Detection of horses infected naturally with equine infectious anemia virus by nested polymerase chain reaction.

The research article discusses the development of a nested polymerase chain reaction (PCR) for detecting equine infectious anemia virus (EIAV) in horses. It emphasizes the test’s efficiency in diagnosing infected horses and identifying novel EIAV variants, proving to be as specific as the conventional Coggins test.

Methodology and Analysis

• The researchers designed the nested PCR to amplify a region in the gag gene of EIAV, aiming to quickly identify proviral DNA from the blood of naturally infected horses.
• To validate this test’s effectiveness, the researchers conducted the procedure on DNA prepared from white blood cells of 122 field horses from 15 stables with reported EIAV cases. One seronegative stable also took part in the study to serve as a control group.
• 88 horses yielded amplifications with the expected size of fragments when tested using two different sets of primers targeting the gag region. They confirmed these amplified products’ specificity with a hybridization process involving a digoxigenin-labeled probe.

Identification of Gag Gene Subtypes

• The research further delved into distinguishing two different subtypes of the gag gene, subtype A and subtype B, using Gag-nested PCR-restriction fragment length polymorphism analysis. Subtype A was found to be more prevalent among tested infected horses.
• The researchers identified subtype A as a potential novel EIAV variant in Canada, with 84.6% nucleotide and 93% deduced amino acid sequence identities shared with the Wyoming strain prototype.
• Meanwhile, the sequence of subtype B was almost 100% identical to the prototype, thus not suggesting any significant alterations.

Comparison with the Coggins Test

• On comparing the effectiveness of the newly developed nested PCR test and the traditional Coggins test (agar gel immunodiffusion assay), the researchers pointed out the equal specificity of both the methods.
• However, the nested PCR assay proved to be a more effective diagnostic test as it detected more EIAV positive horses in the study, providing a potential edge in future EIAV diagnoses.