Equine lentivirus, comparative studies on four serological tests for the diagnosis of equine infectious anaemia.

This research paper focuses on comparing four serological tests used for diagnosing equine infectious anemia, a disease caused by the equine lentivirus. It evaluates the popular Coggins-test, two different types of ELISA tests, and a Western blot test, analyzing their effectiveness, sensitivity, and reliability.

Comparison Between the Tests

• Since 1970, the most commonly used method for diagnosing equine infectious anemia has been the agar gel-immunodiffusion test, also known as the Coggins-test.
• Recently, ELISA tests have been introduced, which are faster and, theoretically, more sensitive.
• Furthermore, Western blot assays have been used to clarify questionable results from the Coggins-test.

Evaluating ELISA Tests

• The competitive ELISA test offered nearly equivalent results to the Coggins-test. This commercial product has been designed to have a just-adequate sensitivity to prevent false-positive results, which could lead to inaccurate identification of “reactor horses.”
• On the other hand, a non-competitive commercial ELISA test resulted in inconsistent findings. This inconsistency led to unnecessary panic among horse owners when their horses were falsely identified as positive.

Caution Required in Interpreting Western Blots

• Serums from strongly positive horses resulted in up to eleven bands in a Western blot test. Medium positives produced fewer bands, and the weakest reactors showed only the p26 band, which corresponds to the core protein of the equine lentivirus.
• Interestingly, 5% of healthy horses also demonstrated a single p26 band, showing that a positive result should not be solely based on this band’s appearance.
• For more accurate results, a positive Western blot for an equine lentivirus should demonstrate banding with its core protein plus at least one glycoprotein.