Containment Facilities

To prevent infections in laboratory animals, these should be housed in facilities, in which certain protective measures reduce the risk of infections. This is especially important for breeding colonies, as infections in these will spread to a number of studies, and reestablishment of a breeding colony is a time-consuming, expensive and occasionally an impossible procedure. However, as experimental facilities normally house a number of different studies, some of which would be as time-consuming and expensive to restart, these should also be protected in an appropriate way. Animals deriving from facilities in which no protective measures are applied are called conventional.

Barrier Housing

In animal units, in which the staff is allowed to move freely around, protective measures are used for decontamination of the staff, materials, and fresh air entering the unit, i.e., a barrier is physically as well as mentally in front of the unit (Figure 11.6). Such a barrier may be run at different levels. Basically, materials and diets are autoclaved or chemically decontaminated at entry, and the staff should not be allowed contact to animals of the same species within a certain period, e.g., 48 h. In the same way, animals should only be introduced if health monitoring has documented the absence of unwanted infections. In breeding units, this normally means that new breeding animals are only introduced by rederivation. In breeding units, staff members are only allowed to enter through a 3-room shower, while in experimental units, the staff in some facilities are allowed to enter after changing their clothes, only. Ingoing and preferably also outgoing air is filtered, and the air pressure in the facility is maintained at approximately 15 mmHg above the surrounding pressure to prevent air-borne infection. In some facilities, protection is further enhanced by the use of facemasks and gloves by the staff (Figure 11.7). However animals kept in barrier-protected facilities may (even if the staff is equipped with protective clothing) only be kept free of certain species-specific infections. They will not be free of infections shared between

Figure 11.7 An animal technician dressed for working in a barrier-protected animal unit (Ellegaard Göttingen Minipigs, Denmark).

their own species and humans.2 Therefore, they will have a bacterial flora in their gastrointestinal, respiratory, and genital systems and on their skin, which can never be fully defined.

Animals bred in barrier-protected facilities are sold under different terms. Preferable, the term microbiologically defined should be used to indicate that the animals have been protected and health monitored. Occasionally, the term specific pathogen free (SPF) is used, however, without always clearly defining which specific pathogens are actually considered. Some commercial breeders have their own registered trademarks, such as Virus Antibody Free (VAFTM) or Cesarian-Originated Barrier-Sustained (COBSTM).

If the aim is to protect the surroundings, e.g., because animals of an unknown or a known but unacceptable microbiological quality are housed, all containment facilities may be run in the opposite direction, i.e., with a negative air pressure and all the decontamination procedures applied for staff and materials leaving the facility.

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