is another disease spread by snails in tropical countries . Some locals call this infection “ swimmer ’s itch , ” you may have seen movies where people in the jungle were told not to urinate while swimming , because “ the bugs will swim up your ding - dong . ” Katayama ’s Fever usually results in severe urinary tract infections , but some forms of the disease enter the nerves system where they lay eggs in the brain . While this disease has a low mortality rate , life for the infected human host is usually extremely uncomfortable .