Milk testing scheme shows main mastitis bacteria

Herds struggling with persistent high cell counts and repeat cases of mastitis should test milk samples to see whether Strep. uberis is the cause, as this notoriously hard-to-shift pathogen is accounting for an increasing proportion of infections.

Latest results from Intervet's Cephaguard® bacteriology scheme (subsided milk testing scheme, available from your vet) confirms this bug has been the biggest problem bug on farms this year, responsible for 23% of clinical cases. It has also caused 18% of high somatic cell counts (SCCs). Vying for second place with Staph. aureus, is E. coli (see chart).

The incidence of Strep. uberis mastitis won't have been helped by prolonged periods of housing during the summer floods. And those who took advantage of a dry autumn to extend the grazing season could simply find themselves delaying the winter onslaught of mastitis, warns Intervet's large animal veterinary adviser Rosemary Booth.

"Winter housing inevitably brings a higher environmental exposure, particularly for loose housed herds. This is why doing some bacteriology testing is so important to know what you are dealing with," she says.

"Once indoors, the risk of toxic E. coli mastitis also increases as some herds start winter calving, and contamination builds up in bedding. It is important to test milk samples regularly because mastitis-causing bacteria change and behave in different ways.

"Strep. uberis frequently causes persistent infections which are often resilient to treatment and can create problems with Bactoscans as well. Unfortunately, its ability to behave as both an environmental and contagious bacteria makes it harder to control. Farmers need to discuss a control plan with their vet and have both environmental and contagious bacteria control policies in place."

Although Strep. uberis can be treated with most antibiotics, Miss Booth says there is no quick fix and the problem is preventing recurring infections. Often a cow is treated, recovers and just when the milk is being put back in the tank, mastitis returns. "Early treatment and an aggressive treatment plan developed together with your vet are sometimes needed," she says.

However, Miss Booth says treating cases of E. coli is made easier by combination therapy using tubes of Cephaguard LC together with injectable Cephaguard 2.5%. "Because it is licensed for combination therapy, there is no extended milk withdrawal period."