NEWS AND VIEWS
Investigation, detection, resolution TRIM SIZE: 210 X 297 mm
New Zealand Veterinary Journal
Volume 68 | Number 5 | September 2020 | ISSN 0048–0169
Volume 68 Number 5 September 2020
In this issue ISSN 0048-0169
• Detection of M. bovis in NZ calves by swabbing palatine tonsillar crypts • Poultry farm biosecurity in NZ • Association of yearling weight and milk production in dairy heifers • Acute and chronic digital lameness in horses: outcomes after MRI • Intrathecal procaine and xylazine for surgical anaesthesia in calves • Association of BCS change before parturition with milk yield in Argentinian dairy cows • Comparison of topical treatments for healing of disbudding wounds in calves
13-07-2020 11:12:05
Sarah Fowler, EditorIn-Chief of the NZVJ, reveals highlights of the September issue. AS REPRESENTED BY our cover image, there is a strong bovine theme running through the September issue of the New Zealand Veterinary Journal (NZVJ). For readers active in the cattle business we have articles reporting on the association between yearling weight and milk production in dairy heifers, a comparison of treatments for thermocautery disbudding wounds in calves, and the use of intrathecal procaine with xylazine for anaesthesia of calves undergoing umbilical surgery. For those not into cows, there are articles on disease risk and biosecurity on poultry farms in New Zealand and a comparison of outcomes for horses whose digital lameness was diagnosed with the help of magnetic resonance imaging while they were still acutely lame or once the lameness had become chronic.
16 – VetScript September 2020
Also included in this issue is the first report to be published in the NZVJ stemming from the recent outbreak of Mycoplasma bovis in New Zealand cattle. A clinical communication by Kelly Buckle and colleagues describes the first use of swabs from the mucosa of the palatine tonsillar crypt for the detection of M. bovis DNA. Kelly, a veterinary pathologist and incursion investigator with the Ministry for Primary Industries (MPI), reports that in 2017 (when MPI first detected M. bovis in New Zealand cattle) there were limited tools for detecting infection in cattle that were not showing clinical signs. “Worldwide there is poor understanding of anatomical sites for detection of M. bovis, particularly in non-milking animals,” she states. To fill this information gap, a small pilot project was initiated to determine the best sites to sample healthy but potentially infected cattle to detect the presence of M. bovis DNA by polymerase chain reaction (PCR). Kelly, along with colleagues from MPI and Massey University, focused on the palatine tonsils, as M. bovis had previously been cultured from this location in experimentally infected calves, and, fortuitously, the palatine tonsils are easily visible during the slaughter process in New Zealand, once the head has been removed and hung for inspection. To test the theory that the tonsil would be a useful site for detecting M. bovis DNA, Kelly took samples from the first lot of cattle slaughtered as part of the M. bovis eradication programme, which were clinically well calves that came from an infected herd. Once the calves had been slaughtered, paired mucosal samples were taken from their tonsillar crypts and the mainstem bronchi. Subsequent tests of these samples using real-time PCR showed that 93% of the calves were positive for M. bovis DNA, and that detection was seven times more sensitive when the palatine tonsils were swabbed than when swabs were taken from the mainstem bronchi.
“IF YOU THINK OF IT A BIT LIKE THOSE COVID-19 TESTS EVERYONE KNOWS ABOUT, WE BASICALLY INVENTED A COVIDLIKE TEST FOR M. BOVIS IN CATTLE.”
These results contributed to the development of the surveillance tools that have since been used in MPI’s ongoing efforts to control and eradicate this pathogen. What’s more, and given that this novel detection site has proven so useful in the New Zealand outbreak, the test is also likely to be used in M. bovis control efforts overseas. Kelly explains, “If you think of it a bit like those COVID-19 tests everyone knows about, we basically invented a COVIDlike test for M. bovis in cattle.” Kelly also hopes that sharing this tool will allow biosecurity-conscious farmers around the world to begin testing cattle entering their farms. She notes that in addition to the article’s authors, a large number of people helped to accomplish this work, including those involved in the 2017 M. bovis response, MPI Verification Services and the abattoir managers. We will await with interest more reports on studies relating to the New Zealand M. bovis outbreak.
Members of the NZVA can access any articles published in the NZVJ by logging in to SciQuest (www.sciquest.org.nz). More information about the NZVJ can be found at www.vetjournal.org.nz. You can contact the editors at nzvj@vets.org.nz.
