I hope that all of you ,using horse manure, are aware of a nasty thing living in the guts of all horses and there's plenty of it in their manure also .
It's latin name is
Clostridium tetani.
Take care not to puncture or cut yourselves deeply enough ( where is lack of oxygen at the skin and muscle tissue ) ,when working at your garden.
Before a century ago ,when the use of horses for transport was still common,stepping onto a nail which came off from a horseshoe ,
could prove to be fatal .
(...)Tetanus is a potentially fatal disease characterized by muscular spasms caused by a neurotoxin produced by the bacterium
Clostridium tetani. These organisms, and their spores, are found in the intestinal tract of horses and other species and are abundant in the soil, where they can survive for many years. The spores can enter open wounds, particularly puncture wounds, where they proliferate under the right conditions.(...)
https://ceh.vetmed.ucdavis.edu/health-topics/tetanus
https://en.m.wikipedia.org/wiki/Tetanus