Journal of the American Association for Laboratory Animal Science : JAALAS最新文献

Swine are commonly used in biomedical research as surgical models and in other experiments requiring the use of anesthesia. Isoflurane is a common inhalant anesthetic used in swine that has been shown to alter hematologic parameters in other species. However, the effects of isoflurane on hematologic parameters of swine over time have not been defined. In this study, we examined the effect of isoflurane anesthesia on hematologic parameters in 29 female Yorkshire/Landrace hybrid domestic swine at 3 timepoints. A secondary objective was to compare hematologic values in isoflurane-anesthetized animals that received intramuscular tiletamine-zolazepam (TZ) or a combination of ketamine-acepromazine-hydromorphone (KAH) for induction. Swine were induced with TZ or KAH, followed by nose cone delivery of 3.5% to 5% isoflurane to facilitate endotracheal intubation, and maintained with 1.75% to 3.5% isoflurane. Venous whole blood was collected for hematologic analysis at baseline upon recumbency after intramuscular administration of TZ or KAH, and at 30 min (T30) and 60 min (T60) of isoflurane administration. There were significant decreases in red blood cell (RBC) count, hematocrit (Hct), and hemoglobin after 30 min of isoflurane anesthesia, and between 30 and 60 min of isoflurane anesthesia. Hct decreased from 35.4% at baseline to 31.8% after 30 min of isoflurane anesthesia, and 31.1% after 60 min of isoflurane anesthesia. The decrease in RBC parameters was accompanied by a significant increase in reticulocyte count at T30 and T60 compared with baseline. When comparing the TZ and KAH groups, Hct and hemoglobin were significantly lower at T30 and T60 in the TZ group, and WBC and neutrophils were significantly higher at T60 in the KAH group. These results indicate that anesthesia alters certain hematologic parameters in swine, thus veterinarians and researchers should take care to avoid misinterpretation of CBCs when blood is collected from anesthetized swine.

This study aimed to evaluate the effect of opioids on thermal threshold in rabbits. Eight healthy female New Zealand White rabbits randomly received each of 10 treatments at least 7 d apart. Treatments were morphine (1, 3, and 5 mg/kg), buprenorphine (0.05, 0.1, and 0.2 mg/kg), butorphanol (0.4, 0.8, and 1.6 mg/kg), and 0.9% saline all in equivalent volume of saline administered subcutaneously. Sedation scores and thermal threshold were evaluated prior to and at 30, 60, 120, 180, 240, and 300 min after treatment by a blinded observer. Sedation was assessed using a scoring system from 0 (unconscious) to 4 (normal) plus an additional category of 5 for excited behavior or increased activity. Morphine, at all 3 doses tested, increased thermal excursion (thermal threshold minus skin temperature) with effects from 3 to 5 mg/kg lasting to the 240-min evaluation. All morphine doses produced some degree of sedation. Buprenorphine (0.1 mg/kg) increased thermal excursion at 60 and 120 min and produced mild sedation. Two, 6, and 7 of the 8 rabbits took 12 to 18 h to urinate after administration of buprenorphine at 0.05, 0.1, and 0.2 mg/kg, respectively. Both saline and butorphanol had no effect on thermal threshold. Behavioral effects of butorphanol varied with some animals being sedated and some displaying heightened activity. Following butorphanol at 1.6 mg/kg, 5 of the 8 rabbits scored 5 at some time point. All rabbits had eaten and defecated within 12 h of all treatments.

Murine pathogens affect laboratory animal health and research outcomes, and the prevention of pathogen incursion or the elimination of pathogen outbreaks is paramount. To this end, sensitive methods for pathogen detection are continually being developed and improved. Environmental health monitoring has become a popular and sensitive method for pathogen detection. Published methods for environmental sampling include the collection and testing of exhaust air filters, exhaust air duct swabs, and swabs or filter media placement in empty cages with soiled bedding. Our study tested soiled, cotton nesting material (Nestlet™) in occupied cages for the detection of nucleic acid from certain, high-prevalence, murine pathogens. Nesting material from cages housing mice positive for mouse norovirus, Helicobacter spp., and Rodentibacter heylii consistently tested positive for these agents. In addition, nesting material from cages housing naïve mice to which soiled bedding from the infected cages was transferred tested positive for these agents more often than testing the mice directly. This study concluded that testing of particulate material (for example, dust) from soiled nesting material is a sensitive detection method for certain, high-prevalence murine pathogens.

Reports of congenital heart disease in nonhuman primates are rare, and double-chambered right ventricle (DCRV), which is a rare congenital heart disease, in which an abnormal muscle bundle divides the right ventricle into 2 chambers (a proximal high-pressure chamber and a distal low-pressure chamber), has not been previously reported. We diagnosed DCRV antemortem in 2 monkeys bred at The Tsukuba Primate Research Center that presented with cardiac murmurs. Subsequent diagnostic evaluation confirmed DCRV in one case, with the other diagnosed with midventricular obstruction having a pathophysiology similar to DCRV. The monkey that had DCRV exhibited a pathophysiology similar to that in humans with DCRV, while the other monkey had a condition mimicking DCRV which was due to a thrombus. We believe this to be the first report of DCRV and a rare DCRV-like pathophysiology due to a thrombus in the ventricle in nonhuman primates.

Alfaxalone has been studied for anesthetic induction of rabbits with rapid onset and a short duration of action; however, it has been minimally evaluated as an option for anesthetic maintenance. This study compared alfaxalone-based total intravenous anesthesia maintenance protocols against inhaled isoflurane, the current standard for anesthetic maintenance in rabbits. Twenty-four male New Zealand White rabbits were assigned to 1 of 3 treatment groups: isoflurane alone, alfaxalone with buprenorphine, or alfaxalone with midazolam. All rabbits were premedicated with buprenorphine HCl (0.02 mg/kg SC) and induced with alfaxalone (6 mg/kg IM). Following intubation and with supplementation of 100% O2, rabbits were maintained for 1 h on either isoflurane (2.5%) or alfaxalone continuous rate infusion (CRI) (0.2 mg/kg/min). For rabbits on the alfaxalone CRI, boluses of buprenorphine HCl (0.01 mg/kg IV or SC) or midazolam (0.1 to 0.3 mg/kg SC) were given upon induction or adjunctively as needed dependent on positive tail-pinch responses that were conducted at timepoints t0, t15, t30, t45, and t60. Heart rate, invasive blood pressure, respiratory rate, end-tidal CO2, percent O2 saturation, and temperature were recorded every 5 min. Surgical plane of anesthesia was characterized by lack of positive response to a tail clamp and was reached in all anesthetic groups. Results showed significant reduction in heart rate of the alfaxalone groups while there was no significant difference in mean arterial pressure compared with the isoflurane groups. However, respiratory rate in the alfaxalone groups was decreased with associated increases in end-tidal CO2 levels. There were no significant differences noted between alfaxalone treatment groups. The results confirmed that CRI alfaxalone (total intravenous anesthesia) should be considered as a potential anesthetic alternative to isoflurane anesthesia in rabbits, although special attention to respiratory monitoring and management is warranted.

In experiments with cohoused animals, outcome variables can become correlated among cage mates. This is called intracluster correlation. When cage mates are all of the same group, the experiment is similar to a cluster randomized trial in human studies. Intracluster correlation in same-group cage mate experiments is a type of pseudoreplication, and ignoring it in statistical analyses increases false-positive results. Herein, we provide a tutorial on how to account for intracluster correlation in statistical analyses. Specifically, this is done by including cage identifiers as an independent variable in a linear mixed model, a type of ANOVA. Because power analyses must be based on the planned statistical analyses, we also include effect size calculations and sample size calculations (types of power analyses) in the tutorial. Effect size and sample size calculations help assure regulatory committees, such as IACUCs, granting agencies, and journals, that experiments are properly powered. These calculations will show that designing experiments to have more cages and fewer animals per cage is more efficient than fewer cages with more animals per cage. This statistical efficiency, which means more power, can be translated into reduced animal numbers, one of the 3Rs (replace, reduce, refine) of animal research. We then perform cost analyses and show how the costs of more cages with fewer animals overall are often less expensive than the costs of fewer cages with more animals overall. Altogether, accounting for intracluster correlation in the experiment design and analysis of same-group cage mate experiments results in fewer statistical errors, reduced costs, and fewer animals. Finally, analyses are demonstrated using JASP, a free, open-source, user-friendly statistical software, and provide R and SAS code to perform the analyses.

Corynebacterium bovis causes skin disease in immunocompromised mice and possibly rats. In 2022, scaly skin and mortality were observed in 7- to 11-d-old neonates (n = 8) from a primiparous Armenian (Nothocricetulus migratorius) hamster breeding pair in a newly established colony. C. bovis was detected by culture and PCR, and affected animals had moderate to severe acanthotic, hyperkeratotic lesions with intralesional C. bovis confirmed by in situ hybridization. Intrafollicular Demodex cricetuli mites, an ectoparasite found in all laboratory-maintained Armenian hamsters, were also identified in affected animals. To elucidate the role of D. cricetuli on C. bovis-associated disease and maintain adult hamsters without the need for sustained mite treatment, a D. cricetuli-free colony was generated by treating breeding pairs and their 1- to 3-d-old neonates with topical fluralaner (35 mg/kg), and a prospective study was undertaken to compare C. bovis-associated pup mortality in D. cricetuli-free and D. cricetuli-infested hamsters. During the ensuing 22 mo, 4 of 96 (4.2%) litters born exhibited C. bovis-associated disease and/or mortality. The litters were born to 4 different nulliparous breeding pairs (n = 47, 9%). Of the 4 affected litters, 2 were D. cricetuli-infested while 2 were D. cricetuli-free. C. bovis was routinely cultured with a variable bacterial burden that had no association with mortality or skin lesion severity from all hamsters, independent of their D. cricetuli status. The severity of histologic pathology appeared to correlate with clinical presentation and mortality in neonates. Whole genome sequencing was performed on 4 hamster C. bovis isolates, which revealed a close genetic association among the isolates as well as with previously characterized mouse and rat C. bovis isolates.

Health monitoring of rodent colonies has traditionally used live animal (LA) sampling by means such as the use of soiled bedding sentinels (SBS), with the associated expenditure of labor, supplies, and animals. In the spirit of the 3Rs, sentinel-free (SF) approaches are becoming more common. PCR testing of environmental samples is replacing traditional SBS-based testing for routine health monitoring of rodent colonies. Passive sampling of in-cage media exposed to pooled, soiled bedding is effective for detecting some common rodent pathogens. We hypothesized that PCR testing of commercially available media exposed to soiled bedding would be as effective as sampling SBS, or SBS combined with samples from colony animals, for detecting several enzootic organisms of mice (Mus musculus) within our facility. Media were placed in IVC cages and exposed to pooled dirty bedding from all cages on a rack side at biweekly cage changes during a 3-mo period. PCR results of the SF soiled bedding-exposed media were compared with results from feces, pelt, and oral swabs from SBS with and without SBS combined with 10 randomly sampled colony animals from the same rack side over the same period. Detection rates were similar for murine norovirus and Staphylococcus xylosus using SF testing compared with SBS with and without direct colony samples. Five organisms, Proteus mirabilis, Rodentibacter heylii, Staphylococcus aureus, Klebsiella oxytoca, and Klebsiella pneumoniae, were detected by SF testing, but not by LA samples. Demodex musculi, Entamoeba, Proteus mirabilis, Helicobacter spp., and Rodentibacter heylii were detected at significantly higher rates by SF testing compared with SBS with and without colony animal samples. SF testing detected organisms of zoonotic concern (S. aureus, K. pneumoniae) that were undetected by LA testing. SF testing detected organisms at similar rates during 2 consecutive quarters. We conclude that PCR testing of media exposed to pooled soiled bedding effectively detects these common enzootic organisms.