Disseminated coelomic xanthogranulomatosis in eclectus parrots (Eclectus roratus) and budgerigars (Melopsittacus undulatus).

Xanthogranulomatosis is an inflammatory lesion characterized by lipid-containing macrophages, extracellular lipid, hemorrhage, and necrosis. We describe disseminated intracoelomic xanthogranulomatosis in 5 eclectus parrots (Eclectus roratus) and 2 budgerigars (Melopsittacus undulatus). Postmortem, clinicopathologic, and historical case material was reviewed. Ages ranged from 3 to 24 years; there were 5 males and 2 females. Table food was included in the diet of 3/5 cases, and animal products were included in 2/3 cases. Common clinicopathologic abnormalities included leukocytosis (4/5 cases) and elevated concentrations of bile acids (3/4 cases) and cholesterol within 6 months prior to death (2/4 cases). At postmortem examination, all 7 birds had grossly visible, irregular, soft, tan to yellow, amorphous plaques distributed on the surfaces of the viscera and body wall. Histologic evaluation and oil red O stain revealed xanthogranulomatous inflammation with phagocytized and extracellular lipid, necrosis, cholesterol clefts, fibrosis, and mineralization. Infectious agents were not identified with special stains in all cases. Concurrent hepatobiliary disease was present in 6/7 cases, and 6/7 had lipid accumulation within the parenchyma of various visceral organs. Five cases had atherosclerosis of great vessels. We describe a unique form of disseminated coelomic xanthogranulomatosis in 2 psittacine species. This condition should be recognized as a differential diagnosis in cases of disseminated coelomic mass formation and coelomic distension in psittacine birds, particularly in eclectus parrots and budgerigars.

Drug dose and animal welfare: important considerations in the treatment of wildlife.

A recent publication in Parasitology Research by (Old et al. Parasitol Res 120:1077-1090, 2021) raises the topical and often controversial issue of the treatment of wildlife by personnel with little or no formal scientific training (e.g. wildlife carers). In a valuable contribution to the subject, Old and colleagues document a wide range of topical (pour-on) application doses and frequencies of moxidectin (Cydectin®) administered in situ to bare-nosed wombats (Vombatus ursinus) by members of the wildlife carer/treater community in southeast Australia to treat sarcoptic mange disease. This treatment occurred under minor use permits issued by the Australian Pesticides and Veterinary Management Authority (APVMA). These permits do not require veterinary supervision, although carers are registered and are expected to comply with the guidelines of this permit.The prevalence and severity of sarcoptic mange in wildlife is influenced by a variety of factors including mite biology, environmental conditions, population density, animal behaviour and immune susceptibility (Browne et al. Bioscience, 2021). In bare-nosed wombats, combinations of these elements play a substantial role in making the treatment of an already difficult disease more complex. (Moroni et al. Parasit Vectors 13:471, 2020) comment that any pharmacological treatment of free-ranging wildlife must consider these factors when assessing their feasibility and implications, especially in the context of emerging drug resistance and potential long-term ecological impacts. As individuals with significant interest in sarcoptic mange and representing a range of professional research and veterinary expertise, we see value in providing expert commentary on this issue.

Comparison of In-Clinic Diagnostic Testing Methods for Macrorhabdus ornithogaster.

Macrorhabdus ornithogaster is an ascomycete yeast often found at the isthmus of the ventriculus and proventriculus of infected birds. Antemortem diagnosis has traditionally involved direct visualization of organisms on wet-mount or gram-stained fecal preparations, cloacal and crop swabs, or by both methods; however, different in-clinic diagnostic techniques have never been compared to establish an optimum test for the identification of M ornithogaster in an avian patient. We compared 5 microscopically evaluated diagnostic testing methods: fecal Gram's stain, direct fecal wet preparation, macro suspension technique, macro suspension with Gram's stain, and macro suspension stained with new methylene blue. Each technique was performed on 96 fecal samples collected during the treatment of M ornithogaster-infected budgerigars with water-soluble amphotericin B. The macro suspension technique produced statistically higher organism counts than the other 4 techniques and was always estimated to have the largest detection probability. We recommend that the macro suspension technique be implemented as the most efficacious diagnostic test for in-clinic assessment of avian patients possibly infected with M ornithogaster.

Genomic comparisons reveal biogeographic and anthropogenic impacts in the koala (Phascolarctos cinereus): a dietary-specialist species distributed across heterogeneous environments.

The Australian koala is an iconic marsupial with highly specific dietary requirements distributed across heterogeneous environments, over a large geographic range. The distribution and genetic structure of koala populations has been heavily influenced by human actions, specifically habitat modification, hunting and translocation of koalas. There is currently limited information on population diversity and gene flow at a species-wide scale, or with consideration to the potential impacts of local adaptation. Using species-wide sampling across heterogeneous environments, and high-density genome-wide markers (SNPs and PAVs), we show that most koala populations display levels of diversity comparable to other outbred species, except for those populations impacted by population reductions. Genetic clustering analysis and phylogenetic reconstruction reveals a lack of support for current taxonomic classification of three koala subspecies, with only a single evolutionary significant unit supported. Furthermore, ~70% of genetic variance is accounted for at the individual level. The Sydney Basin region is highlighted as a unique reservoir of genetic diversity, having higher diversity levels (i.e., Blue Mountains region; AvHecorr=0.20, PL% = 68.6). Broad-scale population differentiation is primarily driven by an isolation by distance genetic structure model (49% of genetic variance), with clinal local adaptation corresponding to habitat bioregions. Signatures of selection were detected between bioregions, with no single region returning evidence of strong selection. The results of this study show that although the koala is widely considered to be a dietary-specialist species, this apparent specialisation has not limited the koala's ability to maintain gene flow and adapt across divergent environments as long as the required food source is available.

Evidence of amphotericin B resistance in Macrorhabdus ornithogaster in Australian cage-birds.

Amphotericin B is widely used for the treatment of Macrorhabdus ornithogaster infections. To date, however, there have been no randomized controlled trials confirming its efficacy where cure was confirmed by postmortem examination. To determine the efficacy of amphotericin B against M. ornithogaster, a three-part study was undertaken. Treatment outcomes of M. ornithogaster infected birds treated amphotericin B were reviewed. A pilot treatment trial with two naturally infected birds (Melopsittacus undulatus and Agapornis roseicollis) was undertaken, administering amphotericin B at 100 mg/kg twice daily for 30 days. Finally, a randomized controlled trial using experimentally infected chickens treated with amphotericin B at 25 mg/kg and 100 mg/kg twice daily for 10 days was performed. Retrospective analysis indicated treatment failure in 80.4% of 36 cases that met the inclusion criteria. The pilot study showed that amphotericin B did not clear, but significantly decreased Macrorhabdus ornithogaster burden, followed by profound rebound effect of the number of organisms shed in the feces. Finally, the randomized controlled trial found that amphotericin B given at 100 mg/kg did not clear, but significantly decreased the burden of M. ornithogaster compared with both the 25 mg/kg group (P = .037) and the no treatment control group (P = .001). A strong curvilinear correlation between body weight and M. ornithogaster infection burden was present in the infected chickens. These findings represent treatment failure in three scenarios and indicate that treatment with amphotericin B has poor efficacy against Macrorhabdus ornithogaster.

A survey of a mixed species aviary provides new insights into the pathogenicity, diversity, evolution, host range, and distribution of psittacine and passerine adenoviruses.

A Bourke's parrot (Neopsephotus bourkii) originating from an aviary in Australia, containing two species of parrots, five species of finch and a species of dove, was presented for necropsy. The Bourke's parrot died from gastritis caused by Macrorhabdus ornithogaster, but also had an interstitial nephritis and ureteritis with adenovirus-like inclusion bodies within collecting duct epithelial cells. The adenovirus causing the lesions was shown to be Psittacine adenovirus-2 (PsAdV-2) using a PCR assay specific for adenoviruses and sequencing of amplicons. A survey of droppings from other birds in the aviary using the same PCR assay with amplicon sequencing found a high prevalence of infection of PsAdV-2 in Bourke's and scarlet-chested parrots (Neophema splendida). PsAdV-2 was also present in droppings from a Namaqua dove (Oena capensis). Gouldian finches (Erythrura gouldiae), red-billed firefinches (Lagonosticta senegala), and red-throated parrot finches (Erythrura psittacea) were shedding Gouldian finch adenovirus-1 (GFAdV-1). Two novel adenoviruses, an atadenovirus and a siadenovirus, were detected in the droppings from long-tailed finches (Poephila acuticauda). Kidney tissue from three of four scarlet-chested parrots submitted for necropsy from a second aviary were also positive for PsAdv-2. These findings and previously reported findings of widespread PsAdv-2 infection in captive orange-bellied parrots (Neophemia chrysogaster) raise the possibility that PsAdV-2 is enzootic in Australian aviculture. This represents the first report of GFAdV-1 in Australia and first identification of infection in finch species other than the Gouldian finch. Identification of two novel adenoviruses in long-tailed finches suggests that other novel adenoviruses are circulating in other finch species. RESEARCH HIGHLIGHTS Psittacine adenovirus-2 was present in high prevalence in two Australian aviaries. Gouldian finch adenovirus-1 (GFAdV-1) was detected in Australia for the first time. The host range of GFAdV-1 host range was expanded to other finch species. Novel atadenovirus and siadenovirus were detected in Estrildid finches.

A RETROSPECTIVE STUDY OF REPORTED DISORDERS OF THE ORAL CAVITY IN LARGE FELIDS IN AUSTRALIAN ZOOS.

Disorders of the oral cavity are conditions reported by veterinarians that impact the health and welfare of large felids in human care. There have been no studies documenting the prevalence of these conditions and species affected in Australian zoos. A review of the medical records of lions (Panthera leo), tigers (Panthera tigris), cheetahs (Acinonyx jubatus), jaguars (Puma onca), snow leopards (Panthera uncia), Persian leopards (Panthera pardus saxicolor), and cougars (Puma concolor) from 10 Australian zoos and an online survey of zoo professionals from Australian and New Zealand zoos was performed to determine the recorded prevalence of disorders of the oral cavity in these species. Preliminary assessments were also made to determine if there was an association between the occurrence of tooth fractures and diet, feeding practices, species, sex, and age of the animal. The study also examined associations of these conditions with behavior, such as fighting, and husbandry practices, such as the provision of enrichment items. The review found that tooth fractures were common in tigers and lions greater than 8 yr of age. Animal caregivers attributed this to animals chewing on large, hard pieces of bone in some instances, but this could not be verified. Instances of bones being lodged between canine teeth were observed and appeared to be related to the feeding of bones of inappropriate size. Based on these findings, it is recommended that guidelines for bone size fed be developed and that animals over the age of 8 yr receive regular dental examinations under general anesthesia.

Multicentric Septic Osteomyelitis and Arthritis Caused by Staphylococcus aureus in a Gyrfalcon (Falco rusticolus).

An adult female gyrfalcon (Falco rusticolus) was presented with a right-wing droop and weight loss. Radiographic images revealed osteolysis and osseous proliferation of the right shoulder and the mobile vertebra between the notarium and synsacrum. The tentative diagnosis was vertebral osteomyelitis secondary to septic arthritis. The bird did not respond to antibiotic and anti-inflammatory therapy and represented 10 days later, with feathers soiled with feces, an impacted, dilated cloaca, and an inability to stand due to spastic paralysis of the hind legs. The bird's condition did not improve with 24 hours of supportive care and its quality of life was considered poor; therefore, the patient was euthanatized and submitted for postmortem examination. Multicentric septic osteomyelitis and arthritis were confirmed in the mobile vertebra between the notarium and synsacrum and the right shoulder. Despite 10 days of antibiotic therapy, Staphylococcus aureus was isolated from within the 2 locations in which septic osteomyelitis and arthritis were identified. This report describes the clinical features, diagnosis, and pathologic findings of septic osteomyelitis and arthritis caused by S aureus in a falcon.

A Novel Technique for Extracapsular Repair of the Intertarsal Joint in a Duck.

The intertarsal joint is a synovial roll-and-glide joint. Ligament damage and luxations of this joint are often the result of traumatic injury or growth deformities and result in significant functional impairment. A 9-month-old female Pekin duck ( Anas platyrhynchos domesticus) was examined because of progressive, nonweight-bearing lameness of the left leg. Moderate effusive swelling was present at the level of the left intertarsal joint, without radiographic evidence of bone involvement. The duck failed to respond to nonsteroidal anti-inflammatory medications and analgesia and was diagnosed with rupture of the medial collateral ligament. Extracapsular surgical correction using bone tunnels and circumferential nylon suture on the medial aspect of the intertarsal joint led to a complete clinical resolution with normal return to function 2 weeks after surgery. This report reviews the anatomy and function of the intertarsal joint in the duck and details a simple extracapsular repair technique useful in the correction of collateral ligament rupture in this joint of ducks.

Differential Gamma Interferon- and Tumor Necrosis Factor Alpha-Driven Cytokine Response Distinguishes Acute Infection of a Metatherian Host with Toxoplasma gondii and Neospora caninum.

Toxoplasma gondii and Neospora caninum (both Apicomplexa) are closely related cyst-forming coccidian parasites that differ significantly in their host ranges and ability to cause disease. Unlike eutherian mammals, Australian marsupials (metatherian mammals) have long been thought to be highly susceptible to toxoplasmosis and neosporosis because of their historical isolation from the parasites. In this study, the carnivorous fat-tailed dunnart (Sminthopsis crassicaudata) was used as a disease model to investigate the immune response and susceptibility to infection of an Australian marsupial to T. gondii and N. caninum The disease outcome was more severe in N. caninum-infected dunnarts than in T. gondii-infected dunnarts, as shown by the severity of clinical and histopathological features of disease and higher tissue parasite burdens in the tissues evaluated. Transcriptome sequencing (RNA-seq) of spleens from infected dunnarts and mitogen-stimulated dunnart splenocytes was used to define the cytokine repertoires. Changes in mRNA expression during the time course of infection were measured using quantitative reverse transcription-PCR (qRT-PCR) for key Th1 (gamma interferon [IFN-γ] and tumor necrosis factor alpha [TNF-α]), Th2 (interleukin 4 [IL-4] and IL-6), and Th17 (IL-17A) cytokines. The results show qualitative differences in cytokine responses by the fat-tailed dunnart to infection with N. caninum and T. gondii Dunnarts infected with T. gondii were capable of mounting a more effective Th1 immune response than those infected with N. caninum, indicating the role of the immune response in the outcome scenarios of parasite infection in this marsupial mammal.

ESTABLISHING NORMAL FECAL FLORA IN WILD AUSTRALIAN PASSERINE BIRDS BY USE OF THE FECAL GRAM STAIN.

The purpose of this study was to determine the normal fecal bacterial and fungal flora and parasite prevalence in wild passerine birds found at the Australian Botanic Garden (Mount Annan, New South Wales). Wild passerine birds (n = 186) from 28 species were captured with mist nets. Fecal Gram stains (n = 155) were made from 26 species and analyzed for bacterial density, Gram stain morphology, and the presence of yeast. Fecal wet preparations (n = 139) were made from 24 passerine species and were analyzed for parasites. Our results showed that 81.9% of passerines sampled had bacteria present in their feces. The bacteria found were entirely Gram positive and consisted predominantly of cocci. Individuals that were caught on multiple occasions were found to have stable bacterial populations, apart from the red-browed finch (Neochmia temporalis). Insectivores had higher bacterial densities and cocci proportions than nectarivores had. Yeasts were rare in most species, with the exception of the bell miner (Manorina melanophrys) and noisy miner (Manorina melanocephala). The yeast, Macrorhabdus ornithogaster, and parasites were not observed in any fecal samples. These results will help practitioners to assess the health of Australian passerine species submitted for care or housed in zoological collections.

Evolution of circoviruses in lorikeets lags behind its hosts.

The presence of endogenous viral elements in host genomes hints towards much older host-virus relationships than predicted by exogenous phylogenies, with highly mutable single-stranded DNA (ssDNA) viruses and RNA viruses often occupying entangled multispecies ecological niches. The difficulty lies in unravelling the long-term evolutionary history of vertebrate virus-host relationships and determining the age of a potentially ancient tree based only fresh shoots at the tips. Resolving such lineages, and the sometimes great discrepancy amongst evolutionary timescales, is problematic, especially when purifying selection or recombination can significantly alter the accuracy of phylogenetic reconstruction methods. Pathogens which occupy entangled multispecies ecological niches add a further layer of complexity but we show that multi-host scenarios may also provide opportunities to identify allopatric or sympatric paleobiological signals that can unlock longer term phylogenies. We identified host-based, cryptic, sympatric differentiation in beak and feather disease virus in the Psittaciformes tribe Loriini along with endogenous circovirus motifs in Kea (Nestor notabilis) and Gondwanan vicariance estimates to infer the evolutionary timescale of the circoviruses. This demonstrated a chronology of psittacine circovirus speciation aligned to conservative Zealandic divergences for relic circovirus motifs in Kea and a 10million year divergence coinciding with the Papuan central range orogeny that triggered the radiation of Loriini and segregation of an antecedent viral clade in Australian lorikeets. Estimates of circovirus speciation in birds highlighted a Gondwanan dominant group in Neoaves with passerine, columbid and larid circoviruses deeply separated from those in waterfowl, consistent with a Triassic divergence of Galloanserae. The circovirus tree had a deep ancestry in invertebrates with a Palaeozoic expansion in fish and mammals. We show that longer term evolutionary relationships in viruses which have a high rate of mutation and admixture can be disentangled, highlighting that contemporary virus host-switching can be explained by deep intra-lineage host phylogeny.

Toxoplasmosis in a Pet Peach-Faced Lovebird (Agapornis roseicollis).

Toxoplasma gondii atypical type II genotype was diagnosed in a pet peach-faced lovebird (Agapornis roseicollis) based on histopathology, immunohistochemistry, and multilocus DNA typing. The bird presented with severe neurological signs, and hematology was suggestive of chronic granulomatous disease. Gross post-mortem examination revealed cerebral hemorrhage, splenomegaly, hepatitis, and thickening of the right ventricular free wall. Histologic sections of the most significant lesions in the brain revealed intralesional protozoan organisms associated with malacia, spongiform changes, and a mild histiocytic response, indicative of diffuse, non-suppurative encephalitis. Immunohistochemistry confirmed the causative organisms to be T. gondii. DNA isolated from the brain was used to confirm the presence of T. gondii DNA. Multilocus genotyping based on SAG1, altSAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico markers demonstrated the presence of ToxoDB PCR-RFLP genotype #3 and B1 gene as atypical T. gondii type II. The atypical type II strain has been previously documented in Australian wildlife, indicating an environmental transmission route.

Assessment of mosquitofish (Gambusia affinis) health indicators in relation to domestic wastewater discharges in suburbs of Houston, USA.

Personal care products, pharmaceuticals, and other contaminants of emerging concern (CECs) in domestic wastewater treatment plant (WWTP) effluents can impact aquatic organisms. Health indicators were compared for mosquitofish (Gambusia affinis) collected above and below WWTP discharges from five streams in suburban areas of the Houston metropolitan area, Texas, USA. Specimens were evaluated for reproductive, morphological, and histological indicators. Several indicators revealed significant spatial and temporal variation; however, possibly because of their mobility, fish collected upstream and downstream of wastewater treatment plants did not reveal consistent trends based on the endpoints examined. CEC concentrations in water samples from stream reaches below WWTP discharges were quantified for the first time in the Houston Metropolitan area. The 18 CECs detected in stream water had concentrations lower than values currently reported to impact fish. Future research should examine caged fish at each site and fish collected over longer stream reaches that receive successive discharges from WWTP and stronger CEC gradients.

Evaluation of Multidrug Therapy With Azithromycin, Rifampin, and Ethambutol for the Treatment of Mycobacterium avium subsp avium in Ring-neck Doves (Streptopelia risoria): An Uncontrolled Clinical Study.

An uncontrolled clinical study was conducted to evaluate the efficacy of a multidrug protocol in 16 ring-neck doves ( Streptopelia risoria ) from a flock naturally infected with Mycobacterium avium subsp avium. The doves were considered infected on the basis of a high prevalence of infection in a group of 29 birds that were euthanatized from the same flock and clinical signs and pathologic results consistent with infection in the remaining birds. All birds were treated with azithromycin (43 mg/kg), rifampin (45 mg/kg), and ethambutol (30 mg/kg) administered orally once daily for 180 days. Five birds died during treatment and were confirmed positive for mycobacteriosis on postmortem examination. Of the remaining 11 birds, infection and disease were present in 9 (81.8%) at the end of the treatment. Postmortem investigation showed that 2 mycobacterial isolates were resistant to ethambutol, intermediately sensitive to rifampin, and sensitive to azithromycin. Microscopic examination of liver sections equivalent of those that would be taken for biopsy showed that biopsy as a method of monitoring birds for treatment success had poor sensitivity. Toxicity associated with drug therapy was not observed in these doves nor in 6 outwardly healthy ring-neck doves exposed to the same treatment. The results of this study showed that this protocol of azithromycin, rifampin, and ethambutol has poor efficacy when administered for 180 days for treatment of doves infected with M avium subsp avium.

A retrospective epidemiological study of sarcoptic mange in koalas (Phascolarctos cinereus) using wildlife carer admission records.

Outbreaks of sarcoptic mange are sporadically reported in koala populations across Australia, but disease characteristics (e.g., distribution across the body) remain poorly understood. In an area of Northern Victoria regular cases coming into care suggest mange may have become enzootic, and here we characterise those koala mange admission records. In 18% (n = 10) of mange affected koala reports that had a recorded outcome (n = 55), the animals died before the carers could locate them, and of the remaining 45 koalas that were alive upon carer arrival, 80% (n = 36) had to be euthanised due to severe mange. The number of admissions varied among years (highest observed in 2019), and over 60% of affected koala admissions were male. Male admissions peaked in austral spring and again in late austral summer-autumn (mating and birthing seasons), with female admissions only exhibiting the latter peak (birthing season). Fissures of the epidermis of the front paws occurred in 100% of admitted koalas, with 70% also showing these signs elsewhere on ventral surfaces or limbs. Only male koalas had signs of mange on the chest and face, and only female koalas had signs of mange on their back. Collectively, this study suggests sarcoptic mange can be a severe disease in koalas, and that male koalas may play an important role in seasonal transmission dynamics. We discuss how these findings may help inform intervention strategies.

Infection trials in mice suggest that Macrorhabdus ornithogaster is not capable of growth in mammals.

The objective of this study was to determine if Macrorhabdus ornithogaster, a yeast recovered from the junction of the proventriculus and ventriculus of the stomach of parrots and other birds, can infect mice. Fifteen healthy ARC (S) female mice (age 10 weeks) were incoculated with M. ornithogaster by gavage at (two different dosage rates [n = 5]) or intraperitoneal injection (n = 5) (one dosage rate). They were euthanized 5 days later and examined for gross and microscopic evidence of infection. Macrorhabdus ornithogaster was not found to colonize the stomach, peritoneum, or viscera of the challeneged mice. The results of this study show that M. ornithogaster is not able to infect mice by the oral and intraperitoneal routes of administration and suggest that infection in mammals is unlikely to occur.

The effects of decreased body temperature on the onset, duration and action of medetomidine and its antagonist atipamezole in juvenile farmed estuarine crocodiles (Crocodylus porosus).

OBJECTIVE: To determine the efficacy of medetomidine for immobilisation of captive juvenile crocodiles over a range of temperatures, and its reversibility with atipamezole. STUDY DESIGN: Prospective experimental study. ANIMALS: Forty male estuarine crocodiles (body weight 2.0 to 4.8 kg). METHODS: Each crocodile was randomly assigned to one of four temperature groups: Group 1:32 °C; Group 2:27 °C; Group 3:22 °C; and Group 4:17 °C (n = 10 for each group). Medetomidine (0.5 mg kg(-1) ) was administered intramuscularly (IM) into the thoracic limb of all crocodiles. After 50 minutes, all animals from each group received 2.5 mg kg(-1) atipamezole IM in the opposite thoracic limb and time to recovery was documented. Heart and respiratory rates and the degree of immobilisation were monitored every 5 minutes until recovery, and behaviour monitored for 7 subsequent days. RESULTS: Onset of immobilisation occurred at 15 ± 10 minutes in Group 1, and at 30 ± 10 minutes in Groups 2 and 3. In Group 4, animals were not immobilised. Recovery following atipamezole was 10 ± 5 minutes at all temperatures. One-way analysis of variance (anova) demonstrated a significant difference in induction times between groups (p < 0.01) but not in recovery times following atipamezole administration (p < 0.25). Heart and respiratory rates decreased markedly following medetomidine administration and increased markedly following atipamezole reversal. CONCLUSIONS AND CLINICAL RELEVANCE: Medetomidine administered in the thoracic limb of juvenile captive estuarine crocodiles provides profound sedation or immobilisation at temperatures of 22 °C and above. Atipamezole administered in the contralateral thoracic limb results in consistent reversal of the effects of medetomidine and a return to normal behaviour within 15-20 minutes regardless of temperature. Even though immobilisation is not induced at 17 °C, profound reversible sedation does occur reliably and repeatably.

Preliminary studies of alfaxalone for intravenous immobilization of juvenile captive estuarine crocodiles (Crocodylus porosus) and Australian freshwater crocodiles (Crocodylus johnstoni) at optimal and selected sub-optimal thermal zones.

OBJECTIVES: To investigate the character of immobilization given by alfaxalone in juvenile crocodiles at optimal and at suboptimal temperatures. STUDY DESIGN: Prospective, randomized partial crossover study. ANIMALS: Twenty captive male estuarine (weight 0.6-2.5 kg) and five captive male freshwater crocodiles (weight 0.2-0.6 kg). METHODS: Crocodiles were acclimatized for 24 hours at one of the following environmental temperatures; 32 °C, 27 °C, 22 °C or 17 °C, then received 3 mg kg(-1) intravenous (IV) alfaxalone into the dorsal occipital venous sinus. Duration and quality of immobilization was assessed and heart rate (HR) measured. On a separate occasion each crocodile was immobilized at one other environmental temperature. RESULTS: Alfaxalone, 3 mg kg(-1) IV, produced immobilization for 55 (range 15-100 minutes in estuarine, and 20 (range 20-25) minutes in freshwater crocodiles at 32 °C. There was no significant difference overall in immobilization times between temperatures, other than that, in estuarine crocodiles, duration was shorter at 32 °C than 22 °C. The character of immobilization was unpredictable, with animals recovering without warning, or having extended recoveries requiring assisted ventilation. Assisted ventilation was necessary mainly at the lower temperatures. Median HR in all temperature treatments decreased within 5 minutes post-injection, but the change in HR over the duration of immobilization was affected by the temperature, with a progressively smaller range of fall as temperature decreased. At 17 °C, two estuarine crocodiles appeared to re-immobilize after initial recovery, became severely bradycardiac and required ventilation and re-warming. CONCLUSIONS AND CLINICAL RELEVANCE: Alfaxalone IV in small captive estuarine and freshwater crocodiles provides adequate induction of immobilization at various temperatures. However, the unpredictable results following induction mean it is unsuitable for field use and should be restricted to environments where intubation and ventilation are available, where animals can be warmed to optimal temperature, and where access to immersion in water can be restricted for 24 hours.