Alphaherpesvirus-associated disease in greater bilbies (Macrotis lagotis)

Case report: A captive breeding colony of 9 greater bilbies (Macrotis lagotis) exhibited mild upper respiratory signs and sudden deaths with 100% mortality over a 2-week period. Histologically, acute necrotising and erosive epithelial lesions throughout the upper respiratory system and bronchi were associated with eosinophilic intranuclear inclusion bodies. Inclusions were also present in hepatocytes and adrenocortical cells, but were not always associated with necrosis. Transmission electron microscopy of lung sections revealed nucleocapsids forming arrays within some nuclei. A pan-herpesvirus PCR yielded a 440-bp product, with sequencing confirming homology with the alphaherpesviruses. Viral culture in a marsupial cell line resulted in cytopathic effect consistent with an alphaherpesvirus. Conclusion: This is the first report of a herpesvirus-associated disease in greater bilbies. © 2016 Australian Veterinary Association.

Associations between exposure to viruses and bovine respiratory disease in Australian feedlot cattle

Bovine respiratory disease (BRD) is the most important cause of clinical disease and death in feedlot cattle. Respiratory viral infections are key components in predisposing cattle to the development of this disease. To quantify the contribution of four viruses commonly associated with BRD, a case-control study was conducted nested within the National Bovine Respiratory Disease Initiative project population in Australian feedlot cattle. Effects of exposure to Bovine viral diarrhoea virus 1 (BVDV-1), Bovine herpesvirus 1 (BoHV-1), Bovine respiratory syncytial virus (BRSV) and Bovine parainfluenza virus 3 (BPIV-3), and to combinations of these viruses, were investigated. Based on weighted seroprevalences at induction (when animals were enrolled and initial samples collected), the percentages of the project population estimated to be seropositive were 24% for BoHV-1, 69% for BVDV-1, 89% for BRSV and 91% for BPIV-3. For each of the four viruses, seropositivity at induction was associated with reduced risk of BRD (OR: 0.6–0.9), and seroincrease from induction to second blood sampling (35–60 days after induction) was associated with increased risk of BRD (OR: 1.3–1.5). Compared to animals that were seropositive for all four viruses at induction, animals were at progressively increased risk with increasing number of viruses for which they were seronegative; those seronegative for all four viruses were at greatest risk (OR: 2.4). Animals that seroincreased for one or more viruses from induction to second blood sampling were at increased risk (OR: 1.4–2.1) of BRD compared to animals that did not seroincrease for any viruses. Collectively these results confirm that prior exposure to these viruses is protective while exposure at or after feedlot entry increases the risk of development of BRD in feedlots. However, the modest increases in risk associated with seroincrease for each virus separately, and the progressive increases in risk with multiple viral exposures highlights the importance of concurrent infections in the aetiology of the BRD complex. These findings indicate that, while efficacious vaccines could aid in the control of BRD, vaccination against one of these viruses would not have large effects on population BRD incidence but vaccination against multiple viruses would be expected to result in greater reductions in incidence. The findings also confirm the multifactorial nature of BRD development, and indicate that multifaceted approaches in addition to efficacious vaccines against viruses will be required for substantial reductions in BRD incidence.

Twenty years of Hendra virus: laboratory submission trends and risk factors for infection in horses

Hendra virus (HeV) was first described in 1994 in an outbreak of acute and highly lethal disease in horses and humans in Australia. Equine cases continue to be diagnosed periodically, yet the predisposing factors for infection remain unclear. We undertook an analysis of equine submissions tested for HeV by the Queensland government veterinary reference laboratory over a 20-year period to identify and investigate any patterns. We found a marked increase in testing from July 2008, primarily reflecting a broadening of the HeV clinical case definition. Peaks in submissions for testing, and visitations to the Government HeV website, were associated with reported equine incidents. Significantly differing between-year HeV detection rates in north and south Queensland suggest a fundamental difference in risk exposure between the two regions. The statistical association between HeV detection and stockhorse type may suggest that husbandry is a more important risk determinant than breed per se. The detection of HeV in horses with neither neurological nor respiratory signs poses a risk management challenge for attending veterinarians and laboratory staff, reinforcing animal health authority recommendations that appropriate risk management strategies be employed for all sick horses, and by anyone handling sick horses or associated biological samples.

Confirmation of Elsey virus infection in a Queensland horse with mild neurologic signs

In 2011, a 2-year-old horse in northern Queensland, Australia, was reported to have developed mild neurologic signs, and a blood sample was submitted for laboratory investigation. Virus isolation was performed using the blood sample, and an orbivirus was isolated. This was confirmed to be a strain of Elsey virus (ELSV) after transmission electron microscopy and nucleotide sequencing. The nucleotide sequence was compared with those in GenBank, and had 100% identity with ELSV previously reported from the Northern Territory, Australia. ELSV is taxonomically closely related to Peruvian horse sickness virus.

Effects of exposure to Bovine viral diarrhoea virus 1 on risk of bovine respiratory disease in Australian feedlot cattle

Viruses play a key role in the complex aetiology of bovine respiratory disease (BRD). Bovine viral diarrhoea virus 1 (BVDV-1) is widespread in Australia and has been shown to contribute to BRD occurrence. As part of a prospective longitudinal study on BRD, effects of exposure to BVDV-1 on risk of BRD in Australian feedlot cattle were investigated. A total of 35,160 animals were enrolled at induction (when animals were identified and characteristics recorded), held in feedlot pens with other cattle (cohorts) and monitored for occurrence of BRD over the first 50 days following induction. Biological samples collected from all animals were tested to determine which animals were persistently infected (PI) with BVDV-1. Data obtained from the Australian National Livestock Identification System database were used to determine which groups of animals that were together at the farm of origin and at 28 days prior to induction (and were enrolled in the study) contained a PI animal and hence to identify animals that had probably been exposed to a PI animal prior to induction. Multi-level Bayesian logistic regression models were fitted to estimate the effects of exposure to BVDV-1 on the risk of occurrence of BRD.Although only a total of 85 study animals (0.24%) were identified as being PI with BVDV-1, BVDV-1 was detected on quantitative polymerase chain reaction in 59% of cohorts. The PI animals were at moderately increased risk of BRD (OR 1.9; 95% credible interval 1.0-3.2). Exposure to BVDV-1 in the cohort was also associated with a moderately increased risk of BRD (OR 1.7; 95% credible interval 1.1-2.5) regardless of whether or not a PI animal was identified within the cohort. Additional analyses indicated that a single quantitative real-time PCR test is useful for distinguishing PI animals from transiently infected animals.The results of the study suggest that removal of PI animals and/or vaccination, both before feedlot entry, would reduce the impact of BVDV-1 on BRD risk in cattle in Australian feedlots. Economic assessment of these strategies under Australian conditions is required. © 2016 Elsevier B.V.

Identification of bla(CMY-7) and associated plasmid-mediated resistance genes in multidrug-resistant Escherichia coli isolated from dogs at a veterinary teaching hospital in Australia

Objectives: To determine clonality and identify plasmid-mediated resistance genes in 11 multidrug-resistant Escherichia coli (MDREC) isolates associated with opportunistic infections in hospitalized dogs in Australia. Methods: Phenotypic (MIC determinations, modified double-disc diffusion and isoelectric focusing) and genotypic methods (PFGE, plasmid analysis, PCR, sequencing, Southern hybridization, bacterial conjugation and transformation) were used to characterize, investigate the genetic relatedness of, and identify selected plasmid-mediated antimicrobial resistance genes, in the canine MDREC. Results: Canine MDRECs were divided into two clonal groups (CG 1 and 2) with distinct restriction endonuclease digestion and plasmid profiles. All isolates possessed bla(CMY-7) on an similar to 93 kb plasmid. In CG 1 isolates, bla(TEM), catA1 and class 1 integron-associated dfrA17-aadA5 genes were located on an similar to 170 kb plasmid. In CG 2 isolates, a second similar to 93 kb plasmid contained bla(TEM) and unidentified class 1 integron genes, although a single CG 2 strain carried dfrA5. Antimicrobial susceptibility profiling of E. coli K12 transformed with CG 2 large plasmids confirmed that the bla(CMY-7)-carrying plasmid did not carry any other antimicrobial resistance genes, whereas the bla(TEM)/class 1 integron-carrying plasmid carried genes conferring resistance to tetracycline and streptomycin also. Conclusions: This is the first report on the detection of plasmid-mediated bla(CMY-7) in animal isolates in Australia. MDREC isolated from extraintestinal infections in dogs may be an important reservoir of plasmid-mediated resistance genes.

Sewage disposal and wildlife health in Antarctica

Sewage and its microbiology, treatment and disposal are important to the topic of Antarctic wildlife health because disposal of untreated sewage effluent into the Antarctic marine environment is both allowed and commonplace. Human sewage contains enteric bacteria as normal flora, and has the potential to contain parasites, bacteria and viruses which may prove pathogenic to Antarctic wildlife. Treatment can reduce levels of micro-organisms in sewage effluent, but is not a requirement of the Environmental Protocol to the Antarctic Treaty (the Madrid Protocol). In contrast, the deliberate release of non-native organisms for any other reason is prohibited. Hence, disposal of sewage effluent to the marine environment is the only activity routinely undertaken in Antarctica knowing that it will likely result in the release of large numbers of potentially non-native species. When the Madrid Protocol was negotiated, the decision to allow release of untreated sewage effluent was considered the only pragmatic option, as a prohibition would have been costly, and may not have been achievable by many Antarctic operators. In addition, at that time the potential for transmission of pathogens to wildlife from sewage was not emphasised as a significant potential risk. Since then, the transmission of disease-causing agents between species is more widely recognised and it is now timely to consider the risks of continued discharge of sewage effluent in Antarctica and whether there are practical alternatives.

Persistence of multiple genetic lineages within intra-host populations of Ross River virus

We examined the structure and extent of genetic diversity in intrahost populations of Ross River virus (RRV) in samples from six human patients, focusing on the nonstructural (nsP3) and structural (E2) protein genes. Strikingly, although the samples were collected from contrasting ecological settings 3,000 kilometers apart in Australia, we observed multiple viral lineages in four of the six individuals, which is indicative of widespread mixed infections. In addition, a comparison with previously published RRV sequences revealed that these distinct lineages have been in circulation for at least 5 years, and we were able to document their long-term persistence over extensive geographical distances

Multilocus sequence analysis provides insights into molecular epidemiology of Chlamydia pecorum infections in Australian sheep, cattle and koalas

Chlamydia pecorum is a significant pathogen of domestic livestock and wildlife. We have developed a C. pecorum-specific multilocus sequence analysis (MLSA) scheme to examine the genetic diversity of and relationships between Australian sheep, cattle, and koala isolates. An MLSA of seven concatenated housekeeping gene fragments was performed using 35 isolates, including 18 livestock isolates (11 Australian sheep, one Australian cow, and six U.S. livestock isolates) and 17 Australian koala isolates. Phylogenetic analyses showed that the koala isolates formed a distinct clade, with limited clustering with C. pecorum isolates from Australian sheep. We identified 11 MLSA sequence types (STs) among Australian C. pecorum isolates, 10 of them novel, with koala and sheep sharing at least one identical ST (designated ST2013Aa). ST23, previously identified in global C. pecorum livestock isolates, was observed here in a subset of Australian bovine and sheep isolates. Most notably, ST23 was found in association with multiple disease states and hosts, providing insights into the transmission of this pathogen between livestock hosts. The complexity of the epidemiology of this disease was further highlighted by the observation that at least two examples of sheep were infected with different C. pecorum STs in the eyes and gastrointestinal tract. We have demonstrated the feasibility of our MLSA scheme for understanding the host relationship that exists between Australian C. pecorum strains and provide the first molecular epidemiological data on infections in Australian livestock hosts.