Helping the mangy wild fox

We saw the local fox we have caught whiffs of today.
A nice little red was trotting across our pasture when we
went out at 5 PM to bring the horse herd in. Fox seemed
rather mangy and we would like to help it. I have liquid
ivermectin on hand, how much do I put into what sort
of food item and leave for the fox to find? And how often?
All our horses get annual rabies shots. Are there any other
considerations about having a local fox on the property?

PM MistyBlue, she’s a wildlife rehabilitator, she has treated coyotes for mange.
Meanwhile, here is a link, http://foxwoodrehab.typepad.com/my_weblog/2007/10/treating-sarcop.html

There are a couple of versions of mange, so that article might not be the correct treatment.