With the days getting warmer and the shift to t-shirt weather underway, it seems a fitting time to talk about summer mastitis. Summer mastitis is defined as an intramammary infection of the non-lactating udder seen in warmer months; basically, it is a problem for your dry cows and your maiden heifers.

The main bacteria that cause summer mastitis is Trueperella pyogenes, but Streptococcus dysgalactiae, Peptococcus indolicus and Fusobacterium necrophorum are often also involved in the disease process and can worsen the damage to the udder.

The head fly (Hydrotaea irritans) is the main vector of this disease, as they carry the bacteria between cows. However, teat damage through irritation or trauma, or that one pesky cow in the herd that goes round sucking teats, can also cause outbreaks of this costly disease.

Summer mastitis is usually quite acute and can lead to death due to the toxic nature of the disease if it is not identified and treated rapidly. Treatment is aimed at saving the cow and it is unlikely that the affected quarter will be saved. Conversely, sometimes the disease goes unnoticed in heifers and leads to them calving in with blind quarters. Outbreaks of the disease can be seen, which is incredibly frustrating and costly. As with every disease prevention is better than the cure so…

• Swollen teats, often with flies feeding around them
• Separation from the rest of the group, often lame, dull, anorexic and a significantly raised temperature
• Udder swelling shows the progression of the disease. Udder is swollen and hard with foul-smelling yellow secretions
• Without treatment, abortion or death can follow

Here are our top three tips for reducing summer mastitis:

Reducing nuisance fly numbers will reduce the risk of them carrying the bacteria from udder to udder. There are numerous ways to reduce fly numbers.
This includes chemical control (pour ons, sprays, ear tags) or biological control using friendly flies (parasitic wasps – more info can be found in our March newsletter or by chatting to us)

Flies love to congregate in certain areas of your fields, including under trees and along the hedgerows; places your cows also love to go for some shade when it gets hot! Additional risks come from fields with thistle growth or poached areas. Try to avoid problem fields, or at least avoid overstocking them.

Teat sealant provides a physical barrier to prevent bacteria on the teat from travelling up the teat canal and causing the infection in the first place. Applying sealant to maiden heifers also has shown to be protective. If this is not something you already do, please speak to your vet about exploring this idea, as it is not without risk.

There can be less typical cases that occur outside of the main fly season in the milking herd. It’s possible that some heifers will have what we call a “blind” quarter which is highly likely to be a result of summer mastitis – but with less obvious symptoms.

• Check teats regularly for teat lesions. If any are identified, treat and keep those animals separate from the rest of the group.
• Teat sealants can also help reduce the chance of this type of infection.
• Flies contribute to the spread of the disease, so it’s important to control flies where possible – especially around the udder.