Techniques of embryo transfer and facility decontamination used to improve the health and welfare of transgenic mice.

'Reduction' and 'Refinement' can be achieved in transgenic mouse studies by re-deriving transgenic mouse lines and subsequently maintaining them under high standards of husbandry in a unit with restricted access. This report describes the initial steps of a project to improve the health and welfare of transgenic mice at the European Molecular Biology Laboratory (EMBL), by re-deriving transgenic lines as microbiologically defined animals to be maintained in a barrier unit in a newly constructed animal facility. A pilot study showed that it was possible to transfer embryos obtained from contaminated donor mice in the old facility to specific pathogen free recipients housed in a ventilated cabinet in the new unit, without concomitant carry over of disease. The offspring born following embryo transfer were of high health status and did not show any evidence of contamination with any of the pathogens present in the mice in the old animal unit. Antibodies to various murine viruses (mouse hepatitis virus (MHV), rota virus, reo-3 virus, Theilers encephalomyelitis virus, adenovirus) and parasites were present in sentinel animals from the old animal house whereas the re-derived animals were found to be free of virus antibodies and parasites. Therefore the methods used were considered to be successful in terms of disease prevention and enhancement of welfare. The barrier unit was sterilized without the use of formaldehyde or related substances, to minimize the risks to personnel and to the environment from using potentially dangerous substances. From the results of in vitro and in vivo screening, the protocol for sterilization described here was found to be effective in achieving microbiological sterility of the barrier unit and was cost effective.