Johnes Disease in Cattle
What is Johne’s and how is it spread?
- Caused by a bacterium called Mycobacterium Avian subspecies Paratuberculosis (MAP)
- This targets an animal’s intestine, making the walls thick and unable to absorb protein.
- It is slow to progress. Signs usually appear between 4-7 years of age (although can happen from a year).
- Infections occur either in the womb, or in the first month of life.
- It is spread by ingesting infected faeces, colostrum or milk (the first being the most common route)
Why is it significant?
**LOSS OF PROFIT– It can have a massive negative impact on your herd’s productivity and profitability.
In dairy cattle studies have shown that those with Johne’s : produce 4000kg less milk in their life; are 5 x more prone to lameness; are 2 x more prone to SCC/mastitis problems and are 1.8 x more prone to gut issues.
Beef animals will struggle to finish and achieve a good slaughter weight.
**Beef herd accreditation via CHeCS: To achieve accreditation, you need to undertake whole herd testing as part of the scheme requirements.
** It is likely that testing will become more rigorous in the future and that it will be a pre-requisite before a milk-buyer will take a farm on as a supplier, so it is worthwhile getting a headstart! The National Johnes Action Plan started in April 2015 – it aims to engage over 80% of dairy farmers in England and Wales, who should all know their status and have an action plan in place by April 2016.
What are the signs?
Only 1% of infected individuals will go on to show signs. These may include diarrhoea (like ‘pea green soup’!), loss of condition despite a good appetite and normal temp, drop in milk and a swelling under the jaw (‘bottle jaw’). There is no cure, and the disease ultimately ends in malnutrition and death.
How do we diagnose a suspected case of Johne’s?
If we suspect Johne’s we confirm our diagnosis through lab tests. Usually we take a blood sample, but milk and dung samples can also be helpful.
How do I find out if I have hidden cases in my herd?
Undertake a herd screening test. This is done by taking blood, milk and/ or dung samples from several individual cows which are
- 3 – 7 years old
- affected by lameness
- ‘Poor doers’
- Repeat high SCC/ mastitic cows
- Showing a drop in milk yield
If you milk record you can have milk samples from appropriate cows automatically selected. Contact your recording organisation for more info. Bulk milk testing is not recommended for screening as it isn’t sensitive enough. A negative result on bulk milk can still occur in a herd with high levels of infection.
Uh oh, my herd status is positive, now what?
Time to look at some control strategies.
- Improve management- Breaks disease transmission from cow to calf. Change management of calving, colostrum and milk. Treat every cow as if infected.
- Improve management and individual testing- Test individuals to find which are at risk, direct management appropriately.
- Improve management, test and cull- As above but cull any positive animals immediately.
- Breed to Terminal Sire – All offspring fattened for slaughter, no home bred replacements, buy in from low risk farms.
- Firebreak Vaccination – Only used to buy time whilst finding a better strategy. Limited efficacy, can interfere with TB test results (false positives).
These are not ‘one size fits all’. To decide which will work best on your farm, have a chat to one of the large animal vets.
I’m Johnes free! Now what?
Ongoing monitoring is recommended via targeted 30 cow screens. Quarterly surveillance packages are also available through milk recording. Control measures will be hugely important to keep your herd Johne’s free.