Australian Veterinary Journal最新文献

Cryptosporidium spp. sporadically infect a range of Australian native mammals including koalas, red kangaroos, eastern grey kangaroos, bilbies and brush tailed possums and can range from asymptomatic to fatal infections. Traditionally considered a disease of the young or immuno-compromised, and resulting in profuse diarrhoea in other species, here we report an atypical clinical syndrome associated with Cryptosporidium in a captive population of koalas. All affected animals were in-contact adults, and demonstrated anorexia, dehydration and abdominal pain in the absence of diarrhoea. Following euthanasia on welfare grounds, Cryptosporidium infection was confirmed postmortem in three of four symptomatic animals via faecal floatation and/or intestinal histopathology, with enteritis also diagnosed in the fourth koala. Further screening of the captive colony found the outbreak had been contained. Based on sequencing the cause of the infection was C. fayeri, but the source was undetermined. In conclusion, Cryptosporidium should be considered as a possible cause of generalised illness in koalas.

Antimicrobials are one of the most important medical developments of the 20th century and are used to safely treat many common infections in humans and animals. Antimicrobial resistance (AMR) occurs when the microorganisms that cause infection, such as bacteria and viruses, become resistant to medical treatment with antimicrobial agents. Australia was one of the first nations to embark on a comprehensive reform process aimed at protecting humans and animals from the harmful effects of AMR and has remained at the forefront of antimicrobial stewardship globally.

AMR is recognised as a global health priority due to its adverse effects on public health, animal health, welfare and production, and the economy. Inappropriate use of antimicrobials in humans and animals has accelerated the process. A shared One Health approach, working across the human, animal and environmental health sectors, and promoting antimicrobial stewardship across a range of industries, is a key component of how we address AMR.

As a major exporter of high-quality food products, Australia has taken a proactive approach to managing food safety issues, including the use of antimicrobials. Antimicrobials are an essential tool for dairy farmers and veterinarians to ensure the health and welfare of animals in their care. Overall, the Australian dairy industry has very low antimicrobial usage compared to other countries and holds a favourable reputation for low levels of AMR. The industry is, therefore, well-placed to play a leading role in how we address AMR more broadly across the animal health sector. The dairy industry's “as little as possible, as much as necessary” method is particularly commendable and demonstrates their commitment to using antimicrobials responsibly.

In closing, I would like to recognise the important stewardship role dairy cattle veterinarians play in promoting the appropriate use of antimicrobials on dairy farms. These best-practice, evidence-based prescribing guidelines have been developed specifically for the dairy industry and will help attending veterinarians make good decisions about their use (or otherwise) of antimicrobials. I extend my sincere thanks to everyone who contributed to the development of these guidelines and urge all dairy cattle veterinarians to apply this advice. In doing so, you will help safeguard the ongoing, long-term efficacy of antimicrobials, deliver best practice veterinary service, and play an integral role in the global response to AMR.

Dr Mark Schipp

Australian Chief Veterinary Officer

John is Associate Professor of Livestock Health and Production and Head of The Livestock Veterinary Teaching and Research Unit at the University of Sydney. He is a registered specialist in livestock medicine with a keen interest in veterinary clinical practice and dairy cattle management. He completed a Bachelor of Science and Bachelor of Veterinary Medical Scien

Over 40 years there have been profound changes to the Australian dairy production environment. The number of farms decreased from 21,989 in 1980 to 5055 in 2020,^{1, 2} milk production per cow increased from 2888 L/cow per year or 1.9 million cows producing 5.49 million L per year, to 6311 L/cow per year or 8.8 million L from 1.4 million cows. Many dairy farms represent assets valued in the $10 to $100 million or more. The average herd has increased from 85 to 274 cows. Consequently, farm management has less time to engage with the individual cow. These changes influence the delivery of veterinary services as the individual cow now represents a much lower proportion of the enterprise asset value. However, herd health and productivity are critical to an enterprise and farmers are committed to stewardship of their cattle. The challenge for the veterinary profession is to deliver cost-effective services that identify, monitor, and mitigate risks to herd health and productivity. Such services must be designed to deliver better outcomes with greater labour efficiency. In this series of reviews, we evaluate the value of bulk tank milk which provides a readily available and contemporary indicator of herd status of health and production and, where appropriate, compare the value of bulk milk testing to that of individual cow testing, to determine the mastitis,³ viral,⁴ and metabolic status⁵ of herds. We provide quantitative and qualitative reviews of tests that may do this. We also note two coincident and valuable scoping reviews of this area,^{6, 7} one of which includes data on the value of bulk tank milk for parasite evaluation.⁷

Bulk milk somatic cell counts are routinely utilised by processors and veterinary advisors to assess milk quality and udder health. Because this assessment does not capture cows with clinical mastitis, diagnostics at the cow level may also be needed to manage udder health. Additional markers of inflammation or the humoral immune response are primarily available at cow level, except for antibody testing for Mycoplasma bovis, which can be conducted at bulk milk level to support biosecurity efforts. Elevated somatic cell counts are primarily due to intramammary infections, and its causative agents, including those with antimicrobial resistance, can be detected through culture or PCR. Specificity of PCR for contagious pathogens (Streptococcus agalactiae, Mycoplasma bovis) is high (0.90) but sensitivity is variable (0.15–0.99) unless repeated bulk milk testing or cow-level testing is used. For pathogens that may be cow-derived as well as environmental (Staphylococcus aureus, Streptococcus dysgalactiae, Streptococcus uberis), sensitivity of bulk milk testing is low (<30%).³ New technologies such as matrix-assisted laser

Antibiotic-resistant bacteria are a problem in human medicine. The development of antibiotic resistance in bacteria in feedlot cattle could have negative effects on their health and welfare and there is a theoretical possibility of transmission of antibiotic-resistant bacteria from food animals to humans. Alternatives to conventional antibiotics in feedlot health management could reduce the selective pressure for the development of antibiotic resistance. This review assesses the evidence supporting potential alternatives to conventional antibiotics in the prevention and treatment of diseases in feedlot cattle, including nitric oxide, plant extracts, supplemental yeast or yeast products, bacterial probiotics, organic acids, bacteriophages and non-specific immunostimulants. Further research is warranted with lactate utilising bacteria, the organic acid malate, bacteriophages and the non-specific immunostimulants β-1,3 glucan and those based on pox viruses. However, none of the alternatives to conventional antibiotics investigated in this review have sufficient supporting evidence to date to justify their use with feedlot cattle. Frequently, statistically weak results and studies without negative controls are cited as support for similar studies. The health and welfare of feedlot cattle are dependent on the use of products that have robust supporting data to ensure efficacy and to avoid adverse outcomes.

In 2017, highly fatal canine leptospirosis emerged in Sydney, Australia. Based on results of microscopic agglutination testing (MAT), serovar Copenhageni appeared to be the most common causative serovar. Prior to this, no clinical cases had been reported since 1976. In a serosurvey of healthy dogs in Australian shelters in 2004, 2.4% of 431 New South Wales dogs had serological evidence of exposure to Copenhageni, the most prevalent serovar. The aim of this study was to estimate the current prevalence of Leptospira exposure and associated serovars in healthy Sydney dogs, previously unvaccinated against Leptospira. Serum samples from 411 healthy dogs in leptospirosis hotspots and neighbouring suburbs were collected before vaccination. MAT for 23 serovars was performed at the WHO Leptospirosis Reference Laboratory in Queensland, Australia. The overall seroprevalence was 4.1% (17/411) with low titres (1/50–1/200) detected. Eleven dogs were from known leptospirosis hotspots. Eight dogs were known to hunt rodents. One dog had been in contact with a leptospirosis positive dog 1 year prior. Serovar Topaz was the most prevalent serovar (n = 5) followed by serovars Australis (n = 4), Copenhageni (n = 4), Djasiman (n = 2), Cynopteri (n = 1), Javanica (n = 1), Medanensis (n = 1), and Pomona (n = 1). In conclusion, serological evidence of exposure of dogs in Sydney to Leptospira is low, but apparently has increased since 2004. Positive titres to serovars not previously reported to cause disease in dogs could be due to low virulence of those serovars or cross-reactivity with other serovars.

We quantified the sensitivity of surveillance for lumpy skin disease (LSD) and foot and mouth disease (FMD) in cattle in the Kimberley region of Western Australia. We monitored producer and veterinary activity with cattle for 3 years commencing January 2020. Each year, ~274,000 cattle of 685,540 present on 92 pastoral leases (stations) were consigned to other stations, live export or slaughter. Veterinarians examined 103,000 cattle on the stations, 177,000 prior to live export, and 10,000 prior to slaughter. Detection probabilities for the disease prior to transport or during veterinary procedures and inspections were elicited by survey of 17 veterinarians working in Northern Australia. The veterinarians estimated the probabilities that they would notice, recognise, and submit samples from clinical cases of LSD and FMD, given a 5% prevalence of clinical signs in the herd. We used scenario tree methodology to estimate monthly surveillance sensitivity of observations made by producers and by veterinarians during herd management visits, pre-export inspections, and ante-mortem inspections. Average monthly combined sensitivities were 0.49 for FMD and 0.37 for LSD. Sensitivity was high for both diseases during the dry season and low in the wet season. We estimated the confidence in freedom from the estimated surveillance sensitivity given one hypothetically infected herd, estimated probability of introduction, and prior confidence in freedom. This study provided assurance that the Kimberley is free of these diseases and that routine producer and veterinary interactions with cattle are adequate for the timely detection of the disease should they be introduced.

The provision of veterinary services is essential to deliver animal health and welfare outcomes, but over the last several decades demand for veterinary services in animal production systems has broadly declined in Australia. Reduced demand is closely related to a decline in the size of the production animal veterinary workforce, and there is evidence that the percentage of veterinarians participating in the delivery of veterinary services to animal production systems has lessened. Reduced demand for veterinary services in the production animal sector is likely to be attributed to several factors, including challenges around widespread adoption of preventive veterinary services, improved self-efficacy of producers through advancement of knowledge, and potential concern by producers over the role of veterinarians in production animal systems. Declining veterinary engagement results in increased risk at both the individual farm level (diminished expertise to deliver reactive and proactive veterinary services) and at a population level (increased biosecurity risk and risk to social licence to operate). The current environment and the community trust in the profession should be seen as an opportunity to develop and implement a strategy to halt and reverse the decline in demand for production animal veterinary services. Such a strategy will require significant and sustained collaboration between the veterinary profession, Industry and government.