Evaluation of adrenal function in psittacine birds, using the ACTH stimulation test

The effect of ACTH (16 units) on plasma cortisol and corticosterone concentrations in healthy psittacine birds was evaluated. Plasma corticosterone significantly increased (P less than 0.01) from a mean (+/- SD) basal concentration of 3.25 +/ 3.6 ng/ml to 26.47 +/- 9.25 (one hour after ACTH administration) and 25.69 +/- 13.23 ng/ml (2 hours after ACTH administration). For maximal increase in plasma corticosterone as measured by radioimmunoassay (RIA), heat denaturation was necessary to release corticosteroids from steroid-binding proteins. As measured by RIA, plasma cortisol concentrations did not increase, whether or not the heat denaturation step was included. Addition of cortisol to avian plasma did not prevent accurate quantification of cortisol as measured by RIA. Plasma corticosterone concentrations in cockatoos, macaws, Amazon parrots, conures, and lorikeets before and after ACTH administration indicated that the ACTH stimulation test could be used to evaluate adrenal secretory capacity in psittacine birds.     

Thyrotropin stimulation test for evaluation of thyroid function in psittacine birds

Serum thyroid hormone concentrations were determined before and after thyrotropin (thyroid stimulating hormone [TSH]) stimulation in caged psittacine birds to determine whether the TSH stimulation test could be used to evaluate thyroid function in this class of birds. The mean (+/- SD) resting thyroxine concentrations (ng/ml) for the species studied were: cockatoos, 13.63 +/- 6.53 (n = 6); Amazon parrots, 8.19 +/- 6.90 (n = 8); scarlet macaws, 1.34 +/- 0.51 (n = 9); blue and gold macaws, 3.41 +/- 1.78 (n = 8); African gray parrots, 1.42 +/- 0.44 (n = 6); conures, 1.76 +/- 0.77 (n = 5); and cockatiels, 11.83 +/- 6.76 (n = 3). The mean (+/- SD) thyroxine concentrations (ng/ml) 4 to 6 hours after TSH stimulation were 35.10 +/- 13.16, 27.40 +/- 15.93, 6.46 +/- 3.10, 12.36 +/- 6.34, 9.30 +/- 2.90, 13.50 +/- 7.71, and 39.0 +/- 5.66, respectively. Serum tri-iodothyronine concentration did not increase significantly after TSH stimulation. The results demonstrated that the TSH stimulation test can be used to evaluate thyroid function in caged psittacine birds.     

Feather-picking psittacines: histopathology and species trends

Histologic findings are described for 408 feather-picking or self-mutilating psittacines with the use of biopsies from clinically affected and unaffected skin. Inflammatory skin disease was diagnosed in 210 birds, and traumatic skin disease was diagnosed in 198 birds. Criteria used for the diagnosis of inflammatory skin disease included the presence of perivascular inflammation in the superficial or deep dermis of clinically affected and unaffected sites. The primary histologic criteria for the diagnosis of traumatic skin disease were superficial dermal scarring with or without inflammation in the affected sites and an absence of inflammation in the unaffected sites. The inflammatory cells associated with the lesions were typically lymphocytes and occasionally plasma cells, histiocytes, and granulocytes. A preponderance of inflammatory skin disease was seen in macaws (Ara spp.) and Amazon parrots (Amazona spp.). A preponderance of traumatic skin disease was seen in cockatoos (Cacatua spp.) and African grey parrots (Psittacus erithacus). The prevalence of each was approximately equal in several other species, including conures (Aratinga and Pyrrhura spp.), eclectus parrots (Eclectus roratus), quaker parrots (Myiopsitta monachus), cockatiels (Nymphicus hollandicus), parakeets (Cyanorhamphus and Psittacula spp.), and caiques (Pionites spp.). No geographic or gender-based trends were identified. These findings could be helpful for identifying and treating birds with feather-picking disorders.     

Fatty acid profiles of crop contents of free-living psittacine nestlings and of commercial hand-feeding formulas

Research on psittacine nutrition is limited, and nestling requirements are poorly understood. This study analysed fatty acid (FA) profiles of crop contents of free-living scarlet macaws (Ara macao, n = 18), red-and-green macaws (Ara chloropterus, n = 5), Cuban parrots (Amazona leucocephala bahamensis, n = 27), lilac-crowned Amazons (Amazona finschi, n = 33) and thick-billed parrots (Rhynchopsitta pachyrhyncha, n = 32). The same analysis was carried out on 15 commercial parrot hand-feeding formulas. The mean FA concentration of the crop samples of each species ranged from 15% to 53% DM for crop samples and ranged from 6% to 22% for hand-feeding formulas. Long-chain FA represented over 92% of all FA in the crop samples and over 81% of all FA in the commercial formulas. Parrot species shared similarities in saturation profiles of crop samples, ranging between 13%–29% saturated fatty acids (SFA), 12%–40% monounsaturated fatty acids (MUFA) and 39%–58% polyunsaturated fatty acids (PUFA). All studied psittacines, except for the red-and-green macaw, were within the range of values for hand-rearing formulas. Palmitic acid was the most common SFA in scarlet macaws, red-and-green macaws, Cuban parrot, thick-billed parrot and in all but one commercial formula. Palmitic and stearic acids dominated the SFA in the samples of the Lilac-crowned Amazon. Oleic acid was the most common MUFA in all hand-feeding formulas as well as in the crop samples, except for the lilac-crowned amazon and the thick-billed parrot where vaccenic acid dominated. Linoleic acid was by far the most common PUFA found in the crop samples as well as in the hand-feeding formulas. PUFA were largely dominated by the n6 family, both in the crop samples and the formulas. The data presented on nestling diets of free-living parrot species provide a foundation for future researchers to test whether increasing FA concentration in hand-feeding formulas improves nestling development or if species-specific formulas will be advantageous.     

Zoonotic diseases in psittacine birds: apparent increased occurrence of chlamydiosis (psittacosis), salmonellosis, and giardiasis.

Between September 1977 and November 1978, chlamydiosis (psittacoisis) was diagnosed in 52 of 128 parrots, 5 of 12 cockatiels, 2 of 5 cockatoos, 3 of 6 macaws, 1 of 22 conures, 2 of 18 lovebirds, and 6 of 76 parakeets; 2 lories and 1 lorikeet were chlamydiosis negative. Two cases of human chlamydiosis were associated with two submissions of parrots subsequently found to have active infection. Twenty parrots (including 13 that were chlamydiosis positive), 2 cockatiels, 1 macaw, 1 lorie, and 1 parakeet yielded salmonella organisms, of which 16 were identified as Salmonella typhimurium, 8 as untypeable monophasic salmonellae of serogroup B, and 1 as S arizonae. Three S typhimurium from parrots that had been treated with chlortetracycline for chlamydiosis were resistant to tetracyclines, streptomycin, and sulfonamides; another isolate was found to be resistant to chloramphenicol only. Severe giardiasis was diagnosed in parakeets originating from six aviaries.     

Interactions between viscerotropic velogenic Newcastle diseases virus and pet birds of six species. I. Clinical and serologic responses, and viral excretion

Clinical and serologic responses to a psittacine isolate of viscerotropic velogenic Newcastle disease virus (VVNDV) were evaluated in pet birds of six species: budgerigar, yellow-headed Amazon parrot, halfmoon conure, lesser hill mynah, black-headed nun, canary. The clinical response was most marked in the budgerigars, parrots, and conures, and only minimal in the nuns. Between post-exposure days (PED) 3 and 5 some birds developed ruffled plumage, conjunctivitis, and central nervous system dysfunction: ataxia, wing tremors, paralysis of the extremities, and tremors of the head accompanied by nodding and jerking. Mortality by PED 203 was 55% (29/52) in the halfmoon conures, 22% (23/105) in budgerigars, 29% (12/42) in parrots, and 21% (15/71) in nuns. The only clinical signs in canaries and mynahs were progressive death losses, respectively 25% (33/132) and 21% (10/48). The visceral lesions common in chickens with VVNDV were not observed in these six species. Canaries rapidly eliminated Newcastle disease virus (NDV), whereas it was detected for protracted periods in the oral and cloacal secretions of the other five species (for more than a year in parrots). Serologic evaluation by the hemagglutination-inhibition and neutralization tests also indicated prolonged NDV infections in 5 of the 6 species. The seroconversion rate observed in canaries was minimal (13%).     

Chlamydophila psittaci in free-living Blue-fronted Amazon parrots (Amazona aestiva) and Hyacinth macaws (Anodorhynchus hyacinthinus) in the Pantanal of Mato Grosso do Sul, Brazil

Chlamydophila psittaci (C. psittaci) infection was evaluated in 77 free-living nestlings of Blue-fronted Amazon parrots (Amazona aestiva) and Hyacinth macaws (Anodorhynchus hyacinthinus) in the Pantanal of Mato Grosso do Sul, Brazil. Tracheal and cloacal swab samples from 32 wild parrot and 45 macaw nestlings were submitted to semi-nested PCR, while serum samples were submitted to complement fixation test (CFT). Although all 32 Amazon parrot serum samples were negative by CFT, cloacal swabs from two birds were positive for Chlamydophila DNA by semi-nested PCR (6.3%); these positive birds were 32 and 45 days old. In macaws, tracheal and cloacal swabs were positive in 8.9% and 26.7% of the samples, respectively. Complement-fixing antibodies were detected in 4.8% of the macaw nestlings; macaw nestlings with positive findings were between 33 and 88 days old. These results indicate widespread dissemination of this pathogen in the two evaluated psittacine populations. No birds had clinical signs suggestive of chlamydiosis. To the best of our knowledge, this is the first report on C. psittaci in free-living Blue-fronted Amazon parrots and Hyacinth macaws in Brazil.     

Adverse effects of gentamicin in scarlet macaws and galahs

The adverse effects of administration of gentamicin (5 mg/kg of body weight, IM, q 12 h) for 7 days were studied in healthy scarlet macaws (Ara macao) and galahs (Eolophus roseicapillus; cockatoos). Polydipsia and polyuria developed in each species, but were greater and persisted longer in the cockatoos. Peak water intake in the cockatoos more than quadrupled, and remained increased for 23 days after cessation of gentamicin administration. Plasma aspartate transaminase activity increased significantly (P less than 0.05) after treatment in the macaws, and plasma aspartate transaminase and lactate dehydrogenase activities increased in the cockatoos. Single IM administration of gentamicin (5 mg/kg) resulted in mean (+/- SEM) plasma concentration of 20.6 (+/- 1.85) micrograms/ml at 0.5 hour for either species of birds. There were no significant differences between mean plasma gentamicin concentrations for cockatoos and macaws at any time after drug administration, except at 12 hours, when values for cockatoos were significantly (P less than 0.05) greater than those for macaws. The elimination half-life for gentamicin after IM administration of 5 and 10 mg/kg was 1.17 and 1.07 hours, respectively, for macaws and 1.23 and 1.44 hours, respectively, for cockatoos. Correlation between drug disposition and adverse side effects could not be detected.     

Echocardiographic examinations of 60 African grey parrots and 30 other psittacine birds

The aim of this study was to establish reference values for the assessment of cardiac function in birds by measuring structures in the heart of healthy psittacine birds; 60 grey parrots, 10 Amazon parrots, 10 cockatoos and 10 Senegal parrots were anaesthetised with isoflurane and examined echocardiographically. The heart was visualised in two planes (vertical and horizontal views). Depending on the quality of the images, several dimensions of the heart could be measured and various parameters calculated. On the basis of these values, it was possible to establish reference values for each parrot genus. Some relative parameters showed no significant difference between the genera, independent of the bird's size.     

Liver virome of a Little Corella (Cacatua sanguinea) reveals coinfection with a novel parvovirus and two beak and feather disease viruses

Emerging diseases are acknowledged as a growing threat to wildlife, with the continued identification of pathogenic and potentially pathogenic viruses in avian species resulting from ongoing advances in molecular diagnostic techniques. Parvoviruses under the genus Chaphamaparvovirus (subfamily Hamaparvovirinae) are highly divergent. The detection and characterisation of parvoviruses in psittacine birds is limited. This study reports a novel parvovirus, tentatively named psittaciform chaphamaparvovirus 3 (PsChV-3) under the genus Chaphamaparvovirus, identified in an Australian free-ranging little corella (Cacatua sanguinea). The PsChV-3 genome is 4277 bp in length and encompasses four predicted open-reading frames, including two major genes, a nonstructural replicase gene (NS1), and a structural capsid gene (VP1). The NS1 and VP1 genes showed the closest amino acid identities of 78.8% and 69.7%, respectively, with a recently sequenced psittaciform chaphamaparvovirus 2 from Australian Neophema species grass parrots. In addition, the presence of two complete novel beak and feather disease (BFDV) genomes, 1993 and 1868 nt in length, respectively, were detected from the same bird. Both these BFDV genomes contained two bidirectional ORFs encoding the putative Rep and Cap proteins. Phylogenetic analysis showed that the sequenced novel BFDV genomes clustered in a distinct subclade with other BFDVs isolated from Australian cockatoos. This study contributes to the characterisation chaphamaparvoviruses and BFDV in Australian parrots and supports the need for ongoing monitoring and molecular studies into the avian virome in native Australian psittacine bird species.     

Evaluation of assay procedures for prediction of passive transfer status in lambs

OBJECTIVE: To compare 4 assay procedures for prediction of passive transfer status in lambs. ANIMALS: Thirty-one 1-day-old Sardinian lambs. PROCEDURE: Serum IgG concentration was determined by use of single radial immunodiffusion. The following were determined: serum total protein concentration as measured by refractometry (ie, refractometry serum total protein concentration), serum total protein concentration as determined by the biuret method (ie, biuret method serum total protein concentration), serum gamma-globulin concentration as determined by serum protein electrophoresis, and serum gamma-glutamyltransferase (GGT) activity as measured by spectrophotometry. Accuracy of these assays for estimation of serum IgG concentration in 1-day-old lambs was established by use of linear regression analysis. RESULTS: Refractometry serum total protein concentration, biuret method serum total protein concentration, and serum gamma-globulin concentration were closely and linearly correlated with serum IgG concentration. The natural logarithm (ln) of serum GGT activity was closely and linearly correlated with serum IgG concentration (ln). Refractometry serum total protein concentration, biuret method serum total protein concentration, and gamma-globulin concentration accounted for approximately 85%, 91%, and 95% of the variation in serum IgG concentration, respectively. Serum GGT activity (ln) accounted for approximately 92% of the variation in serum IgG concentration (ln). CONCLUSIONS AND CLINICAL RELEVANCE: For prediction of passive transfer status in 1-day-old lambs, serum GGT activity or biuret method serum total protein concentration determination will allow for passive transfer monitoring program development. Immediate refractometry serum total protein concentration determination is beneficial in making timely management and treatment decisions. Serum gamma-globulin concentration determination can be used as a confirmatory test.     

Epizootiologic aspects of viscerotropic velogenic Newcastle disease in six pet bird species

Pet birds of 6 species were exposed to a psittacine isolate to viscerotropic velogenic Newcastle disease (VVND) virus to evaluate the impact of VVND in those species. Species examined were the budgerigar, yellow-headed Amazon parrot, canary, halfmoon conure, lesser hill mynah, and blackheaded nun. Five of the 6 species were highly susceptible to infection with VVND virus. Canaries were relatively refractory to infection with the virus. Contact birds of the same species developed infections almost as rapidly as did the birds directly exposed to nebulized VVND virus. Mortality was most marked for the conures. Less than half of the parrots exposed to nebulized virus died of VVND. Of the directly exposed budgerigars, mynahs, and nuns, 16% to 22% died during an observation period of postexposure days 0 through 28.     

Protein electrophoresis of psittacine plasma

BACKGROUND: Although protein electrophoresis (EPH) has been widely applied in human and veterinary medicine, it has only recently been implemented in the analysis of avian samples. OBJECTIVE: The purpose of this study was to examine the application of protein EPH to the analysis of psittacine plasma samples. Our goals were to describe protein fraction mobility, establish reference intervals for some common species, determine the coefficient of variation (CV) of the chosen method, and examine the effects of sample handling and sample condition. METHODS: Heparinized plasma samples from several common psittacine species (minimum sample size 50 each) were examined using the Beckman Paragon system and SPEP-II gels. Total protein was measured by refractometry. Reference intervals (95%) were calculated by the rank methods. RESULTS: Fraction migration patterns were found to vary among common psittacine species. Day-to-day CV for the EPH fractions ranged from 2.2% to 10.5%; within-run CV ranged from 4.8% to 10.8%; and total CV ranged from 3.2% to 14.8%. The highest CV was noted for the poorly defined alpha-globulin fraction. Prolonged refrigeration, repeated freeze-thawing, hemolysis, and lipemia altered the results. CONCLUSIONS: Protein fractions from psittacine species were variable in terms of migration pattern and protein concentration, which necessitates the use of species-specific reference intervals. Avian protein electrophoretic patterns and values should be interpreted based on knowledge of the CV associated with the technique as well as on the effects of sample handling and condition.     

Flow cytometric analysis of nuclear DNA for sex identification in three psittacine species

OBJECTIVE: To evaluate flow cytometric analysis for sex identification in 3 psittacine species, establish reference values for blood cell DNA content for each species, and determine effects of sample storage on DNA content. ANIMALS: 36 orange-winged Amazon parrots, 41 budgerigars, and 39 cockatiels. PROCEDURE: Blood samples were stained and analyzed by use of flow cytometry to measure cellular DNA content. Samples were analyzed immediately after collection and after being stored at 4 C for 48 and 72 hours. RESULTS: Mean DNA content (picograms per cell) was 3.248 for Amazon parrots, 2.702 for budgerigars, and 2.946 for cockatiels; DNA concentrations in samples analyzed immediately overlapped in a male and a female Amazon parrot and among 19 cockatiels. For budgerigars, DNA overlap between sexes was not detected in samples analyzed immediately or after storage for 72 hours. Sex was identified correctly in 94.4% of Amazon parrots, 100% of budgerigars, and 51.3% of cockatiels. For both sexes, DNA content in samples analyzed immediately was significantly different from that of stored samples. CONCLUSIONS AND CLINICAL RELEVANCE: Flow cytometric analysis was accurate for sex identification of Amazon parrots and budgerigars. Sample storage at 4 C for 48 or 72 hours caused variability in DNA content.     

Investigation of Japanese quail (Coturnix japonica) as a pharmacokinetic model for cockatiels (Nymphicus hollandicus) and Poicephalus parrots via comparison of the pharmacokinetics of a single intravenous injection of oxytetracycline hydrochloride

The purpose of this study was to determine whether Japanese quail (Coturnix japonica) would serve as a pharmacokinetic animal model for two small companion parrots: cockatiels (Nymphicus hollandicus) and Poicephalus parrots. Oxytetracycline (OTC) was the pharmacologic agent chosen for this study as it is eliminated primarily by renal glomerular filtration and undergoes minimal metabolism. A single intravenous injection of 20 mg/kg oxytetracycline hydrochloride was administered to the three study groups and blood samples were obtained at 5, 10, 15, and 30 min post-OTC injection as well as 1, 2, 4, 8, 12 and 24 h post-OTC injection. Quantification of plasma OTC was accomplished using a standardized microbial inhibition assay. Naïve-pooled data (NPD) analysis of the plasma concentration–time profile of OTC best fit a two-compartment open model for all three avian species. Noncompartmental analysis of the mean data yielded the following parameters for quail, cockatiels and Poicephalus parrots respectively: λ_z = 3.14, 4.57, 3.71 h; AUC = 38.9, 42.7, 49.6 μg·h/mL; and Cl = 514, 468, 403 mL/h/kg. Based on the similarity of these pharmacokinetic parameters, it appears that quail could be used as a model species to predict the appropriate OTC dosing regimen for small psittacine birds. A bootstrap procedure was also applied to these sparse data sets for both compartmental and noncompartmental analysis. The bootstrap procedure allowed for the calculation of variability of parameters; however, the estimates of the parameters were very similar to those calculated using the NPD and the data mean values.     

Seroprevalence of psittacine beak and feather disease in wild psittacine birds in New South Wales

SUMMARY A haemagglutination inhibition assay was used to detect antibody to psittacine beak and feather disease virus in sera from wild sulphur crested cockatoos (Cacatua galerita), galahs (Eolophus roseicapillus), short-billed corellas (Cacatua sanguinea), eastern long-billed corellas (Cacatua tenuirostris) and other psittacine birds in New South Wales. The seroprevalence of psittacine beak and feather disease ranged from 41% to 94% in different flocks, indicating infection with the virus is widespread in wild populations.     

Identification of apolipoprotein A‐I in the α‐globulin fraction of avian plasma

Background: Plasma protein electrophoresis is frequently used in birds as a tool for the diagnosis and monitoring of disease. Identification of proteins in individual peaks can help improve our understanding of changes in protein concentration in physiologic and pathologic conditions. Objective: The aim of this study was to verify the presence and identity the protein(s) in the prominent α‐globulin peak of orange‐winged parrots (Amazona amazonica), black kites (Milvus migrans), and rock pigeons (Columba livia). Methods: Heparinized plasma samples were obtained from 12 birds of each species. Agarose gel electrophoresis and total protein concentration were determined using standard techniques. One plasma sample from each species was then electrophoresed using high‐resolution agarose gels to isolate the α‐globulin band. Gel strips were digested in trypsin and peptides were extracted and analyzed using liquid chromatography with tandem mass spectrometry. De novo sequencing was used to identify the protein based on homology scoring against a protein database. Results: Electrophoresis verified the presence of a single prominent α‐globulin peak, usually in the α₁‐region, that had a median concentration of 9.4 g/L (range, 2.1–11.7 g/L, 21.6% of total protein) in parrots, 12.2 g/L (10.4–13.2 g/L, 35.9%) in kites, and 10.7 g/L (9.0–11.5 g/L, 40.0%) in pigeons. Mass spectrometry and sequencing analysis unequivocally identified the protein as a mature circulating form of apolipoprotein A‐I (apo A‐I) in all 3 species. Conclusions: Apo A‐I accounts for the prominent α‐globulin peak and comprises a major proportion of total protein concentration in diverse avian species. As a high‐density lipoprotein and negative acute phase protein with a pivotal role in cholesterol homeostasis, further study is warranted to determine the significance of changes in apo A‐I concentration in avian electrophoretograms.     

Cloacal papillomatosis in the absence of herpesvirus and papillomavirus in a sulphur-crested cockatoo (Cacatua galerita)

CASE HISTORY A 21-year-old male sulphur-crested cockatoo (Cacatua galerita) was presented following the sudden appearance of blood associated with the passage of faeces and urates.

CLINICAL AND PATHOLOGICAL FINDINGS: There was fresh blood-staining of the feathers around the vent. The dorsal mucosal wall of the proctodeum was erythematous and roughened in appearance. An endoscopic biopsy was performed, and histological examination revealed multiple fronds of epithelium; the mucosa varied from simple to pseudostratified columnar epithelium, with diffuse hyperplasia of goblet cells. The underlying connective tissue stroma was well vascularised and was infiltrated with mixed inflammatory cells, comprising granulocytic cells and macrophages. PCR testing for both herpesvirus and papillomavirus, using consensus primers, was negative.

DIAGNOSIS: Cloacal papillomatosis.

CLINICAL RELEVANCE: This case manifested typical clinical signs and histological lesions of cloacal papillomatosis in the absence of demonstrable herpesvirus or papillomavirus. Veterinarians need to consider this disease in the differential diagnosis of blood in the droppings of parrots and cockatoos even in countries where psittacine herpesviruses are exotic diseases.     

Prevalence and Risk Factors of Feather Plucking in African Grey Parrots (Psittacus erithacus erithacus and Psittacus erithacus timneh) and Cockatoos (Cacatua spp.)

Feather plucking, or the removal by a parrot of its own feathers, is thought to be one of the most common behaviour presentations in veterinary practices that treat avian patients. However, its aetiology is poorly understood. The aims of this study were to estimate the prevalence of feather plucking within the population of African grey parrots (Psittacus erithacus erithacus and Psittacus erithacus timneh) and cockatoos (Cacatua spp.) registered with 9 veterinary practices in the United Kingdom (UK) and to explore the association between frequently hypothesised risk factors and feather plucking in these species. A questionnaire was sent to the owners of 400 African grey parrots and 310 cockatoos registered with 9 UK veterinary practices. Returned questionnaires from 137 African grey parrots and 92 cockatoos were analysed, of which 39.4% of African grey parrots and 42.4% of cockatoos had exhibited feather-plucking behaviour at some point in their lifetime. Multivariable logistic regression modelling demonstrated that increasing hours of sleep and length of ownership were significantly associated (P < 0.05) with feather plucking in African grey parrots. Pet shop origin, cage location against ≥1 wall and ≥1 vacation taken by owners each year were significantly associated (P < 0.05) with feather plucking in cockatoos. The high prevalence of feather plucking in these commonly kept pets highlights this problem as a welfare concern, whereas the risk factor analysis challenges many frequently cited hypotheses regarding its aetiology. Further research is required to explore whether there is a causal relationship between the significant risk factors identified in this study and feather-plucking behaviour.     

Validation of a novel high-sensitivity radioimmunoassay procedure for measurement of total thyroxine concentration in psittacine birds and snakes.

OBJECTIVE: To validate a novel high-sensitivity radioimmunoassay (RIA) procedure developed to accurately measure the relatively low serum total thyroxine (T4) concentrations of birds and reptiles and to establish initial reference ranges forT4 concentration in selected species of psittacine birds and snakes. ANIMALS: 56 healthy nonmolting adult psittacine birds representing 6 species and 42 captive snakes representing 4 species. PROCEDURE: A solid-phase RIA designed to measure free T4 concentrations in dialysates of human serum samples was used without dialysis to evaluate total T4 concentration in treated samples obtained from birds and reptiles. Serum T4 binding components were removed to allow assay of undialyzed samples. Assay validation was assessed by determining recovery of expected amounts of T4 in treated samples that were serially diluted or to which T4 was added. Intra- and interassay coefficient of variation (CV) was determined. RESULTS: Mean recovery of T4 added at 4 concentrations ranged from 84.9 to 115.0% and 95.8 to 119.4% in snakes and birds, respectively. Intra- and interassay CV was 3.8 and 11.3%, respectively. Serum total T4 concentrations for 5 species of birds ranged from 2.02 to 768 nmol/L but ranged from 3.17 to 142 nmol/L for blue-fronted Amazon parrots; concentrations ranged from 0.21 to 6.06 nmol/L for the 4 species of snakes. CONCLUSIONS AND CLINICAL RELEVANCE: This new RIA method provides a commercially available, accurate, and sensitive method for measurement of the relatively low serum T4 concentrations of birds and snakes. Initial ranges for the species evaluated were established.