These include, decreasing milk production in lactating females, continuous weight loss and fading hair coat colour. Despite the animal s worsening condition, they tend to be alert and the temperature and appetite are usually normal. The immune system becomes compromised by the continual loss of protein, rendering the animal more susceptible to all types of stress. Currently, there is no single, good test for Paratuberculosis, therefore a combination of post mortem examination, differential staining of bacteria, culture of organisms and serology are used. Herd testing rather than individual animal testing increases diagnostic success rates.
Fecal testing is relatively specific if the proper culture media on a species basis is utilized.
Veterinary practitioners should be aware that cattle and goats are easiest to culture, that elk are not as easy to culture as cattle however relative success can be realized, and that bison and sheep are very difficult to culture on routine media. Animals may shed organisms intermittently and repeated samples may be necessary to confirm infection. Traditionally, garnering results from culture testing for Paratuberculosis takes up to three months. Recent technological advances in DNA analysis techniques are reducing positive identification to two to four weeks rather than months. Standard serologic tests vary in sensitivity and specificity but are generally not satisfactory at identifying subclinical cases.