Modelling the elimination of river blindness using long-term epidemiological and programmatic data from Mali and Senegal

The onchocerciasis transmission models EPIONCHO and ONCHOSIM have been independently developed and used to explore the feasibility of eliminating onchocerciasis from Africa with mass (annual or biannual) distribution of ivermectin within the timeframes proposed by the World Health Organization (WHO) and endorsed by the 2012 London Declaration on Neglected Tropical Diseases (i.e. by 2020/2025). Based on the findings of our previous model comparison, we implemented technical refinements and tested the projections of EPIONCHO and ONCHOSIM against long-term epidemiological data from two West African transmission foci in Mali and Senegal where the observed prevalence of infection was brought to zero circa 2007–2009 after 15–17 years of mass ivermectin treatment. We simulated these interventions using programmatic information on the frequency and coverage of mass treatments and trained the model projections using longitudinal parasitological data from 27 communities, evaluating the projected outcome of elimination (local parasite extinction) or resurgence. We found that EPIONCHO and ONCHOSIM captured adequately the epidemiological trends during mass treatment but that resurgence, while never predicted by ONCHOSIM, was predicted by EPIONCHO in some communities with the highest (inferred) vector biting rates and associated pre-intervention endemicities. Resurgence can be extremely protracted such that low (microfilarial) prevalence between 1% and 5% can be maintained for 3–5 years before manifesting more prominently. We highlight that post-treatment and post-elimination surveillance protocols must be implemented for long enough and with high enough sensitivity to detect possible residual latent infections potentially indicative of resurgence. We also discuss uncertainty and differences between EPIONCHO and ONCHOSIM projections, the potential importance of vector control in high-transmission settings as a complementary intervention strategy, and the short remaining timeline for African countries to be ready to stop treatment safely and begin surveillance in order to meet the impending 2020/2025 elimination targets

Risk factors for house-entry by malaria vectors in a rural town and satellite villages in The Gambia.

Background: In the pre-intervention year of a randomized controlled trial investigating the protective effects of house screening against malaria-transmitting vectors, a multi-factorial risk factor analysis study was used to identify factors that influence mosquito house entry. Methods: Mosquitoes were sampled using CDC light traps in 976 houses, each on one night, in Farafenni town and surrounding villages during the malaria-transmission season in The Gambia. Catches from individual houses were both (a) left unadjusted and (b) adjusted relative to the number of mosquitoes caught in four sentinel houses that were operated nightly throughout the period, to allow for night-to-night variation. Houses were characterized by location, architecture, human occupancy and their mosquito control activities, and the number and type of domestic animals within the compound. Results: 106,536 mosquitoes were caught, of which 55% were Anopheles gambiae sensu lato, the major malaria vectors in the region. There were seven fold higher numbers of An. gambiae s.l. in the villages (geometric mean per trap night = 43.7, 95% confidence intervals, CIs = 39.5–48.4) than in Farafenni town (6.3, 5.7–7.2) and significant variation between residential blocks (p < 0.001). A negative binomial multivariate model performed equally well using unadjusted or adjusted trap data. Using the unadjusted data the presence of nuisance mosquitoes was reduced if the house was located in the town (odds ratio, OR = 0.11, 95% CIs = 0.09–0.13), the eaves were closed (OR = 0.71, 0.60–0.85), a horse was tethered near the house (OR = 0.77, 0.73–0.82), and churai, a local incense, was burned in the room at night (OR = 0.56, 0.47–0.66). Mosquito numbers increased per additional person in the house (OR = 1.04, 1.02–1.06) or trapping room (OR = 1.19, 1.13–1.25) and when the walls were made of mud blocks compared with concrete (OR = 1.44, 1.10–1.87). Conclusion: This study demonstrates that the risk of malaria transmission is greatest in rural areas, where large numbers of people sleep in houses made of mud blocks, where the eaves are open, horses are not tethered nearby and where churai is not burnt at night. These factors need to be considered in the design and analysis of intervention studies designed to reduce malaria transmission in The Gambia and other parts of sub-Saharan Africa

Journal of African Christian Biography: v. 3, no. 1

A publication of the Dictionary of African Christian Biography with U.S. offices located at the Center for Global Christianity and Mission at Boston University. This issue focuses on: 1. “Creole Saga”: The Gambia’s Liberated African Community in the 19th Century: The Stories of J. A. B. Horton, G. C. Nicol, J. R. Maxwell, and J. D. Richards by Asi Florence Mahoney. Introduction by Gabriel Leonard Allen. 2. The Contribution of Daniel William Alexander to the Birth and Growth of Eastern Orthodoxy in East Africa. 3. Biographies by Stephan Hayes and Louise Pirouet. Introduction by Fr. Evangelos Thiani. 4. Recent Print and Digital Resources Related to Christianity in Africa

Utilization of ‘swamp’ rice fields by members of the anopheles Gambiae complex in Gambia

Background Whilst it is well known that rice production in Africa increases the production of Anopheles gambiae mosquitoes, most studies have investigated this in irrigation schemes. Here I examine the colonisation of 'swamp' rice fields by An. gambiae mosquitoes in The Gambia and examine some of the factors responsible for the presence and absence of these vectors in field and semi-field conditions. This work is of relevance to large-scale larval control programmes that have identified rice fields as a major source of malaria vectors in The Gambia.Methods Larval and adult mosquito surveys were carried out in rice fields near Tamba Koto village in rural Gambia from June to January, 2006, a period that included the wet season, the period of most malaria transmission. Three transects each 500m long and 200m apart situated on the edge of the River Gambia floodplains were routinely surveyed. Larval sampling using area sampler and dippers was done at regular intervals along each transect. Adult sampling with emergence traps placed over water. I compared three different water treatments that were commonly found under field conditions in Gambian rice fields: the presence of algae, cow dung and urea. The number of larvae and pupae were counted daily for 14 days in 16 artificial breeding sites of plastic bowls filled with tap water, each with a different treatment and an untreated control bowl. This trial was repeated four times over 12 weeks period.Results Three hundred and seventy-five (375) anopheline larvae were caught during the larval survey in the field, with 349 larvae (93%) collected within the first 350m from the landward edge of the paddy fields. Out of the An. gambiae complex collected, 36 (45%) were An. arabiensis, 23 (29%) were An. gambiae sensu stricto and 21 (26%) were An. melas. A total of 263 adult mosquitoes were collected during the adult emergence study. Sixty - eight belonged to the An. gambiae complex, 139 were culicines, 30 were Aedes, and 26 were anophelines which could not be identified by Polymerase Chain Reaction. Out of the 68 An. gambiae sensu lato, 61 were An. arabiensis, 4 were An. gambiae s.s. and 1 was An. melas. Of the 68 An. gambiae s.l. caught, 62 (91.1%) were caught along the edges of rice fields. Although fish are common and evident animals in rice fields, there have been relatively few studies on the ecology of indigenous species. We did not find fish in any of the sampling points within 350m of the village, but did find them far away close to the river.A total of 17,467 mosquito larvae were collected from 16 bowls during four months of the semi field trial. Of these 75% were early instars and 25% late instars. Of the total number of mosquito larvae sampled, 6,233 (36.7%) were identified as anopheline and 11,234 (63.3%) culicine. Of the anophehnes sampled, 5164 (83%) were early instars whilst 1069 (17%) were late instars. Field surveys showed that paddies closest to the land had no fish and were rich in cow dung.More anopheline larvae were produced from cow dung treatments (n=l,718; 33.3%) and, bowls treated with algae (n=l,453; 28.1%) compared to water alone (n=l,064; 21%).Similar numbers were found in bowls with urea (n=929; 18%) compared with water alone. Similar trends were observed for culicine larvae. Out of 8,021 early stage larvae,2,675 (33%) were found in bowls with cow dung, 2,554 (32%) from algae, 1,532 (19%)) from water alone and 1,260 from urea (16%).One hundred and thirty-eight adult mosquitoes of An. gambiae complex were identified. Fifty-nine were An. gambiae s.s., 74 were An. arabiensis and 2 An. melas. Out of 59 An. gambiae s.s., 24 (41%) were recorded from cow dung treatments and 21 (36%) from algae treatments. Of the 74 An. arabiensis, 35 (47%)) were recorded form cow dung whilst 28 (38%) were from algae. This result indicated that both cow dung and filamentous algae supported production and development of An. gambiae complex. Discussion Anopheles arabiensis was the dominant member of the An. gambiae complex in the study area. Nearly all breeding of both An. gambiae complex species and culicines took place in rice paddies within 350m zones from the edge of the paddies closest to human settlement. Both types of mosquitoes were collected together and were more likely to be found on the edges of paddies compared to the centres. Most aquatic invertebrates were also more frequently found in rice fields close to villages. In contrast, fish were more common in rice fields close to the river. It is impossible to be certain that fish are important predators of mosquitoes in this setting since mosquitoes may simply colonise different habitats to fishes. Here the paddies containing highest numbers of mosquitoes were situated closest to the village and were demarcated by raised embankments to prevent salt water encroachment, which could have also prevented fish from getting in them. Both cow dung (Organic manure) and algae (Biofertilizer) favoured larval breeding of both anopheline and culicine species. These results suggest that since most cow dung was found in paddies close to the settlement, this may also have contributed to higher numbers of larvae in the same areas. Larval control measures should therefore target rice fields close to human settlements and along the edges of rice paddies for successful source reduction

Serological Evaluation of Onchocerciasis and Lymphatic Filariasis Elimination in the Bakoye and Falémé foci, Mali

In Mali, ivermectin-based onchocerciasis elimination from the Bakoye and Falémé foci, reported in 2009–2012, was a beacon leading to policy shifting from morbidity control to elimination of transmission (EOT). These foci are also endemic for lymphatic filariasis (LF). In 2007–2016 mass ivermectin plus albendazole administration was implemented. We report Ov16 (onchocerciasis) and Wb123 (LF) seroprevalence after 24–25 years of treatment to evaluate if onchocerciasis EOT and LF elimination as a public health problem (EPHP) have been achieved

Calibration and uncertainty issues of a hydrological model (SWAT) applied to West Africa

International audienceDistributed hydrological models like SWAT (Soil and Water Assessment Tool) are often highly over-parameterized, making parameter specification and parameter estimation inevitable steps in model calibration. Manual calibration is almost infeasible due to the complexity of large-scale models with many objectives. Therefore we used a multi-site semi-automated inverse modelling routine (SUFI-2) for calibration and uncertainty analysis. Nevertheless, the question of when a model is sufficiently calibrated remains open, and requires a project dependent definition. Due to the non-uniqueness of effective parameter sets, parameter calibration and prediction uncertainty of a model are intimately related. We address some calibration and uncertainty issues using SWAT to model a four million km2 area in West Africa, including mainly the basins of the river Niger, Volta and Senegal. This model is a case study in a larger project with the goal of quantifying the amount of global country-based available freshwater. Annual and monthly simulations with the "calibrated" model for West Africa show promising results in respect of the freshwater quantification but also point out the importance of evaluating the conceptual model uncertainty as well as the parameter uncertainty

A system dynamics approach to water resources and food production in the Gambia

The Gambia, a country in West African, faces an increasingly daunting situation. They do not produce enough food needed to feed the population, yet population growth remains high, and the current area of land under cultivation is approaching total arable land available. Climate changes complicate matters further as the majority of farms lack irrigation and are dependent on rainfall to provide water to their crops. The purpose of this thesis is to provide the first 1st iteration of a system dynamics model that could be useful as a tool to assist decision in the Gambia better understand long-term implications of policies before they are implemented. Contained within this thesis is the foundation of a system dynamics simulation model designed specifically for the Gambia that incorporates five interconnecting sectors: climate, population, land use, food production, and water resources. The model is demonstrated through four simulated scenarios over a 100-year period and an analysis of the long-term model behaviour of the model is provided. The simulated scenarios include the reduction in total fertility rate, increased irrigation, increase in crop yields, and extreme reduction in precipitation. The simulations unanimously show the long-term dangers posed by population growth and climate change in the Gambia

A new hotspot for Temminck’s Red Colobus (Piliocolobus badius temminckii) in The Gambia: the feasibility of a community approach to conservation

The geographic range and abundance of Temminck’s red colobus, Piliocolobus badius temminckii, in The Gambia is not well documented. In March 2019, line transect surveys were conducted at a number of data deficient forests in The Gambia to establish species presence or absence, contribute to a greater understanding of the species at a national scale and identify prior- ity sites for conservation. One area around Sambel Kunda in the Central River Region was found to be exceptionally productive with an observed Temminck’s red colobus population of 587 individuals, a maximum group size of 60, and connectivity to robust populations along a riparian corridor to the east. Surveys were supported by the collation of community perceptions using prin- ciples of Rapid Assessment Program (RAP) methodology to evaluate the feasibility of an integrated community development and primate conservation project. The results of interviews and meetings in the Sambel Kunda area revealed an absence of hunting and increasing population trends for all primate species, including red colobus. Excepting the Central River Region, Temminck’s red colobus populations were otherwise in decline or locally extinct, predominantly as a result of indiscriminate hunting to protect agricultural crops. Meetings with the Village Development Committees confirmed that the greatest proximal threat to red colobus in the study area was the rapid escalation in forest clearance to produce charcoal for local markets and timber for export to offset climate-change-induced declines in agricultural revenues. Local Gambians are aware that they urgently need to adopt sustainable forestry practices to mitigate climate change impacts and protect timber and non-timber resources but are currently unsure how they would develop and implement such a model. Given the uncertainty and complex nature of the range-wide threats facing the red colobus populations, we suggest prioritizing the Sambel Kunda area as a site of international importance for the protection and recovery of this Critically Endangered species. A community approach to the conservation of red colobus in the Sambel Kunda area should be implemented without delay through site designation, capacity building for biodiversity monitoring, sustainable for- estry practices, community engagement and education and by growing awareness of Temminck’s red colobus as a flagship species

An Assessment of the Level of Awareness of Eye Health Care Services Provided by Onesight in the Gambia

The objective of the Scorecard study was to assess the intervention of OneSight with respect to Awareness of their services in The Gambia and the perception of Gambians on eye care in The Gambia. More specifically in this paper, the scorecard assesses the level at which people are aware of the existence, the activities and the services offered by OneSight in The Gambia. The research employed both quantitative and qualitative methods. The study revealed that the majority of the sampled respondents are aware of refractive error i.e., about 90%. Their major source of information about eye care issues was through radio however, they gather important information from other sources such as healthcare workers and television. Most of the respondents who are aware of eyesight-related problems, typically obtained information through Government clinics, only 2.8% got their information from OneSight. It was also discovered that 94.6% of the respondents sought eye care treatment from health facilities as opposed to a home or local treatments. Based on the findings, practical implications and an agenda for future research are suggested. For instance, it is recommended that OneSight should strengthen community outreach programs, improve its communication strategies, create more visibility, and conduct more publicity events for more awareness about its programme and activities