Health and safety

The short version

• Keep new animals apart for about 4 weeks before they join your colony.
• After that, keep your colony closed: new breeders come from your own animals.
• Keep wild mice out. They carry bugs and a virus called LCMV.
• Watch for sick animals: hunched, rough fur, getting thin, runny eyes or nose, sneezing, or not moving when you open the cage. Never feed a sick rodent to a snake.
• Feeder rodents can carry Salmonella, even frozen. Wash your hands, never thaw feeders in a microwave used for people's food, and keep children under 5, older adults, pregnant women and people with weakened immune systems from handling feeders; those are the four groups the CDC names for feeder rodents [5].

Biosecurity

• Quarantine new animals about 4 weeks in a separate area [1] (see Getting started).
• A closed colony. Once it's running, new breeders come from your own animals. Outside animals only after quarantine.
• Keep wild mice out. They carry parasites and LCMV. Seal food in bins, close gaps, and trap around (not in) the rodent room.
• Separate tools and gloves for the rodent room and the snake room; wash hands between them.

Problems seen in Mastomys colonies

• Skin growths (papillomas). About 8% a year in one colony, more often in older breeders [2]. A papillomavirus causes skin tumors in M. coucha [3]. Don't breed affected animals.
• Stomach tumors. In lab colonies, older Mastomys often get gastric carcinoids, a kind of stomach tumor [4]. That's one more reason to retire breeders by about a year.
• Mites and mange. A lab colony treated mange with ivermectin [2], and the NIH colony used ivermectin-medicated feed when mites were suspected [1]. Ask a vet for treatment; doses for rodents and for snakes are not interchangeable. Rodent mites can also bite people and reach a snake room, so treat any mite problem as urgent.
• General signs of illness (lab-rodent standard): hunched posture, rough coat, weight loss, discharge from the eyes or nose, sneezing, not moving when the cage opens. Isolate or cull, and never feed a sick rodent to a snake.

Not much has been written about breathing illness in Mastomys. When the NIH colony was tested, it had no LCMV and no Mycoplasma pulmonis [1].

Keeping people safe

Salmonella. Frozen feeder rodents have caused multistate outbreaks: 41 people in 21 states in 2014 [5], and 46 people in 22 states in 2011–12, more than a third of them aged 5 or under [6]. The FDA's advice [7]:

• Freezing doesn't kill Salmonella.
• Wash hands after handling feeders, live or frozen, and anything they touched.
• Children under 5, older adults, pregnant women and people with weakened immune systems shouldn't handle feeders [5].
• Never thaw feeders in a microwave used for people's food.

LCMV (lymphocytic choriomeningitis virus). In 2012, LCMV spread at a feeder-rodent business. Of 97 workers tested, 31 (32%) had antibodies, a sign they had caught it, and 4 got meningitis. About 21% of the mice there were infected, and the colonies were destroyed [8]. The virus came from mice. It's a reason to buy only from known breeders, keep wild mice out, and wear gloves and a dust mask when dumping bedding.

Step by step: every visit to the rodent room

1. Put on gloves. Use the rodent-room gloves and tools, not the snake-room ones.
2. Wear a dust mask if you'll be dumping bedding.
3. Look at every animal for signs of illness: hunched posture, rough coat, weight loss, eye or nose discharge, sneezing, not moving when the cage opens.
4. Look for mites. Treat any mite problem as urgent, and ask a vet for treatment.
5. Isolate or cull any sick animal. Never feed it to a snake.
6. Check that food is sealed in bins and there are no gaps where wild mice could get in.
7. Wash your hands before you go near the snakes.

Sources for this chapter

1. Safronetz, D. et al. (2021), Viruses, PMC8065687
2. Kagira, J. M. et al. (2005), Scandinavian Journal of Laboratory Animal Science, PDF
3. Rösl, F. (2008), Mastomys coucha as a model for papillomavirus skin cancer, Central European Journal of Public Health
4. Nilsson, O. et al. (1992), gastric carcinoids in Mastomys, PMC2589773
5. CDC, Salmonella infections linked to frozen feeder rodents (2014)
6. CDC, MMWR (2012), Salmonella from feeder rodents
7. FDA, Salmonella, feeder rodents and pet reptiles
8. CDC, LCMV at a rodent breeding facility (2012)