Neglected tropical diseases

Zanzibar: gearing up to eliminate schistosomiasis

07 March 2012 | Geneva

On 30 January 2012, the pharmaceutical, chemical and life science company, Merck KGaA, pledged to increase 10-fold its donation of praziquantel tablets through WHO for the treatment of schistosomiasis (bilharziasis).

The Deputy Minister of Health of Zanzibar, Dr Sira Mamboya, the Chairman of the Managing Board of Merck KGaA, Dr Karl-Ludwig Kley watching school girl ingesting praziquantel at Ngwachani Primary School, Pemba Island, Zanzibar.
©Lester Chitsulo WHO

To mark this substantial increase – from 25 million to 250 million donated tablets per year – a symbolic hand-over of praziquantel was held on 28 February 2012 at the Ngwachani Primary School, on Pemba Island, Zanzibar. Schoolchildren were treated for urogenital schistosomiasis during the event. A booklet for use in schools to educate children about schistosomiasis, funded by Merck and published by WHO, was also launched.

Elimination of schistosomiasis in Zanzibar is now possible through Merck’s increased donation, disease awareness programmes and snail control at disease transmission sites using integrated control activities for other diseases such as malaria.

The ceremony was attended by the Deputy Minister of Health of Zanzibar, Dr Sira Mamboya, the Chairman of the Managing Board of Merck KGaA, Dr Karl-Ludwig Kley, the Director of WHO’s Department of Control of Neglected Tropical Diseases, Dr Lorenzo Savioli, and officials of the administrative and health authorities in Pemba.

About schistosomiasis

Schistosomiasis is a parasitic disease that leads to chronic ill-health. Infection is acquired from contaminated freshwater containing the larval forms (cercariae) of blood flukes, known as schistosomes.

The centimetre-long worms mature in the human bladder and intestines, laying eggs that can cause massive damage to tissues and organs. Once released by the body into water through faeces and urine, the eggs hatch and larvae (miracidia) penetrate suitable snail hosts. The cercariae emerge from the snail into water from where they penetrate a human host, causing infection and perpetuating the life-cycle.


WHO's strategy for schistosomiasis control targets mainly school age children who are most vulnerable for infection. It aims to reduce morbidity through the regular treatment with praziquantel, the only available medicine, through school-based and/or community-based deworming programmes.

Praziquantel is safe and efficacious, with transient side-effects. It has been successfully used over the past 30 years. Although re-infection may occur, providing at least three treatments during childhood greatly reduces the risk of serious manifestations of schistosomiasis in adulthood.

Praziquantel is also safe in pregnancy, and it is recommended that women, and adolescent girls of child-bearing age, should not be excluded from public health interventions.

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