To monitor rodent colony health in research facilities, soiled-bedding sentinel (SBS) animals have traditionally been used. SBS can be tested by various methods, which may include serology, PCR analysis, and necropsy. Several pathogens are unreliably detected by using SBS or transmitted poorly through soiled bedding, and collection and evaluation of SBS samples can be time-intensive. Recently, exhaust air dust (EAD) testing through PCR analysis has emerged as an adjunct or replacement method for rodent colony health monitoring. EAD monitoring may provide a more efficient, sensitive, and humane method for monitoring health status. Using both EAD and SBS health monitoring, we evaluated colony health over the course of 1 y in 3 research barrier rooms in which mice were housed exclusively on IVC racks. Three pathogens—Helicobacter spp., Rodentibacter spp. (previously Pasteurella pneumotropica), and murine norovirus (MNV)—were not excluded in 2 of the rooms, and we expected that these mice would test positive with some regularity. EAD monitoring was significantly more sensitive than SBS for detection of the bacterial agents. SBS failed to detect Helicobacter spp. at time points when EAD had 100% detection in the rooms that did not exclude the bacteria. The detection of MNV did not differ between health monitoring systems at any time point. The findings suggest that EAD is especially valuable in detecting bacteria poorly transmitted through soiled bedding. In addition, the corresponding results with MNV detection suggest that EAD surveillance can reliably be implemented as an alternative to SBS monitoring in a facility in which mice are housed exclusively on IVC racks.

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Rodent vivaria have traditionally used soiled bedding sentinel (SBS) health-monitoring programs to detect and exclude adventitious pathogens that could affect research results. Given the limitations of SBS, a likely reduction in animal usage, and a decrease in animal care staff labor, exhaust air dust (EAD) health monitoring has been evaluated by several groups for its efficacy in detecting pathogens when used as a complete replacement for traditional SBS health-monitoring programs. Compared with SBS, EAD has also been shown to provide increased sensitivity for the detection of multiple pathogens. After implementing EAD at our institution, we conducted an analysis to compare the annual costs of the 2 health-monitoringprograms. The EAD program was found to be 26% less expensive than SBS. In addition to these cost savings, EAD decreased the amount of time spent by the staff on heath-monitoring activities. For veterinary technicians, this decrease in time was calculated as a savings of 150 h annually, almost 3 h each week. Finally, the EAD program replaced the use of live sentinel animals, decreasing the associated yearly usage from 1,676 animals to zero.

Ornithonyssus bacoti, commonly known as the tropical rat mite, is a zoonotic ectoparasite that occasionally infests research rodent colonies. Most infestations have been attributed to wild rodents that harbor the mite and spread it to research animals, often during building construction or other activity that disrupts wild rodent populations. Although infestation may be clinically silent, severe outbreaks have been reported to cause pruritis, dermatitis, decreased reproductive performance, and anemia in rodents. In mid 2020, our institution experienced increased activity of wild mice, which were found to be infested with O. bacoti, diagnosed by microscopic exam and confirmed by fur swab PCR analysis. We elected to add O. bacoti to our quarterly health monitoring exhaust air dust (EAD) testing PCR panel, increase wild mouse control measures, and treat the environment with a sustained-release synthetic pyrethroid spray in an attempt to prevent colony animal infestation. Initial quarterly EAD health monitoring results in September of 2020 were negative for O. bacoti. However, in early 2021, multiple IVC racks tested positive for O. bacoti at quarterly testing. Treatment consisted of providing permethrin soaked nesting material and surface spray treatment of the room and hallway with a sustained-release synthetic pyrethroid. Historically in the literature, O. bacoti outbreaks of research mice were not identified until mite burden was high enough to cause dermatitis on animal care workers. Due to modern molecular diagnostics and proactive PCR-based health monitoring surveillance, we were able to identify the outbreak earlier than would have otherwise been possible. To the best of our knowledge, this is the first report to successfully identify O. bacoti using environmental health monitoring PCR techniques. This outbreak demonstrates the importance of screening for O. bacoti in facilities with the potential for wild rodent infestation and highlights unique considerations when managing O. bacoti infestations. In addition, a novel permethrin-soaked enrichment item was developed for cage-level treatment.