glanders vs syphilis

glanders

noun
  • An infectious disease of horses, mules and donkeys caused by the bacterium Burkholderia, one species of which may be transmitted to humans. 

syphilis

noun
  • A disease spread via sexual activity, caused by the bacterium Treponema pallidum. 

How often have the words glanders and syphilis occurred in a corpus of books? (source: Google Ngram Viewer )