Summer Mastitis

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Summer mastitis is a separate syndrome to the usual mastitis affecting cattle. As the name suggests, it is predominantly seen during the summer period which is thought to be related to the seasonal presence of the sheep head fly (Hydrotea irritans) that may be involved in disease transmission. It is usually seen in dry cows and heifers with dry cow therapy thought to offer some protection against disease. The disease is characterised by the formation of a large abscess in the affected quarter that may burst through the skin.

No single causal pathogen appears to be responsible for the condition with a variety of organisms being isolated from clinical cases. These include Arcanobacter pyogenes, Streptococcus dysgalactiae , Peptococcus indolicus, Bacteroides melaninogenicus and Fusobacterium necrophorum. In the UK, A. Pyogenes is the most commonly isolated seen in 85% of cases (Hillerton, 1988).

Clinical Signs

The clinical signs seen include a very hard, hot, painful and swollen quarter and teat. Thick, foul smelling pus may or may not be drawn out when stripping is attempted. Systemic signs may also be seen with a raised body temperature, depression and inappetence. Death may occur particularly if treatment is delayed. If in late gestation, abortion is a possibility. If the cow survives, the affected quarter is very unlikely to return to normal function.

Although rare, the condition can affect males. These animals may present with suspected hind limb lameness.


Treatment should include parenteral antibiotics, NSAIDs and regular stripping of the affected quarter which may be facilitated by prior intramuscular injection of oxytocin. Penicillin based antibiotics are usually used due to their effectiveness against the most commonly isolated pathogen (A. pyogenes). Stripping is preferable to using intramammary antibiotic tubes. Occasionally, it is not possible to strip the affected quarter due to considerable discomfort of the cow or a blocked teat canal/cistern. In these cases, a teat amputation or incision into the teat cistern may be necessary to establish drainage.


Prevention is through dry cow therapy (antibiotics and internal teat sealants) and fly control. Hydrotea irritans tends to favour wooded areas with certain pastures seemingly at higher risk. Avoidance of these pastures is therefore recommended during the summer period.

References and Further Reading

Biggs, A., 2009. Mastitis in Cattle, 1st Edition. The Crowood Press Ltd.

Blowey, R., Edmondson, P., 2010. Mastitis Control in Dairy Herds, 2nd Edition. CABI International.

Hillerton, J.E., 1988. Summer Mastitis – the current position. In Practice 10:131-137.