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BACKGROUND The effectiveness of mosquito repellents, whether applied topically on the skin or released from a wearable device, is determined by the evaporation rate. This is because a repellent has to be present in the form of a vapour in the vicinity of the exposed skin that needs protection. Therefore, gravimetric techniques were used to investigate the direct evaporation of selected liquid repellents, their permeation through polymer films, and their release from a microporous polyethylene matrix. RESULTS Evaporation of a repellent into quiescent air is determined by its air permeability. This is a product of the vapour pressure and the diffusion coefficient, i.e. SA=PAitalicsatDA. It was found that repellents could be ranked in terms of decreasing volatility as: ethyl anthranilate > citriodiol > dimethyl phthalate > N,N‐diethyl‐meta‐toluamide (DEET) > decanoic acid > ethyl butylacetylaminopropionate > Icaridin. Experimental SA values, at 50 °C, ranged from 0.015 ± 0.008 mPa m2 s−1 for the least volatile repellent (Icaridin) to 0.838 ± 0.077 mPa m2 s−1 for the most volatile (ethyl anthranilate). The release rate from microporous polyethylene strands, produced by extrusion‐compounding into ice water baths followed a similar ranking. These strands featured an integral skin‐like membrane that covered the extruded strands and controlled the release of the repellent at a low effective rate. CONCLUSION The high thermal and thermo‐oxidative stability together with the low volatility of the mosquito repellents ethyl butylacetylaminopropionate and Icaridin make them attractive candidates for long‐lasting wearable mosquito‐repellent devices. Such anklets/bracelets may have utility for outdoor protection against infective mosquito bites in malaria‐endemic regions. © 2019 Society of Chemical Industry

Nanocomposite strands with mosquito repellent DEET or Icaridin incorporated in a poly(ethylene-co-vinyl acetate) (EVA) matrix, with either pyrogenic silica or an organoclay as a nanofiller, were prepared by a twin-screw extrusion compounding technique. The nature and levels of the repellent and nanofiller that was used affected the material phase morphology. The repellent release was followed as a function of aging time in convection ovens set at 30 and 50 C. The experimental release data of the mosquito repellent from the microporous polymer swellable matrix strands was mathematically modeled and fitted using a range of semi-empirical models. In the majority of case, the Korsmeyer-Peppas power law model provided the best data fit. As expected, the wide range of internal morphologies also resulted in quite different release profiles. These models were found to be valuable as they provided insights into the mechanism of repellent release from EVA swellable matrices. It was possible to differentiate between diffusion and relaxation mechanisms. Surprisingly, strands containing nominally more than 30 wt% Icaridin showed accelerating mass loss during the initial phase, consistent with Super Case II transport. Diffusional exponents as high as 1.81 were found. Furthermore, the internal microporous region of the extruded EVA strands was covered by a surface membrane that acted a diffusion barrier that, in effect, controlled the release rate of the mosquito repellents. Some of the investigated samples exhibited release profiles that suggest that longer lasting effective release of repellents is possible than currently achieved by available commercially products. K E Y W O R D S controlled release, microporous system, modeling, repellent 1 | INTRODUCTION Collectively, the mosquito-borne diseases of malaria, Dengue, Yellow fever, O'nyong-nyong fever, Zika and lymphatic filariasis (elephantiasis) are the single biggest cause of morbidity and mortality in humans. These mosquito-transmitted infections occur at the global scale and involve a wide range of viral and other pathogenic

Goats play a crucial role in improved livelihoods and food security in Africa. Indigenous and locally developed types exhibit a wide range of phenotypic diversity, but are commonly well adapted to the harsh environment in which they need to survive and produce. They have various functions in communities in developing countries, from providing food security to being a liquid form of cash and playing a role in ceremonial occasions. The Southern African goat population exceeds 35 million animals, most of which are kept in small-scale traditional production systems in communal areas. These traditional production systems are characterised by informal, lowly-skilled labour, small numbers of animals and limited resources. Most goats are part of mixed crop-livestock systems, where different livestock species and crop farming compliment one another. The productivity and offtake from these animals are relatively low. Some goats form part of agropastoral production systems, with marginally higher management and resource inputs. Both of these systems are dependent on a high degree of variability where the keepers/farmers can exploit various resources as and when necessary. Goats possess a range of adaptive mechanisms that enable them to deal with harsh and challenging environments, making them the ideal species for use in these production systems. This chapter aims to provide background information on the current smallholder management practices of goat keepers in Southern Africa.