Summer Mastitis – Management and Prevention

Summer mastitis predominately occurs during the warm summer months,  but the term is used to describe the mastitis which occurs in dry cows and heifers at pasture. Summer Mastitis is a separate problem from the normal mastitis or somatic cell count challenge in dairy herds.

Summer mastitis is caused by a number of strains of bacteria and is linked specifically to the sheep headfly.  External routes of infection occur through the teat skin or teat canal, particularly if these are damaged. There is also the possibility of infection originating internally, with bacteria spreading from other parts of the body – particularly via the blood.

Once a quarter is infected, summer mastitis may spread between quarters – or even between animals. The initial symptoms are a swollen, painful teat or a quarter. This can be easily identified as flies will be attracted to the unpleasant smell of yellow secretions.

If left untreated, the bacterial toxins will damage the udder tissues to such an extent that the quarter could be lost. Further signs of the illness are swelling of the hind legs, separation from the herd, abortion and even death, so treatment must be prompt.

Treatment of Summer Mastitis should involve regular and repeated stripping of the affected quarter, to remove as much affected material as possible. It should be noted that the stripping material must be disposed of in a safe way to limit infection of other cows.

This must be followed by the use of antibiotics to combat infection, and anti-inflammatories to counter the swelling and reduce temperature. Antibiotics can reduce the disease by up to 80%.

It is important to isolate heifers and cows with Summer Mastitis to help prevent spread of the illness. Care should be taken to clean the pus after stripping, as the discharge will contain large numbers of bacteria which could lead to further infections as flies may spread the bacteria.

Summer mastitis can be avoided with a number of measures. Effective dry cow therapy as an aid to control can be a good starting point – through the use of a long-term intra-mammary antibiotics, teat end sealants and good hygiene measures at drying-off are also important.

In some circumstances, intra-mammary antibiotics may require re-administration during the dry period, although care should be taken with milk withdrawal periods. Also, minimise exposure to flies from early on in the fly season by the use of pour-on anti-parasitic treatments. Fly repellents such as Stockholm tar can be used.

Maintain good teat condition pre-drying off, ensure good dry cow nutrition and observe animals on a regular basis. Also avoid areas where flies are a particular problem, such as near rivers and woods.

As soon as conditions favour the fly population, there is a good case for treatment of dairy cows and heifers with a residual pour-on such as deltamethrin or alphacypermethrin. Although control measures of Summer Mastitis are expensive on time and materials, the savings are worthwhile.