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Why Vaccination Could Help Reduce Mastitis In Flocks
Sheep farmers battling ongoing mastitis rates of 10% or above could benefit from a new vaccine, which has been shown to halve incidence and improve recovery rates.
Mastitis is one of the main causes of culling on farm. This, together with treatment costs and sub-optimal lamb growth rates due to reduced milk availability, makes it a costly problem. It is also a significant animal welfare issue.
The Vimco vaccine from Hipra was licensed for use in the UK last year. Since then a number of farms have begun vaccinating, with vets reporting a reduction in incidence of 50-90%.
Five tips to reduce mastitis riskMastitis is an inflammation of the ewe's udder and is usually caused by a bacterial infection. The main risk period for clinical mastitis is between the first week post-lambing and peak lactation (three to four weeks after lambing). To reduce the risk:
See also: Mastitis costs 3.84kg to weaning, Texel study shows
Often farmers will have management steps in place to limit mastitis but can still experience rates of 10% or above in flocks. It's these farmers that could consider using the vaccine, in discussions with a vet.
Vet Joe Henry from Black Sheep Farm Health in Northumberland says farmers should be targeting a 2-3% mastitis incidence across the whole flock and no more than 5% in gimmers, which tend to be more prone to infections.
Is the vaccine for me?At a cost of about £6 a ewe, Mr Henry says the vaccine is not cost-effective for every flock. "That's why it's only appropriate if you've got high rates of mastitis of over 10%," he says.
Vet Joe Henry © Crest Photography
Consequently, recording and understanding mastitis rates are a must before turning to the vaccine. This could also help identify if mastitis is higher in certain groups of animals, such as gimmers or ewes carrying triplets.
By understanding which animals are affected, it may then be appropriate to target the vaccine at these groups, rather than blanket-treating the whole flock.
Will Barker, of Castle Veterinary Surgeons, believes targeted use of the vaccine is particularly appropriate on commercial systems where broader use may not be economically viable.
He suggests it may be appropriate to use it across the whole flock when mastitis incidence is above 10% but target at-risk groups when incidence is slightly lower at 5-10%.
Mr Henry also stresses the importance of undertaking bacteriology to understand the mastitis causing pathogens on farm.
"The vaccine is only for Staph aureus. There are some cases where you get pasteurella and E coli or mixed infections, but Staph aureus is the main cause of mastitis in sheep," he explains. "If, when you investigate, it's not Staph aureus, the vaccine is not appropriate."
How it's working on farmMr Henry used the mastitis vaccine on two of his clients' farms. These farms had both struggled with Staph aureus infections and had mastitis rates of above 10% in gimmers.
They vaccinated gimmers and ewes carrying triplets. One farm had orf and vaccinated for that at the same time.
Following vaccination, mastitis rates halved on these farms. On one of the farms the number of ewes dying as a result of mastitis also fell from one-third to 10%, meaning they had cull ewes to sell.
Mr Barker saw similar results on six farms that vaccinated last season. They saw a 50-90% reduction in incidence.
Vaccinated ewes that got mastitis were also less ill with it and were easier to treat. About half of ewes that got mastitis stayed milking and didn't lose quarters.
"I think [the vaccine] is very significant within certain flocks because mastitis is a huge cause of economic loss and is a welfare issue," Mr Barker says.
"It will obviously work better if measures are being taken to ensure management and nutrition are optimised."
Case study: Steven Nesbitt, Alwent Hall, County DurhamVaccinating against mastitis has resulted in a 75% drop in mastitis rates at Alwent Farm, which means more lambs are growing to their full potential pre-weaning and antibiotics use has reduced by about 30-40%.
Steven Nesbitt runs 120 ewes, with most of his income coming from the sale of pedigree tups and breeding females.
The flock is made up of 24 Texels, including a nucleus flock of six to eight ewes that are flushed annually. Embryos are then implanted into 96 North Country Mule recipients.
Getting lambs off to a good start is vital to Steven Nesbitt's pedigree Texel operation
In the past, mastitis rates of about 10% across the flock had suppressed lamb growth due to sub-optimal milk supply in affected ewes, and the need to bottle-feed lambs.
With the whole pedigree flock performance-recorded, this early growth is particularly important as it affects breeding values and subsequent stock value.
A bout of mastitis can very quickly mean "your best lamb is suddenly not your best lamb". At the ewe level, affected animals also proved difficult to cure, resulting in higher-than-desirable antibiotics use.
Mr Nesbitt tried numerous ways to reduce mastitis, including disinfecting buildings and housing ewes and lambs for longer at lambing so they were being turned out in warmer weather, but nothing seemed to work.
As a result, and after speaking to vet Will Barker of Castle Veterinary Surgeons, he decided to vaccinate every female due to lamb against mastitis. The results were marked.
"It worked absolutely marvellously," he says. "We saw a huge impact at lambing. We only had three [cases of mastitis]. I was relieved it worked, as it's pricey."
While it might be expensive, with only three pedigree lambs ending up on the bottle as a result of their dams getting mastitis, and antibiotics use reducing by 30-40%, Mr Nesbitt is sufficiently convinced to use it again.
"If it does the same again next year, we'll use it every year," he says. "People in the area are reporting that it's been quite a bad year for mastitis and we've had the best we've ever had, at these sheep numbers."
Principal Cause Of Mastitis In Ewes Identified
Two bacterial pathogens have been identified as the principal causes of mastitis in commercial sheep flocks involved in a Farming Connect-funded Welsh study.
Fourteen different strains of bacteria were found in milk samples from the 12 flocks during the 2023-24 lambing season.
Staphylococcus aureus (in 43% of samples) and Mannheimia haemolytica (in 17% of samples) were the most common.
See also: Tips for managing ewe mastitis during lambing
Farmers in the Farming Connect study were mostly members of its sheep discussion group in Montgomeryshire, led by independent sheep consultant Kate Phillips.
Flocks averaged 563 ewes, but ranged in size from 100 to 1,415, and scanned at an average of 155%. The mastitis incidence averaged 3.8%.
The study was to understand the factors influencing mastitis incidence, to enable farmers to develop strategies to improve ewe health and reduce culling for this disease.
Of the ewes in the study with mastitis, 10% died – the 90% that survived were all culled.
Antibiotics resistanceDuring a recent webinar, Kate said the study had looked at which pathogen strains on individual farms were resistant to antibiotics.
Only 7% of samples with Staph aureus were resistant to the first-line antibiotics tetracycline and tylosin, while 25% of those with M haemolytica were resistant to tetracycline only.
However, tetracycline was not effective at treating Streptococcus dysgalactiae, the third most common pathogen found in milk samples from the 12 flocks – and the main cause of joint-ill in lambs.
As many as 25% of ewes in a flock can be affected with mastitis.
Some studies have shown much higher rates, but when one ewe has it, the flock is at increased risk because of its contagious and transmissible nature, Kate said.
"Underfeeding protein and energy in pregnancy and lactation increases the risk of mastitis, so make sure appropriate levels are fed,'' she advised.
Poor condition scoreLow body condition score at lambing has also been linked to subclinical and clinical mastitis, she added, while poor hygiene at lambing time allows environmental bacteria to multiply, increasing the chance of infection.
Good udder conformation is associated with decreased risk of mastitis, according to AHDB, although 81% of the ewes in the Farming Connect study had normal udders and 71% of teats were undamaged.
The chance of developing acute mastitis increases when ewes rear two or more lambs, regardless of ewe age, and the mastitis risk increases the longer ewes and lambs stay indoors.
This study found that most of the ewes with mastitis were rearing twins.
Some 86% of the recorded ewes lambed inside, and were housed for an average 6.6 weeks, with all flocks bedded on straw.
Silage and concentrates were fed pre-lambing to 80% of ewes; 20% had hay and concentrates, though some ewes were grazing.
While creep feeding is thought to have a role in reducing the demand for milk, thereby avoiding aggressive suckling, half of the flocks that had cases of mastitis fed lamb concentrates.
The study also looked at orf levels and found it present on only 3% of udders.
Of the ewes in the study with mastitis, farmers reported that 83% were given some form of pain relief, which vet Dr Fiona Lovatt, of Flock Health, said was "really good news it because it is an incredibly painful disease".
She added that while a vaccine is available for Staph aureus (given five weeks and two weeks pre-lambing), a farmer needs to be confident it was the mastitis pathogen in their flock before deciding whether to vaccinate ewes just before lambing in the following year.
Vet Charles Marwood Highlights Costs And Causes Of Mastitis
By far the most common causes of mastitis are bacteria, these get into the udder through the teat canal. There are both contagious and environmental causes of mastitis. Contagious mastitis is spread in the parlour, via hands, clothes and units. Environmental mastitis, the bacteria are present in bedding, pasture and on the teat skin before milking or suckling.
Bacteria get into the udder when the teat canal is open, they can stay in the udder for days or weeks until conditions are right to cause infection.
Severity of mastitis infections is graded from mild 'subclinical' cases where the animal shows no sign of infection, to severe 'toxic' cases where the animal is sick and can potentially die from the infection. The average cost of a mastitis case is more than £200, with over 40 cases per 100 cows per year, that's in excess of £8000/100 cows/year. But mastitis rates vary enormously.
People have devoted their careers to research mastitis, and much is understood about the different bacteria, the risk factors, diagnosis and treatments.
Cattle and sheep are exposed to low levels of challenge every day. When their immune system is doing its job, the infection is cleared with a spike in white blood cells. The severity of mastitis can be related to the type of bacteria involved but more importantly the ability of their immune system to fight the infection. In severe, toxic cases, the animal has often had a weak or poor immune response, allowing the infection to overwhelm the udder. Symptoms in these severe cases are caused by the toxins produced by the bacteria, even dead bacteria will release these toxins.
Understanding the immune system is important to reduce the severity of mastitis. Nutrition, energy balance, weight loss, milk yield, heat stress, trace elements and other underlying disease all affect the ability of animals to cope with infection.
In the last 50 years there has been a change in common causes of mastitis in cattle. Before milk recording, dry cow therapy and best practice in milking parlours, higher levels of chronic contagious mastitis were seen, where bulk milk cell counts were high. An understanding of its control; prompt treatment of clinical cases, culling chronics, dry cow therapy, parlour maintenance and post-milking teat disinfection has dramatically changed the type of mastitis we now commonly see.
Far more environmental causes are now seen. The two most common causes are Strep uberis and E. Coli. These bacteria love moist organic bedding material (straw and sawdust) and present in dung.
Controlling hygiene in the environment will reduce levels of bacteria, but pre-milking teat preparation will further reduce levels of bacteria before teat canal is open during the milking process.
The dry period is also recognised as a risk factor for new infections. The first two weeks and last two weeks are particularly important when the teat canal is not fully sealed. Teat sealants and environment management have dramatically reduced levels of new infection. Dry period infections tend to sit dormant in the udder until after calving, even for several weeks, waiting for a period of stress or lowered immunity to cause mastitis.
Lactation origin, environmental infections are now the most common mastitis. Mastitis treatment records and milk recording data gives us really useful data to easily look at trends, seasonality and risk factors. Freezing mastitis milk samples is also useful, to confirm any significant underlying causes and rule out contagious problems.
Managing their environment, milking hygiene and maximising immunity are key to reducing rate and severity of mastitis. Vaccines are now available for the control of mastitis. There may be cost benefits to vaccination, especially if there is a trend to more severe cases.
Mastitis rates in sheep vary considerably, up to 15% in some flocks, averaging 1-5% but higher in lowland flocks and indoor lambing. Most cases are in nursing ewes, severity ranges from mild to severe toxic cases, which can result in death. With poor milk yields, early culls and death, the economic cost can be significant. Subclinical cases in nursing ewes may only present after weaning or pre-tupping.
Most of the bacteria involved are present in the environment, on the teat skin or in the mouths of suckling lambs. Risk factors are damaged teat skin due to hard suckling, orf lesions and flies. Higher rates are seen in ewes nursing twins with hungry growing lambs, particularly if milk yields drop during a cold snap, east winds in May can be a classic trigger.
Far less research has been done into sheep mastitis, but there can be many different bacteria involved. Common causes include Staph aureus and Mannheimia haemolytica. Pathology in the udder is often severe and toxin release causes further damage. Early treatment with a broad-spectrum antibiotic and anti-inflammatories gives the best chance of recovery. But permanent damage to the udder may already have been done.
Recognising the risk factors and maintaining milk yields by supplementary feeding can reduce levels. Vaccination is now also an option, licenced specifically for the control of Staph aureus, this may be helpful in flocks with this particular bacteria. Vaccination requires two doses pre-lambing.
Mastitis is a complex disease, with many different causes, risk factors and severity. Impacts can be costly and frustrating. Trends in dairy cattle are towards environmental causes and using farm data we can get a good idea of risk factors. Severity of cases is often linked to the type of bacteria but also the animal's immune response. In certain cases, vaccination may be a cost benefit, boosting specific immunity.
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