Mouse husbandry

Head / Coordinator GMC

PD Dr. Markus Brielmeier
Phone ++49 (89) 3187 2298
Fax ++49 (89) 3187 3321

Mailing address

Research Unit Comparative Medicine
Helmholtz Zentrum München - German Research Center for Environmental Health
Ingolstädter Landstr. 1
85748 Neuherberg


The GMC health monitoring concept

The concept of the GMC, on the one hand being part of an integrated research network and on the other hand harboring mice with varying hygienic status and thereby representing a challenging experimental animal unit, is based on a working compromise. This takes into account the basic specific research requirements. These include, from the scientist's point of view, a modular design with mouse rooms and laboratories adjacent to each other, simultaneous handling and analysis of mice from different hygienic sources, unrestricted transfer of mice between the modules, frequent access of numerous users from different facilities, and a shared infrastructure. From the hygienic point of view, mice and personnel from different areas/facilities/institutions, the use of a shared infrastructure and continuous flow of mice between the different modules require standardized measures and efficient means to avoid cross contamination and disease during the phenotyping workflow. Measures for husbandry, first of all use of IVC caging,  barrier- and import regulations including an exclusion list for pathogens have been implemented in order to prevent spreading of pathogens from infected to non-infected colonies and to minimize the risk of carry-over and dissemination of infections in the GMC.

To improve the knowledge of the actual hygienic status, a custom-tailored sentinel monitoring program was implemented, which uses sentinel mice standardised according to strain, age and gender, thereby avoiding the use of valuable mutant animals. To account for monitoring of mice in IVC racks, environmental samples are used in addition to Sentinels. In case of detection of new pathogens the GMC database allows to trace back suspicious animals and the origin of infection.

Despite available state-of-the-art equipment and standardised operating procedures in the mouse rooms and laboratories, residual risks arising from specific scientific needs of this unique research facility remain unresolved. These include the handling of mice in the phenotyping instruments outside the IVCs or changing stations, the fluctuation and individual discipline of the personnel, unknown susceptibility of mutant mice to pathogens and an unpredictable influence of the stress exerted on the mice due to the fast workflow within the phenotypical screens. Experience of the last ten years shows that these residual risks can be effectively controlled by the implemented organizational and technical measures.


Husbandry and procedures


Mice in the GMC are housed in type II long (GM500) polyeterimide cages in individually ventilated caging (IVC) systems (Sealsafe plus TM, Tecniplast, Bugugiate, Italy). The IVCs operate at positive pressure; their exhausts are connected to the ventilation (HVAC) system. Mice are transferred to new cages with forceps in Class II changing stations with adjustable height, which offers maximum convenience to the user and ensures job safety.


All users completely change their garment and shoes and wear caps and masks before entering the GMC. Gloves are mandatory for animal handling. Entry into the GMC is regulated by an electronic admission control system (SiPort TM, Siemens). All heat-resistant materials are autoclaved, while other materials are treated with disinfectants. Water is filtered through 0.2 µm filters. Mice are fed with irradiated standard and breeding rodent diet (Altromin 1314) ad libitum.

Import of mice:

Upon arrival, all mice imported into the GMC are transferred into autoclaved GM500 cages in the import class II changing station placed in the lobby of the GMC (Fig. 1). Cages with imported mice are brought through the disinfection chamber, which serves as a sluice and transferred again to autoclaved IVCs and placed into the IVC racks in the respective module.

Hygienic status:

Mice are only accepted for import to the GMC if a recent health report of the sending unit according to FELASA recommendations fits the exclusion list and has been approved by an ad hoc committee of laboratory animal scientists and microbiologists. In general, mice are not accepted from units with reported infections with ectoparasites or treatable endoparasites.

Sentinel monitoring:

Outbred 8 week-old male SPF Swiss mice are used as sentinels. Two sentinels are placed into Bioscreen TM sentinel cages in the IVC rack every 3 months. Sentinels are kept on a mixture of new bedding and aliquots of soiled bedding (50:50) from all cages of the IVC racks in each mouse room. This mixture is renewed weekly concomitant with the change of the bedding in the IVCs. Health monitoring is carried out by on-site examination of the sentinel mice every three months.