Schistosomiasis – a Neglected Tropical Disease

Also known as bilharziasis, schistosomiasis is a water-borne disease caused by parasitic blood flukes called schistosomes. Three major schistosome species that infect humans are Schistosoma haematobium (Africa and Middle East), Schistosoma mansoni (Africa and South America) and Schistosoma japonicum (East Asia). S. haematobium causes urogenital schistosomiasis while S. mansoni and S. japonicum cause intestinal schistosomiasis.

The disease is caused primarily by deposition of parasite eggs, in blood vessels surrounding the bladder or intestines by adult worms. Urogenital schistosomiasis is often characterized by haematuria (blood in urine). Other signs and symptoms include vaginal bleeding, lesions of the cervix and vagina and painful sexual intercourse in women. In men, the disease can induce pathology of the seminal vesicles, prostate and other organs. Long term complications associated with this disease include infertility, bladder cancer, ureteral fibrosis and hydronephrosis. Symptoms commonly presented in intestinal schistosomiasis are abdominal pain, diarrhoea, and blood-stained stool. Advanced cases may be associated with liver enlargement.

Schistosomiasis Global Trend

According to the World Health Organization (WHO, 2014), in 2012 there were still 240 million patients with schistosomiasis globally, of which 45.8 % were children aged between 5 and 14 years.

However, Schistosomiasis Fact sheet – Updated January 2017

        • Estimates show that at least 218 million people required preventive treatment for schistosomiasis in 2015.
        • More than 66.5 million people were reported to have been treated for schistosomiasis in 2015.

Schistosomiasis in Africa

Schistosomiasis is the second most common NTDs after hookworm in Sub-Saharan Africa. Children and young adults bear most of the burden resulting from this disease in Africa. Sub-Saharan Africa accounts for 93% (192 million) of the world estimated 207 million cases of schistosomiasis.

The highest prevalence of this infection is seen in Nigeria (29 million), which is closely followed by United Republic of Tanzania (19 million), Ghana, and Democratic Republic of Congo (15 million) making up the top five countries in Africa with schistosomiasis.

Schistosomiasis in Nigeria

Schistosomiasis transmission has been reported from 78 countries. In Nigeria, three species (S. mansoni, S. haematobium and S. intercalatum) are endemic, which led to the formation of a national schistosomiasis control programme in the late 1980s.

Estimates in the mid-1990s suggested that more than 100 million people were at risk for this disease and that 25.8 million people were actually infected (Chitsulo et al., 2000). More recently, the number increased to 29 million (Moné et al., 2010), which corresponds to 14% of the global number of Schistosoma infections.