and isolators might be suitable alternatives. In some instances, it might be acceptable to house different species in the same room, for example, if two species have a similar pathogen status and are behaviorally compatible. Some species can have subclinical or latent infections that can cause clinical disease if transmitted to another species. A few examples might serve as a guide in determining the need for separate housing by species:

• Bordetella bronchiseptica characteristically produces only subclinical infections in rabbits, but severe respiratory disease might occur in guinea pigs (Manning and others 1984).

• As a rule, New World (South American), Old World African, and Old World Asian species of nonhuman primates should be housed in separate rooms. Simian hemorrhagic fever (Palmer and others 1968) and simian immunodeficiency virus (Hirsch and others 1991; Murphey-Corb and others 1986), for example, cause only subclinical infections in African species but induce clinical disease in Asian species.

• Some species should be housed in separate rooms even though they are from the same geographic region. Squirrel monkeys (Saimiri sciureus), for example, might be latently infected with Herpesvirus tamarinus, which can be transmitted to and cause a fatal epizootic disease in owl monkeys (Aotus trivirgatus) (Hunt and Melendez 1966) and some species of marmosets and tamarins (Saguinus oedipus, S. nigricollis) (Holmes and others 1964; Melnick and others 1964).

Intraspecies separation might be essential when animals obtained from multiple sites or sources, either commercial or institutional, differ in pathogen status, e.g., sialodacryoadenitis virus in rats, mouse hepatitis virus, Pasteurella multocida in rabbits, for Cercopithecine herpesvirus 1 (formerly Herpesvirus simiac) in macaque species, and Mycoplasma hyopneumoniae in swine.

All animals should be observed for signs of illness, injury, or abnormal behavior by a person trained to recognize such signs. As a rule, this should occur daily, but more-frequent observations might be warranted, such as during postoperative recovery or when animals are ill or have a physical deficit. There might also be situations in which daily observations of each animal is impractical, for example, when animals are housed in large outdoor settings. Professional judgment should be used to ensure that the frequency and character of observation minimize risks to individual animals.

It is imperative that appropriate methods be in place for disease surveillance and diagnosis. Unexpected deaths and signs of illness, distress, or other deviations from normal in animals should be reported promptly to ensure appropriate