Anderson, R. M. — Page 2

bioRxiv2019

Domains of transmission and association of community, school, and household sanitation with soil-transmitted helminth infections among children in coastal Kenya

IntroductionFew studies have simultaneously examined the role of sanitation conditions at the home, school, and community on soil-transmitted helminth (STH) infection. We examined the contribution of each domain that children inhabit (home, village, and school) and estimated the association of sanitation in each domain with STH infection.\n\nMethodsUsing data from 4,104 children from Kwale County, Kenya, who reported attending school, we used logistic regression models with cross-classified random effects to calculate measures of general contextual effects and estimate associations of village, school, and household sanitation with STH infection.\n\nFindingsWe found reported use of a sanitation facility by households was associated with reduced prevalence of hookworm infection but not with reduced prevalence of T. trichiura infection. School sanitation coverage > 3 toilets per 100 pupils was associated with lower prevalence of hookworm infection. School sanitation was not associated with T. trichiura infection. Village sanitation coverage > 81% was associated with reduced prevalence of T. trichiura infection, but no protective association was detected for hookworm infection. General contextual effects represented by residual heterogeneity between village and school domains had comparable impact upon likelihood of hookworm and T. trichiura infection as sanitation coverage in either of these domains.\n\nConclusionFindings support the importance of providing good sanitation facilities to support mass drug administration in reducing the burden of STH infection in children.\n\nAuthor SummaryInfection by whipworm and hookworm results from either ingestion of eggs or larvae or through skin exposure to larvae. These eggs and larvae develop in suitable soils contaminated with openly-deposited human faeces. Safe disposal of faeces should reduce transmission of these soil-transmitted helminths (STH), yet evidence of the impact of sanitation on STH transmission remains limited. We used data collected during a large, community-wide survey to measure prevalence of STH infections in coastal Kenya in 2015 to examine the relationship between sanitation conditions at home, school, and village and the presence of STH infection among 4,104 children who reported attending schools. We found that sanitation access at home and school sanitation coverage, but not the overall level of village sanitation coverage, was protective against hookworm infection. In contrast, only high village sanitation coverage, but not home or school sanitation, was protective against whipworm infection. Current STH control strategies emphasise periodic deworming through mass drug administration (MDA) of at-risk populations, including school-age children. Our findings highlight the need for continued efforts, alongside MDA, to extend access to good sanitation facilities at homes, schools, and across communities.

epidemiology↗

bioRxiv2018

Longitudinal changes in the prevalence and intensity of soil-transmitted helminth infection following expanded community-wide mass drug administration in the delta region of Myanmar

Mass drug administration (MDA), targeted at school-aged children is the method recommended by the World Health Organization for the control of morbidity induced by soil-transmitted helminth (STH) infection in endemic countries. However, MDA does not prevent reinfection between treatment rounds. In countries with endemic infection, such as Myanmar, the MDA coverage, who is targeted, and rates of reinfection in given environmental and social settings will determine how effective mass drug treatment is in suppressing transmission in the long-term. In this paper, data from an epidemiology study on STH, conducted between June 2015 and June 2016 in the delta region of Myanmar, are analysed to determine the risks of STH infection in the whole community over a year which included two MDA rounds. Risk ratios (RRs) for the four-month reinfection period were below one, whereas RRs for the six-month reinfection period were above one, indicating that more people were infected after six months of exposure post-MDA. Evidence of predisposition, as measured by the Kendall Tau-b statistic, was found for all STH species and across all age groups. This study demonstrates that a six-month gap between MDA in these communities is enough time for STH infection to return to pre-MDA levels and that the same individuals are being consistently infected between MDA rounds.\n\nAuthor summaryMass drug administration (MDA), treating either whole communities or targeted groups without a prior diagnosis, is used as a control strategy for many neglected tropical diseases, including soil-transmitted helminth (STH) infection. MDA takes place at set intervals, aiming to reduce morbidity caused by the target disease and potentially interrupt transmission. In this study we measure STH infection in two villages in the delta region of Myanmar over the course of a year, both before and after MDA rounds, to quantify the effect of treatment on infection and to identify groups with persistent infections. We found that whilst overall prevalence of STH infection decreased over the year, intensity of infection, measured by eggs per gram of faeces, did not significantly decrease. We also found evidence to suggest that particular people are predisposed to STH infection. This is possibly due to non-compliance to MDA, or behavioural and social factors. The findings presented here will provide evidence to support continuing Myanmars MDA programme for STH control and using accurate diagnostics to identify and target \"predisposed\" people for sustained treatment.

epidemiology↗