Estimating the population at risk with soil transmitted helminthiasis and annual drug requirements for preventive chemotherapy in Ogun State, Nigeria

Abstract

Soil transmitted helminth (STH) infections are among the most common human infections worldwide with over 1 billion people affected. Many estimates of STH infection are often based on school-aged children (SAC). This study produced predictive risk-maps of STH on a more finite scale, estimated the number of people infected, and the amount of drug required for preventive chemotherapy (PC) in Ogun state, Nigeria. Georeferenced STH infection data obtained from a cross-sectional survey at 33 locations between July 2016 and November 2018, together with remotely-sensed environmental and socio-economic data were analyzed using Bayesian geostatistical modelling. Stepwise variable selection procedure was employed to select a parsimonious set of predictors to predict risk and spatial distribution of STH infections. The number of persons (pre-school ages children, SAC and adults) infected with STH were estimated, with the amount of tablets needed for preventive chemotherapy. An overall prevalence of 17.2% (95% CI 14.9, 19.5) was recorded for any STH infection. Ascaris lumbricoides infections was the most predominant, with an overall prevalence of 13.6% (95% CI 11.5, 15.7), while Hookworm and Trichuris trichiura had overall prevalence of 4.6% (95% CI 3.3, 5.9) and 1.7% (95% CI 0.9, 2.4), respectively. The model-based prevalence predictions ranged from 5.0 to 23.8% for Ascaris lumbricoides, from 2.0 to 14.5% for hookworms, and from 0.1 to 5.7% for Trichuris trichiura across the implementation units. The predictive maps revealed a spatial pattern of high risk in the central, western and on the border of Republic of Benin. The model identified soil pH, soil moisture and elevation as the main predictors of infection for A. lumbricoides, Hookworms and T. trichiura respectively. About 50% (10/20) of the implementation units require biannual rounds of mass drug administration. Approximately, a total of 1.1 million persons were infected and require 7.8 million doses. However, a sub-total of 375,374 SAC were estimated to be infected, requiring 2.7 million doses. Our predictive risk maps and estimated PC needs provide useful information for the elimination of STH, either for resource acquisition or identifying priority areas for delivery of interventions in Ogun State, Nigeria.

Health workers’ perspectives on school-based mass drug administration control programs for soil-transmitted helminthiasis and schistosomiasis in Ogun State, Nigeria

“…Ogun State, Nigeria, was selected as the study location due to its high prevalence of STH (19.2%) and SCH (32.2%) and the inconsistent support of partner programs for NTD control [ 24 , 25 ]. MDA commenced in Ogun State 22 years ago directed to STH and SCH treatment [ 25 ].…”

“…Four LGAs in Ogun State were purposively selected based on recommendations from the Department of Public Health, Ogun State Ministry of Health. The following LGAs were included in the study: Ikenne, with a prevalence of 12.6% for STH and 1.46% for SCH; Abeokuta North, with a prevalence of 22.4% for STH and 15.40% for SCH; Abeokuta South, with a prevalence of 27.5% for STH and 1.61% for SCH; and Obafemi Owode, with a prevalence of 21.1% for STH and 8.78% for SCH [ 24 ].…”

Soil-transmitted helminths: A critical review of the impact of co-infections and implications for control and elimination

“…This approach is considered cost effective and appropriate because children have the highest infection rates and can be reached easily through schools. In 2018, a total of 576 million (59.9%) of the estimated 1.1 billion children requiring deworming medication received treatment and this number is expected to continue rising [ 89 ]. Despite its contribution to controlling STH morbidity, targeted drug administration alone appears unsuccessful at eliminating STH infections due to the resurgence of reinfections, limited efficacy of current drugs, gaps in drug availability, and the risk of antihelminthic drug resistance [ 64 ].…”

Understanding the impact of covariates on the classification of implementation units for soil-transmitted helminths control: A case study from Kenya

“…MBG models allow the inclusion of spatially referenced covariates to assist the prediction of disease prevalence at unsampled locations 9 . Previous work on the mapping of STH prevalence has made use of environmental and socioeconomic covariates, as well as indicators of improved access to sanitation facilities, and drinking water facilities [10][11][12][13][14] . Whilst the scienti c rationale for the inclusion of these covariates is well established, the statistical advantages that are accrued from their use have not been fully investigated.…”