A study published in the February 2009 issue of Small Ruminant Research compared the ELISA method of diagnosing caprine arthritis encephalitis virus (CAEV) using samples of milk whey and the usual blood samples. Samples of each were taken from 66 lactating dairy goats whose infection status for CAEV was already known. All of the goats whose blood samples tested positive for CAEV also had positive tests using the milk samples; the same was true for those with negative tests.
The researchers concluded that using ELISA on milk whey samples is an appropriate method for diagnosing CAEV, and it may be even better because the test is non-invasive (no need to draw blood) and may be less expensive.
Any goat keeper can learn to draw blood from his or her goats (you can find detailed instructions in Goat Health Care), but for those who are milking their goats, wouldn't it be nice to just save a sample and send it in to the lab for annual testing?