Haywood Farm Vets Newsletter JUNE 2024

DIGITAL DERMATITIS - tips for getting DD under control

Digital Dermatitis (DD) is a very common infectious cause of lameness in UK cattle - many of you will recognise the characteristic painful skin lesion between the heel bulbs in the hind feet.

Treponemes are the bacteria thought to cause DD - they attach to the hairs on the back of the heel and swim very slowly down the hairs and infect deep in the skin in the hair follicles causing an ulcerated skin infection between the heel bulbs. A cow infected with DD typically walks on her toe, avoiding putting weight on her affected heel.

DD Lesions:

DD lesions can be classified into 4 different "M" stages:

M1: small lesion <2cm with clear edges

M2: red/grey ulcerated lesion >2cm - painful and active

M3: healing M2 lesion with dark scab after treatment

M4: chronic DD lesion

Once an infected cow is treated the DD bacteria can become dormant deep in the skin and it is these carrier cows that are the main source of infection in the herd; spreading it via slurry where the Treponemes can survive for up to 3 days.

The DD infection cycle:

When a cow is first infected with DD it takes 4 months for the infection to develop into an active lesion. The active M2 lesions are the tip of the iceberg with DD - these are the obvious ones that are lame, you pick up and treat with antibiotic spray. Even when she is treated and the M2 becomes a healing M3 and then eventually a dormant M4, the Treponeme bacteria encyst and hide away, deep in the skin. These chronic M4 lesions can flare into new M1 and M2 active lesions within a few days and so without a DD control plan in place you get a continual cycle of spreading infection and new, active, contagious lesions.

Digi Control Plan:

Summertime can be a really good opportunity to hit DD hard whilst either cows are out at grass, or conditions for housed animals are drier underfoot.

Digi Treatment:

Treatment of active DD lesions is relatively simple - lift the foot, clean and dry around the heel bulb and apply a topical antibiotic spray to the lesion allowing it to dry before a second spray and walking out onto a clean yard.

Once the active lesion is healed, it is regular footbathing, a clean foot and a clean walking surface that keeps the affected skin healthy and stops chronic M4 lesions flaring. A lot of infected cows NEVER get rid of the infection so getting footbathing right for your farm is an incredibly important part of controlling DD.

Blitz Therapy:

If you have a lot of active DD lesions in the herd, it can be really useful to treat all the active lesions at once to dampen down the infection pressure to uninfected cows.

How to do Blitz Therapy:

Step 1. Identify every cow with a DD lesion

Not all cows infected with DD will be lame, so mobility scoring is not a reliable way of detecting all lesions. Instead, feet must be inspected individually. The easiest way to do this is when the cows are in the parlour during milking. Washing the feet off first and using an inspection mirror and torch will all increase the chances of spotting all lesions.

For dry cows, young-stock or robotic herds this can be carried out at the feed barrier but is tricky if the feet are dirty.

All cows with active/recurring lesions should be marked up for treatment.

Step 2. Treat every DD lesion at once

The key to success with Blitz Therapy is to treat ALL cows with lesions simultaneously.

When selecting a treatment to use it is important that it:

1. Resolves the infection quickly
2. Minimises pain to the cow
3. Uses antibiotics responsibly
4. Reduces the risk of encouraging the Treponeme bacteria to encyst, deep in the skin

Antibiotic footbaths are not a suitable Blitz treatment option as you would end up treating a lot of uninfected feet too. Also, the antibiotic products used in footbaths are not licensed and so carry a seven-day milk withhold.

When used correctly, the licensed topical antibiotic sprays fulfil all the treatment objectives and are therefore the product of choice for use in blitz treatment.

Lesions should be treated until they are in the healing M3 stage, with a black scab and are no longer painful. Typically, 3 consecutive days of treatment is required although this may be less for smaller, earlier lesions and more for larger chronic lesions.

Cows should not be foot bathed whilst they are being blitz treated.

What happens after Blitz Therapy?

Once the active DD lesions are under control it is essential to prevent old DD lesions flaring up and causing new DD lesions.

Hygiene:

Slurry not only acts as a way for DD to spread between cows, but also causes the necessary skin damage needed for DD to take hold. The dirtier the cows, the greater the risk of DD. Keeping cattle cleaner is essential and can be achieved through more effective scraping out, robotic slurry collectors, targeting the timing of automatic scrapers to periods of least cow traffic and minimising slurry pooling in high traffic areas eg. collecting yard or cross passageways.

Foot bathing:

Traditionally foot bathing has been used as a treatment for DD, however, its role is one of prevention; to prevent new infections in the first instance and to also prevent chronic M4 lesions flaring up. Long-term control is reliant on successful control of these dormant lesions. ‘Flare ups’ are common when there is a break in foot bathing or where it is only used in the face of an outbreak.

There is limited evidence behind many footbathing products, but formalin and copper sulphate are still the gold standard. Make sure you know the volume of your footbath and calculate the amount of formalin or copper you need to add to the water to make the correct dilution.

Formalin is a nasty chemical to work with - you should be wearing a mask and eye protection and only mixing in a well ventilated area.

Frequency of footbathing is dependent on the individual farm situation, however, it is often the case that the more frequent the better for control and for herds struggling to control DD, footbathing every milking can really help.

The footbath should be designed to make it easy and stress-free for both farmer and cows. The aim should be to achieve at least three dunks of each hind foot in a 12cm deep solution, which usually requires a footbath 3.7-4m long and designed with optimal cow flow in mind.

For many farms DD is a constant challenge, impacting on the welfare and productivity of the herd. Achieving long-term control is possible through implementation of blitz treatment of all actively infected cows, followed by appropriate prevention measures, including footbathing. However, due to the nature of DD and its ability to recur, it is important that any control measures implemented are continued and regularly reviewed.

COCCI IN LAMBS - are you having hidden losses?

Coccidiosis is one of the most important causes of scour in young lambs, which can result in reduced growth rates, persistent ill-thrift, and can sometimes even be fatal. It is becoming increasingly common in the UK, especially in more intensive systems.

Coccidiosis in lambs can be seen as clinical disease, presenting as lambs with diarrhoea, but also can have subclinical effects. These lambs will show no obvious symptoms but when monitored, will record reduced feed intakes and poorer growth. A study of housed lambs showed subclinical disease reduced feed conversion rates by around 10% which meant lambs took an extra week to fatten, despite showing no obvious signs of disease.

Lambs which show clinical signs will take much longer to recover and can take many more weeks to reach slaughter weight long-term. A 2005 study estimated that an extra 3 weeks to slaughter would cost £4.40 per lamb in feed – not counting the extra cost of any handling and treatments.

What is coccidiosis?

Coccidiosis is caused by a parasite called Eimeria. This parasite is common in farm environments and most lamb flocks will encounter infection at some stage. Many different species can infect sheep, and most can live in the gut without causing damage or any clinical signs. The two species of importance to sheep in the UK are Eimeria crandallis and Eimeria ovinoidalis, both these types cause disease.

Eimeria life cycle:

Oocysts (eggs) are shed in the muck of sheep. These eggs are tough, survive in the environment for up to 18 months and mature in the environment for several days when temperature and moisture conditions are suitable. If these eggs are eaten by young lambs without immunity, they enter the cells lining the gut and reproduce, causing huge damage as they do so. These infected gut cells produce very large numbers of oocysts/eggs which are then shed in the muck to contaminate the environment and start the cycle again.

What are the clinical signs?

Coccidiosis causes clinical signs due to damage to the intestinal lining. This prevents the absorption of water and other nutrients, leading to diarrhoea and poor growth. In many cases this damage will never fully heal, meaning poor growth rates for the rest of the lamb’s life. The damage to the gut, along with reduced immunity (due to a lack of nutrients) can increase the severity of other gut diseases (such as Nematodirus, a gut worm which can affect young lambs at a similar time of year).

Clinical signs are most commonly seen in young lambs 4-8 weeks old, usually with most/all of the group affected:

• Profuse diarrhoea or scour, often with mucus or flecks of blood
• Staining of the tail and surrounding area due to the diarrhoea
• Abdominal pain causing a ‘tucked up’ appearance and straining when passing faeces
• Severe weight loss in the later stages
• Dehydration (sunken eyes, dull, weak lambs) which if untreated can lead to death

Clinical disease due to coccidiosis can occur both indoors and in grass-based systems. As they age, lambs develop immunity to Eimeria, and in most cases older lambs do not develop coccidiosis unless they were not exposed to infection at a young age.

Are my lambs at risk of coccidiosis?

Eimeria oocysts are present in the environment in most flocks, however this does not always mean every flock will have signs of disease. Two factors affect whether lambs in a flock are at risk of clinical coccidiosis.

1. The level of contamination of the environment with oocysts.

Low levels of contamination can be beneficial as it will stimulate the lamb’s immune system to develop immunity without causing clinical disease. However, if there is a heavy environmental challenge this can lead to clinical disease. High levels of oocysts in the environment can be caused by:

• Lambs housed or grazed at a high stocking density
• Dirty conditions in fields or buildings
• Feed and water troughs that can be contaminated with muck
• Mixing young, susceptible lambs with older lambs – the older lambs will have developed immunity to coccidiosis so won’t show clinical signs but can still be shedding oocysts into the environment, putting younger lambs at risk
• Grazing younger lambs on fields where older, earlier-born lambs have already grazed (and so contaminated the ground with oocysts)

2. Animals with poor immunity are most susceptible to clinical coccidiosis. This is a higher risk in certain cases:

• Young lambs that have never been exposed to Eimeria and are still developing their immunity after birth
• Lambs which have had inadequate colostrum intake and/or poor-quality colostrum at birth. This will also be influenced by the condition of the ewe
• Lambs which are under stress – for example due to poor nutrition, cold/wet weather, or other diseases (such as Nematodirus)
• Concurrent flock diseases such as Border disease which can lower flock immunity

How do I diagnose coccidiosis?

Early diagnosis is crucial as clinical coccidiosis can be a significant welfare concern and can be fatal. It also can lead to poor weight gain long-term which has huge economic impacts for sheep farms. Effective treatment can minimise these effects if diagnosis is made promptly.

The main diagnostic test for young lambs with diarrhoea is to check for coccidia oocysts in a muck sample - we do these in our lab at HFV meaning you get results the same day.

How do I treat cocci?

There are three different drugs available for treating cocci:

Diclazuril

• Vecoxan
• Dycoxan
• Coxicert

This drug kills the cocci in the gut on the day you treat but doesn't persist, so timing is critical; you need to dose "just in time" and if you're a bit early you may have to dose again.

Toltrazuril

• Tolracol

This drug kills all the stages of cocci in the gut and in the gut cells and persists in the guts of lambs for 1-2 weeks which gives their immune system chance to catch up so they can fight off any further cocci challenge. The persistency also means there's a bit more wriggle room with timing.

Decoquinate

• Deccox

Deccox doesn't kill the cocci oocysts, just stops the reproduction cycle so allows time for the lamb to build up immunity and kill off the cocci themselves. This is an in-feed medication that you will need a written prescription for and there are two feeding rates - a treatment rate and a prevention rate.

Currently feed mills are struggling to source Deccox - this should be a short term stock issue that is resolved in the next month or so - we will let you know if it is any longer than that.

OUR TEAM IS GROWING - a warm welcome to Els!

Els graduated from the University of Glasgow in 2015, having previously completed a three-year degree at the Royal Veterinary College. Working in Northamptonshire, she has developed a passion for building strong client relationships, focussing on preventative health planning and promoting responsible antibiotic use on farm.

Els has come home to Shropshire having grown up locally in Prees and is enjoying a return to her roots and working in the countryside she grew up in. Outside of work she enjoys family time with her husband Tim, her children Joshua and Willow and their spaniel Isla.

We are very proud to be building a team of committed farm vets who share the same ethos, but bring their own qualities, ideas and experience. And, although we're growing, HFV will always remain independent and small enough to personally know you, your families and your farms.

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