Summer mastitis is a serious and often underestimated condition affecting dry cows, heifers, and occasionally calves, typically during the warmer months (June to September). It is most commonly seen in humid, fly-prone environments, particularly in wooded or shaded pastures. Summer mastitis is a mixed bacterial infection, with Trueperella pyogenes being the primary pathogen. Other organisms such as Streptococcus dysgalactiae and anaerobes may also be involved. The disease is often transmitted by flies, particularly the head fly (Hydrotaea irritans), which acts as a vector, depositing bacteria at the teat end.
Key Risk Factors
- Warm, wet weather
- Presence of flies and poor fly control
- Injury or open teat canals, especially in dry cows
- Grazing in wooded or overgrown fields
- Lack of teat sealant or dry cow therapy
Prevention Strategies
- Fly control: Use pour-ons, sprays, or insecticidal ear tags.
- Teat sealants: Consider internal sealants for dry cows and heifers.
- Pasture management: Avoid high-risk grazing areas during peak fly activity.
- Monitor stock daily for early signs of udder changes or illness.
Clinical Signs
- Swollen, hot, and painful udder (usually one quarter)
- Thick, foul-smelling secretion
- High temperature, lethargy, and loss of appetite
- Lameness (due to systemic illness)
- In severe cases, abortion or death
- Early intervention is critical to reduce permanent damage or systemic illness.
