Schistosomiasis is caused by a parasitic infection which comes from snails in fresh water. The parasites that cause schistosomiasis are primarily in Africa, Brazil, the Middle East, and Southeast Asia. Overall more than 200 million people worldwide have or are at risk for developing this disease. Schistosomiasis is considered a "neglected tropical disease" reflecting problems of the public health and medical communities in effectively controlling this disease. Substantial progress has been made in many areas at reducing or elimination this condition, but it is persistant in many places in the world. Global warming may cause changes in where the disease is located.

This is a picture of B. glabrata snails in a petri dish. This species of snails can harbor Schistosoma mansoni, the species that causes the most cases of schistosomiasis.

These are pictures of Schistosoma eggs. There are 3 main species of Schistosoma: S. mansoni, S. haematobium, and S. japonicum. S. haematobium causes urinary disease, and the other two species cause intestinal disease. The eggs can be distinguished from the shape and spine orientation: S. mansoni is oblong with a spine that is at an angle; S. haematobium is oblong with a spine that is at the end; and S. japonicum is round and without a spine.

The parasite releases eggs within the host. Animals and people infected with schistosomiasis develop granulomas around the eggs to contain the reaction. This is a picture of a mouse lung granuloma around a S. mansoni egg.  

If you want to find out more about schistosomiasis, you can visit the information page at the World Health Organization.

https://www.who.int/news-room/fact-sheets/detail/schistosomiasis