Neglected tropical diseases

WHO data show unprecedented treatment coverage for bilharzia and intestinal worms

14 December 2018 | Geneva −− The latest data on treatment for schistosomiasis (bilharzia) and soil-transmitted helminthiases (intestinal worms) show encouraging trends towards the goal of attaining a minimum target of treating at least 75% of school-aged children in areas endemic for these parasitic infections, making it technically feasible to achieve the global targets set for 2020.

In 2017, almost 99 million people were treated for schistosomiasis worldwide, most of whom were in countries in WHO’s Region of Africa – making up for almost 88% of the global total.


A further 9.4 million treatments were provided globally in 2017 than in 2016,” said Dr Amadou Garba-Djirmay, Medical Officer who heads the global schistosomiasis elimination programme. “And if we compare the figures of the past two years, it means that the global treatment for school-aged children increased from 53.7% in 2016 to 68.0% in 2017 which very close to reaching the target of 75%.

Many countries in WHO's African Region remain highly endemic for schistosomiasis and carry the world’s heaviest burden.

But with higher numbers of school-aged children being treated – reaching more than 69% of all children requiring treatment in 2017 – an encouraging trend has emerged towards achieving WHO’s 2020 NTD roadmap goal of eliminating morbidity from schistosomiasis in some countries in Africa. For other African countries where the disease is highly endemic, it is time they start to implement WHO-recommended control programmes.

We need to provide free medicines to equitably treat everyone – and this includes women of childbearing age and all adults at risk of the disease – if we are to achieve universal health coverage,” said Dr Garba-Djirmay. “Despite a slight increase in treatment coverage from 14.3% in 2016 to 16.9% in 2017, overall treatment for adults has remained low; the main reason is the unavailability of the medicine (praziquantel1) for all age groups.

Numbers of people treated for schistosomiasis and soil-transmitted helminthiases in 2017

In 2017, more than 98.7 million people received free preventive treatment for schistosomiasis (81.1 million school-aged children and 16.9 million adults) and 743 million people received preventive chemotherapy for soil-transmitted helminthiases (188 million preschool-aged children, 410.1 million school-aged children and 127.9 million women of reproductive age).

Scale up of treatment for these two groups of children reached almost 70% in 2017 and this now brings us closer to achieving the 2020 NTD Roadmap target,” said Dr Antonio Montresor, Medical Officer who heads WHO’s global deworming programme. “Our next steps are to reach and deworm all women of reproductive age and to implement measures directed towards the control of roundworms (strongyloidiasis).”

Globally, 272.7 million preschool-aged children, 596 million school-aged children and 688 million women of reproductive age are estimated to require preventive treatment with albendazole2 or mebendazole3 . Currently, women of childbearing age are not targeted for treatment for intestinal worms. This is the reason for such low coverage as the medicines are not donated.

WHO encourages combined treatment for schistosomiasis and intestinal worms in areas where the two diseases occur concurrently. Large-scale preventive treatment is recommended with anthelmintic medicines (praziquantel for schistosomiasis and albendazole or mebendazole for intestinal worms) as a short-term measure to control the morbidity associated with these infections.

Beyond treatment, which reduces the intensity of worms, other measures that can sustainably address both diseases are health and hygiene education that encourages healthy behaviours and access to adequate sanitation and safe water.

The diseases

Schistosomiasis is an acute and chronic parasitic disease caused by trematode worms of the genus Schistosoma. Infection occurs when larval forms of the parasite – released by freshwater snails – penetrate the skin during contact with infested water.


Transmission occurs when people suffering from schistosomiasis contaminate freshwater sources with their excreta containing parasite eggs, which hatch in water. In the body, the larvae develop into adult schistosomes. Adult worms live in the blood vessels where the females release eggs. Some of the eggs are passed out of the body in the faeces or urine to continue the parasite’s lifecycle. Others become trapped in body tissues, causing immune reactions and progressive damage to organs.

There are two major forms of schistosomiasis – intestinal and urogenital. Intestinal schistosomiasis usually results in diarrhoea and blood in the stool; enlargement of the liver and of the spleen and portal hypertension are common in advanced cases.

Urogenital schistosomiasis is characterized by the presence of blood in the urine. Chronic infection results in fibrosis of the bladder and ureter that can evolve to hydronephrosis and create conditions for bladder cancer. In women, urogenital schistosomiasis may cause vaginal bleeding, pain during sexual intercourse and nodules in the vulva – now described as female genital schistosomiasis. In men, urogenital schistosomiasis can induce disease in the seminal vesicles and prostate.

Soil-transmitted helminthiases (STH, also known as intestinal worms) are caused by a group of intestinal parasites comprising Ascaris lumbricoides (roundworms), Trichuris trichiura (whipworms), Necator americanus and Ancylostoma duodenale (hookworms). STH are transmitted by faecal contamination of soil; they adversely affect nutritional status and impair cognitive processes.

©The END Fund

Transmission occurs when eggs that are passed in the faeces of infected people. Adult worms live in the intestine where they produce thousands of eggs each day. In areas that lack adequate sanitation, these eggs contaminate the soil.

1Since 2007, Merck donates ‘praziquantel’ - the recommended treatment against all forms of schistosomiasis - through WHO. In 2017, this donation was increased to 250 million tablets annually. From 2007 to 2018, Merck has donated more than 900 million tablets for school age children.
2Both albendazole and mebendazole are donated to national ministries of health through WHO in all endemic countries for the treatment of all children of school age. Since 2011-2018, GlaxoSmithKline (GSK) has donated more than 1.4 billion tablets of albendazole for use in the preventive treatment of school-age children for control of STH alone.
3Since 2012-2018 Johnson & Johnson (J&J) has donated close to one billion tablets of mebendazole to treat school-age children

Ashok Moloo

Ashok Moloo
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