Phase III of National Johne's Management Plan launches
Phase III of the National Johne’s Management Plan (NJMP) took effect this week.
The NJMP aims to manage and reduce the incidence of Johne’s disease on dairy farms in Scotland, England, and Wales by implementing one of the six control strategies monitored on each farm by British Cattle Veterinary Association (BCVA) accredited Johne’s vet advisers.
Phases I and II strived to control and reduce the incidence of Johne’s disease. Phase III aims to build on Phase II’s successes and incorporate new developments and requirements.
Key changes for phase III include:
All herds must obtain an average test value (ATV) for their herd to help assess the level of disease present and allow progress to be tracked over time.
The minimum requirement to generate an ATV will be a 60-cow random screen. The 30-cow targeted screen is no longer an acceptable option.
The creation of a national Johne’s control index target of ATV 5.5, with a goal to achieve this by 2030.
The ability, through the creation of a national Johne’s tracker database, to track progress nationally using ATV, % incidence and other drivers of infection within herds.
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“To protect that achievement, we must keep moving forward and address the concentration of infected animals in herds that have yet to engage with the initiative fully.
“Under phase III, regular vet/farmer dialogue and tailoring control programmes to the needs of the individual farm will remain the central component of the initiative.
“What phase III adds is a requirement for all dairy farmers to determine their ATV, on top of which we have set a national target for the average of all herd ATVs to reach 5.5 by 2030.
“ATV is a robust indicator of disease prevalence and a good guide to success in managing and reducing the incidence of Johne’s on a farm. It will provide a benchmark against which a farmer can assess their performance against their peers and the industry’s expectations and provide a stronger focus for the dialogue between the vet and the farmer. “Given what many farmers have achieved already, we believe the 2030 target is eminently achievable.
“Teamwork will be the key to success, and the vet/farmer relationship will be at the heart of this. However, more widely, all supply chain elements must pull together to deliver continued progress on Johne’s disease control.
“The launch of phase III comes after a protracted engagement and communication process set in train in 2022.
Pat Wilson spoke to senior animal health and welfare scientist, Dr Miranda Poulson and senior knowledge exchange manager (Scotland) with ADHB, Doreen Anderson, who told us more about the disease, its transmission and how to control it.
Johne’s disease
Johne’s disease, also known as Paratuberculosis, is a chronic, contagious bacterial disease of the intestine that primarily affects sheep and cattle. It is most commonly seen in dairy cattle and goats, as well as other ruminant species.
AHDB will focus on a range of support over the next year, which will help Dairy farmers tackle Johne’s prevalence in their herds. These events will include focusing on improving the hygiene in your calving area and biocontainment techniques, as well as helping you better understand your sample results.
Q. What causes Johne’s disease?
A. The disease is caused by a bacterium called Mycobacterium avium subsp. paratuberculosis, often referred to as MAP.
Q. What are the clinical signs?
A. Due to ongoing control strategies, we rarely see overt clinical signs other than increases in other infectious diseases, such as lameness and mastitis, and impacts on fertility and milk production.
Infected cows often test positive and are managed out of the herd before clinical signs are apparent. If the disease were not picked up on testing, it would eventually progress to wasting and increasingly severe diarrhoea.
Q. How is the disease transmitted and spread?
A. Most infections are acquired in the first few days of a calf’s life. Calves are usually infected by ingesting faecal material contaminated with the bacteria, such as dirty bedding or faeces on the dam’s udder when they suckle.
Other potential infection routes include through contaminated milk or colostrum if the dam is affected, or directly from the cow to the calf across the placenta during pregnancy. However, these two routes are less common.
Q. Is the disease more likely to affect adult or young animals?
A. It is common for calves to be infected in the days after birth, but as Johne’s progresses very slowly, it is uncommon to see clinical signs before cows are three years old. Cows are likely to test positive before you start to see clinical signs.
Q. How is the disease diagnosed?
A. It can be diagnosed by looking for antibodies to the bacteria in milk, blood or the DNA of the bacteria in faeces.
New diagnostic tests are always being developed, but at the moment, dairy cows are most commonly tested through their milk, often at the time of milk recording.
Due to the nature of the tests, infected animals can test negative. Identifying risky animals and managing them appropriately is key to controlling Johne’s disease rather than just culling test-positive animals. You should always discuss your Johne’s test results with your vet.
Q. Can it be prevented or is it a case of controlling the disease?
A. Johnes’ disease cannot be cured, so once a cow is infected, it is infected for life. Preventing calves from becoming infected is the best long-term way to control Johne’s disease in your herd.
Q. How can the disease be controlled?
A. Risk management is an essential part of controlling Johne’s disease on the farm. By understanding how animals can become infected, you can put measures in place that will work for your system.
Cows that have tested positive for Johne’s disease should not be allowed to calve in the same place as cows that have never tested positive.
Scrupulous cleanliness in calving pens is key. You should also avoid pooling colostrum and ideally should not feed colostrum or milk from infected cows to calves unless it has been pasteurised.
You can also use Johne’s test results to make breeding decisions. Research has found that daughters born to cows who were test-negative for Johne’s disease when they calved, but go on to test positive later, are more likely to become test-positive later than those born to cows who never test positive.
Therefore, you may not want to breed replacements from cows that have tested positive.
You could use a simple method like putting a red tag in the ears of cows that have tested positive, so you can easily differentiate them and manage them differently.
Q. What about vaccination?
A. There is a vaccine against Johne’s disease but limited efficacy. This is mainly because calves are usually infected in the first few days of life, meaning they are already infected by the time they get vaccinated.
The vaccine does not prevent infection; it also can’t stop an infected cow from shedding the bacteria in her faeces and infecting others in the herd.
However, it does extend the time before an infected cow shows clinical signs, so she has a longer productive life.
Vaccination shouldn’t be used as the sole control method. You should only vaccinate if you have a clear exit strategy and understand the implications of vaccinating. Once a herd is vaccinated, it can become difficult to tell whether an animal is infected because the tests cannot tell the difference between antibodies from infection and antibodies from a vaccine.
Q. Where can I learn more about Johne’s disease and how to control it?
A. It’s a Red Tractor requirement in Great Britain for all assured farms to have a MJMP in place. This plan is tailored to your farm and uses one of six strategies to manage Johne’s disease depending on your system, the level of Johne’s disease in your herd and your priorities on your farm.
It is put in place with the help of a vet accredited by the BCVA. It is then reviewed annually, and you can change to a different control strategy if appropriate.
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