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EDITORIAL

EDITORIAL

occur frequently in snakes, acanthocephalans and Spirometra spp. have not been reported to cohabitate.

References 1. Annand EJ, Reid PA. Clinical review of two fatal equine cases of infection with the insectivorous bat strain of Australian bat lyssavirus. Aust Vet J 2014;92:324– 332. 2. Metcalfe S, Hulands-Nave A, Bell M et al. Multicentre, randomised clinical trial evaluating the efficacy and safety of alfaxalone administered to bitches for induction of anaesthesia prior to caesarean section. Aust Vet J 2014;92:333– 338. 3. Bertalan A, Glass EN, Kent M et al. Late-onset cerebellar abiotrophy in a Labrador Retriever. Aust Vet J 2014;92:339–342. 4. Ridoutt C, Lee A, Moloney B et al. Detection of brucellosis and leptospirosis in feral pigs in New South Wales. Aust Vet J 2014;92:343–347.

5. Tyrell LD, Larsen JWA, Anderson N. Breech-strike on mulesed, clipped and unmulesed Merino ewes and hoggets in south-eastern Australia. Aust Vet J 2014;92:348–356. 6. Palmer DG, Lyon J, Palmer MA et al. Evaluation of a copro-antigen ELISA to detect Fasciola hepatica infection in sheep, cattle and horses. Aust Vet J 2014;92:357–361. 7. Hill AG, Ladds PW, Spratt DM. Acanthocephalan infection and sparganosis in a green tree snake (Dendrelaphis punctulata). Aust Vet J 2014;92:362–364.

AE Jackson Editor in Chief L Cabral Education Coordinator and Editorial Officer doi: 10.1111/avj.12242

LETTER TO THE EDITOR Mycoplasma bovis in Australian dairy herds In a recent review, Fox1 reported that surveys in various countries including Australia indicate herd-level prevalences of Mycoplasma spp. are as high as 55–100%. The conclusion about the prevalence in Australia was based on an earlier Australian study,2 which was also recently cited by Horwood et al3). We would like to inform readers that Mycoplasma bovis is indeed currently present in some Australian dairy herds and is causing serious disease in some of these herds,4 but that relatively few Australian dairy herds are currently infected. We base this conclusion on research studies conducted by some of us in 2012.5 In one study, 238 dairy herds were selected randomly from all herds supplying a major Australian dairy processor and one bulk vat milk sample from each herd was tested using an M. bovis polymerase chain reaction (PCR) assay (Pathoproof™, Dairy Technical Services Ltd, VIC, Australia). Only one herd (0.4%) tested positive. The herd-level prevalence was estimated as 0.9% (95% probability interval 0.1–3.7%), and the diagnostic sensitivity (the proportion of herds with M. bovis present in the cows milked into the vat that test positive) of this PCR was estimated as 76% (95% probability interval 34–98%). We also assessed PCR results after serial dilution of milk from three PCR-positive cows. All samples remained test positive after dilutions up to 1 in 1000, suggesting that vat milk may test positive even when relatively few quarters are infected. M. bovis commonly causes sub-clinical udder infections1,6 but, at any particular time, some cows with M. bovis udder infections are likely to have clinical mastitis and be withheld from the bulk vat and so not be detectable in bulk vat milk. In further work, using the same PCR, we tested 55 quarter milk samples from cows from 17 south-eastern Australian dairy herds with clinical mastitis that had yielded no pathogens on conventional culture. None of these 55 sampled tested positive for M. bovis. Australian dairy veterinary practitioners report that they rarely observe clinical signs in cattle that are suggestive of disease due to M. bovis. Given that M. bovis can cause serious clinical disease that is unresponsive to most treatments, and that some clinical signs due to M. bovis are only rarely caused by other factors,7 this provides

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further evidence that M. bovis is currently uncommon in Australian dairy herds. The earlier conclusion that the prevalence M. bovis in dairy cattle in North Queensland and Victoria was high2 was based on results of a PCR assay described in a 1997 paper.8 Analytical sensitivity and analytical specificity of this PCR were also described. In this context, analytical sensitivity describes the lowest concentration of organisms that can be detected and analytical specificity describes the ability of the assay to react only to DNA from M. bovis. However, diagnostic sensitivity (the proportion of infected subjects that test positive) and diagnostic specificity (the proportion of uninfected subjects that test negative) were not reported. While these can be affected, in part, by analytical sensitivity and specificity, they are distinct concepts. In subsequent work, in addition to amplifying DNA from M. bovis, this PCR assay also amplified other DNA fragments.9 This highlights the importance of assessing diagnostic sensitivity and specificity of assays along with analytical sensitivity and specificity. For example, this was done recently for an ELISA for foot and mouth disease.10 Diagnostic sensitivity and specificity can be estimated using ‘gold standard’ samples from known infected and known uninfected populations. Latent class models offer an additional or alternative approach that does not require gold standard samples.11,12

References 1. Fox LK. Mycoplasma mastitis; causes, transmission, and control. Vet Clin North Am Food Anim 2012;28:225–237. 2. Ghadersohi A, Hirst RG, Forbes-Faulkener J et al. Preliminary studies on the prevalence of Mycoplasma bovis mastitis in dairy cattle in Australia. Vet Microbiol 1999;65:185–194. 3. Horwood P, Schibrowski M, Fowler E et al. Is Mycoplasma bovis a missing component of the bovine respiratory disease complex in Australia? Aust Vet J 2014;92:185–191. 4. House JK, Sheehy P, Bosward K, Gunn A. Mycoplasma: a re-emerging pathogen. 2011. Countdown Symposium 2011, Dairy Australia, Melbourne, Australia, 23–28. http://www.primarylogic.com.au/wp-content/uploads/2013/01/Mastitis -symposium-2011-text-FOR-WEB.pdf

© 2014 Australian Veterinary Association

EDITORIAL 12. Toft N, Jørgensen E, Højsgaard S. Diagnosing diagnostic tests: evaluating the assumptions underlying the estimation of sensitivity and specificity in the absence of a gold standard. Prev Vet Med 2005;68:19–33.

J Morton Jemora Pty Ltd, Geelong, Victoria, Australia

J Malmo Maffra Veterinary Centre, Maffra, Victoria, Australia

J House

EDITORIAL

5. Penry J, Malmo J, Mein G et al. Molecular testing of milk: interpretation and application in Australian dairy herds. IN: Proceedings of the 53rd Annual Meeting of National Mastitis Council, Fort Worth, Texas, USA, 2014;133–146. 6. Jasper DE. The role of Mycoplasma in bovine mastitis. J Am Vet Med Assoc 1982;181:158–162. 7. Maunsell FP, Woolums AR, Francoz D et al. Mycoplasma bovis infections in cattle. J Vet Intern Med 2011;25:772–783. 8. Ghadersohi A, Coelen RJ, Hirst RG. Development of a specific DNA probe and PCR for the detection of Mycoplasma bovis. Vet Microbiol 1997;56: 87–98. 9. Mansell PD, Browning GF. Preliminary investigations into the prevalence and importance of Mycoplasma bovis to the Australian dairy industry. Report on DRDC Project (UM078). University of Melbourne, Werribee, Victoria, Australia, 1999. Report available from Dairy Australia, Melbourne, Australia. 10. Colling A, Morrissy C, Barr J et al. Development and validation of a 3ABC antibody ELISA in Australia for foot and mouth disease. Aust Vet J 2014;92:192– 199. 11. Enøe C, Georgiadis MP, Johnson WO. Estimation of sensitivity and specificity of diagnostic tests and disease prevalence when the true disease status is unknown. Prev Vet Med 2000;45:61–81.

University of Sydney, Camden, NSW, Australia

G Mein Werribee South, Victoria, Australia

M Izzo The Vet Group, Timboon, Victoria, Australia

J Penry Dairy Science Department, University of Wisconsin, Madison, WI, USA

doi: 10.1111/avj.12243

OBITUARY

Sandra Joan Duncan 1952–2013

S

andra Joan Duncan was born in 1952. She had one younger brother and she spent her early years in Mentone where she developed her love of animals. Sandra attended The University of Melbourne where she completed her degree in veterinary science in 1974. She was one of a group of 39 boys and 11 girls. Sandra was a dedicated student determined to do well, graduating with honours. After graduation, Sandra worked as a small animal clinician at the University Clinic at Werribee where she remained until 1977. During this period she tutored fourth and fifth year students. She also met Gordon Duncan and 6 months after he graduated, in 1977, they travelled overseas, working in the UK in small animal practice. After two very cold English winters they returned to Melbourne in 1978, married in 1979 and in 1980 Sandra’s daughter Clare was born, followed by Ruth in 1981. Sandra and Gordon moved to their 20-acre property at Tooradin in 1983 and in 1984, her son Bruce arrived. Sandra took a step back from her career to be a full-time mother but as her children grew, she started to focus once again on her professional life. Animal welfare had always been an important interest for Sandra. In 2000, she accepted a casual teaching role at Box Hill Institute teaching the Animal Technicians who cared for animals used in research. She completed a Certificate IV in Training and Assessment and the Diploma of VET Practice. Teaching in this field gave her an opportunity to have some real influence on how animals used in research should be treated. Sandra was renowned for her high calibre teach-

© 2014 Australian Veterinary Association

ing and admired for her professionalism and excellence in delivering current best practice to her students. Sandra became a category A member of the Box Hill Institute Animal Ethics Committee (AEC) bringing her veterinary and teaching skills to bear on how animals should be used in the teaching environment and ensuring that all animal use for teaching at the Institute met the required legislative, welfare and ethical standards. She truly embraced this area of the veterinary profession, attending many conferences to ensure that she remained at the forefront of laboratory animal medicine, management and welfare. In 2010, Sandra accepted a part-time role as Animal Welfare Officer (AWO) at the Austin Hospital. Even in the week before she passed, she was emailing about SOPs that she needed to review before the next AEC meeting at the Austin. Sandra was well-respected for her professional approach with research staff and she was frequently sort after for animal welfare and surgical guidance. In 2012, she became a category A member of the RSPCA AEC. During the last three years of her life, Sandra battled ovarian cancer. She passed away quietly with her family beside her on 24 August 2013. Sandra will be missed by everyone she knew and by everyone with whom she worked. For such a ‘tiny’ woman, her shoes will be very hard to fill. Susan Maastricht doi: 10.1111/avj.12229

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Mycoplasma bovis in Australian dairy herds.

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