Summer mastitis, often known as “August Bag” is a common problem in the UK in grazing animals. As the name suggests, it is usually in the summer months from June to September. As the numbers of flies increases, the risk also increases as the disease is spread between animals by biting flies. Unsurprisingly cases will often be found in fields with ponds or trees, which provide a good environment for the flies. It is an acute disease of the non-lactating udder and is common in both dairy and beef herds. Dry cows and heifers are particularly susceptible, but calves can also be affected. The primary causative agent is Trueperella pyogenes, but mixed infections can also occur.

Clinical Signs of Summer Mastitis

Affected animals will suffer acutely with a hard, hot and painfully swollen udder. They will often be separated away from the rest of the group, will be anorexic and have a significantly raised temperature. They can also show hindlimb lameness, especially on the affected side. Pus-like secretions, which may be tinged with blood, can be seen discharging from the affected teat. Cows can occasionally die from septicaemia as a consequence of summer mastitis.

Whilst the typical presentation is relatively simple, it is also worth considering heifers that calve down with a ‘blind quarter’ may have previously suffered from summer mastitis, which went undetected.

Treatment of Summer Mastitis

Prompt treatment is essential in order to save the cow. Unfortunately, affected quarters will very rarely recover. Attention should be focussed on saving as much as possible – namely a pregnancy, a viable calf and as much milk production as possible from the remaining quarters. Regular stripping out of the affected quarter is essential to remove as much infected material and pus from the udder as possible. This discharge can be infective so should be collected and disposed of safely, not purely left on the ground.

Treatment should comprise of anti-inflammatories and antibiotics. Anti-inflammatories are necessary to reduce swelling and reduce the cow’s temperature, thus alleviating discomfort. Antibiotics are equally important, to counteract the infection. Trueperella is sensitive to penicillin-based drugs, and affected cows should be given injectable systemic antibiotics, as well as intra-mammary antibiotics if possible.

Control and Prevention of Summer Mastitis

Prevention of the disease is important due to the constant threat that is posed on grazing herds and the low chance of recovery of infected animals. Protection of the udder is important, either by way of teat sealants and/or long acting dry cow antibiotics. If using dry cow tubes, protection will often be obtained for 3 – 4 weeks, so repeated treatments though the dry period may be necessary. If dry cow tubes are replaced, ensure a strict hygiene protocol is followed otherwise a severe mastitis may follow. If antibiotics are used, withdrawal periods need to be considered. Long-acting, pour-on fly repellents can also be used to prevent fly contact with cows.

Alternatively, susceptible cows can be removed from high risk pastures to reduce the chances of infection. Equally, cull cows should be slaughtered before the summer months to prevent any risk of losing the value of the animals. If these control measures still struggle to control the disease, moving the herd’s calving to low risk periods may be necessary.

Summer mastitis will continue to be a problem on certain farms for many years so control measures are well worthwhile in the long run.