When we think of deadly creatures, our minds often gravitate toward large predators. However, the most lethal killers in the natural world happen to be quite small.
Snail parasites are responsible for thousands of deaths annually, having infected nearly 250 million people, primarily in regions across Asia, Africa, and South America. This parasitic disease is known as schistosomiasis, and despite its ease of transmission, it remains relatively unknown. The parasite resides in freshwater environments worldwide, primarily latching onto snails, and waiting for other organisms to enter the water. Once it detects a potential host, it attaches to the skin and burrows into the host's blood vessels, where it can reproduce and live for decades.
Interestingly, it's not the parasite itself but its eggs that cause the infection. These eggs possess sharp barbs that pierce through the host's body, allowing them to return to the water, where they seek out a snail to complete their life cycle.
In 1970, the invention of a drug called praziquantel revolutionized the fight against schistosomiasis, offering an affordable means to eliminate the parasite. This led many countries to abandon efforts to eradicate snails in favor of modern medical treatments. However, researchers at Stanford University observed that countries adopting a more ecological approach experienced lower infection rates. They began to consider more effective methods for combating schistosomiasis, such as introducing predators into the ecosystem to target the snails.
Susanne Sokolow, a disease ecologist at Stanford University, noted the need to reintroduce snail predators specific to regions like Senegal in West Africa. Human activities often alter the environment and displace some of these natural predators. Sokolow collaborated with a local nonprofit to devise a "creative engineering" strategy for reintroducing snail predators. This involved constructing ladders over dams to facilitate predator access, ultimately offering a more environmentally sustainable solution to combat schistosomiasis.
[Sources: Upstream Alliance; Science Friday]