The AALAS journals have provided a home for a long string of laboratory animal-focused review articles over the years. Some of these articles have been submitted by prominent research scientists who generally publish in more mainstream journals but understand the importance of the Association’s specialty interest in laboratory animal topics such as research animal genetics, nomenclature, and breeding strategies. It is important for all involved in vertebrate research to understand these concepts to ensure that the best animal models can be chosen and important potential research variables are recognized and controlled. The article republished here (Lynch CJ. 1969. TheCommentary
Neuroscience research has been increasingly active during the last 2 decades, largely driven by the high prevalence and increasing burden of neurologic disorders. While rodents are essential models for biomedical research of neurologic disorders, they lack similar brain anatomy and protein expression profiles to humans, thus limiting their translational value as models of traumatic brain injury, stroke, Alzheimer’s disease, and Parkinson’s disease. The use of ferrets as a model species in neuroscience has been increasing due to their neuroanatomical similarities with humans, including a gyrencephalic brain and larger white matter-to-gray matter ratio. Compared with nonhuman primates, sheep, and swine, ferrets also have the advantages of reduced size, lower housing costs, and lower phylogenetic order. These, among other advantages, make ferrets a promising species to bridge research gaps and complement traditional rodent studies. Although modern neuroscience research in ferrets relies heavily on advanced imaging techniques such as magnetic resonance imaging (MRI), most of the preclinical MRI installations are not designed or optimized for use with ferrets. In this paper we discuss the intricacies and limitations that need to be considered when performing ferret MRI procedures. Reviews of ferret biologic peculiarities, anesthetic protocols, management of complications, and the impact of these factors on MRI outcomes are presented. Standardizing anesthesia protocols for the conduct of MRI in ferrets will aid in better physiologic monitoring as well as imaging outcomes that ultimately benefit the science being conducted.
Eradication of pathogens from mouse colonies is crucial for scientific research reproducibility and animal welfare. The previously described techniques for eradicating pathogens by rederivation through embryo transfer or caesarian technique can be costly and technically challenging. The objective of our study was to assess the efficacy of iodine immersion combined with cross-fostering for eradicating murine norovirus (MNV) and Helicobacter spp. in laboratory mice. The iodine immersion technique was modified to prevent pathogen transmission and reduce the risk of cannibalism. The hypothesis of this study was that iodine immersion combined with cross-fostering of pups would be as effective at eliminating MNV as it is at clearing Helicobacter in laboratory mice. This study was performed on newborn litters of various mice strains housed in a room positive for both these pathogens. The pups were immersed in warmed, diluted iodine within 48 h of birth, and then cross-fostered to a Swiss Webster dam negative for MNV and Helicobacter. The presence of MNV and Helicobacter in donor dams, weanlings, and adult post-immersion animals was tested using fecal PCR. All 27 litters born to MNV- and Helicobacter-positive dams tested negative for both pathogens at weaning and at 8 wk postweaning. Follow-up PCR exhaust dust testing from the housing racks confirmed a negative status for MNV and Helicobacter over multiple quarterly pathogen screening tests conducted over an 18-mo period. This study is, to our knowledge, the first to demonstrate successful eradication of MNV through iodine immersion combined with cross-fostering, proving this method to be effective for eliminating MNV and Helicobacter spp. in affected colonies.
The antidiabetic properties of Uncaria gambir are not yet fully understood, particularly concerning how it affects diabetic animal models. Further investigation in this aspect is pivotal before initiating clinical evaluations. This study aimed to investigate the antidiabetic activity of U. gambir and how it influences blood glucose levels in diabetic Sprague–Dawley rats. In this study, 28 rats were divided into 7 groups. The groups were as follows: a nondiabetic rat group, a nondiabetic rat group given U. gambir, a diabetic rat group, a diabetic rat group given glibenclamide, and 3 diabetic rat groups given U. gambir at 3 doses (200, 300, and 400 mg/kg). Diabetes was induced using streptozotocin (50 mg/kg) given by intraperitoneal injection. Blood glucose levels were measured weekly, and the animals were euthanized at the end of the experiment. Intracardiac blood and tissues such as the pancreas, liver, and skeletal muscle were collected for further analysis. The results showed that administering U. gambir to diabetic rats resulted in significantly lower blood glucose levels than untreated diabetic rats. U. gambir has a complex mechanism to reduce blood glucose levels. including increase of insulin production, preservation of the islets and pancreatic β cells, and optimization of glycogenesis, as reflected in a significant increase in liver glycogen levels. These findings suggest that U. gambir’s multicompound and multitarget capabilities in controlling blood glucose levels may have utility for treatment of diabetes.
There are few reports describing spontaneous neoplasms in cynomolgus macaques, despite the frequent use of this species in laboratory research. This report describes cytologic, histologic, and immunohistochemical findings of a cutaneous to subcutaneous nerve sheath tumor located within the haired skin of the abdomen of a 2.5-y-old, intact, female, captive Mauritius cynomolgus macaque. The nerve sheath tumor was well demarcated, partially encapsulated, densely cellular, and extended from the subcutis to the most superficial dermis, abutting the epidermis. Neoplastic cells formed intersecting streams and had a high mitotic count (18 per 2.37 mm2). Due to the substantial morphologic overlap of this neoplasm with amelanotic melanoma, particularly the close association with the epidermis, immunohistochemistry was required for definitive diagnosis. Neoplastic cells were immunoreactive to vimentin, S-100, SOX10, laminin, collagen IV, and CD56, and negative for melan-A, tyrosinase, MITF, and HMB45. This immunohistochemical profile is diagnostic for nerve sheath tumor based on human and canine criteria and rules out amelanotic melanoma. Despite incomplete excision, the nerve sheath tumor had not grossly recurred after 1 mo, at which point the animal was euthanized for unrelated reasons. This report underscores the importance of using an immunohistochemical panel in cases of cutaneous and subcutaneous spindle cell neoplasms, as there is substantial morphologic and immunohistochemical overlap between nerve sheath tumors and melanocytic neoplasms due to their shared neuroectodermal origin. To our knowledge, this is the first report of a nerve sheath tumor in a cynomolgus macaque, and one of the few reports of spontaneous neoplasia in this species.
Corynebacterium bovis (Cb), the etiologic agent of Corynebacterium-associated hyperkeratosis (CAH) in nude mice, may impact research outcomes. Little is known about the differences in the course and severity of CAH in different outbred athymic nude mice stocks. Three genetic stocks (designated A, B, and C), 1 of which was obtained from 2 geographically separate colonies with distinct microbiota (A1 and A2), were inoculated topically with 1 × 108 cfu of a pathogenic Cb field isolate (no. 7894; n = 6/stock) or sterile media (n = 2/stock; controls). Clinical signs were assessed daily and scored 0 to 5 based on lesion severity. Mice were euthanized at 14 (A1, A2, B, and C) or 28 (B) days postinoculation (dpi), macroscopic changes were documented, and 6 skin samples per mouse were obtained and histologically scored 0 to 4 based on the presence and severity of hyperkeratosis, acanthosis, inflammation, and bacterial colonies. No stock A1 or control mice developed clinical disease; 1 of 6 stock B mice developed mild CAH (mean peak clinical score [MPCS]: 0.33) at 14 dpi (14-d group); 2 of 6 stock B (28-d group) developed mild CAH at 15 dpi (MPCS: 0.33); and all stock C and A2 mice developed significant clinical signs at 5 dpi (MPCS: 2.5 and 3, respectively), which resolved by 11 dpi. Despite differences in clinical presentation, all Cb-infected mice had hyperkeratosis and/or acanthosis with associated bacterial colonies. Stocks A1 and B, which had minimal or no clinical signs, were colonized with Corynebacterium amycolatum (Ca). In contrast, stocks C and A2 were not colonized with Ca, raising the possibility that Ca and/or other components of the skin microbiota may mitigate clinical signs but not necessarily all histopathologic changes associated with infection. These findings suggest host genetics and/or the skin microbiota can markedly influence the presentation of CAH in nude mice.
Environmental enrichment is the provision of different substrates to mimic an animal’s natural environment and encourage natural, species-specific behavior. However, the use of enrichment to improve breeding efficiency in mouse models for neurologic conditions is not well described. There are reports that diminished environmental stimuli and chronic isolation can result in the early expression of the Parkinson phenotype in mice with a genetic predisposition to the disease. In this study, we compared the provision of crinkle paper, DietGel, and their combination on reproductive parameters in B6.Cg-Tg(THY1-SNCA*A53T)M53Sud mice. We found that enhanced enrichment combined with enhanced nutrition increased dam weight and decreased the interlitter intervals. In addition, enhanced enrichment increased the production index, number of pups born, pups weaned, and the percent survival of pups. This study underscores the importance of incorporating enrichment to enhance the reproductive parameters in mice that are models of Parkinson disease.
Animal models enable investigation of the impact of stress on emotional-behavioral performance to facilitate understanding of posttraumatic stress symptoms experienced in humans. Refinement of animal stress models could lead to a reduction in the number of subjects needed to detect statistically significant stress effects, in accordance with Russel and Burch’s three Rs of research. We assessed whether performance of experimental procedures (that is, stress exposure and poststress behavioral testing) during the dark or light phases of the 12-h light/12 h-dark cycle is a refinement that could accomplish this reduction. At 3 h into either the light or dark phase, male and female adult Sprague–Dawley rats underwent a single-day traumatic stress exposure. Rats then underwent behavioral testing for exploratory behaviors, startle responses, and conditioned fear responses at 2 h, 1 d, and 9 d after stress exposure. Distance traveled in the elevated plus maze (EPM) by both male and female rats was significantly reduced in the dark phase compared with the light phase. Male rats of the dark phase group also spent less time in the open arms of the EPM, and traveled less, spent less time in the center, and spent more cumulative time freezing in the open field. Female rats of the dark phase group spent more cumulative time freezing in the EPM and exhibited significantly more tone-cued conditioned freezing responses. Our results suggest that performing experimental procedures during the dark phase of the light cycle may be a useful refinement mechanism, as procedures performed during this period had the greatest effect on behavioral outcomes in both males and females. Light cycle phase is an experimental variable that should be considered when designing experiments to maximize behavioral effects, including those in response to stress.
Chlamydia muridarum (Cm) is a moderately prevalent, gram-negative, intracellular bacterium that affects laboratory mice, causing subclinical to severe disease, depending on the host’s immune status. The effectiveness of various antibiotic regimens aimed at eradicating Cm in both immunodeficient and immunocompetent laboratory mice was evaluated. NSG mice were cohoused with Cm-shedding BALB/cJ mice for 14 d to simulate natural exposure. Four groups of 8 infected NSG mice were treated for 7 d with either 0.08% sulfamethoxazole and 0.016% trimethoprim (TMS) in water, 0.0625% doxycycline in feed, 0.124%/0.025% TMS in feed, or 0.12% amoxicillin in feed. A control group was provided standard water and feed. The impact of treatment on gastrointestinal microbiota (GM) was investigated using next-generation shotgun sequencing on the last day of treatment. TMS and amoxicillin had negligible effects on GM, while doxycycline had the largest effect. All antibiotic-treated NSG mice exhibited clinical disease, including dehydration, hunched posture, greater than 20% weight loss, and dyspnea, leading to euthanasia 21 to 40 d posttreatment (32.6 ± 4.2 d; mean ± SD). Untreated controls were euthanized 14 to 33 d postexposure (23.75 ± 5.9 d). All mice were fecal PCR positive for Cm at euthanasia. Histologic evaluation revealed multifocal histiocytic and neutrophilic bronchointerstitial pneumonia and/or bronchiolitis featuring prominent intralesional chlamydial inclusion bodies in all mice. Subsequently, groups of 8 C57BL/6J, BALB/cJ, NOD.SCID, and NSG mice infected with Cm were treated with 0.124%/0.025% TMS in feed for 7 (BALB/cJ and C57BL/6J) or 21 d (NSG and NOD.SCID). All immunocompetent and NOD.SCID mice were negative for Cm by PCR 14 d posttreatment, remained clinically normal, and had no evidence of Cm infection at necropsy, and all NSG mice remained Cm positive and were euthanized. While these findings highlight the difficulties in eradicating Cm from highly immunodeficient mice, eradication of Cm from immunocompetent or moderately immunocompromised mice with antibiotics is feasible.
The laboratory opossum, Monodelphis domestica, serves as a critical marsupial model in biomedical research. Proper feeding approaches are essential for promoting animal growth and wellbeing. In this study, we systematically evaluated food scattering and potential food contamination from feces across 4 feeding methods: direct placement of food pellets on bedding and using 3 different types of containers. We conducted timed daily observations of food scattering and marking behaviors in 22 animals, capturing images by photograph at specific intervals over the course of a week. Body weight was measured before and after the trial. Our findings revealed that the containers did not prevent food scattering behaviors, as evidenced by comparable survival curves for food scattering across all methods (P > 0.05, log-rank test). Although the paper tray and ceramic dish delayed the occurrence of food marking by feces, indicated by a significant extension in the time to marking events (P = 0.009 and P < 0.001, respectively), these containers introduced new animal welfare concerns. The paper tray increased bleeding incidents in digits and paw pads nearly 8-fold (P = 0.0002), presumably due to sharp edges. The ceramic dish was associated with urine marking, and small but statistically significant weight loss (0.7%, P < 0.05). By 144 h, all cages showed food contamination regardless of the feeding method. The results suggest that containers provide minimal benefit in preventing food contamination, and some types of containers may pose health risks. Therefore, we propose that placing food pellets directly on the bedding, a practice used for 45 y of laboratory opossum maintenance, is acceptable for promoting optimal health and operational efficiency for this species. Our results fill a significant gap in care practices and offer insights into optimal colony management for this important research model.
Soft-pelleted, high-fat diets (HFD) are greasy and crumble easily leading to food wastage and hair coat grease accumulation when mice are fed using commercially available feeders. The ideal HFD feeder design should reduce food wastage, facilitate mouse weight gain, and minimize variables such as hair coat grease accumulation that have the potential to alter scratching behaviors. Our study compared the feeding efficiency of 2 commercially available feeders (feeders A and E) to 4 novel feeder designs (feeders B, C, D, and F). Novel feeders had alterations in feeding aperture size, feeding surface area, feeder configuration, and level of food presentation. Male C57BL/6NCrl mice (n = 120; 4/cage) were randomly assigned to cages containing one of the 6 feeder types and were fed HFD for 12 wk. Feeders and cage bottoms were weighed before use and then weekly at the time of cage change. Mice were weighed before starting the HFD and then biweekly. Scratching behavior was video recorded at 0, 4, 8, and 12 wk. Hair coat grease accumulation was visually scored biweekly. Feeder A use was associated with the highest feed cost due to HFD wastage ($36.98 ± 1.54/cage/wk). Mice fed using Feeder A had the highest average weight gain (23.75 ± 0.8 g, P < 0.005). However, mice also had significantly higher hair coat grease accumulation scores (P < 0.05) and significantly increased scratching frequency at 4 wk (P < 0.05) when compared with mice fed using other feeder types. Novel feeder designs utilized 10 to 21 times less HFD dispensed when compared to feeder A. Mice fed using novel feeders also displayed improved welfare, as evidenced by low hair coat grease accumulation scores, and no significant differences in scratching frequency when compared with baseline behavior.
Unnecessary and excessive fluid therapy increases the risk of adverse effects such as pulmonary edema. To prevent this, a mini-fluid challenge (MFC) has been utilized to predict whether fluid therapy will improve circulatory dynamics in human intensive care medicine. The study described here investigated whether MFC is also efficacious in pigs. Thirty-two domestic pigs anesthetized and maintained under mechanical ventilation were treated with successive IV fluid administrations of 2, 1, 1, and 2 mL/kg over a 10-min period for a total dose of 6 mL/kg of Ringer lactate. The percentage increase in mean arterial pressure (MAP) at 2, 3, and 4 mL/kg of cumulative fluid administration was examined to determine whether responders could be identified that would benefit hemodynamically from higher doses of fluids. For the purposes of this study, a 10% increase or more in MAP after 6 mL/kg of fluid administration defined responders, and an increase of less than 10% in MAP was used to define nonresponders. The percentage increase in MAP at 2, 3, and 4 mL/kg fluid administration was evaluated to determine whether this could predict responder status. Eleven of the 32 animals were determined to be responders. Responder status was predicted with high accuracy by the administration of 3 mL/kg (AUC = 0.98) and was moderately predicted with administration of 2 mL/kg (AUC = 0.80), as well as pulse pressure variation (AUC = 0.75). Thus, MFC may be helpful to maintain tissue perfusion in pigs through the use of managed fluid therapy.
The Whitten effect is a widely used tool for manipulating the mouse estrous cycle and generating reproductively active females within the laboratory setting. Typically, peak numbers of sexually receptive mice occur following exposure to male pheromones, resulting in a higher number of successful copulations on the third day after exposure. Although this method has improved efficiencies, the percentage of females mated and subsequently deemed to be pregnant/pseudopregnant remains relatively low, around 50%. In experiment 1, we aimed to 1) further understand cyclicity; 2) determine whether the initial cycle stage plays an importance on day 3 receptivity; and 3) identify any repetitive patterns/cycle stabilization. Mice (n = 27) were assigned to group cages according to cycle stage (proestrus, estrus, metestrus, diestrus). Experiment 2 was developed to determine an optimum treatment to promote receptivity by exposure to various pheromone stimuli. Mice (n = 45) were randomly assigned to 5 treatment groups (PBS-treated sham soiled bedding, male soiled bedding, live male, pregnant females, and lactating females). In both experiments, daily vaginal cytology was performed for 21 days to determine the cycle stage. Results from experiment 1 indicate that the initial cycle stage did not contribute to day 3 receptivity, although synchronization within several groups/cages was noted, and that the greatest numbers of estrous animals were obtained on days 6 and 7. Experiment 2 revealed that exposure to live males and lactating females both significantly improved receptivity compared with the PBS, male soiled bedding, and pregnant female groups. These results indicate that current strategies used for routine synchronization could be further improved through alternative housing regimens without compromising animal welfare.
Body temperature is an easily measured clinical parameter that provides important information about an animal’s health and welfare. In the context of animal experiments, temperature monitoring provides relevant data needed to manage animal care and has been embraced as a means of assessing humane endpoints. At the same time, temperature measurement in the sense of the 3Rs (Replacement, Refinement, and Reduction) should not cause any additional pain or distress to the animals. Therefore, the use of noninvasive, accurate, and cost-effective methods for temperature monitoring is of great importance in research laboratories. The purpose of this study was to determine the accuracy and consistency of different temperature measurement methods in black-haired C57BL/6NCrl mice. Body surface temperature measured by noninvasive infrared thermography was compared with established methods: subcutaneous and rectal temperature measurements. The study was conducted on 50 adult female mice, and measurements were taken for 5 d. Temperatures were measured using previously implanted subcutaneous temperature transponders, followed by infrared thermometry and rectal probes. The analyzed data showed that mouse temperature measurement using an infrared camera is an adequate method for noncontact and noninvasive temperature assessment in female C57BL/6NCrl mice and promotes laboratory animal welfare refinement.
Mice are the most commonly used models of infectious disease, and disease in mice is similar to that of humans. As a consequence, standard hematology and biochemistry reference values in mice are essential to evaluate functional changes caused by experimental treatments, although very few data in the literature provide a comparative reference range. The aim of this investigation was to establish the reference intervals for major hematology and biochemistry analytes in 2 inbred mouse strains, BALB/c and C57BL/6, at 3 different age ranges. Parameters were assessed in 600 mice (300 male and 300 female) of BALB/c and C57BL/6 strains at 6 to 8 wk, 10 to 14 wk, and 6 to 9 mo of age. Reference intervals were calculated by nonparametric or robust methods according to sample size, and statistical analyses were performed to assess the changes in relation to sex, age, and strain. The data demonstrate that strain, sex, and age have significant effects on the hematologic and biochemical profiles of mice. Hemoglobin, Hct, MCH, MCHC, neutrophils, eosinophils, and ALP were found to be significantly greater in BALB/c mice. In contrast, WBC, lymphocytes, basophils, glucose, total protein, albumin, and urea were found to be significantly greater in C57BL/6 mice in all age ranges. Lymphocytes and ALP progressively decreased with age, while neutrophils increased with age in both strains. The study successfully defined and established reference intervals for hematologic and biochemical analytes in 2 inbred mouse strains at 3 different age ranges. The reference values reported here could be useful in characterizing the phenotype of experimental mice and assessing the changes caused by investigational treatments.
Social housing remains one of the best forms of environmental enhancement for nonhuman primates (NHPs). The gradual steps (GS) method, a 2-step plan involving an initial phase of limited physical contact (protected contact [PC]) prior to full contact (FC), is widely used for introducing macaque pairs. Recent evidence has suggested that administration of diazepam prior to FC introduction, without a PC phase, improves the success rate of pairings among adult male rhesus macaques (Macaca mulatta). Nevertheless, given the popularity of the standard GS method, there is considerable interest in using diazepam along with this technique. We hypothesized that administering a single dose of diazepam prior to the PC phase would improve the success rates of isosexual pairings of unfamiliar adult macaques. Twelve males and 12 females were studied in each of 3 groups, with 2 different doses of oral diazepam (2.5 or 3.2 mg/kg) and controls introduced without diazepam. Pairs were deemed successful after 14 consecutive days of compatible FC housing. Among males, success rates for the low diazepam, high diazepam, and control groups were 67%, 50%, and 67%, respectively. Among females, the corresponding values were 50%, 33%, and 17%. There were no significant differences in overall introduction success rates for either sex. However, among females, the success rates during the initial PC phase were significantly higher in introductions involving the lower dose of diazepam (83%) than among controls (33%). Descriptively, in both sexes, less severe wounding patterns were observed with the lower dose compared with either the high dose or control groups. Our results suggest that diazepam administration prior to the PC phase of the GS method does not improve pairing outcomes for either sex in rhesus macaques. However, diazepam may have some utility in moderating wounding during unsuccessful introductions.
To maintain rodent colonies free from harmful infectious agents, laboratory animal care programs frequently employ the use of sterilized caging and supplies. Sterilized caging is important for preventing the spread of infectious pathogens from contaminated fomites, for biocontainment, and for safety. We designed several experiments to determine the effects of commonly encountered processes on steam penetration and substrate heat exposure. We used biologic indicators as a proxy for steam penetration. We used the time bedding spent above 121 °C as a proxy for substrate cumulative heat exposure. This temperature was measured using a high-temperature data logger. We first examined the effect of stacking cages with various bedding types on steam penetration. We then autoclaved soiled bedding and studied the variables of bedding type, bagging style, presence of diet and water in the cage, and amount of time between cage change out on steam penetration and cumulative heat exposure. For clean bedding, we found adequate steam penetration regardless of bedding type, cycle program, or location of the cage in the bulk autoclave. For the soiled bedding experiments, there were no differences between bedding types noted. Placement of cages inside plastic bagging increased the amount of time the bedding spent above 121 °C on average but not significantly. There was no difference in steam penetration of bedding or time spent above 121 °C for 2- or 4-wk cage change-out schedules. When cages were autoclaved with diet and water, the time the bedding spent above 121 °C was significantly less than when autoclaving bedding alone, but there was adequate steam penetration for all cages. This study demonstrates that common practices in the industry are effective. Based on the results of this study, it is recommended that each institution evaluate their autoclaving practices and confirm that those practices are sufficient and effective.
Dystocia, a common murine reproductive condition, is classified as either obstructive, a result of fetal factors such as an oversized fetus, or functional, a result of dam factors such as advanced age. Treatment is based on the dam’s clinical condition and the underlying etiology, but usually requires euthanasia. A prospective study was conducted to characterize the etiology of murine dystocia to determine if treatment is warranted. The signalment and experimental, clinical, and breeding histories were obtained, and a targeted serum chemistry panel, radiographs, and a gross necropsy were conducted on mice presenting with clinical signs consistent with dystocia. Obstructive dystocia was diagnosed if the pelvic canal width was less than the diameter of the fetal head closest to the cervix or a fetus was lodged in the pelvic canal. Functional dystocia was diagnosed based on clinicopathologic abnormalities. A total of 54 mice were evaluated over 7 mo with 45/54 (83%) confirmed to have dystocia with the remaining 9 (17%) having other reproductive abnormalities. Of the confirmed cases, 27/45 (60%) were C57BL/6 or on a C57BL/6 background, and the average age at presentation was 181 ± 85 d. The number of mice categorized as having an obstructive (n = 16) compared with a functional (n = 11) dystocia was not significantly different than those in which the definitive category could not be ascertained (n = 18). Neither clinical signs nor clinical pathology were significantly different between mice categorized as having an obstructive compared with a functional dystocia. Hunched posture, lethargy, and vaginal discharge were the most common presentation. Azotemia (BUN: 66.6 ± 10.2 mg/dL, mean ± SE), hypoglycemia (96.11 ± 8.5 mg/dL), and hyperglobulinemia (3.13 ± 0.14 mg/dL) were common. Differentiating obstructive from functional dystocia could not be determined cageside with strong confidence.
Pigs are extensively used for biomedical research as animal models given their similarities to humans including size, arterial capacity, and cutaneous structure. While their size also allows for the use of clinically available anesthesia equipment (for example, endotracheal tubes and ventilators), anecdotes exist with respect to stress reactions after exposure to volatile anesthetics. Over 3 mo at our institution, 11 pigs (Sus scrofa domesticus) exposed to isoflurane anesthesia during 2 research protocols were euthanized after exhibiting clinical signs of malignant hyperthermia, including hyperthermia, hypercapnia, skeletal muscle rigidity, dyspnea, tachycardia, and hypotension. This group was composed of intact Yorkshire/Landrace crosses (68 to 91 kg) purchased from a research breeder. While malignant hyperthermia is caused by a mutation in ryanodine receptor 1 (RYR1), another unnamed porcine stress syndrome is caused by a dystrophin defect. We analyzed the incidence of the RYR1 mutation and a dystrophin variant in 9 of the originally clinically affected pigs and in 56 subsequent pigs. All animals tested negative for the RYR1 mutation, while the dystrophin variant was found in 2 out of 7 clinical (28.6%) and 22 out of 46 (47.8%) subsequently tested female pigs. Creatine kinase, indicative of muscle damage, was slightly elevated at baseline in dystrophin variant-positive carriers, albeit not significantly. However, for the original clinically affected pigs, the increase in body temperature while under anesthesia was significantly greater in dystrophin variant-positive carriers (7.9 ± 0.8 °C) compared with noncarriers (5.2 ± 0.6 °C, P = 0.046). Taken together, we describe the suspected involvement of a dystrophin variant as one of the genetic etiologies in an unnamed condition that has been anecdotally experienced by pig researchers but not reported. We propose naming this condition volatile anesthesia porcine stress syndrome (VAPSS), which is an umbrella term that includes multiple genetic origins, the most well-known of which is malignant hyperthermia stress syndrome in pigs. Identifying other etiologies for VAPSS has implications for genetic and clinical screening to improve welfare in pigs bred for biomedical research and agricultural purposes.