CAUSES OF MORTALITY AND COMORBIDITIES IN CAIMAN LIZARDS (DRACAENA GUIANENSIS) AT SIX ZOOLOGICAL INSTITUTIONS.

An understanding of the main causes of mortality in caiman lizards (Dracaena guianensis) under managed care is imperative to promote optimal husbandry, health, and welfare. A retrospective review of morbidity and mortality in caiman lizards from North American zoological institutions between 2005 and 2020 was conducted. Postmortem data, including gross necropsy and histopathology findings, were available for 32 caiman lizards (n = 12 subadults, n = 20 adults) from six zoological institutions. Necropsy reports were evaluated to collect general demographic data, categorize cause of death (accident/trauma, congenital/genetic, degenerative/geriatric, infectious, deposition disease, neoplastic, unknown, and multifactorial), and assess common comorbidities. Infectious disease was the most common cause of mortality in adult lizards (8/20; 40%) with amoebiasis and bacterial etiologies being overrepresented. Demise due to traumatic/accidental injury was the second most common cause of death in adult lizards (3/20;15%) and included blunt force trauma or suspected drowning. Infectious disease (4/12; 33.3%) and trauma/accidental injury (4/12; 33.3%) were also the most common causes of death in subadults. The most common comorbidities or other incidental findings identified during necropsy included trematode parasitism (15/32; 46.9%), arteriosclerosis (11/32; 34.4%), and adrenocortical hyperplasia (6/32; 18.8%). This retrospective review suggests that management practices to prevent and control infectious diseases and mitigate traumatic injury play a pivotal role in the long-term care and survival of caiman lizards in managed care.

Bioencapsulation is a feasible method of terbinafine administration in Emydomyces testavorans-infected western pond turtles (Actinemys marmorata).

OBJECTIVE: To evaluate the pharmacokinetics of terbinafine administered to western pond turtles (Actinemys marmorata) via oral gavage and bioencapsulated in earthworms. ANIMALS: 7 western pond turtles. PROCEDURES: A randomized complete crossover single-dose pharmacokinetic study was performed. Compounded terbinafine (25 mg/mL; 30 mg/kg) was administered through oral gavage (OG) directly into the stomach or bioencapsulated (BEC) into an earthworm vehicle. Blood (0.2 mL) was drawn from the jugular vein at 0, 0.5, 1, 2, 4, 8, 12, 24, 48, 72, and 120 hours after administration. Plasma terbinafine levels were measured using high-performance liquid chromatography. RESULTS: Peak plasma terbinafine concentrations of 786.9 ± 911 ng/mL and 1,022.2 ± 911 were measured at 1.8 ± 2.8 and 14.1 ± 12.3 hours after OG and BEC administration, respectively. There was a significant (P = .031) increase in area under the curve with BEC compared to OG. Using steady-state predictions, with once-daily terbinafine administration, 3/7 and 7/7 turtles had plasma concentrations persistently greater than the minimum inhibitory concentration (MIC) for Emydomyces testavorans for the OG and BEC administration routes of administration, respectively. With administration every 48 hours, 3/7 turtles for the OG phase and 6/7 turtles for the BEC phase had concentrations greater than the E. testavorans MIC throughout the entire dosing interval. CLINICAL RELEVANCE: Administration of terbinafine (30 mg/kg) every 24 or 48 hours via earthworm bioencapsulation in western pond turtles may be appropriate for the treatment of shell lesions caused by E. testavorans. Clinical studies are needed to assess the efficacy of treatment.

PHARMACOKINETICS OF A SINGLE DOSE OF INTRAMUSCULAR AND ORAL MELOXICAM IN YELLOW STINGRAYS (UROBATIS JAMAICENSIS).

Elasmobranchs are popular display animals in public aquaria and zoos, but medical management gaps remain in the understanding of the pharmacokinetics of analgesics and pain management in these species. Meloxicam is a nonsteroidal anti-inflammatory drug that has been evaluated intravenously and intramuscularly in teleosts, but has yet to be studied in any elasmobranch species. The pharmacokinetics of meloxicam were determined in 17 yellow stingrays (Urobatis jamaicensis). All stingrays were determined to be healthy from complete physical examinations and baseline bloodwork performed prior to study inclusion. A single dose of 1 mg/kg meloxicam intramuscularly was administered to all rays, followed by a 2 mg/kg oral dose after an 8 wk washout period. Blood samples were collected from the mesopterygial vein at baseline and nine time points up to 96 h after administration of meloxicam. Plasma concentrations were determined using reversed-phase high-performance liquid chromatography. Pharmacokinetic analysis was performed using a noncompartmental technique. The mean peak plasma concentrations for intramuscular and oral meloxicam were 1.29 and 0.42 µg/ml, respectively. The mean terminal half-lives of meloxicam after intramuscular and oral administration were 5.75 and 15.46 h, respectively. Based on these findings, the recommended meloxicam dosage and frequency for yellow stingrays is 2 mg/kg orally once daily. Due to rapid elimination with the intramuscular administration, maintaining clinically relevant plasma concentrations may be difficult using this route. Further studies are needed to determine multidose pharmacokinetics of meloxicam in yellow stingrays, as well as single-dose and multidose pharmacokinetics in other elasmobranch species.

REVIEW OF HISTOLOGIC LESIONS AND MORTALITY IN RIO CAUCA CAECILIANS (TYPHLONECTES NATANS) OVER A 22-YEAR PERIOD.

Rio Cauca caecilians (Typhlonectes natans) are a unique, fully aquatic species of amphibian from the order Gymnophiona. They are housed in several zoological institutions and aquaria with limited information available regarding health and disease. This retrospective study evaluates common pathologic findings and causes of mortality of Rio Cauca caecilians from three different institutions over a 22-y period. Comparisons to previous medical health surveys were conducted with evaluation according to age class and sex to determine whether the primary causes of mortality and common histologic findings have remained similar over time and between institutions. Between 1997 and 2019, the 62 mortalities included males (15/62; 24.2%), females (26/62; 41.9%), and undetermined sex (21/62; 33.9%). The majority of examined individuals were adult (38/62; 61.3%), followed by juveniles (13/62; 21.0%), neonates (9/62; 14.5%), and undetermined age class (2/62; 3.2%). Thirteen (21.0%) individuals were euthanatized. Adult females (16/62; 25.48%) represented the largest group. In adults, the most common lesion and contributor to death was renal disease (28/38; 73.7%) followed by skin disease (16/38; 42.1%), including oomycete dermatitis (8/38; 21.1%) from Saprolegnia sp. Other common findings included bacterial dermatitis, gastrointestinal nematodiasis, and adrenal hyperplasia. This retrospective study will provide a useful reference to help guide veterinary care, management decisions, and collection management planning for this caecilian species in managed care.

An integrative review of lateral line depigmentation in marine and freshwater fish.

OBJECTIVE: To qualitatively review reports on lateral line depigmentation (LLD) in marine and freshwater fish. SAMPLE: English-language publications concerning LLD published before March 1, 2020. PROCEDURES: Electronic searches of CAB abstracts, PubMed, and Web of Science databases and the proceedings of the International Association of Aquatic Animal Medicine were performed. Records were systematically screened and selected for inclusion in an integrative review. Bibliographies of records included in the review were examined to identify other records to be screened. Included records were qualitatively reviewed. Evidence level and quality were graded according to previously described criteria. Information pertinent to epidemiological factors, etiopathogenesis, clinical and histopathologic findings, treatment, and prevention of LLD was collected. RESULTS: 401 records were screened, and 24 unique publications (16 peer-reviewed articles, 1 textbook, and 7 abstracts) were included in the study; 12 (50%), 1 (4%), 6 (25%), and 5 (21%) were classified as evidence level I (experimental), II (quasi-experimental), III (nonexperimental), and V (clinical reports or clinician experience), respectively. Seventeen (71%) and 7 (29%) reports were classified as high quality and good quality, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: LLD should be considered a clinical observation indicative of a dermatologic response of fish to suboptimal conditions; LLD should continue to be adopted as the preferred term to describe the classic signs. Whereas gross findings are similar among species, histologic findings can vary. Evidence-based treatment of LLD for individual fish consists of source control (changing tanks or systems), topical treatment with 0.01% becaplermin gel, supportive care, and antimicrobial treatment when warranted. For schools of fish, treatment and prevention of LLD should be focused on improving suboptimal environmental and physiologic conditions.

SAFETY AND EFFICACY OF MILBEMYCIN OXIME AND LUFENURON TO TREAT ARGULUS SPP. INFESTATION IN SMOOTH BACK RIVER STINGRAYS (POTAMOTRYGON ORBIGNYI) AND MAGDALENA RIVER STINGRAYS (POTAMOTRYGON MAGDALENAE).

Fish lice, ectoparasites of the genus Argulus, are branchurian crustaceans that can significantly impact fish health by causing mechanical damage to cutaneous barriers and increasing susceptibility to other infections. While many treatments have been reported in teleosts and invertebrates, there are no published treatments for elasmobranchs. This study evaluated the safety and efficacy of a commercial formulation of milbemycin oxime and lufenuron in freshwater stingrays for treatment of Argulus spp. Seven juvenile Magdalena river stingrays (Potamotrygon magdalenae) and 10 juvenile smooth back river stingrays (Potamotrygon orbignyi) had severe infestations of Argulus spp. that were identified visually and microscopically. Animals were treated with milbemycin oxime and lufenuron (at 0.015 mg/L and 0.30 mg/L, respectively) in a 6-hr immersion once weekly for two treatments. They were visually examined for skin lesions as well as behavior and appetite daily by animal care staff. A subset of animals was euthanized and necropsied on days 8, 9, 43, and 78 after treatment initiation. There were no Argulus spp. detected at the time of the second treatment. Complete gross and histologic evaluations were completed for all animals. At all time points, no gross abnormalities were detected with the exception of thin body condition in some animals; no Argulus spp. were noted. Histologic lesions were all attributed to poor nutritional state at the time of acquisition. No histologic evidence of acute or chronic toxicosis was detected. The commercial formulation of milbemycin oxime and lufenuron, applied at the dose and for the exposure time used in this study, effectively eradicated Argulus spp. in a population of juvenile P. magdalenae and P. orbignyi, and did not cause mortality or clinical gross or histologic evidence of acute or chronic toxicity.

IRON STORAGE DISEASE IN AFRICAN GREY PARROTS ( PSITTACUS ERITHACUS) EXPOSED TO A CARNIVOROUS DIET.

Within a 2-wk period, three African grey parrots ( Psittacus erithacus) presented for emergency treatment. All three parrots had depressed behavior, an inability to fly, and significant weight loss. Plasma chemistry abnormalities included severe hypoproteinemia and elevated liver enzymes in all parrots. Two of the parrots died, and histologic examination with hematoxylin and eosin and Prussian blue stains revealed severe hepatic iron storage. Quantitative analysis confirmed high hepatic iron concentrations. Iron accumulation was attributed to ingestion of a carnivorous bird diet or selectively eating too much fruit and vegetables high in ascorbic acid. Management entailed husbandry changes including switching the remaining parrots to a low-iron diet. Psittacine species exposed to carnivorous bird diets are at risk of developing iron storage disease.

Protective immunity of a modified-live cyprinid herpesvirus 3 vaccine in koi (Cyprinus carpio koi) 13 months after vaccination.

OBJECTIVE: To evaluate the long-term protective immunity of a cyprinid herpesvirus 3 (CyHV3) vaccine in naïve koi (Cyprinus carpio koi). ANIMALS: 72 koi. Procedures-Vaccinated koi (n = 36) and unvaccinated control koi (36) were challenge exposed to a wild-type CyHV3 strain (KHVp8 F98-50) 13 months after vaccination. RESULTS: The CyHV3 vaccine provided substantial protective immunity against challenge exposure. The proportional mortality rate was less in vaccinated koi (13/36 [36%]) than in unvaccinated koi (36/36 [100%]). For koi that died during the experiment, mean survival time was significantly greater in vaccinated than in unvaccinated fish (17 vs 10 days). CONCLUSIONS AND CLINICAL RELEVANCE: The CyHV3 vaccine provided substantial protective immunity against challenge exposure with CyHV3 13 months after vaccination. This provided evidence that koi can be vaccinated annually with the CyHV3 vaccine to significantly reduce mortality and morbidity rates associated with CyHV3 infection.

Inhibition of transplantation tolerance by immune senescence is reversed by endocrine modulation.

The senescent immune system responds poorly to new stimuli; thymic involution, accumulation of memory cells against other specificities, and general refractoriness to antigen signaling all may contribute to poor resistance to infection. These same changes may pose a significant clinical barrier to organ transplantation, as transplantation tolerance requires thymic participation and integrated, tolerance-promoting responses to novel antigens. We found that after the age of 12 months, mice became resistant to the tolerance-inducing capacity of the monoclonal antibody therapy anti-CD45RB. This resistance to tolerance to cardiac allografts could be overcome by surgical castration of male mice, a procedure that led to thymic regeneration and long-term graft acceptance. The potential for clinical translation of this endocrine-immune interplay was confirmed by the ability of Lupron Depot injections, which temporarily disrupt gonadal function, to restore tolerance in aged mice. Furthermore, we demonstrated that the restoration of tolerance after surgical or chemical castration depended on thymic production of regulatory T cells (T(regs)); thymectomy or T(reg) depletion abrogated tolerance restoration. The aging of the immune system ("immune senescence") is a significant barrier to immune tolerance, but this barrier can be overcome by targeting sex steroid production with commonly used clinical therapeutics.

Generation of adaptive regulatory T cells by alloantigen is required for some but not all transplant tolerance protocols.

BACKGROUND: Because CD4CD25Foxp3 regulatory T cells (Tregs) are essential for the maintenance of self-tolerance, significant interest surrounds the developmental cues for thymic-derived natural Tregs (nTregs) and periphery-generated adaptive Tregs (aTregs). In the transplant setting, the allograft may play a role in the generation of alloantigen-specific Tregs, but this role remains undefined. We examined whether the immune response to a transplant allograft results in the peripheral generation of aTregs. METHODS: To identify generation of aTregs, purified graft-reactive CD4CD25 T cells were adoptively transferred to mice-bearing skin allograft. To demonstrate that aTregs are necessary for tolerance, DBA/2 skin was transplanted onto C57BL/6-RAG-1-deficient recipients adoptively transferred with purified sorted CD4CD25 T cells; half of the recipients undergo tolerance induction treatment. RESULTS: By tracking adoptively transferred cells, we show that purified graft-reactive CD4CD25 T lymphocytes up-regulate Foxp3 in mice receiving skin allografts in the absence of any treatment. Interestingly, cotransfer of antigen-specific nTregs suppresses the up-regulation of Foxp3 by inhibiting the proliferation of allograft-responsive T cells. In vitro data are consistent with our in vivo data-Foxp3 cells are generated on antigen activation, and this generation is suppressed on coculture with antigen-specific nTregs. Finally, blocking aTreg generation in grafted, rapamycin-treated mice disrupts alloantigen-specific tolerance induction. In contrast, blocking aTreg generation in grafted mice treated with nondepleting anti-CD4 plus anti-CD40L antibodies does not disrupt graft tolerance. CONCLUSIONS: We conclude that graft alloantigen stimulates the de novo generation of aTregs, and this generation may represent a necessary step in some but not all protocols of tolerance induction.

Blockade of GITR-GITRL interaction maintains Treg function to prolong allograft survival.

Involvement of Treg in transplant tolerance has been demonstrated in multiple models. During the active process of graft rejection, these regulatory cells are themselves regulated and inactivated, a process termed counter-regulation. We hypothesize that ligation of the costimulatory molecule glucocorticoid-induced TNF receptor-related protein (GITR) on Treg inhibits their ability to promote graft survival, and by blocking GITR ligation graft survival can be prolonged. To this aim, we have designed a soluble GITR fusion protein (GITR-Fc), which binds GITR ligand and inhibits activation of GITR. Here, we show that GITR-Fc prolonged mouse skin graft survival, and this prolongation is dependent on Treg. In a full MHC-mismatched skin graft setting, GITR-Fc significantly improved graft survival when used in combination with MR1, anti-CD40L, while GITR-Fc alone did not demonstrate graft prolongation. These results demonstrate that disruption of binding of GITR with GITR ligand may be an important strategy in prolonging allograft survival.