If fresh and not to deep
Brush off the excess (outdoor and using something you want to throw away or can disinfect afterwards to get rid of spores), then ...
First try soaking garment in two quarts of water with 2 cups of borax. Then launder as usual using hottest water recommended for fabric. If chlorine bleach is allowed use it as a wash booster, if not try an oxygen based bleach in wash treatment.
Or, soak affected garment in bucket of cool water to which one cup of white vinegar has been added. Leave for several hours, then launder using hottest water and a good TOL detergent.
You can also try blotting stained area (after brushing off) with a sponge or cloth soaked in hydrogen peroxide. The stuff you get in brown bottles from chemists is fine. Check for colorfastness before applying because peroxide can bleach fabrics.
If fabric is white, and or color safe you can also try dabbing with a diluted chlorine bleach and water solution, wait a moment, then launder as usual.