Evaluating survey designs for targeting preventive chemotherapy against Schistosoma haematobium and Schistosoma mansoni across Sub-Saharan Africa: a geostatistical analysis and modelling study

Abstract Background Schistosomiasis control programmes primarily use school-based surveys to identify areas for mass drug administration of preventive chemotherapy. However, as the spatial distribution of schistosomiasis can be highly focal, transmission may not be detected by surveys implemented at districts or larger spatial units. Improved mapping strategies are required to accurately and cost effectively target preventive chemotherapy to remaining foci across all possible spatial distributions of schistosomiasis. Methods Here, we use geostatistical models to quantify the spatial heterogeneity of Schistosoma haematobium and S. mansoni across Sub-Saharan Africa using the most comprehensive dataset available on school-based surveys. Applying this information to parameterise simulations, we assess the accuracy and cost of targeting alternative implementation unit sizes across the range of plausible schistosomiasis distributions. We evaluate the consequences of decisions based on survey designs implemented at district and subdistrict levels sampling different numbers of schools. Cost data was obtained from field surveys conducted across multiple countries and years, with cost effectiveness evaluated as the cost per correctly identified school. Results Models identified marked differences in prevalence and spatial distributions between countries and species; however, results suggest implementing surveys at subdistrict level increase the accuracy of treatment classifications across most scenarios. While intensively at subdistrict level resulted in the highest classification accuracy, this sampling strategy resulted in the highest costs. Alternatively, sampling the same numbers of schools currently recommended at district levels but stratifying by subdistrict increased cost effectiveness. Conclusions This provides a new tool to evaluate schistosomiasis survey designs across a range of transmission settings. Results highlight the importance of considering spatial structure when designing sampling strategies, illustrating that a substantial proportion of children may be undertreated even when an implementation unit is correctly classified. Control programmes need to weigh the increased accuracy of more detailed mapping strategies against the survey costs and treatment priorities

Relationship between oral declaration on adherence to ivermectin treatment and parasitological indicators of onchocerciasis in an area of persistent transmission despite a decade of mass drug administration in Cameroon

BACKGROUND: Onchocerciasis control for years has been based on mass drug administration (MDA) with ivermectin (IVM). Adherence to IVM repeated treatment has recently been shown to be a confounding factor for onchocerciasis elimination precisely in rain forest areas where transmission continues and Loa loa co-exists with Onchocerca volvulus. In this study, participants’ oral declarations were used as proxy to determine the relationship between adherence to IVM treatment and parasitological indicators of onchocerciasis in the rain forest area of Cameroon with more than a decade of MDA. METHODS: Participants were recruited based on their IVM intake profile with the aid of a semi-structured questionnaire. Parasitological examinations (skin sniping and nodule palpation) were done on eligible candidates. Parasitological indicators were calculated and correlated to IVM intake profile. RESULTS: Of 2,364 people examined, 15.5 % had never taken IVM. The majority (40.4 %) had taken the drug 1–3 times while only 18 % had taken ≥ 7 times. Mf and nodule prevalence rates were still high at 47 %, 95 % CI [44.9–49.0 %] and 36.4 %, 95 % CI [34.4–38.3 %] respectively. There was a treatment-dependent reduction in microfilaria prevalence (r(s) =−0.986, P = 0.01) and intensity (r(s) =−0.96, P = 0.01). The highest mf prevalence (59.7 %) was found in the zero treatment group and the lowest (33.9 %) in the ≥ 7 times treatment group (OR = 2.8; 95 % CI [2.09–3.74]; P < 0.001). Adults with ≥ 7 times IVM intake were 2.99 times more likely to have individuals with no microfilaria compared to the zero treatment group (OR = 2.99; 95 % CI [2.19–4.08], P < 0.0001). There was no clear correlation between treatment and nodule prevalence and intensity. CONCLUSION: Adherence to ivermectin treatment is not adequate in this rain forest area where L. loa co-exists with O. volvulus. The prevalence and intensity of onchocerciasis remained high in individuals with zero IVM intake after more than a decade of MDA. Our findings show that using parasitological indicators, reduction in prevalence is IVM intake-dependent and that participants’ oral declaration of treatment adherence could be relied upon for impact studies. The findings are discussed in the context of challenges for the elimination of onchocerciasis in this rain forest area

Situation analysis of parasitological and entomological indices of onchocerciasis transmission in three drainage basins of the rain forest of South West Cameroon after a decade of ivermectin treatment

BACKGROUND: Community-Directed Treatment with Ivermectin (CDTI) is the main strategy adopted by the African Programme for Onchocerciasis control (APOC). Recent reports from onchocerciasis endemic areas of savannah zones have demonstrated the feasibility of disease elimination through CDTI. Such information is lacking in rain forest zones. In this study, we investigated the parasitological and entomological indices of onchocerciasis transmission in three drainage basins in the rain forest area of Cameroon [after over a decade of CDTI]. River basins differed in terms of river number and their flow rates; and were characterized by high pre-control prevalence rates (60-98%). METHODS: Nodule palpation and skin snipping were carried out in the study communities to determine the nodule rates, microfilarial prevalences and intensity. Simulium flies were caught at capture points and dissected to determine the biting, parous, infection and infective rates and the transmission potential. RESULTS: The highest mean microfilaria (mf) prevalence was recorded in the Meme (52.7%), followed by Mungo (41.0%) and Manyu drainage basin (33.0%). The same trend was seen with nodule prevalence between the drainage basins. Twenty-three (23/39) communities (among which 13 in the Meme) still had mf prevalence above 40%. All the communities surveyed had community microfilarial loads (CMFL) below 10 mf/skin snip (ss). The infection was more intense in the Mungo and Meme. The intensity of infection was still high in younger individuals and children less than 10 years of age. Transmission potentials as high as 1211.7 infective larvae/person/month were found in some of the study communities. Entomological indices followed the same trend as the parasitological indices in the three river basins with the Meme having the highest values. CONCLUSION: When compared with pre-control data, results of the present study show that after over a decade of CDTI, the burden of onchocerciasis has reduced. However, transmission is still going on in this study site where loiasis and onchocerciasis are co-endemic and where ecological factors strongly favour the onchocerciasis transmission. The possible reasons for this persistent and differential transmission despite over a decade of control efforts using ivermectin are discussed. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13071-015-0817-2) contains supplementary material, which is available to authorized users

Multi-scale analysis of runoff from a statistical perspective in a small Sahelian catchment under semi-arid climate

In Sahelian and semi-arid regions, understanding the runoff processes and at different spatial scales is critical to assess sources of variation and further improve distributed modelling. In this study, through a multi-scale analysis, runoff measurements on different soil surface features and at different scales of observation were carried over 6 years of monitoring in a typical Sahelian landscape in Burkina Faso. Statistical and dimensional analyses were used to investigate significant differences in runoff response behaviour on plots of 1 m(2), 50 m(2) and 150 m(2), hydrologic units of 6 and 34 ha and the catchment of 37 km(2). Results showed that on both cultivated and bare soils, the runoff excess decreases as the area increases, under similar rainfall pattern and prior antecedent soil moisture conditions. On degraded soils, the processes of runoff generation on the plots of 50 and 150 m(2) are identical and significantly different from those observed on the unit plot (1 m(2)). A minimum plot length of 10 m was found to be sufficient to accurately estimate runoff on degraded soils. On cultivated soils, runoff is significantly different from one site to another because of the spatial variability of hydrodynamic properties of the soil. Such results show that the scale effect on runoff is related to the spatial heterogeneity of soils and is further intensified by the rainfall intensity. Such results highlight the value of quantification of runoff on homogeneous units, hence allowing an innovative approach to the problem of scale transfer

24-Month adherence, tolerance and efficacy of once-a-day antiretroviral therapy with didanosine, lamivudine, and efavirenz in African HIV-1 infected children: ANRS 12103/12167

Background: There is no data on long-term benefit of once-a-day antiretroviral therapy (ART) with combination of DDI, 3TC and EFV to allow its use in future therapeutic strategies. Objectives: To assess 24-month immuno-virological, adherence, tolerance, and effectiveness of a once-a-day ART with DDI, 3TC and EFV. Methods: A phase 2 open trial including 51 children aged from 30 months to 15 years, monitored a once-a-day regimen for 24 months from 2006 to 2008 in the Departement de Pediatrie du CHUSS, at Bobo-Dioulasso in Burkina Faso. We tested immunological and virological response, adherence, tolerance and resistance of the treatment. Results: Children with CD4 >25% at 24 months were 67.4% (33/49) CI 95% [54%, 80%].The proportion of children with viral plasma RNA <300 cp / ml at 24 months of treatment was 81.6 % (40/49) CI [68.0% 91.2%]. Good adherence was obtained with more than 88% adherence > 95% over the 24 months. Drugs were well tolerated. Conclusions: Given the limited number of antiretroviral drugs available in Africa and the inadequacy of laboratory monitoring in support program, once-a-day treatment and especially the DDI-based combination strategies could be anattractive operational option

Enquete sero-epidemiologique sur la tuberculose, la brucellose, la toxoplasmose, la rhinotracheite infectiuse et les salmonelles abortives chez les animaux bresiliens introduits au Bukinafaso

A survey on tuberculosis, brucellosis, bovine infectious rhinotracheitis, toxoplasmosis and abortive salmonellosis has been carried out in Brazilian breeds (Gyr and Gyrolando) introduced in Burkina Faso. The study has concerned two livestock system : The modern system with two herds located in Koubri and Loumbila (rearing station of the Centre National d’Elevage et d’Amélioration Génétique (CNEAG). The traditional system with the agro-pastoral zone’s herd of Kikideni, eastern Burkina Faso. Animals (n = 273) have been tested for the presence of tuberculosis, brucellosis, bovine infectious rhinotrachetis (IBR), toxoplasmosis and salmonellosis.Results have shown a prevalence of 16.42%, 7.32%, 3%, 77.73%, and 76.04%of for brucellosis, tuberculosis, toxoplasmosis, bovine infectious rhinotracheitis and abortive salmonellosis respectively. Results have also revealed a high seroprevalence rate for abortive diseases which are not routinely diagnosed in Burkina Faso such as toxoplasmosis and salmonellosis and the presence of multiple abortive infections within the same animal. This survey suggested systematic control of abortive diseases which could improve animal productivity

Efficacité d’une sensibilisation sur les connaissances, attitudes et pratiques des élèves de la ville de Bobo-Dioulasso sur l’hépatite virale B

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24-Month adherence, tolerance and efficacy of once-a-day antiretroviral therapy with didanosine, lamivudine, and efavirenz in African HIV-1 infected children : ANRS 12103/12167

Background: There is no data on long-term benefit of once-a-day antiretroviral therapy (ART) with combination of DDI, 3TC and EFV to allow its use in future therapeutic strategies. Objectives: To assess 24-month immuno-virological, adherence, tolerance, and effectiveness of a once-a-day ART with DDI, 3TC and EFV. Methods: A phase 2 open trial including 51 children aged from 30 months to 15 years, monitored a once-a-day regimen for 24 months from 2006 to 2008 in the Departement de Pediatrie du CHUSS, at Bobo-Dioulasso in Burkina Faso. We tested immunological and virological response, adherence, tolerance and resistance of the treatment. Results: Children with CD4 > 25% at 24 months were 67.4% (33/49) CI 95% [54%, 80%]. The proportion of children with viral plasma RNA 95% over the 24 months. Drugs were well tolerated. Conclusions: Given the limited number of antiretroviral drugs available in Africa and the inadequacy of laboratory monitoring in support program, once-a-day treatment and especially the DDI-based combination strategies could be an attractive operational option