Ask for herd test results for TB, Brucellosis and CAE. Even in here in MI, not many people test for TB and especially Brucellosis. You can test before you buy, and pay for the test so the host herd doesn't dither. I go to the farm to look at the does, and draw blood out of the ones I'm interested in buying. Of course, you'd therefore have to buy goats that are 6+ months of age.
If you CAN'T find any negative CAE goats, it's honestly NOT a hard disease to manage. I know a few herds who keep a couple positives that are asymptomatic in the main herd. The milk is not used to feed kids and in the many years they've had those does, none of the negatives have ever switched to positive and they test every year.
It CAN transmit horizontally within a herd, but it is pretty unusual.
If you HAD to get CAE positive (or untested), then raising on prevention properly stops it in it's tracks. After catching kids for a few years out of your does and raising on prevention, you could cull the starter positive does and keep your replacement daughters.
I personally worry most about CL and Johnes disease. CL test isn't reliable (ask breeder if they have ever had any abscesses and if so, if they had them tested for CL). I only buy from herds who have heard of CL, CAE, and Johne's. If I want to buy something from them their herd must be abscess free (or had any abscess contents tested and be negative), and no symptoms of Johnes. Then I draw blood.
Understand that false positives/negatives are common with the CL test.
