Mollusk species can also represent hazards or pests for human activities. The bite of the blue-ringed octopus is often fatal, and that of "Octopus apollyon" causes inflammation that can last for over a month. Stings from a few species of large tropical cone shells can also kill: their venom have become important tools in neurological research. Schistosomiasis (also known as bilharzia, bilharziosis or snail fever) is transmitted to humans via water snail hosts, and affects about 200 million people. Snails and slugs can also be serious agricultural pests, and accidental or deliberate introduction of some snail species into new environments has seriously damaged some ecosystems.