Uwem Friday Ekpo

Toward an Open-Access Global Database for Mapping, Control, and Surveillance of Neglected Tropical Diseases

Background After many years of general neglect, interest has grown and efforts came under way for the mapping, control, surveillance, and eventual elimination of neglected tropical diseases (NTDs). Disease risk estimates are a key feature to target control interventions, and serve as a benchmark for monitoring and evaluation. What is currently missing is a georeferenced global database for NTDs providing open-access to the available survey data that is constantly updated and can be utilized by researchers and disease control managers to support other relevant stakeholders. We describe the steps taken toward the development of such a database that can be employed for spatial disease risk modeling and control of NTDs. Methodology With an emphasis on schistosomiasis in Africa, we systematically searched the literature (peer-reviewed journals and ‘grey literature’), contacted Ministries of Health and research institutions in schistosomiasis-endemic countries for location-specific prevalence data and survey details (e.g., study population, year of survey and diagnostic techniques). The data were extracted, georeferenced, and stored in a MySQL database with a web interface allowing free database access and data management. Principal Findings At the beginning of 2011, our database contained more than 12,000 georeferenced schistosomiasis survey locations from 35 African countries available under http://www.gntd.org. Currently, the database is expanded to a global repository, including a host of other NTDs, e.g. soil-transmitted helminthiasis and leishmaniasis. Conclusions An open-access, spatially explicit NTD database offers unique opportunities for disease risk modeling, targeting control interventions, disease monitoring, and surveillance. Moreover, it allows for detailed geostatistical analyses of disease distribution in space and time. With an initial focus on schistosomiasis in Africa, we demonstrate the proof-of-concept that the establishment and running of a global NTD database is feasible and should be expanded without delay.

Spatial distribution of schistosomiasis and treatment needs in sub-Saharan Africa: a systematic review and geostatistical analysis

BACKGROUND Schistosomiasis affects more than 200 million individuals, mostly in sub-Saharan Africa, but empirical estimates of the disease burden in this region are unavailable. We used geostatistical modelling to produce high-resolution risk estimates of infection with Schistosoma spp and of the number of doses of praziquantel treatment needed to prevent morbidity at different administrative levels in 44 countries. METHODS We did a systematic review to identify surveys including schistosomiasis prevalence data in sub-Saharan Africa via PubMed, ISI Web of Science, and African Journals Online, from inception to May 2, 2014, with no restriction of language, survey date, or study design. We used Bayesian geostatistical meta-analysis and rigorous variable selection to predict infection risk over a grid of 1 155 818 pixels at 5 × 5 km, on the basis of environmental and socioeconomic predictors and to calculate the number of doses of praziquantel needed for prevention of morbidity. FINDINGS The literature search identified Schistosoma haematobium and Schistosoma mansoni surveys done in, respectively, 9318 and 9140 unique locations. Infection risk decreased from 2000 onwards, yet estimates suggest that 163 million (95% Bayesian credible interval [CrI] 155 million to 172 million; 18·5%, 17·6-19·5) of the sub-Saharan African population was infected in 2012. Mozambique had the highest prevalence of schistosomiasis in school-aged children (52·8%, 95% CrI 48·7-57·8). Low-risk countries (prevalence among school-aged children lower than 10%) included Burundi, Equatorial Guinea, Eritrea, and Rwanda. The numbers of doses of praziquantel needed per year were estimated to be 123 million (95% CrI 121 million to 125 million) for school-aged children and 247 million (239 million to 256 million) for the entire population. INTERPRETATION Our results will inform policy makers about the number of treatments needed at different levels and will guide the spatial targeting of schistosomiasis control interventions. FUNDING European Research Council, China Scholarship Council, UBS Optimus Foundation, and Swiss National Science Foundation.

Spatial and temporal distribution of soil-transmitted helminth infection in sub-Saharan Africa: a systematic review and geostatistical meta-analysis

BACKGROUND Interest is growing in predictive risk mapping for neglected tropical diseases (NTDs), particularly to scale up preventive chemotherapy, surveillance, and elimination efforts. Soil-transmitted helminths (hookworm, Ascaris lumbricoides, and Trichuris trichiura) are the most widespread NTDs, but broad geographical analyses are scarce. We aimed to predict the spatial and temporal distribution of soil-transmitted helminth infections, including the number of infected people and treatment needs, across sub-Saharan Africa. METHODS We systematically searched PubMed, Web of Knowledge, and African Journal Online from inception to Dec 31, 2013, without language restrictions, to identify georeferenced surveys. We extracted data from household surveys on sources of drinking water, sanitation, and womens level of education. Bayesian geostatistical models were used to align the data in space and estimate risk of with hookworm, A lumbricoides, and T trichiura over a grid of roughly 1 million pixels at a spatial resolution of 5 × 5 km. We calculated anthelmintic treatment needs on the basis of WHO guidelines (treatment of all school-aged children once per year where prevalence in this population is 20-50% or twice per year if prevalence is greater than 50%). FINDINGS We identified 459 relevant survey reports that referenced 6040 unique locations. We estimate that the prevalence of hookworm, A lumbricoides, and T trichiura among school-aged children from 2000 onwards was 16·5%, 6·6%, and 4·4%. These estimates are between 52% and 74% lower than those in surveys done before 2000, and have become similar to values for the entire communities. We estimated that 126 million doses of anthelmintic treatments are required per year. INTERPRETATION Patterns of soil-transmitted helminth infection in sub-Saharan Africa have changed and the prevalence of infection has declined substantially in this millennium, probably due to socioeconomic development and large-scale deworming programmes. The global control strategy should be reassessed, with emphasis given also to adults to progress towards local elimination. FUNDING Swiss National Science Foundation and European Research Council.

Urinary schistosomiasis among preschool children in a rural community near Abeokuta, Nigeria.

BackgroundThe control of schistosomiasis in Nigeria is mainly by mass treatment with praziquantel through the school system, with an absence of any provision for pre-school children. We therefore determined the prevalence and intensity of urinary schistosomiasis in pre-school children between the ages of 1-6 years in Ilewo-Orile a rural and endemic community, near Abeokuta, Nigeria as part of providing information on the neglected tropical diseases among this age group. Two urine samples were collected from each pre-school child. The samples were tested for microhaematuria using reagent strips and then processed and examined with a microscope for Schistosoma haematobium ova.ResultsOf the 167 children examined 97 (58.1%) had infection, with no significant difference (P = 0.809) in infection rates between boys (57.1%) and girls (59.2%). Both prevalence and intensity of infection did not increase significantly with age (P = 0.732). The overall geometric mean egg count was 1.17 eggs/10 ml urine. There was no significant association (P = 0.387) between intensity in boys (1.16 eggs/10 ml urine) and girls (1.19 eggs/10 ml urine). 47.4% of the children had microhaematuria which did not increase significantly with age (P = 0.526). Focus group discussions with guardians and caregivers revealed that infection of pre-school children early in life was due to exposures through bathing in the stream by their mothers, while the older children would visit the stream for washing, fetching of water, bathing and swimming.ConclusionCommunity participatory health education is needed in this community as a first step in reducing infection and transmission of the disease, while the rehabilitation and repair of the existing water borehole system in the community should be effected. The results of this study have shown that pre-school children also harbour infection and are a source of transmission of schistosomiasis in endemic communities. Planning and provision for their treatment should be considered in control programmes.

Helminthiasis and Hygiene Conditions of Schools in Ikenne, Ogun State, Nigeria

Background A study of the helminth infection status of primary-school children and the hygiene condition of schools in Ikenne Local Government Area of Ogun State, Nigeria was undertaken between November 2004 and February 2005 to help guide the development of a school-based health programme. Methods and Findings Three primary schools were randomly selected: two government-owned schools (one urban and the other rural) and one urban private school. No rural private schools existed to survey. A total of 257 schoolchildren aged 4–15 y, of whom 146 (56.8%) were boys and 111 (43.2%) were girls, took part in the survey. A child survey form, which included columns for name, age, sex, and class level, was used in concert with examination of stool samples for eggs of intestinal helminths. A school survey form was used to assess the conditions of water supply, condition of latrines, presence of soap for handwashing, and presence of garbage around the school compound. The demographic data showed that the number of schoolchildren gradually decreased as their ages increased in all three schools. The sex ratio was proportional in the urban school until primary level 3, after which the number of female pupils gradually decreased, whereas in the private school, sexes were proportionally distributed even in higher classes. The prevalence of helminth infection was 54.9% of schoolchildren in the urban government school, 63.5% in the rural government school, and 28.4% in the urban private school. Ascaris lumbricoides was the most prevalent species, followed by Trichuris trichiura, Taenia species, and hookworm in the three schools. Prevalence of infection in the government-owned schools was significantly higher than in the private school (χ 2 = 18.85, df = 2, p<0.0005). A survey of hygiene conditions in the three schools indicated that in the two government schools tapwater was unavailable, sanitation of latrines was poor, handwashing soap was unavailable, and garbage was present around school compounds. In the private school, in contrast, all hygiene indices were satisfactory. Conclusions These results indicate that burden of parasite infections and poor sanitary conditions are of greater public health importance in government-owned schools than in privately owned schools. School health programmes in government-owned schools, including deworming, health education, and improvement of hygiene conditions are recommended.

Prevalence of malnutrition among settled pastoral Fulani children in Southwest Nigeria

BackgroundThere is a dearth of information on the health of pastoral Fulani children living in southwestern Nigeria. These are fully settled pastoralists whose economy are centred on cattle and farming. In other to monitor and plan appropriate nutritional intervention for their children, a cross-sectional study was carried out to determine the prevalence of malnutrition of pastoral Fulani children.FindingsFulanis children aged 6 months to 15 years, living in 61 settlements in Kwara, Ogun and Oyo States in Southwestern Nigeria participated in the study. Heights and weights of 164 girls and 167 boys were measured. Their anthropometric indices, height-for-age (HA), weight-for-height (WH), and weight-for-age (WA) Z-scores determined. The prevalence of stunting (HAZ < -2), wasting (WHZ < -2) and underweight (WAZ < -2) was 38.7%, 13.6%, and 38.7%, respectively when compared to the reference NCHS/WHO standard used for defining stunting, wasting and underweight. Boys were more malnourished than the girls were, but this was not significant (stunting: χ2 = 0.36; df = 1; P = 0.54); (underweight: χ2 = 1.10; df = 1; P = 0.29); and (wasting: χ2 = 0.00; df = 1; P = 0.98) The mean of Z-scores of Height-for-age, Weight-for-age and Weight-for-height in children were -1.502, -1.634 and -0.931 respectively. The SD was 1.52, 1.09 and 1.20 respectively. Using WHO Malnutrition Classification systems, 38.7% of the children were found to be malnourished.ConclusionThese results indicate high prevalence of malnutrition among settled pastoral Fulani children, possibly due to changes in food habits and lifestyle occasion by the transition from nomadic to sedentary living. We suggest the inclusion of Fulanis settlements in nutritional intervention for these areas.

Bayesian Geostatistical Model-Based Estimates of Soil-Transmitted Helminth Infection in Nigeria, Including Annual Deworming Requirements

Background The acceleration of the control of soil-transmitted helminth (STH) infections in Nigeria, emphasizing preventive chemotherapy, has become imperative in light of the global fight against neglected tropical diseases. Predictive risk maps are an important tool to guide and support control activities. Methodology STH infection prevalence data were obtained from surveys carried out in 2011 using standard protocols. Data were geo-referenced and collated in a nationwide, geographic information system database. Bayesian geostatistical models with remotely sensed environmental covariates and variable selection procedures were utilized to predict the spatial distribution of STH infections in Nigeria. Principal Findings We found that hookworm, Ascaris lumbricoides, and Trichuris trichiura infections are endemic in 482 (86.8%), 305 (55.0%), and 55 (9.9%) locations, respectively. Hookworm and A. lumbricoides infection co-exist in 16 states, while the three species are co-endemic in 12 states. Overall, STHs are endemic in 20 of the 36 states of Nigeria, including the Federal Capital Territory of Abuja. The observed prevalence at endemic locations ranged from 1.7% to 51.7% for hookworm, from 1.6% to 77.8% for A. lumbricoides, and from 1.0% to 25.5% for T. trichiura. Model-based predictions ranged from 0.7% to 51.0% for hookworm, from 0.1% to 82.6% for A. lumbricoides, and from 0.0% to 18.5% for T. trichiura. Our models suggest that day land surface temperature and dense vegetation are important predictors of the spatial distribution of STH infection in Nigeria. In 2011, a total of 5.7 million (13.8%) school-aged children were predicted to be infected with STHs in Nigeria. Mass treatment at the local government area level for annual or bi-annual treatment of the school-aged population in Nigeria in 2011, based on World Health Organization prevalence thresholds, were estimated at 10.2 million tablets. Conclusions/Significance The predictive risk maps and estimated deworming needs presented here will be helpful for escalating the control and spatial targeting of interventions against STH infections in Nigeria.

Biting behaviour of Simulium damnosum complex and Onchocerca volvulus infection along the Osun River, Southwest Nigeria

BackgroundStudies on biting behaviours and infectivity status of insect vectors are pre-requisites in understanding the epidemiology of the vector- borne diseases and planning effective control measures. A longitudinal study was carried out to investigate the transmission index of Simulium damnosum complex species along Osun River, South Western Nigeria. Adult flies were collected on human attractants from 07:00 to 18:00 hours for two consecutive days from February 2008 to June 2009 at three communities: Osun Eleja, Osun Ogbere and Osun Budepo. The infectivity rate was determined by dissection and Polymerase Chain Reaction amplification (PCR) of 0-150 genes of Onchocerca parasite using the pool screening technique.ResultsThe results indicated that the majority of the flies collected at the three sampling points were nulliparous as they accounted for 53.90%, 57.86% and 59.58% of the flies dissected at Osun Budepo, Osun Ogbere and Osun Eleja, respectively. The parous rate was higher during the dry season than the wet season but the difference was not statistically significant (p < 0.05). The biting activity of the parous flies showed two peaks at Osun Budepo and three peaks at Osun Eleja and Osun Ogbere. Of the 1,472 flies dissected and 1,235 flies screened by molecular method, none was infected with Onchocerca parasite at the three sampling points however the annual biting rates at the three communities were higher than 1,000 considered as tolerable value for a person living in an onchocerciasis zone by Word Health Organization.ConclusionThe study has provided the baseline data for further study on onchocerciasis transmission dynamics and the need to intercept man- simuliid vector contact at the study area.

Schistosoma haematobium infections in preschool children from two rural communities in Ijebu East, south-western Nigeria

There is an urgent need for information on schistosomiasis in preschool children, who are often excluded in mass treatment programmes. The prevalence and intensity of Schistosoma haematobium infection were determined in preschool children aged ≤ 6 years in two rural communities in Ijebu East, south-western Nigeria. Two urine samples each were collected from 83 preschool children from the two communities, tested for microhaematuria using reagent strips and then processed and examined with a microscope for S. haematobium eggs. Focus group discussions on perceptions of the disease and water contact practices were held in the communities with their guardians, caregivers and preschool children, using an interview guide. The prevalence of S. haematobium in the two communities was 14 (16.9%), with no significant differences (P = 0.661) in infection rate between boys (18.4%) and girls (14.7%). Both prevalence and intensity of infection did not increase significantly with age in both Korede and Obada community. However, there were significant differences in prevalence of infection between the two communities (P = 0.035). There was no association (P = 0.750) between intensity in boys (0.176 eggs/10 ml urine) and girls (0.110 eggs/10 ml urine). Focal group discussions with guardians and caregivers revealed that preschool children acquired infection early in their lives through exposure to infected stream water by their mothers, while the older children visit the stream for playing, bathing and swimming. It has therefore become imperative for preschool children to be included in the planning of schistosomiasis intervention programmes as a means of reducing transmission.

Preliminary study on temporal variations in biting activity of Simulium damnosum s.l. in Abeokuta North LGA, Ogun State Nigeria.

BackgroundSimulum damnosum Theobald sensu lato (s.l.) is the vector of the parasitic filarial worm Onchocerca volvulus Leuckart which causes onchocerciasis. In order to understand the vector population dynamics, a preliminary 12 months entomological evaluation was carried out at Abeokuta, the Southwest Zone of Nigeria, an onchocerciasis endemic area, where vector control has not been previously initiated. S.damnosum s.l. flies were caught on human attractants between 700 to1800 hours each day, for 4 days each month, from August 2007 to July 2008. The flies caught were classified as either forest-dwelling or savanna-dwelling groups based on the colour of certain morphological characters. Climatic data such as rainfall, humidity and temperature were also collected monthly during the period of survey.ResultsA total of 1,139 flies were caught, 596 (52.33%) were forest-dwelling group while 543 (47.67%) were savanna-dwelling group of S. damnosum s.l. The highest percentage of forest-dwelling group was caught in the month of August 2007 (78.06%) and the least percentage of forest-dwelling groups was caught in November 2007 (8.14%). The highest percentage of savannah-dwelling group was caught in the month of November 2007 (91.86%) and the least percentage of savannah-dwelling group was caught in August 2007 (21.94%). There was no significant difference between the population of forest and savannah-dwelling groups of the fly when the means of the fly population were compared (P = 0.830). Spearman correlation analysis showed a significant relationship between monthly fly population with monthly average rainfall (r = 0.550, n = 12, P = 0.033), but no significant relationship with monthly average temperature (r = 0.291, n = 12, P = 0.179). There was also a significant relationship between monthly fly population and monthly average relative humidity (r = 0.783, n = 12 P = 0.001). There was no significant correlation between the population of forest-dwelling group of S. damnosum s.l. and monthly average rainfall (r = 0.466, n = 12, P = 0.064) and monthly average temperature (r = 0.375, n = 12, P = 0.115) but there was significant correlation with monthly average relative humidity (r = 0.69, n = 12, P = 0.006). There was significant correlation between savannah-dwelling group and monthly average rainfall (r = 0.547, n = 12, P = 0.033), and monthly average relative humidity (r = 0.504, n = 12, P = 0.047) but there was no significant correlation with monthly average temperature (r = 0.142, n = 12, P = 0.329)ConclusionThe results from this study showed that both the forest and the savannah dwelling groups of S. damnosum s.l. were caught biting in the study area. This could have implications on the transmission and epidemiology of human onchocerciasis if not monitored.