[kanisha]

Just curious, do any of you routinely screen your flock for Johnes? It seems to come up here often as a potential health problem. 
Do any of you have prevention strategies in place?

[waterbuffalofarmer]

No we don't, genetics are all good and we buy off reputable good sellers who test their flocks regularly for ailments. Vets haven't mentioned testing for said disease though, is it quite prevalent in UK ATM?

[kanisha]

when I wrote here I meant on this forum.  Which got me to wondering how easy is it to test a flock and  or routinely screen for it. Does anyone routinely screen for it either with their flocks or incoming stock? 

[Tim W]

I screen my flocks every year for MV/CLA/OJD/Toxo/Enzo

Test all incoming stock for above too ---read below for vets thoughts on OJD testing



I would suggest that OJD is massively underdiagnosed in the national flock though the actual figures are not known.  On average there have been 40 OJD cases a year sent to the AHVLA though it was found in 6% of ewes in a fallen stock pilot project that looked at 106 ewe carcasses.  One of the challenges is that 30% of cases are ‘paucibacillary’ which means they shed low numbers of MAP organism and have lower antibody response.
There is a blood test which has good specificity (ie not many false positives) but very low sensitivity – especially for the paucibacillary form.  It would make sense to blood test thin culls as well as take a pooled faecal sample for culture and PCR testing to check for freedom from the disease.
One of the best ways to demonstrate freedom from OJD would be to have a fallen stock regularly examined post mortem.

So I use a pooled faecal sample on an annual basis and then bloods for all bought in animals
I also tend to PM any fresh fallen stock

[kanisha]

thank you for the replies. I guess cost is an issue but if you can  use a pooled faecal sample for annual testing then it must help to keep costs down.  Food for thought.

[farmers wife]

It depends on whether you are seriously breeding to increase your flock or selling high quality breeding stock as Tim does.  As the vet says to me if you have no issues ie animals dropping dead, poor weights etc etc then it depends on whether you can afford/justify these tests.  Its going to cost you for tests and then if you can afford to start culling.


If you are buying in from all and sundry then you have to question your bio security.  If you test then you have to think about double fencing, gates shut, footpaths - doing one not the other is pointless.  Again if you keep cattle you would have to do the same.  I dont know costs but for SAC for cattle then its £5 each per animal per test min plus yearly licence fee. Something that we are considering as the risks are high. 


My sheep continually break through fences, wonder the forest and do what suits them for this reason its pointless.


I agree if you have healthy animals dropping dead then PM but again you would need to find a good farm practice that takes this seriously.

[kanisha]

SAC?
 A Pooled faecal sample exam  of the flock would seem more cost effective. 

[Tim W]

See attached document for SAC prices

If you are keen to start thinking about where your flock health status lies then I would suggest that screening for MV is a good way to start (£30 for 12 samples I think)

Pooled OJD is about £70 I think

[kanisha]

Thanks for the details . You see MV as more of a problem?

[Tim W]

I am told that MV could be more prevalent (and there are definitely hot spots) 
It also has better developed tests
And is potentially cheaper to test for

[kanisha]

Yes, was just wondering about  establishing what level of testing might be required and or how to go about that. Given that so many don't test.
 Bit like cat populations with  FIV infection. For the most part you don't see it, but are aware its circulating from time to time. Will have to consider lifestyle and prevention strategies before i get to routine testing.

thanks :-)

[CarolineR]

Hi, I work for SAC (we are a lab that provide Johne's disease testing, interpretation and post-mortem examinations to vets in practice).

The Johne's disease blood test is not great in sheep if they do not have clinical signs (symptoms). So, testing a sheep (or goat) that is thin or has diarrhoea might be worthwhile, but testing a totally healthy sheep is much less likely to spot it if they do have Johne's disease. Cattle are better to test when healthy, they are more likely to show up if they are positive.

Postmortem examination is definitely the best way to be absolutely sure that a sheep did not have Johne's disease, as, as is mentioned in the posts above, there is a "paucibacillary" form in sheep that you do not have to worry about in cattle usually - "paucibacillary" means "very little bacteria" and in this form, blood tests and poo tests are commonly negative because there is very few bacteria in the diseased part of the gut, even if the animal is dying of Johne's disease.

That said, if your own vet has recommended testing for Johne's disease when you buy in, then of course I would always advise you go with their advice- like anything else veterinary, your own situation (local geography, local hotspots, your own farm situation) may mean that testing is worthwhile in some situations where it is not necessarily the most cost effective thing for others, if the interpretation of the test is complicated like this one. But in general, if you are making a list of "stuff to test for" in sheep, then Johne's would be further down my general list for sheep owners except in certain situations. Top of my list would be definitely to get your worming, fluke and footrot quarantine and treatments right, and also to make sure they are vaccinated for clostridial disease (and pasteurella, preferably) and then, with regards to blood tests, knowing your Maedi Visna status, (and also Enzootic abortion and Toxoplasma if you are breeding, not all smallholders do, although I know that would be a daft question for most commercial folks!) would be more useful, although they are not a must-have for everyone. If you buy from Maedi Visna free flocks, or only have a very small flock yourself, then it might not be worth it to you. Currently the majority of sheep people do not test for Maedi visna, although we are trying to increase the number, because it is present in about 2-4 % of farm flocks, so it's not exactly rare.
Obviously Enzootic abortion and Toxoplasma tests can tell you if your flock is at risk of an abortion epidemic, or requires vaccination, so there is a practical benefit there as these diseases are extremely common.

With Maedi Visna, if you get it, you probably won't realise for a few years, and then it can really impact the productivity of your flock, and it's a devil to get rid of (one of the hardest). It is really easy to catch. Johne's disease is harder for sheep to catch from each other so less of them will typically get it than Maedi Visna, which can spread like wildfire but invisibly.
Hope this helps!
If you are interested in these diseases, what they are and how to screen for them, search for Premium Sheep and Goat Health scheme - it has all the info on the SRUC website so you can read all about them even if you are not thinking of joining  the scheme or anything, it's just free information on the website.

Kind regards,
Caroline

[kanisha]

thank you for the comprehensive reply.  the picture is becoming a lot clearer :-)