Management and treatment of summer cattle mastitis

Summer mastitis is defined as intramammary infection of the non-lactating udder, usually in warmer months in temperate countries, such as the UK.

It is characterised by the production of abscesses within the gland – often with the production of large volumes of odoriferous purulent material and varying degrees of toxaemia. The disease is generally regarded as having a complex aetiology, involving a variety of bacteria.

The main agent is Trueperella (formerly Arcanobacterium) pyogenes, which has a widespread presence in the respiratory and genital tract of cattle. However, severe glandular damage is not generally expressed without the presence of such organisms as Streptococcus dysgalactiae, Peptococcus indolicus and Fusobacterium necrophorum.

Transmission of infection is widely regarded as being due to the vector activity of the sheep head fly, Hydrotaea irritans, which is a commonly observed nuisance parasite around livestock in the summer months.

Other factors commonly implicated are trauma and irritation of the udder, which may cause licking and disruption of the keratin seal normally present in the teats of non-lactating cattle. This may not be restricted to females – the author has seen an isolated case in a seven-day-old bull calf.

The presence of cattle with a predilection for sucking the teats of others has also been observed as a significant factor in outbreaks of dry period mastitis.

During the acute phase of the disease, a cow will typically show an enlarged gland, with altered gait due to pain and swelling.

A foul-smelling secretion may be expressible from the teat, containing purulent material. The affected animal may be depressed and, in severe cases, death may ensue due to the effects of bacterial endotoxin. Recovered animals invariably lose the functional use of the quarter. Severely affected animals may show a postrecovery slough of the gangrenous gland.

In less severe cases, the first indication of a problem may be the gland is found to be non-functional post-calving. A typical observation of such cases shows the teat to have a hard central core of fibrous scar tissue as a result of the necrotising effect of endotoxins.

In a herd with a reported high incidence of “blind quarters” in heifers, it is worth investigating pre-lactating heifer management for indicators of poor protection from summer mastitis.

Treatment

As stated, the affected gland usually does not recover functionality. Treatment is generally a salvage exercise to mitigate the toxic effects of the infection. A successful outcome would generally be the animal survives and is fit to be presented for slaughter in due course.

Antibiotics are usually administered; injectable penicillins are indicated (Zastempowska and Lassa, 2012; Hirvonen et al, 1994). Intramammary preparations are generally regarded as ineffective. NSAIDs, such as meloxicam, should be administered, together with supportive oral fluid therapy, to minimise the systemic effects of bacterial endotoxins.

Amputation of the affected teat is sometimes advocated by veterinarians, with the aim of effecting drainage of the purulent secretion. The author is not in favour of this technique – firstly, as the secretion is generally very thick and does not usually drain easily and, secondly, the uncontrolled leakage of material could potentially act as a source of new infections for other animals in the group. Euthanasia of severely affected animals may be indicated where disease has become life-threatening and welfare is compromised.

Prevention

Management of dry cows and prepartum heifers plays a pivotal role in the reduction of summer mastitis incidence. Some farms may have a particularly high incidence – most likely due to ideal conditions for flies to be a severe nuisance.

Avoiding particular problem pastures, especially sheltered areas near woodland, can be very useful. Exposed areas, particularly on windy ridges, generally have lower fly worry problems.

Good pasture management also has a role to play. Often, far-off dry cows and grazing heifers are put in neglected fields. Exuberant thistle and nettle growth will cause scratching and udder irritation, which may result in excessive licking behaviour with disruption of the keratin seal as discussed beforehand. Zealous use of pasture toppers and herbicide sprays should be encouraged in this scenario.

Pour-on fly preparations, generally those containing permethrin, are recommended for vulnerable groups. During times of heavy fly challenge – usually July to August – reapplication of insecticide may be indicated, typically on a four-weekly basis.

Pour-on preparations have the disadvantage the normal diffusion of active ingredient in sebum on the skin may not give a good concentration of insecticide on teats, where sebaceous glands are sparser than on hairy skin. Anecdotally, off-label, direct application of such products to the udder may be of use, where fly challenge is severe.

More traditional topical products, such as Stockholm tar, may be helpful in deterring flies, but need weekly application to be of use. External teat sealing preparations, supplied as a dip that dries into a flexible coating, are, in the author’s experience, of limited use unless repeated frequently.

Intramammary products for summer mastitis prevention are very useful – dry cow preparations were being cited as useful in the 1950s to decrease incidence of summer mastitis (Pearson, 1950).

Despite the apparent physical challenge, with the correct handling equipment and sufficient staff to restrain animals, it is possible to administer dry cow antibiotics to prepartum heifers, which may have a significant reduction in summer mastitis in such groups (Berry, 1998).

Little difference appears between the activity of cloxacillin or cephalosporins as preventive treatments (Johnson et al, 2016).

However, with the pressure to decrease antibiotic use – and with prevention achievable via non-antibiotic measures – it is difficult to justify this use. Concerns also exist that the duration of activity is shorter than the duration of the fly breeding period – particularly in more temperate areas of the country.

Internal teat sealants have been proven to be beneficial in the reduction of infections in the non-lactating udder, which is also true of the summer mastitis complex.

Prevention does, of course, depend on the formation of a proper plug in the infused teat. Regular discussion with farm staff and review of infusion technique should be an important part of a farm health plan.

Animals should be handled gently after infusion to allow the sealant to form the desired plug in the distal teat. The author has encountered issues where cows are dried off and then “run down the road”. The sealant may occasionally be seen distributed over cows’ lower legs after the subsequent gallop.

Internal teat sealants in prepartum heifers has been shown to be advantageous in reducing intramammary infection (Gilbert, 2014). This application could be encouraged where “blind quarters” at calving, due to summer mastitis, are of significance, despite the natural scepticism and reluctance of farm staff.

Conclusion

The summer mastitis complex continues to be a cause of economic loss in dairy and beef cattle. Reduction of incidence of infection may involve both farm management and pharmaceutical intervention.