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HFV News JUNE 2021

In this issue…

  • MCF - the risk of grazing alongside sheep
  • Salmonella - what's your herd status?
  • LDA - late spring risk
  • UK TB strategy update
  • Notes from the DBR

MCF - the risk of grazing with sheep

Malignant Catarrhal Fever (MCF) is a fatal disease of cattle caused by a sheep virus "Ovine herpesvirus-2". This virus is carried by sheep without any ill effect, but when that virus passes on to cattle you see sporadic cases of MCF.

WHAT ARE THE SIGNS OF MCF?

  • dull & depressed
  • snotty discharge from the nose with reddening and crusting of the nose
  • watery eyes
  • blindness and white eyes
  • high temperatures
  • ulcers under tongue
  • sudden death
  • +/- swollen lymph nodes
  • rarely severe bloody scour

HOW DOES IT SPREAD?

The virus spreads from sheep to cattle through saliva and nasal secretions or aerosols when coughing or sneezing - there is no risk of cattle to cattle spread.

Lambs get infected at 3-6months old and shed for a few months. Cattle can show signs of infection several months after contact with sheep - no one really knows why there is such a variable incubation period.

HOW DO WE DIAGNOSE MCF?

  • history of contact with sheep
  • blood sample to check for MCF virus
  • rule out IBR and BVD

HOW DO WE TREAT MCF?

95% affected cattle will die within a few days; the ones that survive longer show a wider range of signs. There is very little effective supportive treatment so animals are usually euthanised.

HOW DO WE PREVENT MCF?

There is no cattle to cattle spread of MCF, so prevention is all about stopping contact between sheep and cattle in sheds, at pasture, with shared water/feed troughs and across fenced boundaries.

Salmonella - what's your herd status?

Salmonella is a bacterial infection; the strains that affect cattle are most commonly found in the guts of infected cattle and passed-on via the muck to other cattle/calves from the environment.

Importantly, Salmonella can also cause disease in humans - the cattle strains are not as infectious to humans as the human specific strains but the risk is still there for farm workers and families.

CLINICAL SIGNS:

  • Diarrhoea (especially after calving)
  • Joint infections
  • Decreased milk yield
  • Abortion
  • Death
  • Pneumonia in calves
  • Poor growth rates
  • Loss of ear tips in calves

Diagnosis can be difficult, as the clinical signs in a a herd that has low level, grumbling spread of infection are less severe to those in a new outbreak in a naive herd.

We can try to grow Salmonella from scour samples but shedding is intermittent so a negative doesn't mean she's not infected, or we can look for antibody levels in blood from cattle over 3 months old, or we can use bulk tank milk surveillance in dairies which shows the herd status and how it changes over time.

HOW DOES SALMONELLA GET ON A FARM?

Herds are often infected by breaches in biosecurity - bought-in animals or contact with neighbouring stock, or by spreading of slurry from other farms or shared watercourses. Wildlife can also play a part in infecting farms, particularly migratory birds. Other risk factors also include pooling colostrum, loose-housing and overstocked calving yards.

HFV BULK TANK MONITORING:

At HFV we run a quarterly bulk tank monitoring service for our dairies to monitor herd level BVD, Lepto and IBR as well as timed checks for Fluke and Neospora. In addition to this we now offer twice a year bulk tank Salmonella surveillance testing which will be free of charge for the next 12 months.

A one-off bulk tank test for Salmonella will pick up 9 out of 10 infected herds, but if we test more frequently we will pick up 98% of infected herds so this becomes a useful ongoing early warning system for changing infection levels over time.

Left Displaced Abomasum (LDA) - late spring risk

An LDA occurs when the abomasum moves from its normal position on the bottom of the right-hand side of the abdomen, and drifts to the left-hand side, ending up on the wrong side of the rumen. It can then fill with gas and rise like a balloon, trapping it in position.

During late pregnancy the large calf and uterus take up an enormous amount of room in the abdomen of the cow and her intakes drop off as the calf grows, squashing the rumen. Once the cow calves there is suddenly a lot more empty space available in the abdomen, plus there's a lag in getting intakes back up, a delay in getting the rumen back up to capacity plus there's a diet change from dries to highs which can lead to gas accumulation in the abomasum. It is a combination of all these risk factors especially in Holsteins, that mean the abomasum is at risk of moving into an abnormal position on the left side:

On top of these "normal" risk factors, there are abnormal risk factors which increase the risk of LDAs further:

  • FAT COWS: have really poor intakes before and after calving, high risk of milk fever and ketosis
  • TWINS: increased risk of retained cleansing and poor intakes before calving
  • FRESH COW DISEASE: lameness, mastitis, retained cleansing, milk fever - all reduce intakes
  • GROUP CHANGES: hit intakes hard
  • DIET CHANGE: from dries to highs

WHAT TO LOOK OUT FOR:

  • Older cow (3rd plus lactation)
  • Freshly calved (7-21 days)
  • Decreased milk yield
  • Off feed - sometimes will eat forage but not concentrates
  • Some may scour, others may have stiff muck
  • Appear ‘empty’ on the left hand side
  • Some may appear dehydrated, with sunken eyes
  • Arched back due to abdominal pain
  • ‘Pear-drop’ smell to their breath

For those of you with stethoscopes on farm; you'll know the characteristic high pitched ping when you listen to the left hand side of a cow with an LDA. Remember to listen along a line between elbow and hip (red line below), stethoscope on the rib and using the other hand flick in a circle around the stethoscope as you move it along that imaginary line.

TREATMENT OF LDA:

The first job is to find and treat any underlying disease (ketosis, metritis, mastitis) - stabilising her medically before surgery helps with recovery post-op. The vast majority of LDA will need surgery to replace the abomasum back to its normal position.

There are a few different surgical methods that you'll see us do - Tom opens up on the right, Paula opens up on the left but both methods end up with the abomasum permanently stitched into position and a rapid recovery for the cow - often they're back to normal intakes in a few hours after the op.

HOW MANY ARE TOO MANY LDA?

Some farms aspire to be LDA free; transition management of every individual is key on these farms to protect rumen fill for every cow. Most farms would run at around 1% LDA; any more than that and we would want to have a chat about common risk factors and prevention strategies for your herd. Sometimes risk factors can affect multiple dry / fresh cows and you can get runs of LDAs - tricky grazing conditions in late Spring can be a common risk factor.

Updated: UK's bTB Strategy

In March 2020 the Government published it's response to the Godfray Review of the UK bTB eradication policy and highlighted 3 key areas to focus on in order to achieve TB free status by 2038:

  1. Accelerating work to develop a deployable cattle vaccine in the next five years
  2. Evolve the wildlife control policy, by phasing out intensive badger culling in the next few years and gradually replacing this with badger vaccination and surveillance. Culling would remain an option where local infections rates indicate it is needed
  3. Improving diagnostic testing to root out bTB more effectively, with deployment of more sensitive tests (Enferplex, IDEXX) plus increased restriction of cattle with inconclusive test (IR) results.

In Jan 2021 a further consultation was launched to set out proposed changes to the bTB policy with a particular focus on cattle TB testing and wildlife control:

PROPOSED CATTLE TB TESTING CHANGES:

• Extending compulsory post-movement TB testing to parts of the Edge Area.

• Revising the interferon-gamma test deployment policy in the High Risk Area (HRA) and Edge Area.

WILDLIFE CONTROL CHANGES:

• No new Badger Disease Control (intensive cull) licences after 1 December 2022.

• New Badger Disease Control (intensive cull) licences issued in 2021 and 2022, could be stopped after two years of culling, rather than the 4 or 5 year cycle

• Restricting Supplementary Badger Cull (SBC) licences to a maximum of two years and these won't be allowed in previously licensed cull areas.

HOW DOES THIS AFFECT US?

1. GAMMA BLOODS

Gamma bloods will now be mandatory for confirmed TB breakdowns (lesions +/- positive culture) in our area if you also had a confirmed TB breakdown within the last 18 months. The government will introduce this change as soon as practicable.

The aim here is to use the blood test to root out any remaining infection that was missed previously. Once again, this highlights the importance of high sensitive skin testing to minimise the number of reactors on your farm passing multiple skin tests.

2. 6 MONTH TESTING

All farms in the High Risk Area (HRA) will now come under the 6 month testing rule; not just those in Shropshire and Staffordshire - this increased frequency of skin testing will start from 1st Jan 2022.

The map below shows all HRA in blue:

If you are a CHECS accredited TB herd, at level 1 or above, then you have the option of keeping your testing interval at 12 months.

3. NEW TB ADVISORY SERVICE

The Government has also announced new services to support farmers in improving biosecurity standards on farms across England. A new bTB Advisory Service will offer bespoke advice to livestock keepers about the practical and cost-effective measures they can take to build herd resilience, including those outlined in the TB biosecurity five point plan: https://tbhub.co.uk/preventing-tb-breakdowns/protect-your-herd-from-bovine-tb/

4. NEW ENTRY LEVEL TB CHECS SCHEME:

Defra has also supported CHECs, (Cattle Health Certification Standards) to deliver the ‘Entry Level Membership’, a new scheme helping farmers work with their vets to reduce the risk of TB breakdowns in their herds.

This scheme will be covered by our bTB health plans as part of your overall HFV herd health plan.

For those of you who are interested in full CHECS TB accreditation, from Aug 2021 the "Entry Level Membership" will be the start of that process. Those of you who are already CHECS accredited, won't need to do this extra step.

ibTB: Mapping bovine TB in England and Wales

Notes from the DBR

Tom is part way through his Diploma in Bovine Reproduction (DBR); a 2 year Masters level post-graduate course run at Liverpool University that culminates in a piece of published clinical research in 2022.

Each module covers a different subject area and part of that teaching is a review of all current research in that topic. We use this update as a way of validating and if need be, updating our protocols and advice on farm so you get something out of the DBR too!

Tom is currently doing a serial scanning project on one of our farms where he is scanning the same fresh cows three times a week for 3 weeks to map and follow what happens to structures on their ovaries and their uterus over a 21 day cycle. Often we only have a snapshot of fertility on the day we scan, whereas this will be an in depth look at what happens to these fresh cows at a really crucial point in their fertility cycle.

Tom will do a summary of his findings next month...

GET IN TOUCH:

Paula: 07764 747855 paula@haywoodfarmvets.com

Tom: 07837 291097 tom@haywoodfarmvets.com

Enquiries: mail@haywoodfarmvets.com

Website: haywoodfarmvets.com

Open hours: M-F 08:30 - 16:30

Out of Hours: 07398 743095

Created By
Paula Scales
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