Treatment with potassium bromide mitigates ataxia and reduces tremor in lambs with perennial ryegrass toxicosis.

Aims: To assess the use of potassium bromide (KBr) as a therapeutic intervention for perennial ryegrass toxicosis (PRGT) in lambs fed ryegrass seed containing lolitrem B. Methods: Male lambs aged 10-12 months (n = 43) were assigned to receive ryegrass seed containing lolitrem B, at a dose of 0.16 mg/kg/day (Groups 2, 3 and 4), or lucerne chaff and molasses (Groups 1 and 5). Lambs in Groups 2 and 3 were observed for clinical signs and gait changes until defined signs of PGRT were observed, when they were transferred, with lambs in Group 1, to the Testing phase of the trial. Lambs in Group 3 were then treated with a single oral dose of 300 mg/kg bromide. Lambs in Groups 4 and 5 received KBr daily from the start of the trial (540 mg/kg bromide over 3 days then 20 mg/kg daily) and were transferred to the Testing phase after 18 days. Clinical examination and gait assessment, and surface electromyography of the triceps muscle, measuring root-mean-square (RMS) voltages, were carried out on Days 0, 1 and 2 of the Testing phase followed by necropsy, histopathology, measurement of concentrations of bromide in serum and CSF and faecal cortisol metabolites (FCM). Results: In Group 3 lambs, mean composite gait scores decreased between Testing phase Day 0 and Days 1 and 2 (p < 0.001), but increased in lambs in Group 2 between Day 0 and Day 2 (p = 0.015). Scores for lambs in Group 3 on Day 2 were lower than for lambs in Group 2 (p < 0.001). Mean RMS voltages on Day 2 were higher in lambs in Group 2 than Group 3 (p = 0.045). Mean concentrations of bromide in serum were >800 µg/mL in lambs in Groups 3 and 4 on Day 2. Concentrations of FCM were higher in lambs from Group 2 than in Groups 1 or 5, but were similar in Groups 2, 3 and 4. Histopathological findings in the cerebellum of lambs from Groups 2, 3 and 4 were similar, showing pyknosis of neurons within the granular layer of the cerebellum and Purkinje neuron proximal axonal spheroid formation. Conclusions and clinical relevance: A single oral dose of 300 mg/kg bromide in lambs with neurological signs of PRGT resulted in reduced composite gait scores and reduced RMS voltages, indicating a significant improvement in clinical signs of ataxia, movement disorder and muscle tremor associated with the neurotoxic effects of lolitrem B.

The first report of cerebral, pulmonary and gastrointestinal angiostrongyliasis in the water rat Hydromys chrysogaster from Queensland, Australia.

We describe the first case of angiostrongyliasis in a water rat, Hydromys chrysogaster, a large rodent adapted to aquatic life, which is endemic to Australia, New Guinea and adjacent islands.

Development of a model for investigation of perennial ryegrass toxicosis in sheep.

AIMS To develop a clinical model of perennial ryegrass toxicosis (PRGT) based on feeding a known dose of lolitrem B and ergotamine, and to produce a consistent clinical presentation for assessment of disease pathophysiology, neurological changes and neurohistopathology. METHODS Male lambs, aged between 10-12 months, were randomly assigned to either Treatment (n=9) or Control (n=9) groups. Lambs in the Treatment group received feed containing a novel endophyte-infested perennial ryegrass seed, commencing on Day 0 of the Feeding phase with a low induction dose, then increasing after 3 days to provide 0.16 mg/kg live bodywight (LBW)/day of lolitrem B and 0.054 mg/kg LBW/day ergotamine. Lambs were examined daily and when defined signs of PRGT were observed they were transferred to the Testing phase. Neurological examinations, assessment of gait, surface electromyography (EMG) and mechanosensory nociceptive threshold testing were carried out and blood samples collected during both phases of the trial, with a full necropsy, histopathological examination and measurement of faecal cortisol metabolites (FCM) performed on Day 2 of the Testing phase. RESULTS Typical clinical signs of PRGT, including ataxia of vestibulocerebellar origin leading to stumbling, were observed in all Treatment lambs. The median interval from the start of the Feeding phase to entry into the Testing phase was 21 (min 18, max 34) days. Histopathological characterisation of neurological lesions included the presence of Purkinje cell vacuolation, pyknotic granular layer neurons and proximal axonal Purkinje cell spheroids. Lesions were most apparent within the vestibulocerebellum. Mean root-mean-square voltages from triceps EMG increased in Treatment lambs between Feeding phase Day 0 and Testing phase Day 2 (p<0.001). Daily water intake during the Testing phase for the Treatment group was less than in Control group lambs (p=0.002), and concentrations of FCM at necropsy were higher in Treatment compared to Control lambs (p=0.02). CONCLUSIONS AND CLINICAL RELEVANCE Lolitrem B and ergotamine dosing in feed on a live weight basis combined with neurological/gait assessment provides an effective model for investigation of PRGT and potential therapeutics. Assessment of gait changes using defined criteria and RMS voltages from EMG appear to be useful tools for the assessment of the severity of neurological changes.

Spillover of avian haemosporidian parasites (Haemosporidia: Plasmodium) and death of captive psittacine species.

CASE REPORT: During February 2014, a yellow-tailed black cockatoo (Calyptorhynchus funereus) and glossy black cockatoo (C. lathami) housed in aviaries on a property in Wamuran, Queensland, were submitted for postmortem. Histopathology and molecular diagnostics demonstrated the presence of Plasmodium sp. infection. The Plasmodium isolate identified has previously only been reported as infecting a healthy wild rufous fantail (Rhipidura rufifrons) in Australia. CONCLUSION: To the authors' knowledge, these are the first reported cases of Plasmodium in Calyptorhynchus. We hypothesised that the maintenance of these two cockatoo species in ground level aviaries in a low-altitude geographic zone resulted in exposure of birds to mosquito vectors of endemic avian Plasmodium. Black cockatoos roost and forage in the mid to high canopy of forests in the wild, outside the likely spatiotemporal distribution of relevant haemosporidian vectors. It is therefore likely that these birds had immunological naivety and susceptibility to infection with Plasmodium circulating in wild passerines.

Genome sequence of an Australian strain of canid alphaherpesvirus 1.

OBJECTIVE: Characterisation of a complete genome sequence of an Australian strain of canid alphaherpesvirus 1 (CHV-1) and its phylogenetic relationship with other varicellovirus species. METHODS: Standard pathology and PCR methods were used to initially detect herpesvirus in hepatic tissue from an infected 4-week-old Labrador Retriever puppy. The complete CHV-1 genome was sequenced using next-generation sequencing technology followed by de novo and reference assembly, and genome annotation. RESULTS: The CHV-1 genome was 125 kbp in length and contained 74 predicted open reading frames encoding functional proteins, all of which have counterparts in other alphaherpesviruses. Phylogenetic analysis using the DNA polymerase gene revealed that the newly sequenced CHV-1 clustered with canid alphaherpesvirus isolated from the UK and shared a 99% overall nucleotide sequence similarity. CONCLUSION: This is the first complete genome of an Australian strain of CHV-1, which will contribute to our understanding of the genetics and evolution of herpesvirus.

Beak and feather disease virus carriage by Knemidocoptes pilae in a sulphur-crested cockatoo (Cacatua galerita).

BACKGROUND: This paper describes the pathology associated with psittacine beak and feather disease in a wild sulphur-crested cockatoo with concurrent knemidocoptic mange, cestodiasis and mycotic encephalitis. METHODS & RESULTS: Large numbers of Knemidocoptes pilae Lavoipierre and Griffiths, 1951 (Acari: Epidermoptidae, Knemidokoptinae) were identified in affected skin associated with enhanced expression of beak and feather disease virus (BFDV) determined by immunohistochemistry. Also, BFDV antigen was demonstrated in high concentration in the gut and faecal sacs of mites, raising the possibility of ectoparasites as fomites and vectors of BFDV transmission. Large numbers of Raillietina spp. cestodes were present in the intestines. Within the brain there was a focally extensive region of necrosis and inflammation associated with branching, septate, pigmented hyphae consistent with zygomycete fungal infection. CONCLUSION: This case highlights the potential immunosuppressive effects of BFDV infection and its potential as a keystone pathogen in the Australian environment.

Herpesvirus in a captive Australian Krefft's river turtle (Emydura macquarii krefftii).

CASE REPORT: A mature, captive Krefft's river turtle (Emydura macquarii krefftii) was presented with severe proliferative and ulcerative lesions of the skin and shell. The areas were biopsied and histopathological examination demonstrated orthokeratotic hyperkeratosis with keratinocytes containing eosinophilic intranuclear inclusions. Molecular diagnostics confirmed the presence of a herpesvirus in the affected tissues. CONCLUSION: This is the first recorded case of herpesvirus infection in an Australian freshwater turtle species.

Review of psittacine beak and feather disease and its effect on Australian endangered species.

BACKGROUND: Since it was first described in the early 1980s, psittacine beak and feather disease (PBFD) has become recognised as the dominant viral pathogen of psittacine birds in Australia. Our aim was to evaluate and review the effect of PBFD and its position as a key threatening process to Australian psittacine bird species. We review the origin/evolutionary pathways and potential threat of PBFD to endangered psittacine bird populations and captive-breeding flocks. CONCLUSIONS: The most recent beak and feather disease virus (BFDV) phylogenetic analyses indicate that all endangered Australian psittacine bird species are susceptible to, and equally likely to be infected by, BFDV genotypes from a range of host psittacine species. Management of the disease in captive-breeding programs has relied on testing and culling, which has proven costly. The risk of PBFD should be considered very carefully by management teams contemplating the establishment of captive-breeding flocks for endangered species. Alternative disease prevention tools, including vaccination, which are increasingly being used in wildlife health, should be considered more seriously for managing and preventing PBFD in captive flocks of critically endangered species.

Beak and feather disease virus genotypes in Australian parrots reveal flexible host-switching.

OBJECTIVE: To discover beak and feather disease virus (BFDV) genotypes in Australian parrots that might threaten vulnerable and endangered psittacine bird species. METHODS: Phylogenetic analyses of new DNA sequence data from Australian birds including the Rep gene (n = 55) and nine whole genomes, were compared with all available published BFDV genomes to assess host- and geographically-based divergence as well as probable host-switch events. RESULTS: Strong support for flexible host-switching and recombination was detected, indicating active cross-species transmission in various subpopulations. CONCLUSION: The data suggested that all endangered Australian psittacine bird species are equally likely to be infected by BFDV genotypes from any other close or distantly related host reservoir species.

Granuloma formation and suspected neuropathic pain in a domestic pigeon (Columba livia) secondary to an oil-based, inactivated Newcastle disease vaccine administered for protection against pigeon paramyxovirus-1.

CASE REPORT: A domestic pigeon developed a sterile granuloma following vaccination with an oil-adjuvant, inactivated La Sota strain of Newcastle disease. The aim of vaccination was to provide protection against pigeon paramyxovirus-1 (PPMV-1), a disease previously considered exotic to Australia. Granuloma formation is considered a rare complication of vaccination against PPMV-1 in pigeons. Clinical signs consistent with neuropathic pain became apparent during the extensive management of the granuloma, which included surgical removal of foreign material, control of the pain and inflammation and protection against antimicrobial contamination. CONCLUSION: PPMV-1 is now considered endemic in Australia and protecting pigeons with vaccination is important. Until a product is registered for use, vaccination remains off-label and the risk of adverse reaction, including sterile granuloma, must be considered.

Necrotising ventriculitis due to combined infection with Rhizopus microsporus var. chinensis and Candida krusei in an eclectus parrot (Eclectus roratus).

Acute necrosis of the ventriculus is a very uncommon lesion in birds. We describe a fatal case of acute necrotising ventriculitis caused by Rhizopus microsporus var. chinensis in a mature female eclectus parrot (Eclectus roratus). The bird presented acutely dull and lethargic, was vomiting and had bright green droppings, suggestive of acute heavy metal poisoning. It was treated with fluids and chelation therapy, but died within 12 h. Necropsy, cytology, histopathology and culture results demonstrated fungal invasion of the ventriculus associated with transmural necrosis, haemorrhage, acute inflammation and abundant R. microsporus var. chinensis and lesser numbers of Candida krusei.

Haemochromatosis in a Brazilian tapir (Tapirus terrestris) in an Australian zoo.

A 23-year-old Brazilian, or lowland, tapir with a 6-month history of loss of body condition developed clinical signs and laboratory findings consistent with liver failure. The animal was euthanased and a diagnosis of hepatic haemochromatosis was made based on histopathology. Two other healthy tapirs in the same collection had chronically elevated serum and tissue iron concentrations. The excessive accumulation of iron in tissues with resultant tissue damage (i.e. haemochromatosis) has been reported in a range of captive species. This and other reported cases of haemochromatosis in the Brazilian tapir would suggest that this condition is an important consideration in the management of this species in zoos. Further research into the endogenous regulation of iron metabolism, especially the role of hepcidin, in tapirs and other species at risk of iron storage disorders may be helpful in the prevention of this condition.

Osteosarcoma in a woma python (Aspidites ramsayi).

Osteosarcoma of the axial skeleton in an 18-month-old woma python (Aspidites ramsayi) is described. A subcutaneous mass overlying the costal arches enlarged progressively over a period of 5 months and, in that time, became ulcerated and more invasive of surrounding tissues. A punch biopsy of the lesion under general anaesthesia provided tissue for histopathology and diagnosis of low-grade osteosarcoma.

Neuroangiostrongyliasis and other parasites in tawny frogmouths (Podargus strigoides) in south-eastern Queensland.

The neurological, clinical and pathological findings and endoparasites in 10 wild tawny frogmouths (Podargus strigoides) presented to the Australian Wildlife Hospital in Beerwah, Queensland during a 28-day period in May 2009 are reported. Affected birds had a history of being found in poor body condition on the ground and unable to fly. Clinical examination revealed paresis with variable but generally weakened deep pain responses, withdrawal reflexes and an inability to perch. Severely affected birds that failed to respond to anti-inflammatory, antibiotic and anthelmintic treatments all had larval Angiostrongylus cantonensis in the brain and or spinal cord, with occasional larvae found in the visceral organs. Other parasites detected included the liver fluke, Brachylecithum podargi, the intestinal nematode, Allodapa suctoria, an unidentified species of Trichostrongylus and unidentified cestodes. Gametocytes of Leucocytozoon sp. were found in peripheral blood smears and low numbers of microfilariae were found in histological sections of various blood vessels of several birds. However, no adult filarioids were recovered. Unidentified subcutaneous mites were identified in the connective tissue of the thoracic inlet. Attempts to treat two birds with ivermectin or oxfendazole-praziquantel were unsuccessful, but a third bird treated with a combination of steroidal and non-steroidal anti-inflammatory therapy followed by moxidectin steadily recovered, such that by 6 weeks post presentation its ability to perch, grasp, fly and judge distances was considered normal and it was subsequently released.

Tracheal resection and anastomosis in a red-tailed black cockatoo (Calyptorhynchus banksii banksii).

Tracheal stricture is an uncommon sequel to tracheitis in birds. We describe a case in a red-tailed black cockatoo that was attributed to a bacterial tracheitis associated with inhaled plant material and was successfully resolved by surgical resection and anastomosis of the trachea.

Detection of Minchinia occulta in samples of pearl oysters Pinctada maxima infected by Haplosporidium hinei.

OBJECTIVE: To determine if juvenile pearl oysters (Pinctada maxima) infected with Haplosporidium hinei are also infected with another haplosporidian parasite, Minchinia occulta. DESIGN: Archived samples of pearl oysters infected with H. hinei were examined using polymerase chain reaction (PCR) assays and in situ hybridisation (ISH) to analyse and identify haplosporidians. A 144-bp and 220-bp region of Minchinia DNA were targeted by PCR and amplified DNA from formalin-fixed H. hinei-infected pearl oyster samples was sequenced. A 25-bp oligonucleotide probe targeting a variable section of the parasite's small subunit rRNA gene was used in ISH. RESULTS: The results of DNA-based diagnostic assays supported each other. The sequences obtained by PCR were found to be almost identical to M. occulta from rock oysters and the ISH assay demonstrated infection with M. occulta in affected pearl oysters. ISH indicated a prevalence of infection of 26.7% in one of the previous outbreaks. CONCLUSION: Pearl oyster spat are susceptible to infection by a Minchinia parasite, most likely M. occulta, which was recently identified in rock oysters within the pearl-producing zones of Western Australia and is associated with mortalities of up to 80% in this species. The occurrence of haplosporidian co-infections in pearl oysters suggests the immunocompetence of juvenile oysters may be an important factor in preventing infection and therefore preventing mortalities such as those occurring in the recent outbreaks of pearl oyster oedema disease.

Intracellular ciliated protozoal infection in silverlip pearl oysters, Pinctada maxima (Jameson, 1901).

The pathology associated with an intracellular ciliate infection in the digestive gland of pearl oysters Pinctada maxima (Jameson, 1901) is described. Histopathological and transmission electron microscopic examination were used to characterise the organism and its location within host cells. The parasite is tear-drop shaped measuring 5.53 microm (range of 2.73-7.47 microm, n=9) in width and 11.15 microm (range of 9.02-16.2 microm) in length with a centrally located lobulated nucleus and a large nucleus:cytoplasmic ratio. The ciliate has nine evenly spaced rows of cilia running obliquely along the length of cell, converging on the pointed end. Infected digestive glands typically had a moderate to severe infiltration with mononuclear hemocyte. A strong correlation existed between the burden of ciliates and the host response; (p<0.001, C=0.315 Pearson Correlation). The use of a single tissue section upon microscopic examination was found to detect only 38-50% of the infections. However, examination of serial haematoxylin and eosin stained sections improved the reliability of detecting infection.

Spore ornamentation of Minchinia occulta n. sp. (Haplosporidia) in rock oysters Saccostrea cuccullata (Born, 1778).

A Minchinia sp. (Haplosporidia: Haplosporidiidae) parasite was identified infecting rock oysters and morphologically described by Hine and Thorne (2002) using light microscopy and transmission electron microscopy (TEM). The parasite was associated with up to 80% mortality in the host species and it is suspected that the parasite would be a major impediment to the development of a tropical rock oyster aquaculture industry in northern Western Australia. However, attempts to identify the parasite following the development of a specific probe for Haplosporidium nelsoni were unsuccessful. The SSU region of the parasite's rRNA gene was later characterized in our laboratory and an in situ hybridization assay for the parasite was developed. This study names the parasite as Minchinia occulta n sp. and morphologically describes the parasite using histology, scanning electron microscopy and transmission electron microscopy. The non-spore stages were unusual in that they consisted primarily of uninucleate stages reminiscent of Bonamia spp. The parasite's spores were ovoid to circular shaped and measured 4.5 microm-5.0 microm x 3.5-4.1 microm in size. The nucleus of the sporoplasm measured 1.5-2.3 microm and was centrally located. The spores were covered in a branching network of microtubule-like structures that may degrade as the spore matures.

Sequence comparison of pigeon circoviruses.

The genome sequences of eight pigeon circoviruses (PiCV) were determined and compared with four previously published sequences. The viruses compared were from the USA, five European countries, China and Australia and included PiCVs from racing, feral, ornamental and meat pigeons and a Senegal dove (Streptopelia senegalensis). The 12 PiCV genomes, ranging from 2032 to 2040 nucleotides in length, displayed similar organizations. Pairwise comparisons showed that the genome nucleotide sequence identities ranged from 85.1% to 97.8% and that the amino acid identities of the putative replication associated (Rep) and putative capsid (Cap) proteins displayed ranges of 91.5-99.1% and 73.0-99.3%, respectively. Comparative analyses identified conserved nucleotide sequences within the Rep gene and 3' intergenic regions, which would be suitable for diagnostic PCR primers, and variable amino acid sequences within the capsid proteins, which should be considered when selecting virus isolates for vaccine development.