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Mastitis causative pathogens determine nature of infection in cows 

Three quarters of current mastitis cases are the result of environmental infections, compared to just 10% in 1967, according to vet Andrew Bradley. 

Speaking at a recent Boehringer Ingelheim Milk Quality Academy meeting, Dr Bradley said this change in the cause of mastitis cases highlighted the need for more care and attention to be paid to reducing the chances of infection being picked up from bedding or other potential environmental sources.

Writing about the meeting, vet Catherine Carty, Herd Health Resident at UCD Veterinary Hospital Dublin, reports that Dr Bradley still maintains that the highest risk time for new infections is the transition period. Added to this, it is often the case that dry cow and transition cow housing isn’t given the same attention as that of the milking herd. Transition cow accommodation, whether straw yards or cubicles, should be kept as clean and as fresh as that of the milking herd to minimise the chances of environmental pathogens causing mastitis. 

There is a small peak of infections picked up in the early dry period, but good dry cow management can go a long way to reducing the chances of these infections occurring, Dr Bradley told the meeting which aimed to collect together some of the latest thinkings and findings for vets in practice. 

Ms Carty goes on to report that, as expected, the risk factors for new mastitis infections picked up in the dry period are quite farm specific; a study of 522 cows across six countries, all given antibiotic dry cow therapies, showed a large variation in the number of quarters acquiring new infections in the dry period. 

Meanwhile, Dutch vet and recognised mastitis expert Dr Ynte Schukken said the rate of inflammation response seen in mastitis cases varies depending on the causative pathogen. The inflammatory response to E. coli takes just a matter of hours, whereas for both Staph. aureus and Strep. uberis the response can be from one to five days.  

The rate of inflammatory response to E. coli influences the speed and effectiveness of cure, with net energy balance a big predictor for a slow response. In many cases a slow inflammatory response can be a precursor to a persistent infection, with both bug and cow factors influencing whether or not an infection persists.

Dr Schukken went on to tell the group that where Staph. aureus is the causative pathogen, it can work in a number of ways. In some herds, there may be a single strain affecting lots of cows, meaning it is a contagious infection. However, in other herds many different strains may be present. This means there is no or little cow to cow spread and, therefore, the source of the infection is the environment.

Dr Schukken’s concluding point was that looking at the rate of new infections and the duration of infections can be important in assessing the pattern of infection.

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