Environment In Sub-Saharan Africa Research Articles

Can Climate Shocks Make Vulnerable Subjects More Willing to Take Risks?

While economists in the past tended to assume that individual preferences, including risk preferences, are stable over time, a recent literature has developed and indicates that risk preferences respond to shocks, with mixed evidence on the direction of the responses. This paper utilizes a natural experiment with covariate (drought) and idiosyncratic shocks in combination with an independent field risk experiment. The risk experiment uses a Certainty Equivalent-Multiple Choice List approach and is played 1–2 years after the subjects were (to a varying degree) exposed to a covariate drought shock or idiosyncratic shocks for a sample of resource-poor young adults living in a risky semi-arid rural environment in Sub-Saharan Africa. The experimental approach facilitates a comprehensive assessment of shock effects on experimental risk premiums for risky prospects with varying probabilities of good and bad outcomes. The experiment also facilitates the estimation of the utility curvature in an Expected Utility (EU) model and, alternatively, separate estimation of probability weighting and utility curvature in three different Rank Dependent Utility models with a two-parameter Prelec probability weighting function. Our study is the first to comprehensively test the theoretical predictions of Gollier and Pratt (Econom J Econom Soc 64:1109–1123, 1996) versus Quiggin (Econ Theor 22(3):607–611, 2003). Gollier and Pratt (1996) build on EU theory and state that an increase in background risk will make subjects more risk averse while Quiggin (2003) states that an increase in background risk can enhance risk-taking in certain types of non-EU models. We find strong evidence that such non-EU preferences dominate in our sample.

Contribution of genes related to grain number (Gn1a and WFP) introgressed into NERICA 1 to grain yield under tropical highland conditions in central Kenya

ABSTRACT In Kenya and many other African countries, improving rice productivity is vital for future food security. To improve rice productivity in Kenya, near-isogenic lines (NIL) were developed by introducing Gn1a and WFP, genes that function to increase grain number per panicle by increasing secondary and primary rachis-branches, into NERICA 1, a registered variety in Kenya. The aim of this study was to determine whether the introduction of these genes has the potential to improve rice productivity under tropical highland conditions in central Kenya. Field experiments were conducted in 2016 and 2017 at a lowland rice field in Mwea, Kenya, under different nitrogen fertilization conditions using three lines of NERICA 1 introgressed with Gn1a and/or WFP (NIL-Gn1a, NIL-WFP, and NIL-Gn1a+WFP) and their recurrent parents, NERICA 1. Two years of field experiments revealed that the introgression lines enhanced grain yield by increasing the number of primary and secondary rachis-branches and the number of grains per panicle. Gn1a and WFP showed additive effects and the introgression of both genes alleviated the negative effects on yield components observed in the introgressed lines, resulting in higher grain yield. Sufficient nitrogen fertilization was required to increase yield in the single-gene introgression lines. However, the line with both Gn1a and WFP achieved reasonable yields even under low fertilizer conditions in Mwea, Kenya. As these introgression lines have similar growing characteristics to their parent variety, they are expected to contribute to increased rice production in Kenya and similar environments in sub-Saharan Africa.

Quantitative assessment of aflatoxin exposure and hepatocellular carcinoma (HCC) risk associated with consumption of select Nigerian staple foods

Aflatoxin contamination of staple grains and legumes has been linked to hepatocellular carcinoma (HCC) and other adverse health outcomes, constituting a substantial public health concern globally. Low-resource food environments in sub-Saharan Africa are often under-regulated and are particularly vulnerable to adverse health and nutrition outcomes associated with aflatoxin exposure. This study identifies levels of HCC risk in the northern Nigerian adult population, leveraging a systematic review of available evidence on aflatoxin contamination in Nigerian maize, groundnut, rice, cowpea, and soybean. Estimated dietary intake (EDI) was computed using publicly available dietary consumption data and a probabilistic quantitative risk assessment was conducted to determine the relative risk of HCC associated with consumption of selected aflatoxin-contaminated commodities. In total, 41 eligible studies reporting aflatoxin contamination were used to model the distribution of aflatoxin concentrations in Nigerian commodities. EDIs for maize, groundnut, rice, and cowpea exceeded the provisional maximum tolerable daily intake (PMTDI) level of 1 kgbw-1 day-1, with maize yielding the highest mean EDI (36.7 kgbw-1 day-1). The quantitative risk assessment estimated that 1.77, 0.44, 0.43, 0.15, and 0.01 HCC cases per year/100,000 population were attributable to aflatoxin exposure through maize, groundnut, rice, cowpea, and soybean, respectively. Sensitivity analysis revealed that aflatoxin concentration, dietary consumption levels, consumption frequency, and other variables have differing relative contributions to HCC risk across commodities. These findings constitute a novel multi-study risk assessment approach in the Nigerian context and substantiate existing evidence suggesting that there is reason for public health concern regarding aflatoxin exposure in the Nigerian population.

Economic growth, international trade, and environmental degradation in Sub-Saharan Africa

PurposeThis study investigates the relationship between economic growth, international trade, and environmental degradation in Sub-Saharan Africa (SSA), focusing on the validity of the environmental Kuznets hypothesis (EKC), the pollution havens hypothesis (PHH), and the factor endowment hypothesis (FEH).Design/methodology/approachThe study uses annual data for 41 SSA countries between 1990 and 2017 and employs the bias-corrected least square dummy variable (LSDVC) estimation techniques. Environmental degradation is indicated by carbon dioxide (CO2), delicate particulate matter (PM2.5) emissions, and deforestation.FindingsThe results confirm the validity of the EKC hypothesis for PM2.5 emissions and deforestation but not for CO2 emissions. The results also indicate that international trade reduces deforestation and that both the PHH and FEH are valid for CO2 emission but not for PM2.5 emissions and deforestation.Practical implicationsIn this paper, the authors are able to illustrate that both economic growth and international trade can harm the environment if unchecked. Therefore, the conclusion of this study offers policy options through which SSA countries can achieve desired economic growth goals without affecting environmental quality. The study can be a benchmark for environmental policy in the region.Originality/valueThe authors provide an in-depth discussion of the growth-trade-environmental degradation nexus in SSA. The EKC, PHH, and FEH’s validity confirm that economic growth remains a threat to the local natural environment in SSA. Hence, the need for a trade-off between economic growth needs and environmental degradation and understanding where to compromise to achieve SSA's economic development priorities.

Genetic Potential of New Maize Inbred Lines in Single-Cross Hybrid Combinations under Low-Nitrogen Stress and Optimal Conditions

Maize (Zea mays, L.) productivity in sub-Saharan Africa (SSA) remains low, despite breeding efforts spanning across decades. Currently, three-way cross hybrids (TWCH) dominate SSA; however, there is the potential to increase yields by using single-cross hybrids. In this study, five new and four elite CIMMYT lines were inter-mated in a half diallel mating scheme to estimate the combining ability of the lines and to determine the stability of their corresponding 36 single-cross hybrids for grain yield under low-nitrogen stress and optimum growing conditions in Zimbabwe and Zambia. The results revealed that the new inbred line CL121290 showed the highest GCA effects under optimum conditions (1.4 tha−1; p < 0.001) and across sites (0.93 tha−1; p < 0.001). The single-cross hybrids G12 (CML311 × DJL173527) and G16 (DJL173887 × CL1211559) were highly stable and were observed as ideal crosses within both the low-nitrogen and optimal environments. However, G18 (CML311 × DJL173887), which was depicted as ideal genotype under the two management conditions, was an unstable genotype. Hybrid G31 (CML311 × CML312) had the least grain yield under low-nitrogen, optimum and across environments. The hybrid G11 (DJL173527 × CL121290) was the highest yielding genotype amongst the new single-cross hybrids and across environments but was unstable and can be recommended for high potential in environments. Overall, the data demonstrated the potential of single-cross hybrids to supplement TWCH in boosting maize productivity under optimal and nitrogen-stress environments in SSA as well as under other areas with similar climatic conditions in the world.

Drought tolerance assessment of citron watermelon (Citrullus lanatus var. citroides (L.H. Bailey) Mansf. ex Greb.) accessions based on morphological and physiological traits

Long-term cultivation of citron watermelon under water-constrained environments in sub-Saharan Africa resulted in the selection and domestication of highly tolerant genotypes. However, information on the magnitude of variation for drought tolerance in citron watermelon is limited for the effective selection of suitable genotypes for breeding. The objective of this study was to determine variation for drought tolerance among South African citron watermelon landrace accessions for selection and use as genetic stock for drought-tolerance breeding in this crop and closely-related cucurbit crops. Forty genetically differentiated citron watermelon accessions were grown under non-stress (NS) and drought-stress (DS) conditions under glasshouse environment. Data of physiological (i.e., leaf gas exchange and chlorophyll fluorescence parameters) and morphological traits (i.e., shoot and root system architecture traits, and fruit yield) were collected and subjected to various parametric statistical analyses. The accessions varied significantly for assessed traits under both NS and DS conditions which aided classification into five groups, namely; A (highly drought-tolerant), B (drought-tolerant), C (moderate drought-tolerant), D (drought-sensitive) and E (highly drought-sensitive). Drought-tolerant genotypes produced more fruit yield with less water compared with drought-sensitive genotypes. Several physiological and morphological parameters correlated with fruit yield under DS condition namely: instantaneous water-use efficiency (r = 0.97), leaf dry weight (r = 0.77), total root length (r = 0.46) and root dry weight (r = 0.48). The following accessions, namely: WWM-46, WWM-68, WWM-41(A), WWM-15, WWM-64, WWM-57, WWM-47, WWM-37(2), WWM-79, WWM-05 and WWM-50) were identified as highly drought-tolerant and recommended for drought-tolerance breeding in this crop or related cucurbit crops such as sweet dessert watermelon.

Pathways of resilience: Predicting school engagement trajectories for South African adolescents living in a stressed environment

School engagement is associated with the resilience of adolescents living in stressed environments in sub-Saharan Africa. Even so, there is scant understanding of the antecedents of African students’ school engagement. In response, this article reports the results of an exploratory study conducted in 2018 and 2020 with a sample of 172 adolescents (average age: 16.02 years; SD = 1.67) from a risk-exposed municipality in South Africa. Clustered school engagement trajectories were identified using a longitudinal variant of k-means based on affective, behavioural, and cognitive school engagement. Evolutionary classification trees were used to identify meaningful predictors of the identified trajectories. The results point to specific combinations of factors – i.e., student age, parental/caregiver warmth, school resource levels, teacher competence – that sustained low and high school engagement trajectories. These combinations direct the attention of school psychologists and other service providers to the multiple systems that matter in varying ways for the school engagement of African students. They also call for continued investigation of the resource combinations that are salient to student engagement across stressed environments in sub-Saharan Africa.

Linkages between Agricultural Diversification, Dietary Diversity, and Nutrition Outcomes in Sub-Saharan Africa: A Systematic Review

An enabling policy environment and good governance are fundamental drivers for agriculture and food systems, framing how they work and for whom in the global efforts to achieve Sustainable Development Goal 2 and food justice for all. The review examined the policy environment in sub-Saharan Africa in relation to linkages between agricultural diversification, dietary diversity, and nutrition. The systematic review of literature entailed searching Ovid MEDLINE, PubMed, Embase, African Journals Online and PsychINFO databases from Jan 1, 2010, to Feb 30, 2021, for eligible studies and technical reports. Publications reporting on agricultural diversification, dietary diversity, and nutrition outcomes in relation to policy environment were included. Qualitative synthesis of the abstracted evidence was conducted. SSA countries recognise the crucial role of agricultural diversification as a pathway to achieving food security with increasing emphasis on smallholder farmers. There is a rich base of policies that are complemented by lived experiences and best practices which can strengthen linkages between agricultural diversification, agribusiness and dietary diversity. For instance, the application of precision farming, agro-ecological zones targeted agricultural intensification and gender sensitive land administration, access and tenure in countries experiencing declining farm size could potentially ensure the youth, men and women have equitable and innovative opportunities of access to elements of improved agricultural systems. Smallholder farmers with the majority in rural settings, maintain de facto agricultural diversity. It is essential for any policy design or intervention to take into account the specific country’s context; pay particular attention to socioeconomic capabilities of the rural population along with fiscal capacity and trade-offs. Empirical evidence on the nexus between agricultural diversification and nutrition is mixed and limited.

A framework for assessing the effects of shock events on livestock and environment in sub-Saharan Africa: The COVID-19 pandemic in Northern Kenya

CONTEXTLivestock are the primary source of greenhouse gas (GHG) emissions from agriculture in most African countries, but there is a paucity of baseline data and monitoring of GHG emissions from livestock in Africa, particularly for extreme or shock events. The COVID-19 pandemic represents a novels shock to livestock systems and may result in indirect effects on livestock emissions and other Sustainable Development Goals (SDGs). Due to the pandemic in 2020, extensive pastoralist livestock systems in Northern Kenya were subjected to restrictions on movement, increased costs of transportation, and closure of livestock markets. OBJECTIVEThe objective of this study was to assess the indirect effects of the COVID-19 pandemic on GHG emissions from livestock systems in Northern Kenya using proxy data and a three-part framework based on changes in 1) herd size, 2) feed availability, and 3) livestock movement. METHODSWe evaluated changes in GHG emissions from livestock systems in Northern Kenya due to the COVID-19 pandemic based on proxy data from crowd-sourced market data, household panel surveys, and remote sensing data on Normalized Difference Vegetation Index (NDVI). Proxy data were obtained before the pandemic in 2019 and after the pandemic in 2020 to compare between years and evaluate the indirect effects of the pandemic and associated restrictions on livestock GHG emissions using the three-part framework. RESULTS AND CONCLUSIONSOverall GHG emissions from livestock in Northern Kenya have decreased due to the pandemic and this was largely driven by reductions in herd size. This reduction in GHG emissions occurred despite an increase in GHG emissions from livestock associated with higher feed availability. Decreased livestock movement due to the pandemic contributed to reductions in GHG emissions from livestock, but such reductions were likely to be small due to limited need for livestock to travel longer distances under the prevailing conditions of high feed availability. SIGNIFICANCEThis research shows that assessments of changes in GHG emissions from livestock systems due to shock events can be conducted successfully based on proxy data and the three-part framework developed here. We found that shock events, such as the COVID-19 pandemic, may lead to unexpected results with respect to the direction and magnitude of changes in livestock emissions depending on contextual factors and environmental conditions. Thus, we call for more spatially explicit and continued data collection to assess and monitor the consequences of shock events on GHG emissions from livestock and related SDGs in Africa.

Design and sizing of a brewery wastewater treatment system in Douala, Cameroon: a technological solution for the protection of the environment in Sub-Saharan Africa

This article aims to design a wastewater treatment plant (WWTP) for brewery industry located in Douala-Cameroon (Central Africa) that can be applicable in Sub-Saharan Africa in similar affinity pattern. More specifically, to characterise wastewater, operate a technical choice for wastewater treatment and to design a WWTP infrastructures. Data were obtained through measurements of the flow of wastewater by the volumetric method and water quality data were collected at the outlet point of the brewery company by sampling and laboratory analysis using standard methods. The main results show that the Chemical Oxygen Demand–COD (1082 mg/l), the Biochemical Oxygen Demand–BOD5 (466 mg/l), the amount of faecal coliforms and of total coliforms (respectively, 0.99 and 6.77 million UFC/100 ml) norms in wastewater are above the Cameroonians and World Health Organisation (WHO) standards for waste disposal. The treatment technology “bacterial bed” was considered the most suitable to treat the brewery wastewater. It has a rate of flow estimated at 2700 m3 per day. The WWTP has seven components, including a sieve (meshes 0.5 cm), a deoiler (ventilation power 3400 Watts), a lamellate decanter (volume 1165 m3), a bacterial bed (cloisonyl, height 2.5 m and surface 676 m2), a second lamellate decanter with processing of calco-carbonic balance (Consumption CO2 81.07 Nm3, diameter 25 m), a bio-digester, a basin of disinfection (surface 338 m2, rate of processing 0.65 g/m3, flow of injection 12 l/h). The construction of this WWTP will enable the improvement of environmental protection around the company and hence, the city of Douala in Sub-Saharan Africa.

What determines students' behavioural intention to use mobile learning management systems Empirical answers from a blended environment in Sub-Saharan Africa

What determines students' behavioural intention to use mobile learning management systems Empirical answers from a blended environment in Sub-Saharan Africa

What determines students' behavioural intention to use mobile learning management systems Empirical answers from a blended environment in Sub-Saharan Africa

What determines students' behavioural intention to use mobile learning management systems Empirical answers from a blended environment in Sub-Saharan Africa

Decolonising religious education in sub-Saharan Africa through the prism of anticolonialism: a conceptual proposition

ABSTRACT Through the lens of an anticolonial (as opposed to postcolonial) analytical framework, this conceptual paper examines decolonising efforts (and failures) in Religious Education (RE) as a school subject in post-independent sub-Saharan Africa. It critiques the missionary/European epistemological hegemony that continues to render RE a colonial rather than a postcolonial project. Beyond rhetoric of the impact of colonialism, the paper laments the perversity of a ‘colonial caged mentality’ affecting the conceptualisation of RE in what is supposed to be a postcolonial milieu in which Africans should design school curricula that suit their particular needs. It calls for the re-conceptualisation of RE de-linked from colonial/Eurocentric thought patterns and presents an ‘envisioned’ decolonised RE (post-confessional, inclusive and multi-faith) that speaks to the political and socio-cultural reality of a postcolonial environment in sub-Saharan Africa. The argument in this paper is that sub-Saharan Africa should yearn for a paradigm shift not only to ensure the decolonisation of the RE curriculum, but also crucially to challenge embedded colonial residues inherent in stakeholders ‘manning the gates’ ensuring that decolonised RE is supported and implemented effectively in the curriculum and schools.

Modelling climate change impacts on maize yields under low nitrogen input conditions in sub-Saharan Africa.

Smallholder farmers in sub-Saharan Africa (SSA) currently grow rainfed maize with limited inputs including fertilizer. Climate change may exacerbate current production constraints. Crop models can help quantify the potential impact of climate change on maize yields, but a comprehensive multimodel assessment of simulation accuracy and uncertainty in these low-input systems is currently lacking. We evaluated the impact of varying [CO2 ], temperature and rainfall conditions on maize yield, for different nitrogen (N) inputs (0, 80, 160kgN/ha) for five environments in SSA, including cool subhumid Ethiopia, cool semi-arid Rwanda, hot subhumid Ghana and hot semi-arid Mali and Benin using an ensemble of 25 maize models. Models were calibrated with measured grain yield, plant biomass, plant N, leaf area index, harvest index and in-season soil water content from 2-year experiments in each country to assess their ability to simulate observed yield. Simulated responses to climate change factors were explored and compared between models. Calibrated models reproduced measured grain yield variations well with average relative root mean square error of 26%, although uncertainty in model prediction was substantial (CV=28%). Model ensembles gave greater accuracy than any model taken at random. Nitrogen fertilization controlled the response to variations in [CO2 ], temperature and rainfall. Without N fertilizer input, maize (a) benefited less from an increase in atmospheric [CO2 ]; (b) was less affected by higher temperature or decreasing rainfall; and (c) was more affected by increased rainfall because N leaching was more critical. The model intercomparison revealed that simulation of daily soil N supply and N leaching plays a crucial role in simulating climate change impacts for low-input systems. Climate change and N input interactions have strong implications for the design of robust adaptation approaches across SSA, because the impact of climate change in low input systems will be modified if farmers intensify maize production with balanced nutrient management.

Electricity access, human development index, governance and income inequality in Sub-Saharan Africa

Consistent with the Sustainable Development Goal 7 of ensuring access to clean and modern energy technologies, this study examined the nexus between access to electricity, human development index, political system environment, income level, and income inequality. We employed a nonparametric regression technique with Driscoll–Kraay standard errors from 1990 to 2017 in Sub-Saharan Africa. The study revealed that income inequality has a negative effect on access to electricity whereas income level and human development have a positive impact on access to electricity. Enhancing the political system environment in Sub-Saharan Africa is crucial to ensuring access to clean and modern electricity. The negative effect of political system on income inequality means that good governance environment reduces income inequality. Income inequality is found to reduce human development, as such, social protection policies that reduce poverty are essential to minimize the vulnerability to poverty. The study highlights that the effective promotion of labor markets and the improvement of socio-economic capacity to manage unemployment, infirmity, and disability will decrease income inequality, hence, promote human development.

On-farm performance and farmers’ participatory assessment of new stress-tolerant maize hybrids in Eastern Africa

The development and deployment of high-yielding stress tolerant maize hybrids are important components of the efforts to increase maize productivity in eastern Africa. This study was conducted to: i) evaluate selected, stress-tolerant maize hybrids under farmers’ conditions; ii) identify farmers’ selection criteria in selecting maize hybrids; and iii) have farmers evaluate the new varieties according to those criteria. Two sets of trials, one with 12 early-to-intermediate maturing and the other with 13 intermediate-to-late maturing hybrids, improved for tolerance to multiple stresses common in farmers’ fields in eastern Africa (drought, northern corn leaf blight, gray leaf spot, common rust, maize streak virus), were evaluated on-farm under smallholder farmers’ conditions in a total of 42 and 40 environments (site-year-management combinations), respectively, across Kenya, Uganda, Tanzania and Rwanda in 2016 and 2017. Farmer-participatory variety evaluation was conducted at 27 sites in Kenya and Rwanda, with a total of 2025 participating farmers. Differential performance of the hybrids was observed under low-yielding (<3 t ha−1) and high-yielding (>3 t ha−1) environments. The new stress-tolerant maize hybrids had a much better grain-yield performance than the best commercial checks under smallholder farmer growing environments but had a comparable grain-yield performance under optimal conditions. These hybrids also showed better grain-yield stability across the testing environments, providing an evidence for the success of the maize-breeding approach. In addition, the new stress- tolerant varieties outperformed the internal genetic checks, indicating genetic gain under farmers’ conditions. Farmers gave high importance to grain yield in both farmer-stated preferences (through scores) and farmer-revealed preferences of criteria (revealed by regressing the overall scores on the scores for the individual criteria). The top-yielding hybrids in both maturity groups also received the farmers’ highest overall scores. Farmers ranked yield, early maturity, cob size and number of cobs as the most important traits for variety preference. The criteria for the different hybrids did not differ between men and women farmers. Farmers gave priority to many different traits in addition to grain yield, but this may not be applicable across all maize-growing regions. Farmer-stated importance of the different criteria, however, were quite different from farmer- revealed importance. Further, there were significant differences between men and women in the revealed-importance of the criteria. We conclude that incorporating farmers’ selection criteria in the stage-gate advancement process of new hybrids by the breeders is useful under the changing maize-growing environments in sub-Saharan Africa, and recommended to increase the turnover of new maize hybrids.

Research agenda for preventing mosquito-transmitted diseases through improving the built environment in sub-Saharan Africa

ABSTRACT Mosquito-transmitted diseases are a major threat to health in sub-Saharan Africa, but could be reduced through modifications to the built environment. Here we report findings from a major workshop held to identify the research gaps in this area, namely: (1) evidence of the health benefits to changes to the built environment, (2) understanding how mosquitoes enter buildings, (3) novel methods for reducing mosquito-house entry, (4) sustainable approaches for reducing mosquito habitats, (5) case studies of micro-financing for healthy homes and (6) methods for increasing scale-up. Multidisciplinary research is essential to build out mosquito-transmitted diseases, and not build them in.

Impact of substrate type, depth and retention time on organic matter removal in vertical subsurface flow constructed wetland mesocosms for treating slaughterhouse wastewater

Population growth and the associated demand for meat products is creating an increasing concern on water over slaughterhouse associated pollution of aquatic environments in Sub-Saharan Africa. In Kenya, increasing volumes of strong slaughterhouse wastewater being discharged either untreated or partially treated has necessitated ardent research into sustainable technologies. Vertical sub-surface flow constructed wetlands offer a promising solution. A study investigating the effect of depth, time and substrate variation on organic matter removal from slaughterhouse wastewater was conducted using vertical sub-surface flow constructed wetlands. Experimental out-door mesocosms designed as cylindrical metal tanks of variable depth and substrate were set up at Egerton University, Kenya. Results showed that organic matter removal was highest at 5 day retention time, with removals of about 50%, 55% and 82% for BOD5, COD and TSS respectively. Deeper (0.8 m depth) mesocosms were noted to have significant differences in treatment for TSS and NH4–N compared to shallow (0.65 m) mesocosms. Sand substrate was observed to perform better in BOD5 and TSS reduction compared to quarry dust and gravel. Increase in substrate size was observed to increase removal efficiency of NH4–N at longer retention time. However, effluent concentration of NH4–N fluctuated with removal efficiency averaging at 26.5%. The study demonstrated that vertical sub-surface flow constructed wetlands operated at a longer retention time of 5 days; with intermittent wastewater feeding, facilitated over 50% removal of organic matter in slaughterhouse wastewater.

Five years following first detection of Anopheles stephensi (Diptera: Culicidae) in Djibouti, Horn of Africa: populations established-malaria emerging.

The Asian malaria mosquito, Anopheles stephensi, is a well-known and important vector of Plasmodium falciparum and P. vivax. Until 2013, its geographical distribution was confined to central and southern Asia including the Arabian Peninsula. In the Horn of Africa (HoA) Region, An. stephensi was first recorded from Djibouti in 2012, when it was linked geographically and temporally with an unusual outbreak of urban P. falciparum malaria. In 2016, An. stephensi was detected in the neighbouring Somali Region of Ethiopia. In order to determine whether An. stephensi populations have become established in Djibouti and contributed to the unusual rise in local malaria cases there, we carried out continuous vector surveillance from January 2013 to December 2017, investigated seasonal changes in An. stephensi population densities and bionomics, analysed available literature describing malaria in Djibouti since 2013, and investigated whether An. stephensi may have contributed to local malaria transmission by detecting circumsporozoite antigen of P. falciparum and P. vivax in female anophelines. From 2013 to 2016, seasonal activity of An. stephensi in urban Djibouti City primarily occurred during the colder, wetter season between September and May, with either no or rare trap catches from June to August. Unlike past years, this species was detected year-round, including the extremely hot summer months of June to August 2017. This change in seasonal occurrence may indicate that An. stephensi populations are adapting to their new environment in sub-Saharan Africa, facilitating their spread within Djibouti City. Among the 96 female An. stephensi investigated for malaria infectivity, three (3.1%) were positive for P. falciparum circumsporozoite antigen, including one P. falciparum/P. vivax VK 210 double infection. Subsequent to the unusual resurgence of local malaria in 2013, with 1684 confirmed cased reported for that year, malaria case numbers increased continuously, peaking at 14,810 in 2017. Prior to 2016, only P. falciparum malaria cases had been reported, but in 2016, autochthonously acquired P. vivax malaria cases occurred for the first time at a rate of 16.7% among all malaria cases recorded that year. This number increased to 36.7% in 2017. Our data indicate that the dynamics of malaria species in Djibouti is currently changing rapidly, and that An. stephensi can be involved in the transmission of both P. falciparum and P. vivax, simultaneously. Considering the extremely high potential impact of urban malaria on public health, the timely deployment of optimal multinational vector surveillance and control programs against An. stephensi is strongly recommended, not only for the HoA Region, but for the entire African continent.

Recurrent Cholera Outbreaks in Sub-Saharan Africa: Moving beyond Epidemiology to Understand the Environmental Reservoirs and Drivers

Recurrent cholera outbreaks in sub-Saharan Africa (SSA) attracted a lot of research interest, raising questions about the effectiveness of current prevention and control methods. However, research on cholera and other water-borne diseases in Africa is dominated by epidemiological studies, while investigations on the environmental drivers and reservoirs of cholera remain scarce. The current discourse relating cholera to the environment in SSA is often limited to the rudimentary statement that, “cholera is caused by the consumption of contaminated water and food”. Yet, beyond this simplistic view, literature elsewhere shows that cholera outbreaks are controlled by its complex interactions with environmental drivers and reservoirs. This brings to question whether cholera can be eradicated in SSA without understanding these complex interactions. The current review seeks to (1) highlight the nature and dynamics of recent cholera outbreaks in SSA, (2) discuss the importance of environmental reservoirs of Vibrio cholerae, and anthropogenic and hydroclimatic drivers in controlling the dynamics of cholera outbreaks, and (3) highlight key knowledge gaps and future research directions, and the need to harness emerging research tools such as modeling, machine learning, data mining, and genomics techniques to better understand the cholera dynamics. By bringing to fore these often-overlooked issues in cholera research, we seek to stimulate discussion, and promote a shift toward cross-disciplinary research on cholera and other water-borne diseases in SSA and beyond.