Napoleon's invasion of Russia was partly doomed by epidemic typhus, primarily carried by bacteria on this parasite
[DOC] [TLE] How Lice Thwarted Napoleon's Invasion of Russia  Cervantes [PAR] Jul 28, 2009 ... His invasion of Russia failed miserably, leaving a trail of corpses from ... march 
but the spread of "war plague" -- typhus -- through Napoleon's Grand Army.