Hypodermic needles are sometimes reused in animal research settings to preserve the viability of and to conserve limited quantities of injected material. However, the reuse of needles is strongly discouraged in human medicine to prevent inju- ries and the spread of infectious disease. No official guidelines prohibit needle reuse in veterinary medicine, although the practice may be discouraged. We hypothesized that reused needles would be significantly more blunt than unused needles and that reuse for additional injections would cause more animal stress. To test these ideas, we evaluated mice that were injected subcutaneously in the flank or mammary fat pad to generate cell line xenograft and mouse allograft models. Needles were reused up to 20 times, based on an IACUC-approved protocol. A subset of reused needles was digitally imaged to determine needle dullness based on the area of deformation from the secondary bevel angle; this parameter was not different between new needles and needles that had been reused 20 times. In addition, the number of times a needle was reused was not significantly related to audible mouse vocalization during injection. Finally, nest building scores for mice that were injected with a needle used 0 through 5 times were similar to those of mice injected with a needle had been used 16 through 20 times. Among the 37 reused needles that were tested, 4 were positive for bacterial growth; the only organisms cultured were Staphylococcus spp. Contrary to our hypothesis, reusing needles for subcutaneous injections did not increase animal stress based on analysis of vocalization or nest building.

Washing and sanitizing rodent cage components requires costly equipment, significant personnel effort, and use of natural resources. The benchmark frequency for sanitation of individually ventilated caging (IVC) has traditionally been every 2 wk. In this study, we investigated the effects of extending this interval on the cage microenvironment, basic markers of health, and the gastrointestinal microbiota of rats. We compared our institutional standard of changing the sanitation interval for rat cage lids, box feeders, and enrichment devices from every 4 wk to an interval of 12 wk. The cage bottom and bedding continued to be changed every 2 wk for both groups. We hypothesized that we would find no significant difference between our current practice of 4 wks and continuous use for 12 wk. Our data showed that intracage ammonia levels remained below 5 ppm for most cages in both groups, with the exception of cages that experienced a cage flood. We found no significant difference between groups in bacterial colony forming units (CFU) on cage components. We used 3 novel methods of assessing cleanliness of enrichment devices and found no significant effect of continuous use for 12 wk on the number of CFU. In addition, we found no significant differences between groups for animal weight, routine blood work, or fecal and cecal microbiomes. These data indicate that a sanitation interval of up to 12 wk for components of rat IVC caging has no significant effects on the microenvironment or health of rats. Using the longer interval will improve efficiency, reduce the use of natural resources, and decrease costs while maintaining high-quality animal care.

Teaching through the use of animals is an integral part of veterinary education. In addition to interactions with privately owned animals, veterinary students often learn using cadavers and institutionally owned animals. Veterinary students also frequently participate in research involving animals. Animal-based research is essential for the development of therapies and techniques that improve the lives of both animals and people. To investigate the perceptions of veterinary students at the North Carolina State University, College of Veterinary Medicine (NCSU-CVM) toward the use of animals in teaching and research, an anonymous survey was provided to current and recently graduated veterinary students. The aims of the study were to 1) gain a general understanding of veterinary student perceptions surrounding the use of animals in research and teaching, 2) determine if providing simple facts about the contributions of animals to medical advancements would increase the acceptance of animal use for teaching and research, and 3) determine if general perceptions regarding the use of animals in teaching and research change over the course of completing the veterinary curriculum. Descriptive statistics and frequency distributions were calculated for applicable response types. χ² tests were used to identify factors that influenced perceptions of the use of animals in teaching and research. A change-indicator variable was created, and binary logistic regression was used to compare responses before and after completion of the educational component of the survey. Of 141 total survey respondents, 78% were accepting of the use of animals in teaching and research, with no significant difference in the overall acceptance after reading 6 facts about animal research. In addition, 24% of respondents stated that their perceptions had changed during the course of their veterinary education. Overall, veterinary students surveyed had a high acceptance of the use of animals in teaching and research.

Rodents used in biomedical research are maintained as specific pathogen-free (SPF) by employing biosecurity measures that eliminate and exclude adventitious infectious agents known to confound research. The efficacy of these practices is assessed by routine laboratory testing referred to as health monitoring (HM). This study summarizes the results of HM performed at Charles River Research Animal Diagnostic Services (CR-RADS) on samples submitted by external (non-Charles River) clients between 2003 and 2020. Summarizing this vast amount of data has been made practicable by the recent introduction of end-user business intelligence tools to Excel. HM summaries include the number of samples tested and the percent positive by diagnostic methodology, including direct examination for parasites, cultural isolation and identification for bacteria, serology for antibodies to viruses and fastidious microorganisms, and polymerase chain reaction (PCR) assays for pathogen-specific genomic sequences. Consistent with comparable studies, the percentages of pathogen-positive samples by diagnostic methodology and year interval are referred to as period prevalence estimates (%P_E). These %P_E substantiate the elimination of once common respiratory pathogens, such as Sendai virus, and reductions in the prevalence of other agents considered common, such as the rodent coronaviruses and parvoviruses. Conversely, the %P_E of certain pathogens, for example, murine norovirus (MNV), Helicobacter, Rodentibacter, and parasites remain high, perhaps due to the increasing exchange of genetically engineered mutant (GEM) rodents among researchers and the challenges and high cost of eliminating these agents from rodent housing facilities. Study results also document the growing role of PCR in HM because of its applicability to all pathogen types and its high specificity and sensitivity; moreover, PCR can detect pathogens in samples collected antemortem directly from colony animals and from the environment, thereby improving the detection of host-adapted, environmentally unstable pathogens that are not efficiently transmitted to sentinels by soiled bedding.

Mice are commonly infected with Nippostrongylus brasiliensis (Nb) to study their immune responses. However, biosecurity measures have not been established for housing Nb-infected mice and rats. Transmission reportedly does not occur when infected mice are cohoused with naive mice. To test this, we inoculated female NOD. Cg-Prkdc^scid Il2rg^tm1Wjl /Sz(NSG;n = 12) and C57BL/6J (B6;n = 12) mice with 750 Nb L₃ larvae. These mice were then cohoused with naïve NSG ( n = 24) and B6 ( n = 24) mice (1 infected and 2 naïve mice per cage (24 cages) for 28 d in static microisolation cages that were changed every 14 d. We also did several studies to determine the conditions that favor horizontal transmission. First, we assessed in vitro development to the L₃ stage of Nb egg-containing fecal pellets maintained under 4 environmental conditions (dry, moist, soiled bedding, and control). Second, we assessed infection of naïve NSG mice ( n = 9) housed in microisolation cages that contained soiled bedding spiked with infective L₃ larvae (10,000/cage). Third, we gavaged NSG mice ( n = 3) with Nb eggs to model the potential for infection after coprophagy. We found that naïve NSG (9 of 24) and B6 (10 of 24) mice cohoused with an infected cagemate passed Nb eggs in feces as early as 1 d after cohousing and intermittently thereafter for varying periods. This shedding was presumably the result of coprophagy because adult worms were not detected in the shedding mice at euthanasia. Although eggs developed in vitro into L₃ larvae under moist and control environmental conditions, none of the NSG mice housed in cages with L₃ -spiked bedding or gavaged with eggs became infected with Nb. These findings indicate that infectious horizontal transmission does not occur when mice are housed with Nb-shedding cage mates in static microisolation cages with a 14-d cage-changing interval. Results from this study can be used to inform biosecurity practices when working with Nb-infected mice.

Pain management in rabbits is a challenging task that is complicated by the rabbit's ability to hide signs of distress and the limited pharmacologic data available for this species. Pharmacokinetic data has shown that in rabbits, meloxicam, a nonsteroidal anti-inflammatory NSAID, reaches plasma concentrations that are known to provide analgesia in dogs and cats; these concentrations could theoretically alleviate pain in rabbits. However, the inhibitory effects of meloxicam on cyclooxygenase (COX) isoforms have not been studied in rabbits. In this study, we measured the products of COX-1 and COX-2 after the oral administration of a single 1 mg/kg dose of meloxicam to New Zealand White rabbits (n = 6). Blood samples were collected before drug administration (T0) and then at predetermined time points over 48 h. Plasma prostaglandin E₂ (PGE₂ ) and thromboxane (TxB₂) concentrations were measured as surrogate markers for COX-1 and COX-2, respectively, by using commercial ELISA kits. After meloxicam administration, both TxB₂ and PGE₂ plasma concentrations fell significantly below baseline, with maximal mean reductions to 80% and 60% of baseline at 8 h, respectively. The reduction in PGE₂ concentrations was followed by a significant increase that moved its mean plasma concentrations toward baseline between 8 and 24 h. Adverse effects such as lethargy, inappetence, or changes in fecal production were not observed in any rabbits. In conclusion, meloxicam appeared to significantly inhibit both COX-1 and COX-2 with a time course similar to previously reported meloxicam plasma concentration–time profiles in rabbits. Our data suggest that a dosage of 1 mg/kg given orally could provide analgesia to rabbits, but a more frequent dosing interval than the currently recommended daily dosing may be required to maintain clinical efficacy.

Opioids are an integral component of pain management for nonhuman primates. These potent analgesics also adverse gastrointestinal (GI) effects that include constipation, bloating, and delayed gastric emptying. Methylnaltrexone bromide (MNTX) is a selective, peripherally acting μ- and κ-opioid receptor antagonist that can be used to mitigate the GI effects associated with opioid administration. Unlike naltrexone, a similar drug in this class, MNTX possesses an N-methyl-quaternary amine group that prevents it from crossing the blood brain barrier. This blockage allows inhibition of peripheral GI opioid receptors without affecting opioid-mediated analgesia in the central nervous system. We conducted a pharmacokinetic analysis of MNTX in serum and CSF of 6 healthy juvenile male rhesus macaques after subcutaneous administration of a 0.15-mg/kg dose. We hypothesized that the macaques would demonstrate a T_max of 0.5 h, similar to that of humans, and that no MNTX would be detected in the CSF. This treatment resulted in a peak serum concentration of 114 ± 44 ng/mL at 0.25 ± 0.00 h; peak CSF at concentrations were 0.34 ± 0.07 ng/mL at the T_max. These data show that subcutaneous administration of MNTX to rhesus macaques may block peripheral adverse effects of opioids without interfering with their central analgesic effects.

Since 2015, the National Institutes of Health has called for its funded preclinical research to include both male and female subjects. However, much of the basic animal research that has studied heart rate and blood pressure in the past has used male rats. Male rats have been preferred for these studies to avoid the possible complicating effects of the female estrous cycle. The aim of the current study was to determine whether blood pressure and heart rates vary as a function of the estrous cycle phase of young normotensive Wistar–Kyoto (WKY) and Spontaneously Hypertensive (SHR) female rats. Blood pressure and heart rate were measured at the same time of day throughout the estrous cycle by using a noninvasive tail cuff sphygmomano- metric technique. As expected, 16-wk-old female SHR rats had higher blood pressure and heart rates than did age-matched female WKY rats. However, no significant differences in mean, systolic, or diastolic arterial blood pressure or heart rate were detected across the different stages of the estrous cycle in either strain of female rats. Consistent with previous reports, heart rates were higher and showed less variation in the hypertensive SHR female rats as compared with the normotensive WKY female rats. These results indicate that studies measuring blood pressure and heart rate can include young female SHR and WKY rats with no effect of estrous cycle stage.

Minimization of potential pain and distress of rodents undergoing euthanasia is a touchstone of veterinary clinical medicine. Evaluation of this issue in postweanling rodents has supported revisions to the AVMA (American Veterinary Medical Association) Guidelines on Euthanasia in 2020. However, relatively little information is available on humane aspects of anesthesia and euthanasia in neonatal mice and rats. These neonates are not reliably euthanized by exposure to commonly used inhalant anesthetic agents due to their physiologic adaptations to hypercapnic environments. Therefore, options such as prolonged inhalant anesthetic gas exposure, decapitation, or use of injectable anesthetics are recommended for neonates. All of these recommended methods have operational implications, ranging from reported job dissatisfaction by animal care staff to rigorous reporting requirements associated with the use of controlled substances. This lack of a euthanasia method that does not entail operational issues hampers the ability of veterinary professionals to provide appropriate guidance to scientists working with neonates. This study was designed to assess the effectiveness of carbon monoxide (CO) as an alternative euthanasia agent for mouse and rat pups on postnatal days (PND) 0 to 12. The study demonstrates that CO may be a potential alternative for preweanling mice and rats at PND6 or older but is not appropriate for neonates at PND5 or younger.