Assessment of quantitative polymerase chain reaction for equine herpesvirus-5 in blood, nasal secretions and bronchoalveolar lavage fluid for the laboratory diagnosis of equine multinodular pulmonary fibrosis.

The research paper presents a study examining the effectiveness of quantitative polymerase chain reaction (qPCR) to detect equine herpesvirus-5 (EHV-5) for the diagnosis of a specific respiratory disease in horses, equine multinodular pulmonary fibrosis (EMPF). Samples of blood, nasal secretions, and bronchoalveolar lavage fluid (BALF) were tested on horses with confirmed EMPF, healthy horses, and horses with non-EMPF pulmonary diseases to establish the diagnostic power of EHV-5 testing.

Research Objective

The main goal of the research was to ascertain the frequency of EHV-5 detection and the levels of the virus in blood, nasal secretions and BALF from the three aforementioned groups of horses. The researchers aimed to better understand the utility and validity of qPCR testing on these biological samples to support a diagnosis of EMPF.

Methodology

• The researchers conducted a prospective study with 70 adult horses, which they divided into four groups based on clinical findings, BALF cytology, thoracic cavity imaging studies, and lung tissue histopathology.
• The four groups consisted of a control group (14 horses), an EMPF-confirmed group (11 horses), an inflammatory airway disease group (32 horses), and a non-EMPF interstitial lung disease group (13 horses).
• For each horse, samples of whole blood, nasal secretions, and BALF were obtained for EHV-5 qPCR testing.
• The researchers then calculated the sensitivities, specificities, and corresponding 95% confidence intervals for the viral loads derived from each sample type, and similarly for blood and nasal secretions combined.

Key Findings

• The detection of EHV-5 in BALF was strongly linked with EMPF, with a sensitivity of 91% and specificity of 98.3%, making it a reliable diagnostic sample.
• The detection of EHV-5 in blood also strongly indicated EMPF, with 91% sensitivity and 83.1% specificity regardless of viral load—suggesting blood as another potentially reliable sample for diagnosis.
• Nasal secrets had the highest sensitivity (72.7%) and specificity (83.1%) for diagnosing EMPF when the viral load was above a set threshold.
• Both blood and nasal secretions testing positive for EHV-5 supported an EMPF diagnosis with a sensitivity and specificity of 90% and 89.8%, respectively.

Conclusions

The paper concludes that while histopathological confirmation via lung biopsy is still the gold standard diagnostic method for EMPF, qPCR tests on BALF or a combination of whole blood and nasal secretions are both clinically useful accompaniments. This is especially relevant in cases involving horses in respiratory distress, where invasive procedures might negatively impact health.