Effects of Maternal Fenbendazole on Litter Size, Survival Rate, and Weaning Weight in C57BL/6J Mice.

Fenbendazole is a broad-spectrum benzimidazole commonly used in laboratory animal medicine as an anthelmintic for elimination of pinworms. This drug is generally regarded as safe, with minimal side effects. Some data in rodent species indicate multiple physiologic effects of fenbendazole, including changes in immune parameters and behavior, but no studies to date have evaluated possible effects on reproduction in mice. The purpose of the current study was to determine the effects of several treatment regimens of fenbendazole on reproductive parameters in C57BL/6J mice. Uninfected mice were given fenbendazole-treated feed continuously or every other week until pups were born or weaned. This treatment also was combined with environmental decontamination. No significant differences in litter size, survival rate, or weaning weight were detected between groups. Under the conditions of this study, fenbendazole treatment does not affect reproduction in C57BL/6J mice.

Contaminated Shipping Materials Identified as the Source of Rotaviral Infection of Exported Mice.

Over a 4-wk period in 2017, we received notification from 7 different institutions that mice exported from our SPF barrier facilities had tested positive for mouse rotavirus (MRV). The exports originated from several different buildings across multiple campuses. Our institution excludes MRV in all of our barrier facilities and has historically been free of this virus. Extensive testing of our rooms from which the exported mice originated did not detect the presence of rotavirus. The single commonality among the 7 shipments was the use of shipping boxes acquired from one vendor. These shipping boxes arrived at our institution prepackaged with unsterilized feed and bedding, which we hypothesized was the source of the rotavirus. To test this hypothesis, we housed naïve sentinel mice in clean cages with feed and bedding transferred from 29 unopened, unused shipping boxes. Sentinel mice were exposed to this bedding and feed for 14 d and then evaluated through MRV serology and PCR assay. Of the 29 sentinels, 24 were seropositive for MRV, and 14 of the 29 were PCR positive. These results provided direct evidence that MRV detected by recipient institutions originated from the contaminated feed or bedding within the shipping boxes. To our knowledge, this report is the first description of contaminated materials in shipping boxes resulting in rotaviral infection of mice during export.

Assessing cervical dislocation as a humane euthanasia method in mice.

Research investigators often choose to euthanize mice by cervical dislocation (CD) when other methods would interfere with the aims of a research project. Others choose CD to assure death in mice treated with injected or inhaled euthanasia agents. CD was first approved for mouse euthanasia in 1972 by the AVMA Panel on Euthanasia, although scientific assessment of its humaneness has been sparse. Here we compared 4 methods of spinal dislocation--3 targeting the cervical area (CD) and one the thoracic region--in regard to time to respiratory arrest in anesthetized mice. Of the 81 mice that underwent CD by 1 of the 3 methods tested, 17 (21%) continued to breathe, and euthanasia was scored as unsuccessful. Postmortem radiography revealed cervical spinal lesions in 5 of the 17 cases of unsuccessful CD euthanasia. In addition, 63 of the 64 successfully euthanized mice had radiographically visible lesions in the high cervical or atlantooccipital region. In addition, 50 of 64 (78%) mice euthanized successfully had radiographically visible thoracic or lumbar lesions or both. Intentionally creating a midthoracic dislocation in anesthetized mice failed to induce respiratory arrest and death in any of the 18 mice subjected to that procedure. We conclude that CD of mice holds the potential for unsuccessful euthanasia, that anesthesia could be valuable for CD skills training and assessment, and that postmortem radiography has minimal promise in quality-control assessments.

Soiled bedding sentinels for the detection of fur mites in mice.

Identification and eradication of murine fur mite infestations are ongoing challenges faced by many research institutions. Infestations with Myobia musculi and Myocoptes musculinus can lead to animal health problems and may impose unwanted research variables by affecting the immune and physiologic functions of mice. The purpose of this study was to evaluate the utility and efficacy of soiled bedding sentinels in the detection of fur mite infestations in colony mice. Female young-adult CRL:CD1(ICR) mice (n = 140) were exposed over a 12-wk period to various volume percentages of soiled bedding (11%, 20%, 50%, and 100%) from fur-mite-infested animals. Mice were tested every 2 wk with the cellophane tape test to identify the presence of fur mite adults and eggs. At the end of 12 wk, all mice exposed to 11%, 20%, and 50% soiled bedding tested negative for fur mites. One of the 35 mice (3%) receiving 100% soiled bedding tested positive for fur mites at the end of the 12-wk follow-up period. These findings suggest that the use of soiled bedding sentinels for the detection of fur mite infestations in colony mice is unreliable.