A common dilemma faced by all animal bioethics committees arises when exceptions are proposed to the use of analgesics in painful procedures. The committee and researcher must weigh the possible confounding effects of including additional drugs (analgesics) in their treatment regimen against the moral obligation to perform humane research. Often neglected in these considerations are the potential confounding effects of unrelieved pain and consistency with pain-relieving practices in human medicine. In this review, we summarize what is currently known regarding the molecular and physiologic effects of pain and analgesics in common animal models used across several therapeutic areas. This work is intended to help provide guidance and assurance that a comprehensive approach has been taken when contemplating how pain relief will be applied in animal research protocols.

The use of animal models in vitamin D deficiency (VDD) research, particularly in regard to maternal deficits, has increased dramatically, yet these studies may be confounded due to ill-conceived experimental timelines. We conducted 2 experiments to (1) characterize the time course of VDD induction and repletion and (2) explore the long-term consequences of VDD on calcium homeostasis and body composition in reproductive-age female mice. Eight-week-old female C57BL/6 mice were randomized to receive either a vitamin D sufficient (VDS) or VDD diet; serum was collected weekly. At week 4, VDD mice were switched to VDS diet, and serum was collected weekly until week 8. Another group of same-age female mice was maintained on VDD diet for 40 wk. Body weights and serum were collected every 2 wk until week 40, when body composition was measured by using echoMRI. Mice did not become VDD until week 3 of the VDD diet and, after decreasing slightly at 4 wk, serum 25-hydroxyvitamin D remained unchanged through 40 wk. Vitamin D repletion to 25-hydroxyvitamin D concentrations considered adequate by the Institute of Medicine took 2 to 3 wk. Prolonged VDD in mice was marked by hypocalcemia and hyperparathyroidism and led to proportional decreases in both lean and fat mass. These data provide guidance in the design of studies using mice as a maternal VDD model, especially those exploring its effects on the developmental origins of health and disease and highlight the importance of monitoring and controlling the calciotropic effects of diet-induced VDD. This study also shows that prolonged VDD in reproductive-age female C57BL/6 mice induces metabolically meaningful changes in absolute, but not relative, body composition.

The inability to translate findings from studies performed in mouse models to the corresponding human condition is well known, especially those involving infectious, atherosclerotic, and other inflammatory diseases. We hypothesize that mice fail to a mount robust or adequate immune response to infectious agents because of physiologic effects of cold stress due to housing temperatures below the mouse thermoneutral zone (TNZ). This hypothesis was tested by comparing the immune response to the Francisella tularensis live vaccine strain in mice housed at a typical vivarium temperature, which is below the TNZ, with that of mice housed at a temperature near their TNZ. Mice maintained at 28 °C displayed elevated antigen-specific T-cell responses compared with mice housed at 22 °C and survived intranasal challenge that was fatal to immunized mice at 22 °C. These results demonstrate that cold stress due to housing below the mouse TNZ results in a blunted immune response and may compromise their translational value a models for infectious diseases and vaccine development.

Because of their ideal size and temperament, rabbits are commonly used in polyclonal antibody production. Immunostimulatory adjuvants—such as Freund complete and incomplete adjuvants as well as various proprietary products—trigger a robust immune response, which increases antibody concentrations. However, these adjuvants can cause excessive soft tissue reactions, prompting concerns regarding animal wellbeing. This study assessed the safety and efficacy of cationic liposome– oligonucleotide complexes (CLDC) as an alternative adjuvant to conventional adjuvants. On days 0 and 14, 15 female New Zealand white rabbits were vaccinated subcutaneously with 15 μg ovalbumin mixed with either CLDC, Freund adjuvant (day 0, complete; day 14, incomplete), or a proprietary adjuvant (n = 5 per group). Antibody titers were measured by direct ELISA on days 0, 14, and 28. Rabbits were palpated daily for lesion development, and all lesions were measured. Rabbits in all groups developed a significant antibody response to ovalbumin over 28 d. However, the differences between groups were not statistically significant. No rabbits in the CLDC group developed skin lesions, whereas 80% of rabbits that received Freund adjuvant and 100% of those that received the proprietary product developed skin lesions. This study demonstrates that CLDC may be a valuable and effective alternative adjuvant for polyclonal antibody production in rabbits—one that avoids the palpable injection-site lesions often seen with other adjuvants.

In the present study, we evaluated the utility of an intraluminal agarose stent (IAS) for end-to-end intestinal anastomoses in rabbits. Female New Zealand white rabbits (n = 14) underwent conventional sutured anastomosis (CSA) with or without an IAS. IAS were used to maintain the luminal diameter for more rapid and accurate suturing, and then was squeezed transluminally to crush it into fragments, which passed through the intestines and were eliminated. The rabbits were euthanized on postoperative day 21. At necropsy, the anastomoses were assessed for adhesion formation, stenosis, and bursting pressure and were examined histologically for collagen content and blood vessel formation. Anastamosis surgery took less time in the IAS group (15.0 ± 2.6 min) than in the CSA-only group (30.1 ± 7.9 min). Only 1 postoperative death occurred (in the CSA group), and postmortem examination revealed evidence of anastomotic leakage. Adhesion formation and stenosis did not differ between groups, but bursting pressure, collagen content, and blood vessel formation were all significantly increased in the IAS group. IAS may decrease the operative time by maintaining a clear surgical field at the anastomotic site. In addition, the use of IAS promotes rapid healing and maintains the luminal diameter during end-to-end intestinal anastomosis.

The Rapacz familial hypercholesterolemic (FH) swine model is well-characterized and used for studies of both spontaneous and inducible atherosclerosis but has not been used for studies of metabolic dysfunction to date. We examined whether parameters of metabolic syndrome including weight and adiposity, serum cholesterol, and glucoregulatory function could be modulated by restriction of caloric intake in the FH swine. Three groups of FH swine (n = 6 per group) were fed without restriction (AL), 80% of AL caloric intake, or 60% of AL caloric intake for 8.8 ± 0.5 mo beginning 2 wk after weaning. Caloric intake influenced the rate and magnitude of body weight gain and change in adiposity, as determined by dual-emission X-ray absorptiometry. At the conclusion of the study, pigs in the AL group reached a total least-square mean body weight of 94.2 kg and fat mass of 31.1%, whereas those fed 80% AL were 71.6 kg and 24.3% fat, and swine fed 60% AL were 46.1 kg and 14.1% fat. Serum cholesterol was greater in AL than 60% AL pigs at the end of the study. At 10 mo of age, intravenous glucose tolerance testing, performed to assess glucoregulatory function, indicated significant differences in serum glucose clearance profiles and insulin sensitivity between the AL- and 60% AL-fed swine. The AL-fed animals showed almost 5-fold lower insulin sensitivity when compared with animals fed 60% AL caloric intake. These results highlight the value of the FH swine model to study metabolic dysfunction due to changes in caloric intake.

The term Horner syndrome refers to the clinical presentation of oculosympathoparesis, comprising miosis, ptosis, and facial anhydrosis. To date, there are 2 reports of postoperative Horner syndrome in pigs. In this species the cervical sympathetic chain and cranial cervical sympathetic ganglion are consistently within the carotid artery sheath. This case study describes the sudden onset of Horner syndrome in 2 pigs, from a study cohort of 8, after the placement of a vascular graft between the carotid artery and external jugular vein. Anesthesia and surgery was uneventful in all the pigs in the study, but 2 pigs demonstrated clinical signs including ptosis, enophthalmos and prolapse of the nictitating membrane immediately after recovery from anesthesia. Horner syndrome was diagnosed in light of the clinical signs. These clinical signs persisted throughout the 2-mo study period and did not appear to improve or deteriorate in that time. Gross examination of the surgery site at the end of the study did not reveal an obvious lesion in the carotid artery sheath. The risk of Horner syndrome after surgery involving the carotid artery in pigs had not been reported prior to this study. Without specific measures to protect the cervical sympathetic ganglion during surgery, the incidence of postoperative Horner syndrome was 25% in our population of pigs. Although the welfare implications of this syndrome are minimal, concerted effort to avoid intraoperative damage to the cervical ganglion is essential for future work.

An adult feline blood donor, group-housed in a closed colony with other blood donor cats in a laboratory animal facility, developed anorexia, abdominal pain, an abdominal mass effect, and hemorrhagic diarrhea. Ultimately Salmonella infection was diagnosed. The index cat and 2 additional cats in the closed colony had clinical signs consistent with Salmonella and yielded Salmonella serotype 4,12:i:– in fecal cultures. An extensive search for the source of Salmonella was unrewarding. With the implementation of individual housing and additional barrier precautions, combined with antibiotic treatment of the index case, all the cats survived and subsequently had multiple, negative Salmonella PCR test results. This case report highlights the potential for unlikely infections to occur, even in a closed colony of research animals, as well as the important role of sanitation in the elimination of this enteric pathogen.

A 10-y-old cranially implanted rhesus macaque (Macaca mulatta) involved in visual research was presented for dull mentation and weight loss. Physical examination revealed alopecia and poor body conditioning, and bloodwork revealed marked hypercortisolemia (23 μg/dL). Differential diagnoses for hypercortisolemia, weight loss, and alopecia included Cushing and pseudo-Cushing syndromes. To further evaluate hypercortisolemia, we compared the urine cortisol:creatinine ratio (UCCR) at baseline and after low-dose dexamethasone suppression (LDDS) testing in the presenting animal and healthy naïve and implanted working monkeys. At baseline, UCCR was 10 times higher in the presenting macaque (118.1 ± 7.1) than in naïve animals (12.5 ± 12.8) and 3 times higher than in healthy implanted working macaques (44.4 ± 6.9); however, levels were suppressed similarly by dexamethasone in both the presenting animal and healthy controls. In addition, healthy implanted working macaques had significantly higher baseline UCCR levels than naïve controls, suggesting chronic stress in working animals. Abdominal ultrasonography and radiographs of the presenting animal revealed marked bilateral adrenal mineralization but no overt adrenal tumor or hyperplasia. Overall, these results excluded endogenous Cushing syndrome and prompted us to evaluate different causes of pseudo-Cushing syndrome, including depression. Using videorecordings to evaluate behavior, we used published criteria for macaque models of depression models, including huddling, to make a presumptive diagnosis of depression. The macaque was treated with fluoxetine (2 mg/kg PO daily), provided increased environmental enrichment, and followed over time by regular UCCR assessment and videorecordings. The animal improved clinically and behaviorally, and UCCR returned to levels observed in working implanted macaques (44.4) after 8 wk of treatment. This case highlights the potential effect of research-related work on stress and pathologic behaviors in macaques and demonstrates the utility of UCCR and LDDS for screening behavioral and hypothalamic–pituitary–adrenal abnormalities in these animals.

Inguinal herniation of abdominal viscera is a relatively common condition in both humans and domestic animal species. In captive rhesus macaques (Macaca mulatta), the highest incidence occurs in overweight, aged males. However, inguinal herniation of the uterus with bilateral adnexa is extremely rare in both human and veterinary medicine. Here we report a previously undescribed uterine inguinal herniation with bilateral adnexa in a 3-y-old female rhesus macaque. Although uterine herniation remains a rare condition in rhesus macaques, it should be considered as a differential diagnosis in animals with unilateral subcutaneous enlargements in the inguinal region.