Staph aureus still a big cause of trouble

4 August 2000

Staph aureus still a big cause of trouble

STAPH aureus mastitis incidence has fallen dramatically since 1980, but it should not be ignored.

Julie Fitzpatrick of the University of Glasgow vet school said that in 1980 16% of clinical mastitis cases were due to Staph aureus. But a study in Devon this year indicates this has fallen to just 3%.

She believed the five-point plan for mastitis control had played an important role in this reduction. It encouraged close inspection of the udder and milk. "Post-milking disinfection is particularly successful in reducing pathogens transmitted during milking. Dry cow therapy treats and prevents Staph aureus built up during lactation and in the early dry period.

"But Staph aureus is underestimated: Some herds still have a major problem with it. And many herds cull cows with repeated clinical cases without vet advice – which can mean prevalence is underestimated.

"Staph aureus is sucessful because it is a subtle disease. It infects, persists, survives and transmits among cows and herds."

As well as producing cell-damaging toxins and being difficult to diagnose, it is also resistant to a large range of antibiotics. Bacteria may sit where antibiotics have trouble getting to it. "Once Staph aureus is established in a gland it is difficult to get rid of. The source is probably infected and older cows which have had increased exposure of the disease or brought in cows."

Prof Fitzpatrick believes future control of Staph aureus mastitis as it becomes less common will depend on improved detection in diseased animals, particularly in herds of increasing size.

She also advised that control on farms should focus on use of individual quarter cell counting, lab bacteriology, using California mastitis test kits, and segregating mastitis cows so they can be milked last. She added that segregated mastitis cows should not be kept with fresh calvers, as this increased risks of infection spreading.

While there is a Staph aureus vaccine licensed in the US, low incidence in the UK and EU meant it was unlikely to be marketed here. However, breeding for mastitis resistance could help reduce incidence, through selecting bulls proven to have low cell count daughters and using gene identification in future, she said. &#42


&#8226 Clinical infection reduced.

&#8226 Difficult to get rid of.

&#8226 Improved detection still important.

Some herds still have a big problem with Staph aureus mastitis, says Julie Fitzpatrick.

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