New Veterinary Diagnostic Techniques for Equine Rhinopneumonitis in 2025

The national standard "Diagnostic Techniques for Equine Rhinopneumonitis" (GB/T 27621-2024) has been published by the National Animal Health Standardization Technical Committee and is set to be implemented on June 1, 2025.This document outlines updated diagnostic methodologies for equine rhinopneumonitis, a viral respiratory disease that affects horses of all ages. It often occurs in young horses and is most prevalent in foals under 2 years of age, and can result in significant health complications and economic losses in the equine industry.The new standard is essential for veterinary diagnostic manufacturers, regulatory affairs managers, and animal health professionals working in China.

Overview of GB/T 27621-2024

The standard provides a structured approach to diagnosing equine rhinopneumonitis, a disease caused by the equine herpesvirus type 1 (EHV-1) and type 4 (EHV-4). It incorporates multiple diagnostic methods, including the following:

Clinical diagnosis
PCR detection
Virus isolation
Serologic testing methods
Microserum neutralization test
ELISA

The new standard replaces the previous version, GB/T 27621-2011, and is intended to improve the detection and management of the disease, ensuring timely interventions to control outbreaks and reduce the risk of transmission within equine populations.

Key Diagnostic Techniques for Equine Rhinopneumonitis

1) Clinical diagnosisEHV-1 and EHV-4 primarily cause respiratory issues in horses, presenting as fever, loss of appetite, depression, nasal discharge, and breathing difficulties. EHV-1 can also lead to sudden, unexplained abortions in pregnant mares, often accompanied by fever and depression. Aborted fetuses are typically stillborn, and live-born foals rarely survive more than a few days. EHV-4 has been occasionally linked to fetal loss as well.In some cases, EHV-1 may cause neurological symptoms, including ataxia, mild paralysis, stiffness, and urinary incontinence, usually alongside fever, respiratory issues, or abortion. Pathological findings include abnormal mucosal folds in the trachea and digestive tract, enlarged lymphoid tissues, and ulcers.In aborted fetuses, signs such as hemorrhages, pulmonary edema, liver necrosis, and fluid buildup in the chest and abdomen are common. Severe cases may exhibit vasculitis, blood clots, and nerve damage from impaired blood flow.2) PCR DetectionPCR is a key method for detecting viral DNA in equine samples such as nasal swabs, blood, or tissue. Both conventional and real-time PCR are highly sensitive, identifying the virus even in early or asymptomatic stages. Real-time PCR is especially useful for measuring viral load to evaluate infection severity. To validate results, fluorescent PCR primers can be used for amplification, with the products sequenced and compared to published EHV-1 or EHV-4 sequences to confirm accuracy.3) Virus IsolationVirus isolation is vital for confirming equine rhinopneumonitis. Samples like nasal swabs or lung tissues are cultured in cell lines such as E-derm (equine-derived) or RK-13, BHK-21, and MDBK (non-equine-derived) to facilitate viral replication. Positive samples display cytopathic effects (CPE), including cell rounding, detachment, lysis, or lack of staining. Samples without CPE are considered negative. This method is often combined with PCR for accurate diagnosis.4) Microserum Neutralization TestThis test detects recent EHV infections by measuring a significant (4-fold or greater) increase in antibody levels between the acute and recovery phases. Blood is collected at symptom onset (acute phase) for the first sample and again 2 to 4 weeks later (recovery phase). If the antibody levels in the recovery sample are at least 4 times higher than in the acute sample, the animal is confirmed to have a recent EHV infection.5) ELISAIndirect ELISA is used to detect and differentiate EHV-1 and EHV-4 antibodies. For the universal test, the result is based on the S/P value of the serum sample. An S/P value ≥0.3 indicates the presence of EHV-1 and/or EHV-4 antibodies, while a value <0.3 indicates their absence.For typing, the S/P value determines whether the sample is positive or negative for EHV-1 or EHV-4 antibodies, following the same threshold of ≥0.3 for positivity and <0.3 for negativity. Commercial kits were used for the assays, performed according to the manufacturer’s instructions.

Relevance to International Regulatory Affairs Experts

The implementation of GB/T 27621-2024 highlights China's commitment to improving veterinary diagnostic standards and aligning them with global best practices. Veterinary regulatory affairs experts in other countries may benefit from understanding this standard, particularly in regions where equine rhinopneumonitis is a concern.The incorporation of advanced diagnostic techniques, such as PCR and ELISA, provides an opportunity for international collaboration in the management of this viral disease, which affects horses worldwide.

Implementation and Compliance for Veterinary Manufacturers

Veterinary diagnostic product manufacturers must ensure their products comply with the requirements set forth in GB/T 27621-2024. This includes updating diagnostic tools such as PCR kits, ELISA assays, and virus isolation protocols to meet the new standards.Manufacturers should also review and revise their product validation procedures to ensure they align with the latest diagnostic methods, ensuring they provide effective solutions for equine rhinopneumonitis detection and management.

Further Information

To access the Diagnostic Techniques for Equine Rhinopneumonitis update, please click here.Read more about New Veterinary Diagnostic Techniques for Canine Distemper