HFV News JULY 2022

Digital Dermatitis (DD)

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 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.

DD 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.

DD 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 incredibly important in control of 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 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 treponemes 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 footbathing or where it is only used in the face of an outbreak.

There is limited evidence behind many footbathing products, with formalin and copper sulphate still the perceived gold standard.

Frequency of footbathing is dependent on the individual farm situation, however, it is often the case that the more frequent the better for control.

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 the bath, which usually requires a footbath 3.7-4m long and designed with optimal cow flow in mind.

CONCLUSION

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.

HFV MEDS UPDATE:

The vet-med supply chain over the last few years has been volatile as you will all know. Old brand names have come and gone, there are new pressures limiting the use of certain types of meds, there have been sudden batch recalls on some favourite meds, and more recently some issues with staples like lamb vaccines and calcium.

At HFV we pride ourselves on providing clear communication between medicine suppliers, wholesalers, vets and clients so we can hold stock, help you plan ahead, find alternatives for the must-haves and put prevention strategies in place to reduce dependency on certain medicines that are coming under more and more scrutiny.

Calciject Shortages

There are some issues with the manufacture and supply of Calciject at the moment which should be back to normal from August. Thankfully, we have quite a stockpile at HFV so if you're struggling to get hold of calcium - don't hesitate to get in touch.

As always - we only recommend using injectable Calcium in a wobbly or down milk fever case. Cows you're just a bit worried might become milk fever cases respond much better to oral calcium boluses such as Bovikalc at calving. The body tightly regulates blood calcium levels so injectable calcium given to a cow with normal blood calcium is rapidly removed from the blood through the kidneys and exits in her urine, and often delays her body mobilising her calcium stores from her bones.

Spirovac 25 dose bottles

There has been a delay in part of the manufacturing process for the 25 dose bottles of Spirovac - one of the Lepto vaccines. Production should resume in Autumn - but until then there should be plenty of the 5 dose bottles available.

Sensiblex

Sensiblex is a tissue relaxant for calving heifers and cows: once the calf is lined up in the birth canal Sensiblex relaxes the cervix and soft tissues which can:

• Reduce injuries to the mother
• Shorten duration of calving
• Reduce risk of held cleansing
• Reduce risk of whites
• Help the birth process for the calf which meant treated heifers had 6 more live calves born per 100 compared to control groups.

Obviously Sensiblex won't solve an over-large calf, a twisted uterus, or a milk fever calving but can help with those that aren't progressing if the calf is lined up correctly.