Acclimation is "the process of becoming accustomed to a new environment."[1]

Quarantine is the "detention of...animals suspected to have communicable disease until they are proved free of infection. The term is often used interchangeably with isolation (separation of a known infected individual from healthy ones until the danger of transmission passes)."[2]

Animals transported from outside the institution may experience mild to moderate stress. This stress results from perturbations in the environment, fluctuations in temperatures during transportation, short-term food and water regulation, noise, or other physical aspects of shipping. Elevated serum corticosteroid concentrations (one method of measuring stress) is often seen following transportation, and a return to normal corticosteroid levels can be used to establish a period of acclimation[3]. The Guide for the Care and Use of Laboratory Animals[4] recommends, "...newly received animals should be given a period of physiologic, psychological, and nutritional stabilization before their use…. The need for an acclimation period has been demonstrated in mice, rats, guinea pigs, nonhuman primates, and goats, and time for acclimation is likely important for other species as well."

In addition to allowing the animal a period of time to acclimate to its new surroundings, this time will also be used to evaluate the animal’s health status. Transportation can expose animals to potential pathogens or exacerbate subclinical infection. Therefore, this time should help allow for any potentially infectious conditions to be identified and/or treated. Exposure to adventitious pathogens can negatively impact research results.

The length of time for acclimation will depend on the type and duration of animal transportation, the species involved, and the intended use of the animals. However, a minimal period of forty-eight (48) hours, excluding the day of arrival, is required to evaluate the animal and allow the animal to acclimate to its new environment. Animals intended for terminal experiments may be used prior to the end of this acclimation period following consultation with and approval by the veterinary staff; such policy exceptions should be documented in the ARC protocol.

Quarantine involves isolation of animals with questionable health status from animals already housed in the colony, and usually employs testing, such as bloodwork and fecal exams. Vaccination of some species is also conducted during quarantine. Depending on the species, the duration of the quarantine period varies. Animals in quarantine are not available to investigators for research purposes.[5]

Mouse Quarantine

Disease detection by sentinel mice exposed to soiled bedding has not proven to be a fail-safe method of disease identification and prevention in mice[6], [7]. As such, health reports received from non-approved vendors cannot be entirely relied on. Mouse quarantine practices, however, have been shown to be effective in preventing infectious diseases at biomedical research facilities[8]. Therefore, in an effort to reduce the potential of importing pathogens from outside sources, mice coming to UCLA from non-approved vendors will enter through a quarantine process managed by DLAM. This process will include additional disease surveillance and basic treatments for pinworm and fur mite infestations. For more information, contact


  1. Veterinary Dictionary: Saunders Comprehensive Veterinary Dictionary 3rd Edition, by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier, 1999.
  2. Encyclopedia Britannica online.
  3. Landi, M. S., J. W. Krieder, et al. (1982). Effects of shipping on the immune function in mice. Am J Vet Res 43(9):1654-7.
  4. Guide for the Care and Use of Laboratory Animals. National Research Council, p. 111, 2010.
  5. ILAR Journal: Preparation of Animals for Use in the Laboratory. 2006:47(4).
  6. Besselen, D. G. et al. Transmission probabilities of mouse parvovirus 1 to sentinel mice chronically exposed to serial dilutions of contaminated bedding. Comp. Med. 2008 Apr;58(2):140-4.
  7. Smith, P. C. et al. Reliability of soiled bedding transfer for detection of mouse parvovirus and mouse hepatitis virus. Comp. Med. 2007 Feb;57(1):90-6.
  8. Marx, J.O., Gaertner, D. J. and A. L. Smith. Results of Survey Regarding Prevalence of Adventitial Infections in Mice and Rats at Biomedical Research Facilities. J Am Assoc Lab Anim Sci. 2017 Sep;56(5): 527–533.

Approved 1/28/02; Revised 5/24/04, 4/12/10, 1/27/20; Updated 1/18/11