Prevalence, genotypes, and infection risk factors of psittacine beak and feather disease virus and budgerigar fledgling disease virus in captive birds in Hong Kong

Psittacine beak and feather disease virus (PBFDV) and budgerigar fledgling disease virus (BFDV) are significant avian pathogens that threaten both captive and wild birds, particularly parrots, which are common hosts. This study involved sampling and testing of 516 captive birds from households, pet shops, and an animal clinic in Hong Kong for PBFDV and BFDV. The results showed that PBFDV and BFDV were present in 7.17% and 0.58% of the samples, respectively. These rates were lower than those reported in most parts of Asia. Notably, the infection rates of PBFDV in pet shops were significantly higher compared to other sources, while no BFDV-positive samples were found in pet shops. Most of the positive samples came from parrots, but PBFDV was also detected in two non-parrot species, including Swinhoe's white-eyes (Zosterops simplex), which had not been reported previously. The ability of PBFDV to infect both psittacine and passerine birds is concerning, especially in densely populated urban areas such as Hong Kong, where captive flocks come into close contact with wildlife. Phylogenetic analysis of the Cap and Rep genes of PBFDV revealed that the strains found in Hong Kong were closely related to those in Europe and other parts of Asia, including mainland China, Thailand, Taiwan, and Saudi Arabia. These findings indicate the presence of both viruses among captive birds in Hong Kong. We recommend implementing regular surveillance for both viruses and adopting measures to prevent contact between captive and wild birds, thereby reducing the transmission of introduced diseases to native species.

Occurrence of Macrorhabdus ornithogaster in exotic birds

Avian gastric yeast (Macrorhabdus ornithogaster) is a microorganism that infects aviary birds worldwide, both captive and wild. A total number of 352 birds, belonging to 18 avian species, were examined from 2019 to 2022 for M. ornithogaster, using fecal smears of live birds or cytological samples of the proventriculus taken at necropsy. These cytological samples were taken from birds that died from different causes. Some of the birds exhibited symptoms such as lethargy, regurgitation, weight loss and anorexia. Faecal samples were collected from all the birds and analysed for gastric yeast using a direct smear and Gram-staining method. The microorganism was diagnosed most frequently in budgerigars (55.5%), the African gray parrot (33.3%), and nymphs (34.3%). The prevalence of M. ornithogaster in canaries was 10%. The infection was detected in 31% of the examined birds, which shows that the occurrence of M. ornithogaster in exotic birds is common. No clinical signs were observed in the vast majority of birds that tested positive for gastric yeast.

COMPARISON OF THREE MIDAZOLAM-BASED SEDATION PROTOCOLS IN BUDGERIGARS (MELOPSITTACUS UNDULATUS) AND BLACK-CHEEKED LOVEBIRDS (AGAPORNIS NIGRIGENIS)

This randomized, crossover study evaluated three sedation protocols administered subcutaneously in nine budgerigars (Melopsittacus undulatus) and nine black-cheeked lovebirds (Agapornis nigrigenis). All protocols included midazolam (5 mg/kg), combined with butorphanol (5 mg/kg) (BM), medetomidine (20 lg/kg) (MM), or alfaxalone (13 mg/kg) (AM). Mortalities from suspected cardiorespiratory arrest were observed when AM was used in lovebirds, even after reduction of alfaxalone dosage to 3 mg/kg, and therefore this protocol was excluded from further use in this species. Induction and recovery times were recorded and their quality assessed. Sedation depth and heart and respiratory rates were measured every 5 min and radiographic positioning was attempted at 10 and 20 min. At 30 min, midazolam and medetomidine were reversed with flumazenil (0.05 mg/kg, SC), and atipamezole (0.2 mg/kg, SC), respectively. MM consistently provided deep sedation in both species, with successful radiographic positioning at every attempt. As expected, heart rate was often lower with MM than with other protocols, but no associated complications were noted. In budgerigars, BM had the lowest radiographic positioning success rate (10 min: 5/9, 20 min: 3/9), whereas in lovebirds it provided significantly deeper sedation (P < 0.001), allowing radiographic positioning in all subjects. In both species, BM provided the shortest recovery times. AM resulted in reliable radiographic positioning of all budgerigars at 10 min, but not at 20 min (5/ 9), and provided consistently poor recoveries. This study highlights how differently two psittacine species of similar size may react to the same sedation protocols. AM sedation cannot be fully reversed and produced significant undesirable effects, several of which have been previously reported with alfaxalone administration to avian species. The authors therefore caution against using alfaxalone-midazolam combinations in budgerigars and black-cheeked lovebirds. Both BM and MM provided reliable sedation in these species, and appear to be suitable alternatives to AM.

Normal behavioral discrimination of envelope statistics in budgerigars with kainate-induced cochlear synaptopathy

Cochlear synaptopathy is a common pathology in humans associated with aging and potentially sound overexposure. Synaptopathy is widely expected to cause "hidden hearing loss," including difficulty perceiving speech in noise, but support for this hypothesis is controversial. Here in budgerigars (Melopsittacus undulatus), we evaluated the impact of long-term cochlear synaptopathy on behavioral discrimination of Gaussian noise (GN) and low-noise noise (LNN) signals processed to have a flatter envelope. Stimuli had center frequencies of 1-3kHz, 100-Hz bandwidth, and were presented at sensation levels (SLs) from 10 to 30dB. We reasoned that narrowband, low-SL stimuli of this type should minimize spread of excitation across auditory-nerve fibers, and hence might reveal synaptopathy-related defects if they exist. Cochlear synaptopathy was induced without hair-cell injury using kainic acid (KA). Behavioral threshold tracking experiments characterized the minimum stimulus duration above which animals could reliably discriminate between LNN and GN. Budgerigar thresholds for LNN-GN discrimination ranged from 40 to 60ms at 30dB SL, were similar across frequencies, and increased for lower SLs. Notably, animals with long-term 39-77% estimated synaptopathy performed similarly to controls, requiring on average a ∼7.5% shorter stimulus duration (-0.7±1.0dB; mean difference ±SE) for LNN-GN discrimination. Decision-variable correlation analyses of detailed behavioral response patterns showed that individual animals relied on envelope cues to discriminate LNN and GN, with lesser roles of FM and energy cues; no difference was found between KA-exposed and control groups. These results suggest that long-term cochlear synaptopathy does not impair discrimination of low-level signals with different envelope statistics.

Sex determination in budgerigars using radiographic pelvimetry

BACKGROUND

The purpose of this study was to assess the pelvimetric values obtained from radiographic pelvis images of budgerigars in terms of sexual dimorphism. The objectives included determining linear osteometric and angle measurements of the pelvis, as well as calculating the length-to-width ratios among different pelvimetric measurements. Additionally, the study aimed to reveal the correlations between age and body weight with both the pelvimetric measurements and ratio measurements in these animals.

METHODS

In this study, measurements of linear distance, angle and length-to-width ratios were obtained from ventrodorsal images of the pelvis in a sample of 60 budgerigars, consisting of 30 males and 30 females. Subsequently, the statistical analysis of the obtained measurement values was performed.

RESULTS

When analysing the morphometric measurement values based on sex, it was observed that all linear measurements (L1, L2, L3, L4, L5, L6, L7, L8, L9, L10 and L11) were higher in males, whereas the angle measurements (A1, LA2 and RA2) were found to be significantly greater in females (p < 0.05). Additionally, both male and female budgerigars exhibited a greater pre-acetabular length of the ilium compared to the post-acetabular length. Moreover, there were mostly positive significant correlations between age and body weight with the pelvic measurement values in both sexes (p < 0.05).

CONCLUSIONS

The obtained biometric measurement values from pelvimetric X-ray images in budgerigars were analysed to assess sexual dimorphism. Furthermore, this study presents fundamental morphometric data that can be valuable for clinical, taxonomic, phylogenetic, ornithological, allometric and characterization studies of budgerigars.

Higher-order dialectic variation and syntactic convergence in the complex warble song of budgerigars

Dialectic signatures in animal acoustic signals are key in the identification of and association with group members. Complex vocal sequences may also convey information about behavioral state, and may thus vary according to social environment. Some bird species, such as psittaciforms, learn and modify their complex acoustic signals throughout their lives. However, the structure and function of vocal sequences in open-ended vocal learners remains understudied. Here, we examined vocal sequence variation in the warble song of budgerigars, and how these change upon contact between social groups. Budgerigars are open-ended vocal learners which exhibit fission-fusion flock dynamics in the wild. We found that two captive colonies of budgerigars exhibited colony-specific differences in the syntactic structure of their vocal sequences. Individuals from the two colonies differed in the propensity to repeat certain note types, forming repetitive motifs which served as higher-order signatures of colony identity. When the two groups were brought into contact, their vocal sequences converged, and these colony-specific repetitive patterns disappeared, with males from both erstwhile colonies now producing similar sequences with similar syntactic structure. We present data suggesting that the higher-order temporal arrangement of notes/vocal units is modified throughout life by social learning as groups of birds continually associate and dissociate. Our study sheds light on the importance of examining signal structure at multiple levels of organization, and the potential for psittaciform birds as model systems to examine the influence of learning and social environment on acoustic signals.

Histological Correlates of Auditory Nerve Injury from Kainic Acid in the Budgerigar (Melopsittacus undulatus)

PURPOSE

Loss of auditory nerve afferent synapses with cochlear hair cells, called cochlear synaptopathy, is a common pathology in humans caused by aging and noise overexposure. The perceptual consequences of synaptopathy in isolation from other cochlear pathologies are still unclear. Animal models provide an effective approach to resolve uncertainty regarding the physiological and perceptual consequences of auditory nerve loss, because neural lesions can be induced and readily quantified. The budgerigar, a parakeet species, has recently emerged as an animal model for synaptopathy studies based on its capacity for vocal learning and ability to behaviorally discriminate simple and complex sounds with acuity similar to humans. Kainic acid infusions in the budgerigar produce a profound reduction of compound auditory nerve responses, including wave I of the auditory brainstem response, without impacting physiological hair cell measures. These results suggest selective auditory nerve damage. However, histological correlates of neural injury from kainic acid are still lacking.

METHODS

We quantified the histological effects caused by intracochlear infusion of kainic acid (1 mM; 2.5 µL), and evaluated correlations between the histological and physiological assessments of auditory nerve status.

RESULTS

Kainic acid infusion in budgerigars produced pronounced loss of neural auditory nerve soma (60% on average) in the cochlear ganglion, and of peripheral axons, at time points 2 or more months following injury. The hair cell epithelium was unaffected by kainic acid. Neural loss was significantly correlated with reduction of compound auditory nerve responses and auditory brainstem response wave I.

CONCLUSION

Compound auditory nerve responses and wave I provide a useful index of cochlear synaptopathy in this animal model.

Auditory Pattern Discrimination in Budgerigars (Melopsittacus undulatus)

Auditory patterns carry information in human speech at multiple levels, including the surface relationships between sounds within words in phonology and the abstract structures of syntax. The sequences of other animal vocalizations, such as birdsong, can also be described as auditory patterns, but few studies have probed how the sequences are perceived at multiple levels. Past work shows that a small parrot species, the budgerigar (Melopsittacus undulatus), exceeds other birds in sequence perception and is even sensitive to abstract structure. But it is not known what level of auditory analysis is dominant in perception or what limits might exist in sensitivity to abstract structure. Here, budgerigars were tested on their ability to discriminate changes in an auditory pattern, AAB, i.e. sound-same different, to ask how they attended to surface relationships among the sounds and the abstract relationships of same/different among the elements. The results show that the budgerigars primarily used surface transitions between the sounds when discriminating the sequences, but were able to use the abstract relationships to a limited extent, largely restricted to two elements. This study provides insight into how budgerigars extract information from conspecific vocalizations and how their capacities compare to human speech perception.

Budgerigars (Melopsittacus undulatus) perceive the Müller-Lyer illusion

A Müller-Lyer figure consists only of a line and arrowheads located at both ends of the line. Many comparative studies have reported that animals perceive Müller-Lyer illusion as humans, but few have used appropriate experimental designs to verify whether animal subjects actually respond to line length alone. The present study investigated whether budgerigars (Melopsittacus undulatus) can perceive the Müller-Lyer illusion by using a method that addresses this problem. Four budgerigars were trained to select a long or short line (counterbalanced across subjects) from two horizontal lines. Next, the same task was conducted using two lines, one of which was situated between arrowheads pointing either right (>>) or left (<<). In the final training phase, the arrowheads were replaced with those pointing inward (><) or outward (<>). The performance of each subject toward each stimulus set of these trainings suggested that they did not determine the length of the line by including the arrowheads. In the test phase, response tendencies to the four figures were compared. Results suggested that budgerigars perceive the Müller-Lyer illusion in the same direction as humans; however, its magnitude is larger than that of humans. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Dimensionally Specific Attention Capture in Birds Performing Auditory Streaming Task

Previous studies in budgerigars (Melopsittacus undulatus) have indicated that they experience attention capture in a qualitatively similar way to humans. Here, we apply a similar objective auditory streaming paradigm, using modified budgerigar vocalizations instead of ABAB-… patterned pure tones, in the sound sequences. The birds were trained to respond to deviants in the target stream while ignoring the distractors in the background stream. The background distractor could vary among five different categories and two different sequential positions, while the target deviants could randomly appear at five different sequential positions and vary among two different categories. We found that unpredictable background distractors could deteriorate birds' sensitivity to the target deviants. Compared to conditions where the background distractor appeared right before the target deviant, the attention capture effect decayed in conditions when the background distractor appeared earlier. In contrast to results from the same paradigm using pure tones, the results here are evidence for a faster recovery from attention capture using modified vocalization segments. We found that the temporally modulated background distractor captured birds' attention more and deteriorated birds' performance more than other categories of background distractor, as the temporally modulated target deviant enabled the birds to focus their attention toward the temporal modulation dimension. However, different from humans, birds have lower tolerances for suppressing the distractors from the same feature dimensions as the targets, which is evidenced by higher false alarm rates for the temporally modulated distractor than other distractors from different feature dimensions.

[Evaluation of housing conditions of budgerigars (Melopsittacus undulatus) and cockatiels (Nymphicus hollandicus) in Germany]

OBJECTIVES

In order to gain information concerning housing conditions of budgerigars and cockatiels, the most frequently kept pet birds in Germany, a country-wide online survey among non-commercial bird owners was performed within the realm of the EXOPET study.

MATERIAL AND METHODS

The received questionnaires (541 for budgerigars and 221 for cockatiels) were initially evaluated descriptively. Based on the suggestions developed by an expert group in the context of the EXOPET-project, the housing conditions were subsequently assessed with regard to socialization, size of cage/aviary, cage accessories, temperature, UV light and amount of free flight.

RESULTS

The most striking deviations from the recommendations occurred in both cockatiels and budgerigars in the parameter free flight (deficiencies in 89.3 % and 85.5 % of the evaluated husbandries). In connection with the resulting lack of exercise, obesity was the most common health impairment observed by budgerigar owners (26.4 %). 82.8 % of the cockatiels and 52.2 % of the budgerigars were also kept in cages or aviaries that were too small. 73.1 % resp. 73.3 % of the budgerigar resp. cockatiel owners stated to provide their birds with the possibility for free flight on a daily basis. In this context, 48.3 % of the budgerigars and 34.0 % of the cockatiels were offered free flight for at least 12 hours per day. Other significant deficiencies were found concerning the cage accessories. Here, deviations from the recommendations were found in 77.8 % of the budgerigar and 69.0 % of the cockatiel husbandries.

CONCLUSION

In order to improve the partly alarming deficits in housing conditions of budgerigars and cockatiels, owner competence must be improved. It seems necessary to provide the animal owner with standardized information concerning the specific pet bird species as well as their individual housing requirements.

Constraints on vocal production learning in budgerigars (Melopsittacus undulates)

Budgerigars (Melopsittacus undulatus) are small Australian parrots with a well-documented, learned vocal repertoire and a high degree of vocal production learning. These birds live in large, social flocks and they vocally interact with each other in a dynamic, reciprocal manner. We assume that budgerigars must process and integrate a wide variety of sensory stimuli when selecting appropriate vocal responses to conspecifics during vocal interactions, but the relative contributions of these different stimuli to that process are next to impossible to tease apart in a natural context. Here we show that budgerigars, under operant control, can learn to respond to specific stimuli with a specific vocal response. Budgerigars were trained to produce contact calls to a combination of auditory and visual cues. Birds learned to produce specific contact calls to stimuli that differed either in location (visual or auditory) or quality (visual). Interestingly, the birds could not learn to associate different vocal responses with different auditory stimuli coming from the same location. Surprisingly, this was so even when the auditory stimuli and the responses were the same (i.e., the bird's own contact call). These results show that even in a highly controlled operant context, acoustic cues alone were not sufficient to support vocal production learning in budgerigars. From a different perspective, these results highlight the significant role that social interaction likely plays in vocal production learning so elegantly shown by Irene Pepperberg's work in parrots.

Genomic evolution of avian polyomaviruses with a focus on budgerigar fledgling disease virus

Gammapolyomaviruses may cause serious inflammatory diseases in a broad range of avian hosts. In this study we investigated genomic evolution of and selection constraint acting on avian polyomaviruses (APyVs). Our analyses suggested that goose haemorrhagic polyomavirus (GHPV) evolves more slowly (3.03 × 10^-5 s/s/y mean evolutionary rate) than budgerigar fledgling disease virus (BFDV), finch polyomavirus (FPyV) and canary polyomavirus (CaPyV) (1.39 × 10^-4 s/s/y, 2.63 × 10^-4 s/s/y and 1.41 × 10^-4 s/s/y mean evolutionary rate, respectively). In general, purifying selection seems to act on the protein coding regions of APyV genomes, although positive Darwinian selection was also predicted in a few positions (e.g., in the large tumor antigen coding region of BFDV and GHPV and in the capsid protein sequences of BFDV). The importance of these aa changes remains elusive. Overall, a better understanding of adaptive changes in the genome of APyVs requires additional data from various incidental hosts and reservoir species.

Anatomical, Histological, and Electron Microscopic Structures of Syrinx in Male Budgerigars (Melopsittacus undulatus)

The syrinx is the main source for phonation in birds, its function is analogous to the mammalian larynx. Birds have both a larynx and a syrinx, but they use only the latter to vocalize. The objective of this work to give a detailed description of the anatomical, histological, and ultrastructural of syrinx in male budgerigars as a model of a passerine bird. The syrinx in the current study was to be found as a tracheobronchial type, it consists of cranial (tympanum) part and caudal (bronchosyringeal) part and, additionally, there are lateral vibrating membranes. The tympanum is formed of the last six tracheal rings, histologically its lamina epithelialis is a pseudostratified ciliated columnar epithelium with goblet cells and interrupted by intraepithelial glands. The secretory acini appear oval and lined by pyramidal secretory cells. The lamina propria–submucosa contain numerous blood capillaries, immune cells, and telocytes (TCs). The electron microscopic examination revealed numerous blood capillaries surrounded by fibroblasts and numerous immune cells, including mast cells and wandering leukocytes, within the tympanum mucosa. Hence, this study provides a detailed knowledge about the syrinx in male budgerigars.

Effects of Kainic Acid-Induced Auditory Nerve Damage on Envelope-Following Responses in the Budgerigar (Melopsittacus undulatus)

Sensorineural hearing loss is a prevalent problem that adversely impacts quality of life by compromising interpersonal communication. While hair cell damage is readily detectable with the clinical audiogram, this traditional diagnostic tool appears inadequate to detect lost afferent connections between inner hair cells and auditory nerve (AN) fibers, known as cochlear synaptopathy. The envelope-following response (EFR) is a scalp-recorded response to amplitude modulation, a critical acoustic feature of speech. Because EFRs can have greater amplitude than wave I of the auditory brainstem response (ABR; i.e., the AN-generated component) in humans, the EFR may provide a more sensitive way to detect cochlear synaptopathy. We explored the effects of kainate- (kainic acid) induced excitotoxic AN injury on EFRs and ABRs in the budgerigar (Melopsittacus undulatus), a parakeet species used in studies of complex sound discrimination. Kainate reduced ABR wave I by 65-75 % across animals while leaving otoacoustic emissions unaffected or mildly enhanced, consistent with substantial and selective AN synaptic loss. Compared to wave I loss, EFRs showed similar or greater percent reduction following kainate for amplitude-modulation frequencies from 380 to 940 Hz and slightly less reduction from 80 to 120 Hz. In contrast, forebrain-generated middle latency responses showed no consistent change post-kainate, potentially due to elevated "central gain" in the time period following AN damage. EFR reduction in all modulation frequency ranges was highly correlated with wave I reduction, though within-animal effect sizes were greater for higher modulation frequencies. These results suggest that even low-frequency EFRs generated primarily by central auditory nuclei might provide a useful noninvasive tool for detecting synaptic injury clinically.

Is consonance attractive to budgerigars? No evidence from a place preference study

Consonant tone combinations occur naturally in the overtone series of harmonic sounds. These include sounds that many non-human animals produce to communicate. As such, non-human animals may be attracted to consonant intervals, interpreting them, e.g., as a feature of important social stimuli. There is preliminary evidence of attraction to consonance in various bird species in the wild, but few experimental studies with birds. We tested budgerigars (Melopsittacus undulatus) for attraction to consonant over dissonant intervals in two experiments. In Experiment 1, we tested humans and budgerigars using a place preference paradigm in which individuals could explore an environment with multiple sound sources. Both species were tested with consonant and dissonant versions of a previously studied piano melody, and we recorded time spent with each stimulus as a measure of attraction. Human females spent more time with consonant than dissonant stimuli in this experiment, but human males spent equal time with both consonant and dissonant stimuli. Neither male nor female budgerigars spent more time with either stimulus type. In Experiment 2, we tested budgerigars with more ecologically relevant stimuli comprised of sampled budgerigar vocalizations arranged into consonant or dissonant chords. These stimuli, however, also failed to produce any evidence of preference in budgerigar responses. We discuss these results in the context of ongoing research on the study of consonance as a potential general feature of auditory perception in animals with harmonic vocalizations, with respect to similarities and differences between human and budgerigar vocal behaviour, and future methodological directions.

Identifying cues for tone-in-noise detection using decision variable correlation in the budgerigar (Melopsittacus undulatus)

Previous studies evaluated cues for masked tone detection using reproducible noise waveforms. Human results founded on this approach suggest that tone detection is based on combined energy and envelope (ENV) cues, but detection cues in nonhuman species are less clear. Decision variable correlation (DVC) was used to evaluate tone-in-noise detection cues in the budgerigar, an avian species with human-like behavioral sensitivity to many complex sounds. DVC quantifies a model's ability to predict trial-by-trial variance in behavioral responses. Budgerigars were behaviorally conditioned to detect 500-Hz tones in wideband (WB; 100-3000 Hz) and narrowband (NB; 452-552 Hz) noise. Behavioral responses were obtained using a single-interval, two-alternative discrimination task and two-down, one-up adaptive tracking procedures. Tone-detection thresholds in WB noise were higher than human thresholds, putatively due to broader peripheral frequency tuning, whereas NB thresholds were within ∼1 dB of human results. Budgerigar average hit and false-alarm rates across noise waveforms were consistent, highly correlated across subjects, and correlated to human results. Trial-by-trial behavioral results in NB noise were best explained by a model combining energy and ENV cues. In contrast, WB results were better predicted by ENV-based or multiple-channel energy detector models. These results suggest that budgerigars and humans use similar cues for tone-in-noise detection.

Formant-frequency discrimination of synthesized vowels in budgerigars (Melopsittacus undulatus) and humans

Vowels are complex sounds with four to five spectral peaks known as formants. The frequencies of the two lowest formants, F1and F2, are sufficient for vowel discrimination. Behavioral studies show that many birds and mammals can discriminate vowels. However, few studies have quantified thresholds for formant-frequency discrimination. The present study examined formant-frequency discrimination in budgerigars (Melopsittacus undulatus) and humans using stimuli with one or two formants and a constant fundamental frequency of 200 Hz. Stimuli had spectral envelopes similar to natural speech and were presented with random level variation. Thresholds were estimated for frequency discrimination of F1, F2, and simultaneous F1 and F2 changes. The same two-down, one-up tracking procedure and single-interval, two-alternative task were used for both species. Formant-frequency discrimination thresholds were as sensitive in budgerigars as in humans and followed the same patterns across all conditions. Thresholds expressed as percent frequency difference were higher for F1 than for F2, and were unchanged between stimuli with one or two formants. Thresholds for simultaneous F1 and F2 changes indicated that discrimination was based on combined information from both formant regions. Results were consistent with previous human studies and show that budgerigars provide an exceptionally sensitive animal model of vowel feature discrimination.

Sarcocystis neurona and Neospora caninum in Brazilian opossums (Didelphis spp.): Molecular investigation and in vitro isolation of Sarcocystis spp

Sarcocystis neurona and Neospora spp. are protozoan parasites that induce neurological diseases in horses and other animal species. Opossums (Didelphis albiventris and Didelphis virginiana) are definitive hosts of S. neurona, which is the major cause of equine protozoal myeloencephalitis (EPM). Neospora caninum causes abortion in cattle and infects a wide range of animal species, while N. hughesi is known to induce neurologic disease in equids. The aims of this study were to investigate S. neurona and N. caninum in tissues from opossums in the northeastern Brazil, and to isolate Brazilian strains of Sarcocystis spp. from wild opossums for comparison with previously isolated strains. Carcasses of 39 opossums from Bahia state were available for molecular identification of Sarcocystis spp. and N. caninum in their tissues, and for sporocyst detection by intestinal scraping. In addition, Sarcocystis-like sporocysts from nine additional opossums, obtained in São Paulo state, were tested. Sarcocystis DNA was found in 16 (41%) of the 39 opossums' carcasses; N. caninum DNA was detected in tissues from three opossums. The sporocysts from the nine additional opossums from São Paulo state were tested by bioassay and induced infection in nine budgerigars, but in none of the gamma-interferon knockout mice. In vitro isolation was successful using tissues from all nine budgerigars. The isolated strains were maintained in CV-1 and Vero cells. Three of nine isolates presented contamination in cell culture and were discarded. Analysis of six isolates based on five loci showed that these parasites were genetically different from each other and also distinct from S. neurona, S. falcatula, S. lindsayi, and S. speeri. In conclusion, opossums in the studied regions were infected with N. caninum and Sarcocystis spp. and represent a potential source of infection to other animals. This is the first report of N. caninum infection in tissues from black-eared opossum (D. aurita or D. marsupialis) and white-eared opossum (D. albiventris). Brazilian opossums are probably infected by different Sarcocystis spp. distinct from S. neurona and S. falcatula, or present a high level of genetic recombination.

Comparison of Two Methods for Determining Prevalence of Macrorhabdus ornithogaster in a Flock of Captive Budgerigars (Melopsittacus undulatus)

Macrorhabdus ornithogaster is a yeast organism that infects multiple species of captive and wild birds. Diagnosis of infection in vivo has proven difficult historically, as shedding can be intermittent, and not all positive animals are clinically ill. We compared polymerase chain reaction (PCR) of cloacal swab samples and fecal Gram's stain (FGS) for diagnosis of active shedding of M ornithogaster in a captive flock of budgerigars ( Melopsittacus undulatus ). Of the 100 birds sampled, 57 (57%) were positive for M ornithogaster by PCR and 24 (24%) were positive for M ornithogaster by FGS. All FGS-tested birds also were positive on PCR. There was a significant association between the two methods, but the overall percent agreement for the two methods was only 67%. Based on these findings, cloacal swab PCR is more likely to diagnose the presence of M ornithogaster than FGS in budgerigars.

Midbrain Synchrony to Envelope Structure Supports Behavioral Sensitivity to Single-Formant Vowel-Like Sounds in Noise

Vowels make a strong contribution to speech perception under natural conditions. Vowels are encoded in the auditory nerve primarily through neural synchrony to temporal fine structure and to envelope fluctuations rather than through average discharge rate. Neural synchrony is thought to contribute less to vowel coding in central auditory nuclei, consistent with more limited synchronization to fine structure and the emergence of average-rate coding of envelope fluctuations. However, this hypothesis is largely unexplored, especially in background noise. The present study examined coding mechanisms at the level of the midbrain that support behavioral sensitivity to simple vowel-like sounds using neurophysiological recordings and matched behavioral experiments in the budgerigar. Stimuli were harmonic tone complexes with energy concentrated at one spectral peak, or formant frequency, presented in quiet and in noise. Behavioral thresholds for formant-frequency discrimination decreased with increasing amplitude of stimulus envelope fluctuations, increased in noise, and were similar between budgerigars and humans. Multiunit recordings in awake birds showed that the midbrain encodes vowel-like sounds both through response synchrony to envelope structure and through average rate. Whereas neural discrimination thresholds based on either coding scheme were sufficient to support behavioral thresholds in quiet, only synchrony-based neural thresholds could account for behavioral thresholds in background noise. These results reveal an incomplete transformation to average-rate coding of vowel-like sounds in the midbrain. Model simulations suggest that this transformation emerges due to modulation tuning, which is shared between birds and mammals. Furthermore, the results underscore the behavioral relevance of envelope synchrony in the midbrain for detection of small differences in vowel formant frequency under real-world listening conditions.

Growth and Metabolic Characterization of Macrorhabdus Ornithogaster

Macrorhabdus ornithogaster ( M. ornithogaster) is an anamorphic ascomycetous yeast found only in the stomach of birds. Infection is often benign but has also been associated with disease in some species of birds under some circumstances. In vitro efforts to grow M. ornithogaster have been largely unsuccessful. In this report, multiple liquid and solid media of varying pH, sugar concentration, and fetal bovine serum (FBS) concentrations, incubated at various temperatures in room air or microaerophilic conditions, were examined for their ability to support the growth of M. ornithogaster, obtained from a budgerigar ( Melopsittacus undulatus). Optimum growth conditions were found to be Basal Medium Eagle's, pH 3 to 4, containing 20% FBS, and 5% glucose or sucrose under microaerophilic conditions at 42°C. Using these conditions, M. ornithogaster was repeatedly passaged without loss of viability. Polyclonal isolates of M. ornithogaster consistently assimilated glucose, sucrose, and trehalose. M. ornithogaster did not grow with prolonged exposure to atmospheric oxygen, but growth in microaerophilic conditions was moderately enhanced by preincubation with atmospheric oxygen for 24 hours. An isolate of M. ornithogaster was found to be infective to day-old chickens, reduce their rate of weight gain, and induce a mild to moderate heterophilic inflammation of the isthmus. M. ornithogaster was reisolated from the chicks 7 days after infection, fulfilling Koch's postulates. A 761-bp sequence of 18S rDNA from this isolate was compared to the originally reported M. ornithogaster sequence and was found to be 97% identical.

Determination of a safe and effective ultraviolet B radiant dose in budgerigars (Melopsittacus undulatus): a pilot study

The object of this study was to establish a minimum dose of ultraviolet B (UVB) radiation capable of producing an erythemal reaction in budgerigars (Melopsittacus undulatus), to determine a threshold dose of UVB for vitamin D photoconversion, and to investigate the use of safer UVB wavelengths. In each of 5 experiments of this study, 20 birds were divided into a control group (n = 10) and a UVB irradiated group (n = 10). Light sources that provide broadband UVB wavelengths (280-315 nm) and narrowband UVB (310-320 nm) were used. Varied doses of UVB radiation were administered to budgerigars by altering exposure time and irradiance. Safety was determined by observing body weight and incidence of photokeratitis and photodermatitis. Efficacy was evaluated by measuring changes in serum 25-hydroxycholecalciferol levels. Serum corticosterone was measured in 1 experiment to monitor stress levels. The results demonstrated that exposure to 180 mJ/cm2 broadband UVB induced vitamin D photoconversion, decreased body weights, and increased serum corticosterone levels. At these wavelengths, UVB-induced lesions were observed. A broadband UVB of 150 to 300 mJ/cm2 was determined as the minimum erythema dose, and the threshold dose for vitamin D photoconversion was calculated to be in the range of 113-225 mJ/cm2. No erythemal lesions or vitamin D photoconversion took place after exposure to up to 1730 mJ/cm2 narrowband UVB radiation. A minimum erythema dose and a threshold dose for vitamin D conversion need to be determined for each species if phototherapy is to be considered as a safe and effective therapeutic or husbandry tool.

[A small bird gives severe consequences]

In this case we report how a 31 year-old woman developed hypersensitivity pneumonitis due to her budgerigar. The suspicion that her pet was the reason for her symptoms was confirmed by the finding of specific IgG antibodies against budgerigar proteins. Clinical studies demonstrated a restrictive lung disorder, increased lymphocytes in bronchoalveolar lavage and ground glass changes in high-resolution computed tomography. The patient's symptoms receded over the course of a few days after removal of the animal, and subsequent IgG levels fell.

Avian polyomavirus infection of a fledgling budgerigar (Melopsittacus undulatus) and differential diagnoses of viral inclusions in psittacine birds--case report and mini-review

A two-week-old budgerigar (Melopsittacus undulatus) of an outdoor aviary died suddenly and was submitted for determination the cause of illness and death. Macroscopically, the sparsely feathered animal was in a poor body condition. Histopathological examination revealed in various mesenchymal and epithelial tissues, numerous up to 15 microm in diameter large intranuclear, amphophilic to basophilic inclusion bodies with a clearing of the centre. Additionally, a feather dysplasia and retention hyperkeratosis of feather follicles was found. Ultrastructurally, viral particles of approximately 35 nm in diameter were detected in the feather follicle epithelium. A PCR for Avian Polyomavirus on fresh skin samples was negative whereas on formalin-fixed kidney samples with a high amount of viral inclusion bodies yielded a positive result. In addition, viral inclusion body diseases, like Avian Poxvirus, Psittacine Beak and Feather disease virus, Avian Adenovirus, Psittacine Herpesvirus and papillomavirus of psittacines are summarized and compared in the present article.

Learned vocalizations in budgerigars (Melopsittacus undulatus): the relationship between contact calls and warble song

The budgerigar (Melopsittacus undulatus) has an extraordinarily complex, learned, vocal repertoire consisting of both the long rambling warble song of males and a number of short calls produced by both sexes. In warble, the most common elements (>30%) bear a strong resemblance to the highly frequency-modulated, learned contact calls that the birds produce as single utterances. However, aside from this apparent similarity, little else is known about the relationship between contact calls and warble call elements. Here, both types of calls were recorded from four male budgerigars. Signal analysis and psychophysical testing procedures showed that the acoustic features of these two vocalizations were acoustically different and perceived as distinctive vocalizations by birds. This suggests that warble call elements are not simple insertions of contact calls but are most likely different acoustic elements, created de novo, and used solely in warble. Results show that, like contact calls, warble call elements contain information about signaler identity. The fact that contact calls and warble call elements are acoustically and perceptually distinct suggests that they probably represent two phonological systems in the budgerigar vocal repertoire, both of which arise by production learning.

The effect of altered auditory feedback on control of vocal production in budgerigars (Melopsittacus undulatus)

Budgerigars learn their vocalizations by reference to auditory information and they retain the ability to learn new vocalizations throughout life. Auditory feedback of these vocalizations was manipulated in three experiments by training birds to produce vocalizations while wearing small earphones. Experiments 1 and 2 examined the effect of background noise level (Lombard effect) and the effect of manipulating feedback level from self-produced vocalizations (Fletcher effect), respectively. Results show that birds exhibit both a Lombard effect and a Fletcher effect. Further analysis showed that changes in vocal intensity were accompanied by changes in call fundamental frequency and duration. Experiment 3 tested the effect of delaying or altering auditory feedback during vocal production. Results showed subsequent production of incomplete and distorted calls in both feedback conditions. These distortions included changes in the peak fundamental frequency, amplitude, duration, and spectrotemporal structure of calls. Delayed auditory feedback was most disruptive to subsequent calls when the delay was 25 ms. Longer delays resulted in fewer errors.

Vocal learning in Budgerigars (Melopsittacus undulatus): effects of an acoustic reference on vocal matching

Budgerigars were trained to produce specific vocalizations (calls) using operant conditioning and food reinforcement. The bird's call was compared to a digital representation of the call stored in a computer to determine a match. Once birds were responding at a high level of precision, we measured the effect of several manipulations upon the accuracy and the intensity of call production. Also, by differentially reinforcing other aspects of vocal behavior, budgerigars were trained to produce a call that matched another bird's contact call and to alter the latency of their vocal response. Both the accuracy of vocal matching and the intensity level of vocal production increased significantly when the bird could hear the template immediately before each trial. Moreover, manipulating the delay between the presentation of an acoustic reference and the onset of vocal production did not significantly affect either vocal intensity or matching accuracy. Interestingly, the vocalizations learned and reinforced in these operant experiments were only occasionally used in more natural communicative situations, such as when birds called back and forth to one another in their home cages.

Multidrug-resistant bacterial ingluvitis associated with squamous cell carcinoma in a budgerigar (Melopsittacus undulatus)

A 2-year-old budgerigar (Melopsittacus undulatus) was presented to the Massey University Veterinary Teaching Hospital for chronic regurgitation. Multiple drug-resistant Klebsiella oxytoca was cultured from the crop. Necropsy revealed a mass in the crop that was histologically diagnosed as squamous cell carcinoma (SCC). To the authors' knowledge, this is the first report of SCC in a budgerigar associated with a multidrug-resistant bacterial ingluvitis.

The discrimination of temporal fine structure in call-like harmonic sounds by birds

Thresholds for discriminating changes in the temporal fine structure of call-like, harmonic sounds were measured in zebra finches (Taeniopygia guttata) and budgerigars (Melopsittacus undulatus). Birds could detect changes in periods as short as 1.225 ms at near 100% accuracy even when spectral and envelope cues were identical, as in time-reversed stimuli. Humans performed poorly on such stimuli, paralleling results from previous studies. Bird thresholds were in the range of those reported in neurophysiological studies of the songbird high vocal center (HVC) to temporally modified conspecific songs. Taken together, these results show that birds can hear differences in temporal fine structure in their natural vocalizations that go beyond human capabilities, but whether these abilities have communicative relevance remains to be seen.

Clinical approach to renal neoplasia in budgerigars (Melopsittacus undulatus)

Renal neoplasia in budgerigars (Melopsittacus undulatus) is seen regularly in general practice and is of interest to many practicing veterinary surgeons. This review article provides an overview of the current knowledge and the most recent reports in avian literature regarding renal tumours in budgerigars, with the emphasis on clinical diagnosis and treatment. The high prevalence of renal neoplasia in budgerigar is discussed, with notes on the most commonly diagnosed tumours, possibility of metastases, sex and age predisposition. The possibility of ultrasonography and radiography in the diagnosis of this pathological condition are compared as well as the possible role of blood and urine analyses. Two studies are described, both of which investigate the possible involvement of a retrovirus as the aetiological agent.

Retrobulbar rhabdomyosarcoma in a budgerigar (Melopsittacus undulatus)

This report describes a retrobulbar rhabdomyosarcoma in a 7-year-old male budgerigar (Melopsittacus undulatus). The bird was presented with orbital distension and exophthalmia of the left eye and died during surgery. Necropsy revealed a tan to grey retrobulbar mass compressing all components of the left eye with obscured vision. In histopathological examination, the mass was composed of sheets of spindle-shaped cells with pleomorphic nuclei, numerous bizarre mitotic figures and mononucleated or multinucleated giant cells and also typically strap cells. Neoplastic cells had no cross-striations in sections stained by phosphotungstic acid haematoxylin. The tumour cells did not invade surrounding tissues, including the retina, and there was no metastasis to other organs. Immunohistochemically, tumour cells were positive for desmin, vimentin and alpha-smooth muscle actin, but were negative for S-100 protein and pancytokeratin.

Feeding and contact call stimulation both induce zenk and cfos expression in a higher order telencephalic area necessary for vocal learning in budgerigars

Stimulation with natural contact calls and feeding were used to assess zenk and fos protein expression in budgerigars (Melopsittacus undulatus), a vocal learning parrot species in which feeding and physical contact often occur in conjunction with vocalization. Although only calls induced gene expression in Field L, the primary telencephalic auditory area, both calls and feeding induced gene expression in the frontal lateral nidopallium (NFl), a brain area in receipt of input from Field L which projects to areas afferent to vocal control nuclei and which is necessary for new call learning. NFl thus appears poised to provide both non-auditory as well as auditory feedback to the vocal system.

Pathogenicity of a highly pathogenic avian influenza virus, A/chicken/Yamaguchi/7/04 (H5N1) in different species of birds and mammals

Outbreaks of highly pathogenic avian influenza (HPAI) have been occurring in domestic poultry in Asia since 1996. In the beginning of 2004, HPAI outbreaks were caused by H5N1 virus in two farms and a group of pet chickens in different areas of Japan. In the present study, the pathogenicity of A/chicken/Yamaguchi/7/04 (H5N1), which had been isolated from a dead chicken during the first outbreak in Japan, was assessed in chickens, quails, budgerigars, ducklings, mice, and miniature pigs by experimental infection. The virus was highly pathogenic to all the birds tested. Mice were susceptible to infection with a low mortality rate and miniature pigs were resistant to infection with the virus.

Duplex shuttle PCR for differential diagnosis of budgerigar fledgling disease and psittacine beak and feather disease

Two common viral diseases in psittacine birds including budgerigar fledgling disease (BFD), generally called avian polyomavirus (APV) infection, and psittacine beak and feather disease (PBFD) have similar clinical manifestations characterized by feather disorders. A duplex shuttle PCR was developed for detection of APV and PBFD virus (PBFDV). Two pairs of oligonucleotide primers were designed to amplify a 298-bp fragment of the t/T antigen region of APV genome and a 495-bp fragment of the capsid protein region encoded by open reading frame (ORF) C1 of PBFDV genome, respectively. In the present study, APV and PBFDV were detected simultaneously in one tube by duplex shuttle PCR using these two pairs of primers. The detection limits were 2 viral copies of APV and 3 viral copies of PBFDV. In the clinical application, we detected 16 APV-positive, 15 PBFDV-positive, and 3 mixed infected samples in 39 samples examined. Sequences of the amplified products were read. The t/T antigen region was conserved in the APV-positive samples as expected. ORF C1 of PBFDV genome showed diversity. Phylogenic analysis indicated that PBFDV ORF C1 consisted of 6 clusters which were related to subfamilies of psittacine birds. Our duplex shuttle PCR could be a useful method for differential diagnosis and molecular epidemiology of BFD and PBFD.

[Hypersensitivity pneumonitis in budgerigar fanciers. A seldom recognised disease?]

A hypersensitivity pneumonitis (HP) can be easily recognized either in acute manifestations, as in farmer lung syndrome, and in subacute, as bird fancier's lung; the following case shows an insidious HP occurred to a 44 year old, non smoker woman, fancier--during the winter--of 8 budgerigars kept in the kitchen. The authors suppose HP is underestimated, considering Italy's likely high number of bird fanciers, versus only 260 general cases of HP that have been reported every year in Italy (1999-2002).

Comparitive sensitivity of polymerase chain reaction diagnosis of psittacine beak and feather disease on feather samples, cloacal swabs and blood from budgerigars (Melopsittacus undulates, Shaw 18005)

A longitudinal study was performed in order to investigate virus excretion and viraemia during a clinical outbreak of the psittacine beak and feather disease in budgerigars (Melopsittacus undulatus). Viral nucleic acid was detected in feathers, cloacal swabs and blood samples. Overall, beak and feather disease virus (BFDV) DNA was detected most commonly in feather samples, followed by cloacal swabs, and least frequently from blood samples. In most cases the viraemia was short lived and correlated with clinical signs, such as feather abnormalities. Sequence analysis of the polymerase chain reaction fragment amplified from the replication-associated gene (ORF V1) indicated a close relationship with other BFDV isolates. Overall the highest level of nucleotide identity was found with the ORF V1 of another budgerigar isolate. Our results suggest that feather samples and cloacal swabs should be taken for polymerase chain reaction diagnosis to determine the presence of BFDV in an aviary, but that detection in these samples may not correlate well with psittacine beak and feather disease.

A behavior analysis of absolute pitch: sex, experience, and species

Absolute pitch (AP) perception refers to the ability to identify, classify, and memorize pitches without use of an external reference pitch. In tests of AP, several species were trained to sort contiguous tones into three or eight frequency ranges, based on correlations between responding to tones in each frequency range and reinforcement. Two songbird species, zebra finches and white-throated sparrows, and a parrot species, budgerigars had highly accurate AP, they discriminated both three and eight ranges with precision. Relative to normally reared songbirds, isolate reared songbirds had impaired AP. Two mammalian species, humans and rats, had equivalent and weak AP, they discriminated three frequency ranges to a lackluster standard and they acquired only a crude discrimination of the lowest and highest of eight frequency ranges. In comparisons with mammals even isolate songbirds had more accurate AP than humans and rats.

The Precedence Effect in Three Species of Birds (Melopsittacus undulatus, Serinus canaria, and Taeniopygia guttata)

The perceived locations of paired auditory images, simulating direct sounds and their echoes, have been recently studied in budgerigars (Melopsittacus undulatus; M. L. Dent & R. J. Dooling, 2003a, 2003b). In this article, the authors extend those experiments to include measurements of the precedence effect using a discrimination paradigm in two additional bird species: canaries (Serinus canaria) and zebra finches (Taeniopygia guttata). Although time courses of summing localization, localization dominance, and echo thresholds were similar across all species, budgerigars had slightly higher overall levels of discrimination. The results from these experiments add further support that the precedence effect in birds is similar to that found in other animals and that the ability to suppress echoes that might degrade localization and auditory object perception may be a general property of the vertebrate auditory system.

Chlamydia psittaci pneumonia presenting as acute generalised peritonism

A 63 year old man presented with the signs of acute generalised peritonism in the presence of a clear chest radiograph. At laparotomy no abnormal findings were noted. Further inquiries revealed a history of recent acquisition of budgerigars, over the following days the chest radiograph developed patchy opacification. Subsequently IgG immunofluorescence confirmed the diagnosis of Chlamydia psittaci. The presentation of psittacosis with gastrointestinal features is well recognised. This is believed to be the first account in the literature of a human case of Chl psittaci pneumonia presenting with acute generalised peritonism indicating an exploratory laparotomy. It is suggested that Chl psittaci pneumonia should be considered in the differential diagnosis of an acute abdomen in the presence of a history of exposure to psittacine birds.