Genetic Mapping and Biochemical Basis of Yellow Feather Pigmentation in Budgerigars.

Parrot feathers contain red, orange, and yellow polyene pigments called psittacofulvins. Budgerigars are parrots that have been extensively bred for plumage traits during the last century, but the underlying genes are unknown. Here we use genome-wide association mapping and gene-expression analysis to map the Mendelian blue locus, which abolishes yellow pigmentation in the budgerigar. We find that the blue trait maps to a single amino acid substitution (R644W) in an uncharacterized polyketide synthase (MuPKS). When we expressed MuPKS heterologously in yeast, yellow pigments accumulated. Mass spectrometry confirmed that these yellow pigments match those found in feathers. The R644W substitution abolished MuPKS activity. Furthermore, gene-expression data from feathers of different bird species suggest that parrots acquired their colors through regulatory changes that drive high expression of MuPKS in feather epithelia. Our data also help formulate biochemical models that may explain natural color variation in parrots. VIDEO ABSTRACT.

Persistent vocal learning in an aging open-ended learner reflected in neural FoxP2 expression.

BACKGROUND: Most vocal learning species exhibit an early critical period during which their vocal control neural circuitry facilitates the acquisition of new vocalizations. Some taxa, most notably humans and parrots, retain some degree of neurobehavioral plasticity throughout adulthood, but both the extent of this plasticity and the neurogenetic mechanisms underlying it remain unclear. Differential expression of the transcription factor FoxP2 in both songbird and parrot vocal control nuclei has been identified previously as a key pattern facilitating vocal learning. We hypothesize that the resilience of vocal learning to cognitive decline in open-ended learners will be reflected in an absence of age-related changes in neural FoxP2 expression. We tested this hypothesis in the budgerigar (Melopsittacus undulatus), a small gregarious parrot in which adults converge on shared call types in response to shifts in group membership. We formed novel flocks of 4 previously unfamiliar males belonging to the same age class, either "young adult" (6 mo - 1 year) or "older adult" (≥ 3 year), and then collected audio-recordings over a 20-day learning period to assess vocal learning ability. Following behavioral recording, immunohistochemistry was performed on collected neural tissue to measure FoxP2 protein expression in a parrot vocal learning center, the magnocellular nucleus of the medial striatum (MMSt), and its adjacent striatum. RESULTS: Although older adults show lower vocal diversity (i.e. repertoire size) and higher absolute levels of FoxP2 in the MMSt than young adults, we find similarly persistent downregulation of FoxP2 and equivalent vocal plasticity and vocal convergence in the two age cohorts. No relationship between individual variation in vocal learning measures and FoxP2 expression was detected. CONCLUSIONS: We find neural evidence to support persistent vocal learning in the budgerigar, suggesting resilience to aging in the open-ended learning program of this species. The lack of a significant relationship between FoxP2 expression and individual variability in vocal learning performance suggests that other neurogenetic mechanisms could also regulate this complex behavior.

Do domestic budgerigars perceive predation risk?

Predation risk may affect the foraging behavior of birds. However, there has been little research on the ability of domestic birds to perceive predation risk and thus adjust their feeding behavior. In this study, we tested whether domestic budgerigars (Melopsittacus undulatus) perceived predation risk after the presentation of specimens and sounds of sparrowhawks (Accipiter nisus), domestic cats (Felis catus), and humans, and whether this in turn influenced their feeding behavior. When exposed to visual or acoustic stimuli, budgerigars showed significantly longer latency to feed under sparrowhawk, domestic cat, and human treatments than with controls. Budgerigars responded more strongly to acoustic stimuli than visual stimuli, and they showed the longest latency to feed and the least number of feeding times in response to sparrowhawk calls. Moreover, budgerigars showed shorter latency to feed and greater numbers of feeding times in response to human voices than to sparrowhawk or domestic cat calls. Our results suggest that domestic budgerigars may identify predation risk through visual or acoustic signals and adjust their feeding behavior accordingly.

Bacterial communities along parrot digestive and respiratory tracts: the effects of sample type, species and time.

Digestive and respiratory tracts are inhabited by rich bacterial communities that can vary between their different segments. In comparison with other bird taxa with developed caeca, parrots that lack caeca have relatively lower variability in intestinal morphology. Here, based on 16S rRNA metabarcoding, we describe variation in microbiota across different parts of parrot digestive and respiratory tracts both at interspecies and intraspecies levels. In domesticated budgerigar (Melopsittacus undulatus), we describe the bacterial variation across eight selected sections of respiratory and digestive tracts, and three non-destructively collected sample types (faeces, and cloacal and oral swabs). Our results show important microbiota divergence between the upper and lower digestive tract, but similarities between respiratory tract and crop, and also between different intestinal segments. Faecal samples appear to provide a better proxy for intestinal microbiota composition than the cloacal swabs. Oral swabs had a similar bacterial composition as the crop and trachea. For a subset of tissues, we confirmed the same pattern also in six different parrot species. Finally, using the faeces and oral swabs in budgerigars, we revealed high oral, but low faecal microbiota stability during a 3-week period mimicking pre-experiment acclimation. Our findings provide a basis essential for microbiota-related experimental planning and result generalisation in non-poultry birds.

Fast visual adaptation to dim light in a cavity-nesting bird.

Many birds move fast into dark nest cavities forcing the visual system to adapt to low light intensities. Their visual system takes between 15 and 60 min for complete dark adaptation, but little is known about the visual performance of birds during the first seconds in low light intensities. In a forced two-choice behavioural experiment we studied how well budgerigars can discriminate stimuli of different luminance directly after entering a darker environment. The birds made their choices within about 1 s and did not wait to adapt their visual system to the low light intensities. When moving from a bright facility into an environment with 0.5 log unit lower illuminance, the budgerigars detected targets with a luminance of 0.825 cd m-2 on a black background. When moving into an environment with 1.7 or 3.5 log units lower illuminance, they detected targets with luminances between 0.106 and 0.136 cd m-2. In tests with two simultaneously displayed targets, the birds discriminated similar luminance differences between the targets (Weber fraction of 0.41-0.54) in all light levels. Our results support the notion that partial adaptation of bird eyes to the lower illumination occurring within 1 s allows them to safely detect and feed their chicks.

Genetic characterization of avian polyomaviruses identified from psittacine birds in South Korea.

Budgerigar fledgling disease (BFD) is a contagious disease caused by avian polyomavirus (APV) in psittacine birds and causes high mortality rates. Here, eight APV-positive cases were confirmed from dead parrots or parrot tissue samples by polymerase chain reaction (PCR). Full-length genome sequencing showed high nucleotide identity (98.84-100%) between the APV strains. Phylogenetic analysis revealed that two genogroups were cocirculating in South Korea. The nucleotide sequences of five strains, collected from different parrot species, were identical; however, pathological lesions were observed in only two parrots, both aged 2 months. Pathology included necrotic spots in the liver, subcutaneous haemorrhage, hepatomegaly, ascites, intranuclear inclusion bodies, hepatocyte karyomegaly, hepatic necrosis, and bile duct proliferation. This suggests that the pathogenicity of APV might be host age-dependent regardless of the host species. This study improves our understanding of APV pathogenicity and provides a more detailed genetic characterization of APV strains.RESEARCH HIGHLIGHTS Eight APV strains were identified in South Korea from 2019 to 2021.By phylogenetic analysis, South Korean APV strains were classified into two clades.

Midbrain-Level Neural Correlates of Behavioral Tone-in-Noise Detection: Dependence on Energy and Envelope Cues.

Hearing in noise is a problem often assumed to depend on encoding of energy level by channels tuned to target frequencies, but few studies have tested this hypothesis. The present study examined neural correlates of behavioral tone-in-noise (TIN) detection in budgerigars (Melopsittacus undulatus, either sex), a parakeet species with human-like behavioral sensitivity to many simple and complex sounds. Behavioral sensitivity to tones in band-limited noise was assessed using operant-conditioning procedures. Neural recordings were made in awake animals from midbrain-level neurons in the inferior colliculus, the first processing stage of the ascending auditory pathway with pronounced rate-based encoding of stimulus amplitude modulation. Budgerigar TIN detection thresholds were similar to human thresholds across the full range of frequencies (0.5-4 kHz) and noise levels (45-85 dB SPL) tested. Also as in humans, thresholds were minimally affected by a challenging roving-level condition with random variation in background-noise level. Many midbrain neurons showed a decreasing response rate as TIN signal-to-noise ratio (SNR) was increased by elevating the tone level, a pattern attributable to amplitude-modulation tuning in these cells and the fact that higher SNR tone-plus-noise stimuli have flatter amplitude envelopes. TIN thresholds of individual neurons were as sensitive as behavioral thresholds under most conditions, perhaps surprisingly even when the unit's characteristic frequency was tuned an octave or more away from the test frequency. A model that combined responses of two cell types enhanced TIN sensitivity in the roving-level condition. These results highlight the importance of midbrain-level envelope encoding and off-frequency neural channels for hearing in noise.SIGNIFICANCE STATEMENT Detection of target sounds in noise is often assumed to depend on energy-level encoding by neural processing channels tuned to the target frequency. In contrast, we found that tone-in-noise sensitivity in budgerigars was often greatest in midbrain neurons not tuned to the test frequency, underscoring the potential importance of off-frequency channels for perception. Furthermore, the results highlight the importance of envelope processing for hearing in noise, especially under challenging conditions with random variation in background noise level over time.

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.

Medullary bone in male budgerigars (Melopsittacus undulatus) with testicular neoplasms.

Medullary bone is a calcium-rich, labile bone normally occurring in female birds with each egg-laying cycle. The stimulus for formation of medullary bone is, in part, the cyclic increase in serum estrogens produced by preovulatory ovarian follicles. Increased bone density due to formation of medullary bone, particularly in pneumatic bones, has been termed polyostotic hyperostosis, even if physiologic. This study investigated the formation of medullary bone in nonpneumatic (femur) and pneumatic (humerus) bones in sexually mature male budgerigars submitted for autopsy. Of the 21 sexually mature male budgerigars submitted for autopsy, 7 (33%) had medullary bone in 1 or more bones examined. All 7 male budgerigars with medullary bone had a testicular neoplasm, which was morphologically consistent with a testicular sustentacular cell tumor, seminoma, or interstitial cell tumor. Medullary bone was not present in the 14 cases with other diseases. Medullary bone formation in pneumatic and nonpneumatic bones can occur in male budgerigars with testicular neoplasms. Radiographic increases in medullary bone density, particularly in the humerus, could provide antemortem indication of testicular neoplasia in male budgerigars.

Effects of Midazolam on Food Intake in Budgerigars (Melopsittacus undulatus).

Currently, drug-induced stimulation of appetite is not commonly performed in hyporexic or anorexic companion psittacine birds. Instead, to prevent a catabolic state and weight loss, supplemental feedings are routinely performed by crop gavage. However, crop gavage is not without complications and is stressful to the patient and labor intensive. The objective of this study was to evaluate the effect of midazolam on food intake in healthy budgerigars. In a randomized, blinded, controlled study, change in food intake after intramuscular administration of midazolam (1 mg/kg) or a placebo-control treatment (0.9% saline) was evaluated in 12 healthy adult budgerigars (Melopsittacus undulatus). Food intake was quantified for 1 hour before and after drug administration. Birds were monitored for feeding behavior as well as signs of sedation. After midazolam administration, a median 6-fold (1.1-28) increase in food intake was recorded. In 3 of 6 (50%) birds, the food intake increase after midazolam administration was >10-fold (median 17-fold [10-28]), whereas in the remaining 3 birds, food intake increased by only 1.7-fold (1.1-1.8). The median amount of food ingested (16.7 g/kg [3.2-43.2 g/kg]) was significantly higher after midazolam administration compared with the control group (1.9 g/kg [0.0-19.7 g/kg], P = .015). The median time birds spent displaying feeding behavior after the midazolam injection was 18% (0-43%), compared with 1% (0-20%) in the control group after saline injection. Five of 6 (83%) birds showed signs consistent with mild sedation after midazolam administration. This study demonstrates that midazolam is an appetite stimulant in budgerigars. Future studies are needed to evaluate whether midazolam's effects on food intake are dose dependent and whether the duration of effect exceeds 1 hour.

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.

[A CASE OF BIRD-RELATED HYPERSENSITIVITY PNEUMONITIS THAT DEVELOPED IN SUBACUTE COURSE AND PRESENTED WITH ACUTE FINDINGS].

A 52-year-old woman presented to a clinic in late August with exacerbated fatigue and dyspnea on exertion for several months. Then, she was referred and admitted to our hospital in late September. Her chest CT showed bilateral diffuse centrilobular micronodules. In her detailed clinical history, she had kept budgerigars indoors for 15 years. These findings suggested she had a bird-related hypersensitivity pneumonitis (BRHP). By a site environmental investigation, 40 budgerigars were kept in a single breeding room and there were large amounts of droppings on the floor. Serum specific antibody for bird antigens and an environmental provocation test were positive. Bronchoalveolar lavage fluid showed lymphocytosis and a low CD4/CD8 ratio. Trans-bronchial lung biopsy showed lymphocytic infiltration of the alveolar wall and interlobular septa. After antigen avoidance as hospitalization, her symptoms and abnormal shadow improved. From these results, the patient was diagnosed as an acute BRHP.BRHP often presents a chronic onset. This case was diagnosed as an acute type despite the 15-years of budgerigars breeding. Increased exposure of antigens due to lack of cleaning after several days' antigen avoidance was suspected with one of the causes of acute onset.

Occurrence and molecular identification of zoonotic microsporidia in pet budgerigars (Melopsittacus undulatus) in Turkey.

Encephalitozoon spp. and Enterocytozoon bieneusi are well-known microsporidian pathogens, recently classified as fungi, infecting humans and reptiles, mammals, and birds. Budgerigars (Melopsittacus undulates) are the most preferred captive pet birds in the households. Prevalence and molecular data on microsporidian species in budgerigars are scarce worldwide. The aim of the present study was to investigate the occurrence and genotypes of Encephalitozoon spp. and E. bieneusi in budgerigars, and to reveal their zoonotic potential. A total of 143 fecal samples were collected from owned healthy budgerigars in Turkey. Encephalitozoon spp. and E. bieneusi were examined by nested PCR targeting the ribosomal internal transcribed spacer (ITS) region and sequenced for identifying Encephalitozoon spp. and E. bieneusi. The overall prevalence of E. hellem and E. bieneusi was 14.7% (21/143) and 3.5% (5/143), respectively. Two genotypes of E. hellem were identified, including one known 1A (n = 18) and a novel TURK1B (n = 3). In addition, we determined two E. bieneusi genotypes, including one known N (n = 2) and a novel TURKM1 (n = 3). E. hellem 1A and novel TURK1B clustered as a sister taxon, and genotype N and novel TURKM1 genotypes fall into group 2 of E. bieneusi in the phylogenetic tree. Novel genotypes of E. hellem and E. bieneusi were described for the first time in the avian host. Moreover, E. bieneusi genotype N was first detected in avian hosts in the present study. This study contributes to the current knowledge on the molecular epidemiology and transmission dynamics of E. hellem and E. bieneusi. LAY SUMMARY: Spore producing microsporidia are ubiquitous, obligate, and intracellular fungus defined as emerging opportunistic pathogens of humans, livestock, companion animals, wild mammals, birds, and water worldwide. The occurrence of microsporidia in animals could be risky for human public health.

Monitoring of free-ranging and captive Psittacula populations in Western Europe for avian bornaviruses, circoviruses and polyomaviruses.

Avian pathogens such as bornaviruses, circoviruses and polyomaviruses are widely distributed in captive collections of psittacine birds worldwide and can cause fatal diseases. In contrast, only little is known about their presence in free-ranging psittacines and their impact on these populations. Rose-ringed parakeets (Psittacula krameri) and Alexandrine parakeets (Psittacula eupatria) are non-native to Europe, but have established stable populations in parts of Western Europe. From 2012-2017, we surveyed free-ranging populations in Germany and France as well as captive Psittacula individuals from Germany and Spain for avian bornavirus, circovirus and polyomavirus infections. Samples from two out of 469 tested free-ranging birds (0.4%; 95% confidence interval [CI-95]: 0.1-1.5%) were positive for beak and feather disease virus (BeFDV), whereas avian bornaviruses and polyomaviruses were not detected in the free-ranging populations. In contrast, avian bornaviruses and polyomaviruses, but not circoviruses were detected in captive populations. Parrot bornavirus 4 (PaBV-4) infection was detected by RT-PCR in four out of 210 captive parakeets (1.9%; CI-95: 0.7-4.8%) from four different holdings in Germany and Spain and confirmed by detection of bornavirus-reactive antibodies in two of these birds. Three out of 160 tested birds (1.9%; CI-95: 0.5-5.4%) possessed serum antibodies directed against budgerigar fledgling disease virus (BuFDV). PaBV-4 and BuFDV were also detected in several psittacines of a mixed holding in Germany, which had been in contact with free-ranging parakeets. Our results demonstrate that Psittacula parakeets are susceptible to common psittacine pathogens and their populations in Western Europe are exposed to these viruses. Nevertheless, the prevalence of avian bornaviruses, circoviruses and polyomaviruses in those populations is very low.RESEARCH HIGHLIGHTS Psittacula parakeets are susceptible to bornavirus, circovirus and polyomavirus infection.Introduced Psittacula populations in Europe have been exposed to these viruses.Nevertheless, they may be absent or present at only low levels in free-ranging Psittacula populations.Free-ranging populations in Europe pose a minor threat of transmitting these viruses to captive Psittaciformes.

SEDATIVE, CARDIORESPIRATORY, AND THERMOREGULATORY EFFECTS OF ALFAXALONE ON BUDGERIGARS (MELOPSITTACUS UNDULATUS).

Alfaxalone is a neurosteroid anesthetic agent that has been extensively used in both human and veterinary medicine for more than 50 yr. Previous studies involving avian species demonstrated various dose ranges and multiple routes of administration. The aim of this study was to evaluate the short-term sedative, cardiorespiratory, and thermoregulatory effects of an intramuscular injection of alfaxalone on budgerigars (Melopsittacus undulatus). A crossover study was performed with a sample size of 10 male budgerigars, previously determined to be healthy based on physical examination. Alfaxalone was administered intramuscularly at two doses: 15 and 20 mg/kg. The lower dose resulted in mild to moderate sedation for 29 ± 5 min, whereas the higher dose resulted in moderate to profound sedation for 29 ± 7 min. A statistically significant decrease in heart rate was observed 2 min after administration of alfaxalone at 15 mg/kg; however, this finding was noted to be transient. A statistically significant decrease in respiratory rate was observed at 6 and 10 min after injection in both groups. Cloacal temperature measurement with a digital thermometer and eye temperature calculated from thermographic images demonstrated a decrease in body temperature over time but was not found to be statistically significant. Intramuscular use of alfaxalone proved to provide short-term sedation in budgerigars, with statistically significant but clinically mild cardiorespiratory effects. Due to a significant decrease in body temperature, active warming is recommended when using alfaxalone in budgerigars.

Reclassification of Bisgaard taxon 37 and taxon 44 as Psittacicella melopsittaci gen. nov., sp. nov., Psittacicella hinzii sp. nov. and Psittacicella gerlachiana sp. nov. within Psittacicellaceae fam. nov. of the order Pasteurellales.

Bacteria isolated from lesions as well as apparently normal tissues of psittacine birds have previously been reported as taxon 37 and taxon 44 of Bisgaard. 16S rRNA gene sequence comparisons revealed a distant relationship to members of Pasteurellaceae at the species, genus and family levels. The polar lipid profile consisted of the major components phosphatidylethanolamine and phosphatidylglycerol. A new family Psittacicellaceae fam. nov. is proposed with the type genus Psittacicella gen. nov. The new genus Psittacicella includes the type species Psittacicella melopsittaci sp. nov. with type strain B96/4T (=CCUG 70858T=DSM 105476T), Psittacicella hinzii sp. nov. with type strain 111T (=CCUG 52861T=CCM 8842T) and Psittacicella gerlachiana sp. nov. with type strain EEAB3T1T (=CCUG 70857T=DSM 105477T). In addition to the major polar lipids, strain 111T possessed the non-identified aminophospholipids APL1 and APL2 and trace amounts of four lipids (L1-L4) whereas strain B94/4T showed the minor unidentified aminophospholipids APL3 and APL2 and trace amounts of unidentified lipid L3. These results demonstrate that strain B96/4T can be distinguished from 111T based on presence/absence of the unidentified lipids APL1 and APL3. The total polar lipid profile of strain EEAB3T1T differed from B96/4Tonly in one minor lipid. Strain B96/4T can further be distinguished from 111T by acid formation from trehalose and raffinose and the α-glucosidase test. Strains 111T and EEAB3T1T can be separated based on acid formation from trehalose and the α-glucosidase test. Strains B96/4T and EEAB3T1T can be separated by acid formation from raffinose and eight signature indels in the RpoB protein.

Establishment of rapid detection method and surveillance of budgerigar fledgling disease virus using a TaqMan Real-Time PCR.

Budgerigar fledgling disease virus (BFDV) infection causes sudden death, abdominal distention, and feather abnormality in psittacine birds. In this study, we developed a TaqMan Real-time PCR assay to detect BFDV by targeting a conserved region in VP1 gene. The detection limit of the assay was 30 DNA gene copies, 1000 times more sensitive than conventional PCR. The coefficients of variation were less than 1.09% in either intra- or inter-assays, indicating high reproducibility. By using this method, the prevalence of BFDV in China was evaluated. 56 feces samples were collected from four psittacine birds breeding facilities in China. The results showed 28 out of 56 samples were positive for BFDV in Real-Time PCR assay, while only 19 samples were positive in PCR assay. Three facilities were positive for BFDV with positive rates from 60% to 87.5%. Further sequence analysis of VP1 genes from the positive samples indicated that VP1 genes fell into two different lineages in phylogenetic tree, suggesting that different genotypes BFDV are co-circulating in China.

Macrorhabdus ornithogaster Infection and Spontaneous Proventricular Adenocarcinoma in Budgerigars ( Melopsittacus undulatus).

Proventricular infection with the anamorphic, ascomycetous yeast Macrorhabdus ornithogaster and disease associated with infection (macrorhabdiosis) have been widely reported in budgerigars ( Melopsittacus undulatus). Proventricular adenocarcinoma has also been previously reported in this species. In a retrospective archival search of clinical cases submitted to a zoo animal and exotic pet pathology service between 1998 and 2013, a total of 28 128 avian submissions were identified, which included 1006 budgerigars kept in zoos or aviaries or as pets. Of these budgerigars, 177 were identified histologically as infected with M. orthithogaster at the time of necropsy. Histologic examination of tissues from budgerigars infected with M. orthithogaster identified an apparent continuum in the development of proventricular isthmus lesions associated with M. ornithogaster that included inflammation, mucosal hyperplasia, glandular dysplasia, and adenocarcinoma. Proventricular adenocarcinoma was identified histologically in 21 budgerigars. Budgerigars with proventricular adenocarcinoma were significantly more likely to have macrorhabdiosis than budgerigars without proventricular adenocarcinoma. Based on odds ratios for archival data, budgerigars were 41 times (95% confidence interval [CI], 33-52) more likely to have macrorhabdiosis than other avian species and 19 times (95% CI, 11-33) more likely to have proventricular adenocarcinoma than other birds. Budgerigars were 323 times (95% CI, 42-2490) more likely to be affected by both diseases simultaneously compared with other avian species. These findings suggest that macrorhabdiosis may be an associated factor for proventricular adenocarcinoma, although the explanation for this statistically significant correlation remains unknown and further investigation is warranted.

Assessment of Three Diet Types on Constitutive Immune Parameters in Captive Budgerigar (Melopsittacus undulatus).

Proper diet and nutrition are essential for maintaining the health of captive birds, but specific nutritional requirements can vary by species. Our knowledge of avian nutrition is predominantly based on data collected from gallinaceous birds, which is the primary basis for the dietary recommendations for companion birds, such as budgerigars (Melopsittacus undulatus) and other psittacine birds, potentially leading to a higher risk of malnutrition. In the wild, budgerigars eat predominantly Australian grass seed of the Astrebla genus, which may not be similar to the commercially available food fed to captive budgerigars, both in nutrient content and in their physiologic effects. In this study, we examined the relationship between diet type and immune function by separating 36 budgerigars into 3 dietary treatments: 1) Roudybush formulated pellet diet (Roudybush BirdFood Inc, Woodland, CA, USA), 2) Kaytee Forti-Diet Pro Health seed mix (Kaytee Products Inc, Chilton, WI, USA), and 3) a natural seed diet containing fresh canary grass, flax, nyger, oat groats, and white millet seeds. We monitored body weight, measured the microbial killing ability of whole blood by Escherichia coli and Candida albicans, and collected blood smears to assess white blood cell counts during a period of 8 weeks. Overall, we observed no significant effects of the 3 different diets on bird microbial killing ability or on white blood cell counts, suggesting similar health outcomes for budgerigars that consume mixed seed and those that receive pellet-based diets during this relatively short-term study.

Comparison of Two Treatment Modalities and PCR to Assess Treatment Effectiveness in Macrorhabdosis.

Macrorhabdosis is a debilitating disease condition that affects budgerigars (Melopsittacus undulatus), cockatiels (Nymphicus hollandicus), and many other bird species worldwide. Macrorhabdus ornithogaster is a pathogen which leads to nonspecific clinical signs, and to date, diagnosis as well as therapy are still challenging. In this study, medical histories of 32 budgerigars and 7 cockatiels with macrorhabdosis diagnosed clinically and by polymerase chain reaction (PCR) within a period of 24 months (from January 2016 to January 2018) were retrospectively analyzed. Macrorhabdus ornithogaster was diagnosed through fecal samples collected over several days and analyzed by microscopic examination or PCR. The effectiveness of 2 different amphotericin B treatment regimens were investigated by PCR. In 23 cases, treatment was performed with amphotericin B via drinking water at 0.1 mg/mL for 28 days. For the remaining 16 birds, an alternative treatment regimen of amphotericin B at 100 mg/kg PO q12h for 10 days was combined with administration of amphotericin B via drinking water at 0.1 mg/mL for 28 days. Fecal samples of all treated flocks were reexamined by PCR 10-14 days post-amphotericin B treatment. More than half (56.4%) of the treated birds tested negative for M ornithogaster irrespective of the treatment regimen. In addition to clinical improvement and microscopic examination of droppings, PCR was used for the first time to evaluate treatment response in birds diagnosed with M ornithogaster. Administration of amphotericin B via drinking water proved to be effective in more than 50% of cases, indicating a less stressful alternative to the oral administration of amphotericin B twice daily.