A 42-year-old man had nausea, vomiting, periumbilical pain, tenesmus, and d
iarrhea shortly after eating seafood. Stool microscopy showed "beaver bodie
s," or Psorospermium haeckelii, a nonpathogenic algal organism often confus
ed with enteric pathogens and commonly found in the excrement of persons co
nsuming crayfish.