Hand hygiene intervention to optimise soil-transmitted helminth infection control among primary school children: the Mikono Safi cluster randomised controlled trial in northwestern Tanzania

Soil-transmitted helminth (STH) infections are highly prevalent in resource-limited countries. We assessed the effect of a combination intervention aiming to enhance handwashing with soap on STH reinfection following mass drug administration among primary school children in Kagera region, Northwestern Tanzania.

Methods
We conducted a cluster randomised trial in sixteen primary schools with known high STH prevalence. Schools were randomly assigned in a 1:1 ratio to either receive the intervention or continue with routine health education. The intervention included teacher-led classroom teaching, parental engagement sessions, environmental modifications and improved handwashing stations. The evaluation involved two cross-sectional surveys in a representative sample of students, with the end-line survey conducted 12 months after the baseline survey. The primary outcome was the combined prevalence of Ascaris lumbricoides and Trichuris trichiura infections at the end-line survey. Secondary outcomes included reported handwashing behaviour, the prevalence and intensity of individual STHs, and hand contamination with STH ova and coliform bacteria. End-line STH prevalence and intensity were adjusted for baseline differences of potential confounders.

Results
At the end-line survey, 3081 school children (1566 from intervention schools and 1515 from control schools) provided interview data and stool specimens. More school children in the intervention group reported the use of water and soap during handwashing compared to school children in the control group (58% vs. 35%; aOR=1.76, 95%CI 1.28–2.43, p=0.001). The combined prevalence of A. lumbricoides and T. trichiura infections was 39% in both trial arms (aOR = 1.19; 95%CI 0.74–1.91). The prevalence of A. lumbricoides was 15% in the intervention and 17% in the control arm (aOR =1.24, 95%CI 0.59–2.59) and that of T. trichiura was 31% in both arms (aOR=1.17, 95%CI 0.73–1.88). No significant differences were found for STH infection intensity in both the main study and the hand contamination sub-study.

Conclusions
The intervention was effective in increasing reported handwashing behaviour at school, but failed to show a similar effect in the home. The intervention had no effect on STH infection, possibly due to infection in the home environment, other transmission routes such as contaminated water or food or limited changes in school children’s handwashing behaviour.

Trial registration
The trial was registered on June 21, 2017, by the International Standard Randomised Controlled Trial Number (ISRCTN45013173).

Peer Review reports
Background
Soil-transmitted helminth (STH) infections are a major global health problem, with more than one billion people estimated to be affected worldwide [1]. The infections are particularly frequent among school children in low- and middle-income countries (LMICs) in whom they are associated with anaemia and impaired physical and cognitive development [2, 3]. Deworming by using anti-helminthic drugs as part of regular mass drug administration (MDA) is advocated by WHO as a strategy for STH control in high prevalence areas in LMICs [1]. In Tanzania, annual MDA campaigns are conducted in primary schools as part of the national neglected tropical diseases (NTD) control programme [4]. However, STH prevalence remains high in many communities [5, 6] as MDA is often followed by rapid re-infection [7]. Poor water, sanitation and hygiene (WASH) practices have been proposed as a likely explanation [8].

The role of handwashing with soap in preventing STH transmission is yet to be established given inconsistent results from recent studies. A systematic review and meta-analysis reported in 2014 suggested that hand hygiene or other individual WASH interventions may reduce the odds of STH re-infection following deworming by 33–70% [9]. However, a more recent review reported inconsistent findings, with hand hygiene effectiveness ranging from zero to 59% [10]. None of the studies included in this review assessed the effect of handwashing with soap alone as a single intervention on STH re-infection after treatment.

We conducted a cluster randomised trial to assess the effect of a combination intervention aiming to enhance handwashing with soap on STH re-infection following MDA among primary school children in Kagera region, northwestern Tanzania. This region has high prevalence of Ascaris lumbricoides and Trichuris trichiura infections, which are species of STH known to be transmitted predominantly through the oral ingestion of worm eggs [5, 6].