How to Clean Up Rodent Droppings Safely

Open up the casita after a long Tucson summer and you might find droppings on the bed, a nest in the dresser drawer and a smell that hits you at the door. First instinct is to grab a broom. Don't.

Deer mice live all around Tucson, and they can carry hantavirus. It's rare, but it's serious, and Arizona health officials and the CDC both say to take care when cleaning up after rodents. The method is easy: air the space out for 30 minutes, put on rubber or plastic gloves, soak the droppings with bleach solution or disinfectant for five minutes, then wipe them up with paper towels and bag them. Never sweep or vacuum dry droppings.

Why the broom is a bad idea

Dry droppings and nest material crumble into fine dust when you sweep or vacuum. If a deer mouse left them, that dust can carry virus particles right into the air you're breathing. Wetting everything first keeps the dust on the floor where it belongs. A dust mask isn't a bad idea either, but the wetting is what really does the work.

The worst messes turn up in spaces that sit shut. The casita that only gets used when family visits. The storage room off the carport. The shed full of Christmas boxes, the RV parked all summer, the pool equipment room, the tack room on a horse property. A pack rat midden built inside a shed is the same deal, since it's full of droppings and urine. Wet it, glove up, bag it. Don't pull it apart dry.

The CDC method, one step at a time

These follow CDC guidance for homes, sheds and outbuildings. For a car, air it out about 20 minutes first, then do the same wet-and-wipe. Mix the bleach fresh the day you use it, and don't mix bleach with any other cleaner. Give yourself more time than you think you'll need. Rushing is how people end up sweeping the last little bit.

• Open doors and windows and let the space air out for 30 minutes before you start
• Wear rubber or plastic gloves
• Mix 1 part bleach to 9 parts water, or use an EPA-registered disinfectant
• Spray droppings, urine spots and nests until very wet and let them soak 5 minutes
• Wipe up with paper towels and put everything in a sealed bag
• Mop or wipe floors and counters with disinfectant
• Wash gloved hands, take the gloves off, then wash bare hands well

Rice-sized, spindle-shaped or piled by a midden

The steps are the same no matter who left the mess, but knowing what you've got tells you what to fix next. Mouse droppings are small and pointed, about like a grain of rice, and a drawer full of them means mice in the house. Roof rat droppings are bigger and spindle-shaped and usually up in the attic, which points to roof rats. Pack rat droppings are dark and oblong and pile up around a midden in the yard.

Attics, crawl spaces and rooms with heavy nesting are a bigger job. Insulation may need to come out and the space is hard to work in, so for those, call about attic and casita cleanup. And cleanup doesn't last if mice can still get in. Seal gaps under casita and shed doors, close pipe openings and screen vents with hardware cloth, or have a tech handle sealing entry points. Store bedding and linens in sealed plastic bins. Part-year residents in Green Valley, and anyone with a casita on a big Foothills lot or a detached garage in midtown, should check closed rooms once a month over the summer.

See also: Attic, Crawl Space and Casita Cleanup, Mouse Control, Rodent Exclusion and Sealing