Schistosomiasis in children: a major public health problem
Schistosomiasis (also known as bilharzia) is one of the most prevalent parasitic diseases. It is a poverty-related disease that leads to chronic illness. The threat posed by schistosomiasis is substantial, with 78 affected countries, 700 million people at risk and an estimated 258 million people infected. More than 90% of patients live in Africa, where the disease affects a large proportion of children under the age of 14.
Schistosomiasis is acquired when people come into contact with fresh water infested with the larval forms (cercariae) of parasitic blood flukes, known as schistosomes. The microscopic adult worms live in the veins draining the urinary tract and intestines. Most of the eggs they lay are trapped in the tissues and the body’s reaction to them can cause massive damage. Left untreated, schistosomiasis can lead to anemia, stunted growth, reduced learning ability and chronic inflammation of the organs, which can be fatal in the most serious cases.
As efforts focus on morbidity control and elimination, there is a pressing need to treat preschool-age children (under 6 years old). No suitable drug formulation is made available for this high-risk group, which accounts for about 10% of the 258 million people already infected. The age group of preschool-age children is strategically important: they play a role in local disease transmission and an active infection acquired at an early age might aggravate the clinical significance of schistosomiasis in later-life.
The ‘gold standard’ treatment for schistosomiasis is praziquantel (PZQ), which was developed in the 1970s. A WHO-recommended global strategy to control schistosomiasis already exists; preventive chemotherapy involves yearly administration of PZQ to entire populations at risk. Tablets (usually 600 mg) are given as single oral doses, but the prophylactic treatment is suitable only for adults and school-aged children. Younger children usually cannot swallow the existing tablets because of their large size and bitter taste. More importantly, clinical data for the treatment of very young children are scarce and an appropriate pediatric drug to treat schistosomiasis does not exist, therefore a large young population remains untreated.
The Pediatric Praziquantel Consortium is developing a PZQ formulation that is more suitable for younger children, including infants and toddlers. The formulation should be smaller, orally dispersible, and have improved taste properties compared to the approved 600 mg tablet.