Field mouse spotted in my garden where I keep ducks - kill or ignore?

From a google search, copy and paste...

Rodents such as rats and mice are associated with a number of health risks. In fact, rats and mice are known to spread more than 35 diseases. These diseases can be spread to humans directly through handling of live or dead rodents, contact with rodent feces, urine, or saliva, as well as rodent bites. Diseases carried by rodents can also be spread to humans indirectly through fleas, ticks, or mites that have fed on an infected rodent.

From this page.
What Diseases Do Mice & Rodents Carry? Rodent Diseases

I grew up on a dairy farm. One day , Dad decided we were, going to bag some grain.
Metal sided round grain bin. Put us kids in and we started bagging. Pretty soon,
rats were running wild. Had to go find the cats and we kids, were pounding on the rats,
with shovels.