section_path: Human interaction/Harm to humans/Disease vectors
section_name: Disease vectors
paragraph_text: Disease vectors
  
  Schistosomiasis (also known as bilharzia, bilharziosis or snail fever), a disease caused by the fluke worm Schistosoma, is "second only to malaria as the most devastating parasitic disease in tropical countries. An estimated 200 million people in 74 countries are infected with the disease – 100 million in Africa alone." The parasite has 13 known species, two of which infect humans. The parasite itself is not a mollusc, but all the species have freshwater snails as intermediate hosts.