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Summer Mastitis

The incidence of Summer Mastitis tends to vary from year to year. With it being a particular problem in many herds this year.

It occurs mainly in the June to September period affecting dry cows and in-calf heifers when fly numbers are highest. In reality, however it can occur at any time of year.


The primary causal organism is Actinomyces pyogenes in conjunction with other organisms that either enhance its activity or allow infection to develop. It is a very severe form of mastitis causing udder damage, high temperature and toxaemia. Infected quarters are generally lost and treatment is focussed at saving the animal and preventing pregnancy loss. The infected quarter becomes swollen and hard. When the quarter is drawn the strippings will be foul smelling. The extract may appear clear or with soft to cheesy type curds and as damage progresses there may be traces of blood.


Where possible prevention is the preferred policy. There are several area's of prevention to consider.

  1. Antibiotics (Dry Cow tubes) / Teat Seals
  2. Fly Control
  3. Grazing Conditions
  4. Teat Damage
  5. Isolation of infected Animals

1) Antibiotics / Teat Seals
Dry cow tubes have been shown to reduce the level of disease by up to 80% but their use has several implications. Firstly, tubes may not be effective for the entire dry cow period and if a second tube has to be given after 1 month you run the risk of breaking the teat seal and introducing infection. It is crucial that all tubing is done under clean conditions. With suckler cows or heifers, in particular, handling to insert dry cow tubes may be difficult. After drying off some farmers have used a teat seal to coat the tip of the teat to try and prevent infection.

2) Fly control
A number of pour-on products are available to control flies. They are based on synthetic pyrethroids such as permethrin and deltamethrin. It is recommended to apply these along the back of the animal but is probably no harm to direct some around the udder area as well. A number of these products will give cover for 4 weeks but in a year when the incidence of Summer mastitis is high, it should be applied every 2 weeks.

Ear tags containing Cypermethrin are also available for fly control. Other farms have been applying Stockholm tar on the udders of susceptible animals. Although it will deter flies it is messy and may need to be applied every 4 - 7 days.

3) Grazing Conditions
Where animals are let graze during the dry period may have a bearing on the level of flies. It is advisable to avoid fields that are well sheltered with a lot of tree cover.

Try and keep the fields topped to reduce tall weeds or old senecent seed heads, which can provide cover for flies or can aid in the spread of infection as animals walk around the area.

4) Teat damage
Animals with any teat soars should be housed. Soars will only attract flies and increase the likelihood of infection.

5) Isolation of Infected Animals
Animals showing signs of infection should be removed from the group and kept isolated. If the infected quarter is milked out, the strippings should be carefully disgarded because of the risk of spreading infection.

Products used for Fly & Lice Control (Cattle)

Product NameSourceMethod of ApplicationActive IngredientDose RateWithdrawal Rate (days)Pack Size 
Pour-on 0.75% w/v
10 ml 3 days Nil 250 ml 1 litre
Ectospec Bimeda
Pour-on 2.5% w/v
10 ml 10 days Nil 500 ml
Poron SP Novartis
Ireland Ltd.
Pour-on 4% w/v
1 ml per 10 kg bw
over 300 kg 40ml
3 days 6 hrs. 1, 2 & 31/2 ltr.
T.P. Whelehan
Son & Co. Ltd.
Pour-on 1.5% w/v
10 mls 14 days Nil 250 & 500 ml
Ridect Pfizer
Pour-on 4% w/v
1 ml per 10 kg bw
over 300 kg 40ml
3 days 6 hrs. 500 ml & 1 litre
Spot On
Schering Plough
Animal Health
Pour-on 1% w/v
10 mls 7 days Nil 250, 500 ml 1 litre
T.P. Whelehan
Son & Co. Ltd.
Ear tag 8.5% w/v
1 tag/animal Nil Nil Box of 10 tags