Sheep Summer Mastitis: Prevention in Dry Ewes

Summer mastitis affects dry ewes and heifers during summer months, causing severe udder damage and systemic illness. Prevention is far preferable to treatment.

Key Facts

Summer mastitis is caused primarily by Trueperella pyogenes, spread by head flies (Hydrotaea irritans)
It affects dry ewes and maiden heifers — animals not currently lactating and therefore often unmonitored
Infection causes severe acute mastitis leading to gangrenous destruction of the affected quarter
Systemic toxemia from the infection causes fever, depression, and rapid physical deterioration
Affected quarters are permanently lost — ewes with gangrenous mastitis must be culled if they survive
Summer mastitis is preventable through fly control and dry cow therapy at drying off

Welfare Considerations

Summer mastitis causes extreme suffering — acute gangrenous mastitis is one of the most painful conditions in cattle and sheep, with systemic toxemia causing rapid deterioration. Animals that survive often do so at the cost of permanent udder loss. The welfare harm is preventable through consistent fly control during the summer risk period and monitoring of dry ewes for early signs of udder heat, swelling, or abnormal secretion. High-welfare flocks check dry ewes regularly rather than leaving them unmonitored through summer, and apply preventive fly repellent treatments to udder skin.

What You Can Do

Apply long-acting fly repellent to the udder and belly of dry ewes at the start of summer fly season
Inspect dry ewes at least weekly for signs of udder swelling, heat, or behavioral changes suggesting mastitis
Use dry ewe therapy at drying off to reduce intramammary infection risk through summer
Treat suspected summer mastitis cases immediately — delay significantly worsens outcomes