Strict quarantine or isolation of all newly acquired rodents for at least 4 weeks greatly helps prevent disease among pet mice and rats. This recommendation is especially important for pet rodents because of the severity of certain diseases that they may harbor without showing signs of illness.
Mice and rats should be purchased from reputable sources. The prospective pet owner should never purchase an obviously or even suspiciously ill rodent. Furthermore, it is never wise to purchase an animal that has been in contact with one appearing ill, even though the intended purchase appears perfectly healthy.
Rats and mice are especially sensitive to the irritating effects of ammonia. This chemical builds up quickly in the bedding from the relatively large volume of urine excreted by pet mice and rats. Bedding must be changed 2-3 times each week, or more often if necessary. Furthermore, ventilation must be adequate to reduce or eliminate the irritating effects of ammonia on the respiratory lining of pet rodents.