Summer Mastitis in Cattle: A Painful Summer Disease

Summer mastitis is a severe, painful bacterial infection of the udder occurring in dry cows and heifers during summer, spread by flies. It causes irreversible teat damage and significant welfare impact without prompt treatment.

Key Facts

Summer mastitis is caused primarily by Trueperella pyogenes and Peptostreptococcus indolicus, often with other organisms
It typically affects non-lactating dairy cows and beef heifers in late pregnancy during warm summer months when flies are active
Head flies (Hydrotaea irritans) are the primary vector, spreading bacteria between animals through udder secretion feeding
Affected quarters become hot, swollen, and acutely painful; secretion becomes thick, foul-smelling, and purulent
Without prompt treatment, the infection destroys udder tissue — affected quarters are usually permanently non-functional
Systemic effects including fever, toxaemia, and reduced appetite indicate advanced infection with serious welfare implications
Prevention includes teat sealants for dry cows, fly control, and topical barrier treatments applied to teats during the dry period

Welfare Considerations

Summer mastitis causes severe, acute suffering. The udder infection involves intense inflammation with heat, swelling, and pain — animals show clear signs of distress including reluctance to move, kicking when touched near the udder, and reduced social interaction. The foul-smelling secretion and systemic toxaemia indicate aggressive bacterial invasion of deep udder tissue. Without early treatment, the infection progresses to abscess formation and irreversible tissue destruction within days. The welfare impact is compounded by the permanent loss of a quarter — affected cows must manage subsequent lactations with a non-functional quarter. The pain of summer mastitis in an untreated animal is severe and prolonged. Prevention through fly control and dry cow teat sealants is far more effective and welfare-positive than treatment after infection is established.

What You Can Do

Apply dry cow teat sealants to all non-lactating cows at dry-off to create a physical barrier against infection
Implement fly control programmes during summer — insecticide ear tags, pour-on treatments, and housing during peak fly activity
Inspect dry cows and heifers daily during summer for signs of udder swelling, heat, or abnormal gait
Seek veterinary treatment immediately if summer mastitis is suspected — delay worsens prognosis for quarter survival
Provide shade and fly-free areas for dry cows during hot weather to reduce fly burden
Work with your vet to develop a dry cow management and fly control programme tailored to your farm's specific risk factors