Results of Survey Regarding Prevalence of Adventitial Infections in Mice and Rats at Biomedical Research Facilities.

Control of rodent adventitial infections in biomedical research facilities is of extreme importance in assuring both animal welfare and high-quality research results. Sixty-three U.S. institutions participated in a survey reporting the methods used to detect and control these infections and the prevalence of outbreaks from 1 January 2014 through 31 December 2015. These results were then compared with the results of 2 similar surveys published in 1998 and 2008. The results of the current survey demonstrated that the rate of viral outbreaks in mouse colonies was decreasing, particularly in barrier facilities, whereas the prevalence of parasitic outbreaks has remained constant. These results will help our profession focus its efforts in the control of adventitial rodent disease outbreaks to the areas of the greatest needs.

Nasal Histopathology and Intracage Ammonia Levels in Female Groups and Breeding Mice Housed in Static Isolation Cages.

Many factors influence ammonia levels in rodent cages, and high intracage ammonia has been associated with specific types of abnormal nasal pathology in mice. The use of autoclaved corncob bedding and the maintenance of low room humidity reduce the accumulation of ammonia in mouse cages. However, there are no engineering standards that define the limits of ammonia exposure for mice housed in static isolation cages. Regulatory guidance indicates that solid bottom cages must be sanitized at least weekly and that cage components in direct contact with animals must be sanitized at least every 2 wk. Common practice is to replace the bottoms and bedding of static isolation cages once weekly. To determine whether changing static isolation cages once weekly is an appropriate performance standard for mice, we prospectively evaluated the relationship between ammonia levels, nasal histopathology, and housing densities in various grouping strategies of mice housed in static isolation cages. Here, we report that the average nasal pathology score per cage and intracage ammonia levels were correlated, but nasal pathology scores did not differ among mice housed in breeding pairs, breeding trios, or female groups. In light of ammonia levels and histopathology scores as performance standards, these results suggest that a weekly cage-change frequency for static isolation cages does not result in adverse effects. Our results provide evidence to support current practices in the use of static isolation cages for housing laboratory mice in modern vivaria.

Perspectives on curriculum needs in laboratory-animal medicine.

Both the United States and Canada have projected shortages of qualified laboratory-animal veterinarians within the next 10 years. This gap is occurring because of retirement, increased regulatory requirements for research animal oversight, and insufficient numbers of veterinarians entering this field. One of the primary means of increasing student interest in nontraditional practice areas, such as laboratory animal medicine, is to ensure that they have appropriate exposure to the topic during their basic clinical training. We outline a recommended curriculum for laboratory animal medicine for North American veterinary medical colleges, which provides strategies for integrating comparative medicine material into the curriculum, incorporates flexibility for a range of delivery methods, and suggests potential resources that may be used to develop this material.

Administration of vaccinia virus to mice may cause contact or bedding sentinel mice to test positive for orthopoxvirus antibodies: case report and follow-up investigation.

Routine testing of bedding sentinels from a barrier room revealed one mouse seropositive to ectromelia virus (EV). Results of hemagglutination-inhibition testing and western blot analysis were confirmatory for orthopoxvirus antibodies. Additional seropositive animals were not identified. Interviews indicated that replication-competent vaccinia virus (VV), Western Reserve strain (VV-WR), recently had been given to mice. Although VV-WR was not expected to spread by contact or via fomites, the case evidence suggested transmission of vaccinia via soiled bedding. In a follow-up experiment, 15 index mice were inoculated with 10(7) plaque-forming units of VV by either subcutaneous or intrarectal instillation. A dedicated contact sentinel and a bedding sentinel were provided for each index mouse. All 15 index mice were positive for antibodies when tested 22 days after inoculation. One mouse, inoculated by the subcutaneous route, appeared ill and developed lesions on the proximal portion of the tail. The contact sentinel mouse housed with this index mouse was the only sentinel to seroconvert. We conclude that VV-WR can spread to contact sentinels and potentially to bedding sentinels. The ability of other VV strains to be transmitted horizontally and the susceptibility of different mouse strains to infection merit further investigation. The use of VV in animal facilities must be managed carefully since the available serologic tests do not distinguish between VV and EV, an exotic agent of major concern to laboratory animal facilities.