Real-time quantitative RT-PCR and PCR assays for a novel European field isolate of equine infectious anaemia virus based on sequence determination of the gag gene.
Authors: Quinlivan M, Cook R F, Cullinane A
Journal: The Veterinary record
Summary
# Editorial Summary Following a 2006 outbreak of equine infectious anaemia in Ireland traced to contaminated Italian plasma imports, researchers sequenced the gag gene of the Irish field isolate and compared it with North American and Asian strains, revealing that this genomic region shows greater variation across geographic populations than previously recognised. Using the Irish isolate's gag sequence as a template, the team developed real-time quantitative RT-PCR and conventional PCR assays with high sensitivity and specificity, enabling simultaneous detection and quantification of viral nucleic acid across multiple sample types. The assays successfully quantified EIAV in postmortem tissues, plasma, and secretions, with particular significance being the first-ever detection and quantification of the virus in nasal, buccal, and genital swabs—establishing these as viable diagnostic specimens. Although phenotypic similarities persisted despite genotypic variation between strains, the improved diagnostic capacity offers practitioners and veterinary authorities more flexible sampling protocols for both clinical diagnosis and epidemiological surveillance, reducing reliance on invasive blood collection in field situations. These molecularly-tailored detection tools are particularly valuable for early identification in at-risk populations and for monitoring viral load dynamics during disease progression or treatment response.
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Practical Takeaways
- •EIA can be transmitted through contaminated plasma products; screening of imported blood products and strict biosecurity protocols are essential to prevent introduction of novel EIAV strains
- •The new RT-PCR assays enable more sensitive detection of EIAV in secretions and tissues, improving diagnostic capability for disease confirmation and epidemiological investigation
- •Genotypic variation in EIAV does not reliably predict phenotype or virulence, so molecular characterization of outbreak strains is important for understanding transmission dynamics and outbreak response
Key Findings
- •The first nucleotide sequence of the gag gene from a European EIAV strain (EIAV(Ire)) was identified from an outbreak in Ireland in 2006, with origin traced to contaminated plasma imported from Italy
- •The gag gene is less conserved than previously believed, with EIAV strains showing considerable genotypic variation despite similar phenotypes
- •Highly sensitive, specific and quantitative RT-PCR and PCR assays were developed based on EIAV(Ire) sequence and successfully detected and quantified EIAV in plasma, postmortem tissues, and swab samples
- •EIAV nucleic acid was detected for the first time in nasal, buccal and genital swabs using RT-PCR, expanding diagnostic capabilities