World class speakers address mastitis meetings

Delegates attending Intervet’s recent meetings “Changing dynamics of mastitis – effective detection and therapy” listened intently as speakers Dr Ruth Zadoks DVM PHD MSc from Cornell University and Andrew Biggs BVSc MRCVS BCVA President and partner at the Vale Veterinary Group in Tiverton, Devon presented some of the most recent findings and opinions on mastitis and mastitis therapy.

Ruth Zadoks works for Quality Milk Production Services at Cornell University, NY where she heads up the molecular lab; her talk was entitled “The pathogenesis and epidemiology of contagious & environmental mastitis with particular reference to Strep. uberis”. 

Highlighting that Strep. uberis can be an environmental or contagious pathogen, she referred to strain typing work around the world which has done much to improve our understanding of how the bacteria can be transmitted.  

“In some countries, such as New Zealand and the UK, work has shown that the bacteria come from many different sources.  In New Zealand, for example, climatic conditions, farm management, and cattle movement patterns work together to create high bacterial loads and mastitis incidence when the cows are most vulnerable - at the mass transition from dry period to lactation,” she remarked.  

“Meanwhile, research in the USA has shown that both environmental sources and other vectors can harbour S. uberis, including bedding, soil, plant matter, water, and insects.  Faecal shedding of S. uberis by dairy cattle contributes to presence of S. uberis in the environment and certain environments, such as straw, allow S. uberis populations to increase massively,” she said.

DNA sequencing work has also suggested that certain strains are more capable of affecting the host more seriously than others and some of these strains cause infections that are more chronic than the average infection.  And although this has been established, she pointed out that we are yet to understand the mechanism behind this.

Andrew Biggs’ talk looked at subclinical mastitis and bacterial profiling.  He began by examining the approaches to mastitis and cell count measuring, discussing the role for individual cow cell counts (ICCCs), bulk milk cell counts, bacteriological testing and NMR’s InterHerd. By looking at the type of data that is typically collected, he demonstrated the vast array of information most farms and vets have about mastitis within individual herds and how under-utilised this often is.

“At a herd level, individual cow cell counts allow us to monitor changes during a lactation and between lactations (during the dry period) which, in turn, can be used to imply new infection and recovery rates for the herd in both lactation and the dry period,” he said.  

“Using whole herd cell count data to indicate trends, but individual cow information to look more closely at the type and origin of infection, mastitis across the herd can be managed,” he said.  “Identifying chronic infections, the bacteria involved and how that cow has performed in the dry period should provide sufficient information for the optimum antibiotic therapy to be planned.”

Mr Biggs also went into some detail about the Intervet Cephaguard diagnostic scheme with which the Vale lab has been involved.  

Data from the 36 herds sampled to-date showed that, in the samples from clinical cases, S. uberis was implicated in 28% of cases, coliforms in 15% and Staph. aureus in 8%.  In the subclincial cases, S. uberis, Staph. aureus and coagulase –ve staphs were most commonly found.  

“As Dr Zadoks has already shown, S  uberis is capable of being an environmental or contagious pathogen, and can cause clinical mastitis but is equally at home causing high cell count subclinical cases,” he said.  

Intervet’s subsidised Cephaguard diagnostic scheme will operate until the end of October 2006 and is run via veterinary practices.  Anyone interested in participating should contact their vet for more information.

Article first published 07/06/06