The Genetics of Schistosomiasis
The parasite Schistosoma is responsible for up to 200 million cases of Schistosomiasis each year. Over 20 million people are seriously disabled by severe anemia, chronic diarrhea, internal bleeding and organ damage caused by the worms and their eggs, or the immune system reactions they provoke. In sub-Saharan Africa alone, Schistosomiasis kills 280,000 people each year.
People become infected with Schistosoma from exposure to water infested with tiny snails that host the parasites. The parasites are released into the water, and burrow into the skin. They travel to blood vessels that supply urinary and intestinal organs, including the liver, where they mature. The female worms release thousands of eggs each day. Eggs shed in urine and feces may make their way into snail-inhabited water, where they hatch to release parasites that seek out snails to begin the cycle again.
The current treatment for Schistosomiasis is an inexpensive drug, praziquantel. While effective, it does not prevent a person becoming re-infected. The parasites can also develop resistance to it. Accordingly, new drugs and other interventions are badly needed to reduce the impact of a disease that lowers quality of life and slows economic development.
Recently published in the leading international journal, Nature, a team of researchers lead by Dr. Najib El-Sayed of MPRI uncovered the genetic blueprint of S. mansoni, the most widespread of the schistosomiasis parasites. The study revealed that S. mansoni is made up of 11,809 genes, approximatelly10 times the size of the malaria parasite genome. The researchers identified a large number of genes encoding enzymes that break down proteins. Subsequent analysis revealed 120 enzymes that could potentially be targeted with drugs to disrupt the worm's metabolism. The researchers also identified 66 commercially available drugs that might also be effective against schistosomiasis. One particularly notable finding is that S. mansoni lacks a key enzyme needed to make essential fats, and must rely on its host to provide these - revealing a potential target for drug development.
As quoted by Dr. El-Sayed to the BBC news, "The genome sequence has given us, for the first time, a comprehensive view of the engines that drive the parasite, the strategies that allow it to survive in us, its human host.
For more information about this study: