New research highlighting a previously unknown genome in the Biomphalaria snail, a known transmitter of the Schistosoma mansoni (S. mansoni) parasite, may explain why this particular snail is such a suitable host for S. mansoni. The discovery, said research team member Mathilde “Matty” Knight, PhD, adjunct professor of microbiology, immunology, and tropical medicine at the George Washington University School of Medicine and Health Sciences, could offer insight into how the parasite can be stopped.
S. mansoni is a shared parasite in humans and the Biomphalaria snail. It spreads schistosomiasis, an infectious, parasitic disease that can lead to cancer, chronic infertility, and female genital schistosomiasis, exposing people to HIV. Over the course of the parasite’s life cycle, it reproduces asexually within the host snail before being released into freshwater rivers and streams, where it comes in contact with humans. Once in the body, the parasite burrows into the area around the intestines it reproduces and lays its eggs. The larvae from the eggs are released back into freshwater in either feces as S. mansoni, or urine as S. hematobium, and again find their way to the snail to repeat the cycle.
There are a variety of snail species capable of serving as a secondary host for the parasite, but the Biomphalaria snail is the most suitable. Additionally, as global warming continues, the snails and the parasites they carry are on the move. “This snail is native to Brazil,” explained Knight, “but in 2015, a case of schistosomiasis was diagnosed in France. They found that people in Corsica were infected with a parasite that is also found in West Africa.”
As it stands, there is only one drug treatment, praziquantel, available for schistosomiasis. The medication, however, does not provide enough peace of mind, explained Knight. Like other drugs for chronic diseases, such as malaria, the parasite can build up a resistance to praziquantel, rendering it ineffective with repeated use.
Knight’s research suggests that the best way to eliminate the parasite, is to target S. mansoni in the snails and cut off its asexual development, effectively ending the life cycle.
Conditions can also be improved in endemic areas by measures such as construction of bathrooms. Schistosomiasis is a disease of poverty, Knight explained, and the needs of the infected population may be ignored by those within their own country.
The World Health Organization has developed a goal for the global elimination of schistosomiasis as a public health threat by the year 2025, taking both the mass administration of praziquantel and targeting the snail as the primary host into account.
Read more information about the study, “Whole Genome Analysis of a Schistosomiasis-Transmitting Freshwater Snail.”
