Elisa testing is not a good individual goat test for disease, most useful as a test for indicating general herd health. Here's a link to help you understand what tests to use for the purpose you intend, as well as an indicator of accuracy of the different tests, good to know before you spend your $$.
After speaking with Dr Everman at WADDL countless times just recently here is what I learned about the different types of testing....
AGID is good in the sense it will NOT give you a false positive, but it will definately give you a false negative if the goat isn't far enough along in the disease to be shedding the organism
Fecal will also never give you a false positive, but again it is pretty much usless unless your goat is showing clinical signs of Johnes...you really only do a fecal if you get a goat that tests positive on an ELISA test twice. Otherwise, if your goat is wasting away and showing all of the other signs, the organism has already been spread onto the ground and its far too late to cull that goat and save the rest of your ground.
Necropsy- well we wont even go there, you goat has either been euthanized for the disease, or died from it....
ELISA while in very rare cases you can get a false positive (ESPECIALLY when using incorrect testing methods...if you want more details on this and what labs NOT to use..... please PM me...) it has the HIGHEST sensitivity for detecting the Johnes organism.
So yes- with ANY Johnes testing, there is a chance you could test a goat and they just arent far enough along to show up in testing, so there is always that risk, which is why most herds will test yearly for Johnes.
But in my opinion from all of the research I have gathered, the correct ELISA test is the best early detection test for Johnes.
An ELISA test only tests for antibodies to disease, not for actual disease itself, therefore false positives are definitely possible.
If you read more than just the page I linked to you will learn a lot more about the tests and their accuracy, even the fecal test can possibly give a false positive for feed through disease that is in the ground etc. while the animal itself may not be infected.
It is my understanding that the only absolute positive test is done on tissue itself, biopsy of intestine, etc.
I definately agree here! Its really unforunate thats the only 100% positive test
I never said WADDL was the holy grail, or that the ELISA test was either, just stating in my opinion (as I said in my post), I prefer the ELISA test, and also testing with a lab that uses correct testing, as opposed to some other labs that are operating WITHOUT approved testing for Johnes...
Speaking with many other breeders across the country, WADDL is by far the lab of choice among them. There must be a reason for that.
"Enzyme-linked immunosorbent assay (ELISA) may be useful in the future. However, this assay lacks standardization and validation across laboratories at the present time, and the difficulty of using culture as the "gold standard" complicates validation of tests. The currently licensed test as formatted for cattle has not yet been shown to be useful in sheep. One report examining its usefulness in goats looks promising, but only relatively small numbers of animals were used, and the test method was modified. Evidence exists that infections in sheep with Corynebacterium pseudotuberculosis, the cause of contagious abscesses in sheep and goats, may cause cross reactions and false positives in ELISA. "
I posted the original link so that the original poster could make up her own mind what tests to do and where to get them done at. One thing I've learned from many years as a nurse is that no one source of information is the only correct one and that any medical test can possibly be inaccurate, we are all only human. I just want to point out that WADDL does have a vested interest in telling you that they have the most accurate testing, they are a business after all, they want your $$ spent there, I'm not saying that they do or don't, it's just something to consider.