of subject animals. For example, the use of protective clothing does not have to keep personnel from interacting with the animals through appropriate postural and auditory cues, such as lip-smacking with many Old World species. Personnel should learn which human gestures and vocalizations are inappropriate and avoid the ones that stress the animals. Among the latter are threat faces, stares, threat vocalizations, imitations of alarm calls, and territorial calls. In some cases, physical contact between personnel and animal can be permitted, depending on the animal species and the hazardous agent. Likewise, social housing of animals used for infectious-disease research can be permitted in some studies. The use of biocontainment cage units with transparent walls, rather than solid or opaque walls, is preferred because they provide animals with visual contact with conspecifics. Recommendations provided in the Guide (NRC 1996) regarding acceptable ranges of illumination, cage size, temperature, humidity, ventilation, and noise level for conventional housing should be followed for biocontainment housing.
The enrichment program for animals in studies of infectious disease need not deviate substantially from that applied to conventionally housed animals. Typically, infected animals can receive the food treats used in the enrichment program for noninfected animals. Similarly, toys or other enrichment devices can be used with animals housed in biocontainment conditions if the devices are disposable or appropriately sanitized.
The source of nonhuman primates for research is steadily shifting from wild-born animals to subjects that are born and raised in captivity. Whereas the psychological well-being of an animal is best promoted in a social context that approximates the species-typical norm, sometimes this is not possible. Some mothers might reject or be unable to care for an infant, the infant might be ill and require special care, or an approved research protocol might preclude maintenance of normal social compositions. Under such conditions, every effort should be made to provide infants and other immature animals with appropriate social stimulation so as to minimize the adverse effects of rearing in socially restricted environments. In the case of macaques, daily, but not continuous, nontraumatic contact with age peers seems to prevent the worst symptoms of isolation rearing (Mason 1991). As outlined in Chapter 3, however, hand rearing will seldom succeed in producing a completely psychologically normal animal.
Some research protocols require that primates be physically restrained for various periods. In general, the least restraint that accomplishes the research objective should be used (NRC 1996). Restraint can be achieved by either