evidence supporting their effectiveness generally shows improvements in disease-specific outcomes relative to the absence of a CHW programme. In this study, we evaluated expanding an existing HIV and tuberculosis (TB) disease-specific CHW programme into a polyvalent, household-based model that subsequently included non-communicable diseases (NCDs), malnutrition and TB screening, as well as family planning and antenatal care (ANC). METHODS: We conducted a stepped-wedge cluster randomised controlled trial in Neno District, Malawi. Six clusters of approximately 20 000 residents were formed from the catchment areas of 11 healthcare facilities. The intervention roll-out was staggered every 3 months over 18 months, with CHWs receiving a 5-day foundational training for their new tasks and assigned 20-40 households for monthly (or more frequent) visits. FINDINGS: The intervention resulted in a decrease of approximately 20% in the rate of patients defaulting from chronic NCD care each month (-0.8 percentage points (pp) (95% credible interval: -2.5 to 0.5)) while maintaining the already low default rates for HIV patients (0.0 pp, 95% CI: -0.6 to 0.5). First trimester ANC attendance increased by approximately 30% (6.5pp (-0.3, 15.8)) and paediatric malnutrition case finding declined by 10% (-0.6 per 1000 (95% CI -2.5 to 0.8)). There were no changes in TB programme outcomes, potentially due to data challenges. INTERPRETATION: CHW programmes can be successfully expanded to more comprehensively address health needs in a population, although programmes should be carefully tailored to CHW and health system capacity

Determining whether community health workers are “deployment ready” using standard setting

Background: Community Health Workers (CHWs) provide basic health screening and advice to members of their own communities. Although CHWs are trained, no CHW programmes have used a formal method to identify the level of achievement on post-training assessments that distinguishes “safe” from “unsafe”. Objectives: The aim of this study was to use Ebel method of standard setting for a post-training written knowledge assessment for CHWs in Neno, Malawi. Methods: 12 participants agreed the definitions of a “just-deployment ready” and an “ideal” CHW. Participants rated the importance and difficulty of each question on a three-point scale and also indicated the proportion of “just-deployment ready” CHWs expected to answer each of the nine question types correctly. Mean scores were used to determine the passing standard, which was reduced by one standard error of measurement (SEM) as this was the first time any passing standard had been employed. The level of agreement across participants’ ratings of importance and difficulty was calculated using Krippendorf’s alpha. The assessment results from the first cohort of CHW trainees were analysed using classical test theory. Findings: There was poor agreement between participants on item ratings of both importance and difficulty (Krippendorf’s alphas of 0.064 and 0.074 respectively). The pass mark applied to the assessment, following adjustment using the SEM, was 53.3%. Based on this pass mark, 68% of 129 CHW trainees were ‘clear passes’, 11% ‘borderline passes’, 9% ‘borderline fails’ and 12% ‘clear fails’. Conclusions: Determining whether a CHW is deployment-ready is an important, but difficult exercise, as evidenced by a lack of agreement regarding question importance and difficulty. Future exercises should allow more time for training, discussion and modification of ratings. Based on the assessment, most CHWs trained could be considered deployment-ready, but following-up their performance in the field will be vital to validate the pass mark set

Allometry for Biomass Estimation in Jatropha Trees Planted as Boundary Hedge in Farmers ’ Fields

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Influence of testing modality on bioefficacy for the evaluation of Interceptor® G2 mosquito nets to combat malaria mosquitoes in Tanzania.

BACKGROUND: Insecticide-treated net (ITN) durability is evaluated using longitudinal bioefficacy and fabric integrity sampling post-distribution. Interceptor® G2 was developed for resistance management and contains two adulticides: alpha-cypermethrin and chlorfenapyr; it is a pro-insecticide that is metabolized into its active form by mosquito-detoxifying enzymes and may be enhanced when the mosquito is physiologically active. To elucidate the impact of bioassay modality, mosquito exposures of the alphacypermethrin ITN Interceptor® and dual adulticide Interceptor® G2 were investigated. METHODS: This study evaluated the performance of Interceptor® G2 compared to Interceptor® against local strains of mosquitoes in Tanzania. Unwashed and 20× times washed nets were tested. Efficacy of ITNs was measured by four bioassay types: (1) World Health Organisation (WHO) cone test (cone), (2) WHO tunnel test (tunnel), (3) Ifakara ambient chamber test (I-ACT) and (4) the WHO gold standard experimental hut test (hut). Hut tests were conducted against free-flying wild pyrethroid metabolically resistant Anopheles arabiensis and Culex quinquefasciatus. Cone, tunnel and I-ACT bioassays used laboratory-reared metabolically resistant An. arabiensis and Cx. quinquefasciatus and pyrethroid susceptible Anopheles gambiae sensu stricto and Aedes aegypti. RESULTS: Against resistant strains, superiority of Interceptor® G2 over Interceptor® was observed in all "free-flying bioassays". In cone tests (which restrict mosquito flight), superiority of Interceptor® over Interceptor® G2 was recorded. Mortality of unwashed Interceptor® G2 among An. arabiensis was lowest in hut tests at 42.9% (95% CI: 37.3-48.5), although this increased to 66.7% (95% CI: 47.1-86.3) by blocking hut exit traps so mosquitoes presumably increased frequencies of contact with ITNs. Higher odds of mortality were consistently observed in Interceptor® G2 compared to Interceptor® in "free-flying" bioassays using An. arabiensis: tunnel (OR = 1.42 [95% CI:1.19-1.70], p < 0.001), I-ACT (OR = 1.61 [95% CI: 1.05-2.49], p = 0.031) and hut (OR = 2.53 [95% CI: 1.96-3.26], p < 0.001). Interceptor® and Interceptor® G2 showed high blood-feeding inhibition against all strains. CONCLUSION: Both free-flying laboratory bioassays (WHO Tunnel and I-ACT) consistently measured similarly, and both predicted the results of the experimental hut test. For bioefficacy monitoring and upstream product evaluation of ITNs in situ, the I-ACT may provide an alternative bioassay modality with improved statistical power. Interceptor G2® outperformed Interceptor ® against pyrethroid-resistant strains, demonstrating the usefulness of chlorfenapyr in mitigation of malaria

Additional file 3 of Influence of testing modality on bioefficacy for the evaluation of Interceptor® G2 mosquito nets to combat malaria mosquitoes in Tanzania

Data associated with the paper, "Influence of testing modality on bioefficacy for the evaluation of Interceptor® G2 mosquito nets to combat malaria mosquitoes in Tanzania"