The study area is the Upper and Middle Modder River basin situated in a semi-arid area of central South Africa. This is an important catchment because of the relatively large nearby towns of Bloemfontein, Botshabelo and Thaba Nchu. Crop production in the basin using conventional production techniques is currently not suitable due to marginal and erratic rainfall, and high evaporative demand, as well as low precipitation use efficiency on the clay and duplex soils caused by large runoff and evaporation losses. A labour-intensive in-field rain-water harvesting (IRWH) technique for crop production recently introduced into a part of the basin occupied by communal farmers has been shown to increase maize and sunflower yields by 30 to 50% compared to conventional tillage, making crop production utilising this technique a feasible proposition for these farmers. The area of land suitable for the IRWH in the basin is estimated to be 80 667 ha, of which 15 000 ha is located in the communal land. The two catchment management options compared in this paper are: • Allowing the 80 667 ha to remain under grassland and utilising the runoff downstream for irrigating maize • Utilising the 80 667 ha for maize production in the basin using the IRWH technique. Results showed that the expected maize production from the options shown above were 23 040t and 137 134t respectively. The large unproductive water losses during storage and conveyance to downstream use points are probably the main reason for this large difference in production. An economic analysis, which enabled the grazing benefit to be included in the first option, shows that the gross margin of this option, expressed as R/m 3 of rain water utilized, could be expected to be between 0.0234 to 0.0254 under current conditions, of which irrigation contributed about 25% or less. The comparable value for the IRWH option was 0.0354. The second option is clearly shown to be the most preferable, with high socioeconomic benefits for the communal farmers who are currently struggling to achieve sustainable livelihoods.

Vector-borne diseases threaten the health of populations around the world. While key interventions continue to provide protection from vectors, there remains a need to develop and test new vector control tools. Cluster-randomized trials, in which the intervention or control is randomly allocated to clusters, are commonly selected for such evaluations, but their design must carefully consider cluster size and cluster separation, as well as the movement of people and vectors, to ensure sufficient statistical power and avoid contamination of results. Island settings present an opportunity to conduct these studies. Here, we explore the benefits and challenges of conducting intervention studies on islands and introduce the Bijagós archipelago of Guinea-Bissau as a potential study site for interventions intended to control vector-borne diseases. This article is part of the theme issue ‘Novel control strategies for mosquito-borne diseases'.

Background: Bubaque is the most populous island of the Bijagos archipelago, a group of malaria-endemic islands situated off the coast of Guinea-Bissau, West Africa. Malaria vector control on Bubaque relies almost exclusively on the use of long-lasting insecticidal nets (LLINs). However, there is little information on local vector bionomics and insecticide resistance. Methods: A survey of mosquito species composition was performed at the onset of the wet season (June/July) and the beginning of the dry season (November/December). Sampling was performed using indoor adult light-traps and larval dipping. Anopheles mosquitoes were identified to species level and assessed for kdr allele frequency by TaqMan PCR. Females were analysed for sporozoite positivity by CSP-ELISA. Resistance to permethrin and α-cypermethrin was measured using the CDC-bottle bioassay incorporating the synergist piperonyl-butoxide. Results: Several Anopheles species were found on the island, all belonging to the Anopheles gambiae sensu lato (s.l.) complex, including An. gambiae sensu stricto, Anopheles coluzzii, Anopheles melas, and An. gambiae/An. coluzzii hybrids. Endophagic Anopheles species composition and abundance showed strong seasonal variation, with a majority of An. gambiae (50% of adults collected) caught in June/July, while An. melas was dominant in November/December (83.9% of adults collected). Anopheles gambiae had the highest sporozoite rate in both seasons, with infection rates of 13.9% and 20% in June/July and November/December, respectively. Moderate frequencies of the West African kdr allele were found in An. gambiae (36%), An. coluzzii (35%), An. gambiae/An. coluzzii hybrids (42%). Bioassays suggest moderate resistance to α-cypermethrin, but full susceptibility to permethrin. Conclusions: The island of Bubaque maintained an An. gambiae s.l. population in both June/July and November/ December. Anopheles gambiae was the primary vector at the onset of the wet season, while An. melas is likely to be responsible for most dry season transmission. There was moderate kdr allele frequency and synergist assays suggest likely metabolic resistance, which could reduce the efficacy of LLINs. Future control of malaria on the islands should consider the seasonal shift in mosquito species, and should employ continuous monitoring for insecticide resistance.

Background Some people produce specific body odours that make them more attractive than others to mosquitoes, and consequently are at higher risk of contracting vector-borne diseases. The skin microbiome can break down carbohydrates, fatty acids and peptides on the skin into volatiles that mosquitoes can differentiate. Results Here, we examined how skin microbiome composition of women differs in relation to level of attractiveness to Anopheles coluzzii mosquitoes, to identify volatiles in body odour and metabolic pathways associated with individuals that tend to be poorly-attractive to mosquitoes. We used behavioural assays to measure attractiveness of participants to An. coluzzii mosquitoes, 16S rRNA amplicon sequencing of the bacteria sampled from the skin and gas chromatography of volatiles in body odour. We found differences in skin microbiome composition between the poorly- and highly-attractive groups, particularly eight Amplicon Sequence Variants (ASVs) belonging to the Proteobacteria, Actinobacteria and Firmicutes phyla. Staphylococcus 2 ASVs are four times as abundant in the highly-attractive compared to poorly-attractive group. Associations were found between these ASVs and volatiles known to be attractive to Anopheles mosquitoes. Propanoic pathways are enriched in the poorly-attractive participants compared to those found to be highly-attractive. Conclusions Our findings suggest that variation in attractiveness of people to mosquitoes is related to the composition of the skin microbiota, knowledge that could improve odour-baited traps or other next generation vector control tools.

IntroductionAs 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 analysisMATAMAL 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 ofPlasmodium 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 ofP. falciparumparasitaemia, 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 toP. falciparumand anopheline mosquitoes; vector parous rates, species composition, population density and sporozoite rates; prevalence of vector pyrethroid resistance; prevalence of artemisinin resistance inP. falciparumusing genomic markers; ivermectin’s impact on co-endemic diseases; coverage estimates; and the safety of combined MDA.Ethics and disseminationThe 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 numberNCT04844905.

The Water Administration System (WAS) is designed to be a management tool for irrigation schemes and water control offices that want to manage their water accounts and supply water to clients through canal networks, pipelines and rivers. The ultimate aim of WAS is to optimise irrigation water management and minimise management-related distribution losses in irrigation canals. This research projects focused on the implementation of the water release module of the WAS program at the Vaalharts irrigation scheme. The WAS consists of four modules that are integrated into a single program that can be used on a single PC or a multi-user environment. The four modules are an administration module, a water release module, water accounts module and a water request module. The first three modules are already implemented at Vaalharts, while module four is implemented only partially. This module links with the water request module and calculated water releases for the main canal and all its branches allowing for lag times and any water losses and accruals. To precisely calculate this water release, accurate data is needed to ensure that the correct volume of water is released into the canal network. This can be done by verifying existing data with field data. To optimise the management of the irrigation scheme the fully implemented WAS program need to be installed and running at the scheme. A series of data and calculation verifications need to be executed. The exercise will show the adequacy and correctness of the available database WAS uses to do the release calculation from. This will ensure improved management of the irrigation scheme, catchment and water resource sustainability. It is planned that the information generated from this project will be used in the compilation of integrated catchment management information system, currently underway at the Central university of Technology, Free State, South Africa. It is for this reason that all data should be verified, as trustworthy results and service through management can then be offered to the community and irrigation area.

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