The three soil-transmitted helminthes (STH), Ascaris lumbricoides, Trichuris trichiura, and hookworm, infect more than a billion people worldwide particularly in developing countries where sanitation and hygiene is poor, inadequate or lacking.
A decade ago, the World Health Organization (WHO) endorsed the global strategy of drug administration to children and other high risk groups. Although this did reduce illness with these parasites, it does little tom prevent reinfection.
Because of this shortcoming, researchers from the Swiss Tropical and Public Health Institute looked at what effect did the access and use of appropriate sanitation measures like toilets and latrines have on reducing the risk of becoming infected with these roundworms.
In a study published this week in the journal PLoS Medicine, the authors performed a systemic review and meta-analysis (A systematic review uses predefined criteria to identify all the research on a given topic; a meta-analysis is a statistical method that combines the results of several studies) on publications that included data on sanitation availability and use and a population infected with one or more of the STH.
People who had access to these facilities and actually used a latrine were half as likely (odds ratio 0.51) to be infected with these soil-transmitted parasites.
The findings of the study confirm that providing access to, and promoting use of, sanitation facilities is an effective control measure for soil-transmitted helminthiasis.
As pointed out in the Editor’s Summary:
Because infected individuals excrete helminth eggs in their feces, in regions where people regularly defecate in the open, the soil becomes contaminated with eggs. People pick up roundworm or whipworm infections when they ingest these eggs after they have matured in the environment by eating raw, unwashed vegetables or by not washing their hands after handling contaminated soil (a common transmission route for children). In the case of hookworm, the immature, infective stages of the worms, which hatch in the soil, can penetrate human skin, and people usually become infected by walking barefoot on contaminated soil.
The authors say there should be more emphasis on improving access to adequate sanitation in addition to drug administration (deworming) and health education.
In addition to the three parasites discussed in the study, the authors note that increased access to sanitation would also improve the control of other neglected tropical diseases (such as schistosomiasis and trachoma) and would reduce the incidence of diarrhea and consequently child mortality in low-income countries.