Abstract
Equine influenza (EI) is a highly contagious disease caused by viruses of the H3N8 subtype. The rapid diagnosis of EI is essential to reduce the disease spread. Many rapid antigen detection (RAD) tests for diagnosing human influenza are available, but their ability to diagnose EI has not been systematically evaluated. The aim of this study was to compare the performance of 22 RAD tests in the diagnosis of EI. The 22 RAD tests were performed on fivefold serial dilutions of EI virus to determine their detection limits. The four most sensitive RAD tests (ImmunoAce Flu, BD Flu examan, Quick chaser Flu A, B and ESPLINE Influenza A&B-N) were further evaluated using nasopharyngeal samples collected from experimentally infected and naturally infected horses. The results were compared to those obtained using molecular tests. The detection limits of the 22 RAD tests varied hugely. Even the four RAD tests showing the best sensitivity were 125-fold less sensitive than the molecular techniques. The duration of virus detection in the experimentally infected horses was shorter using the RAD tests than using the molecular techniques. The RAD tests detected between 27% and 73% of real-time RT-PCR-positive samples from naturally infected horses. The study demonstrated the importance of choosing the right RAD tests as only three of 22 were fit for diagnosing EI. It was also indicated that even RAD tests with the highest sensitivity serve only as an adjunct to molecular tests because of the potential for false-negative results.
Highlights
equine influenza A virus (EIV) is a member of the family Orthomyxoviridae of the genus Influenza virus A.3
Viruses of the H3N8 subtype are a major cause of respiratory disease in horses throughout the world with the exception of the equine population in New Zealand and Iceland where Equine influenza (EI) has never been recorded.[5,6]
We evaluated the sensitivity of selected rapid antigen detection (RAD) tests licensed in Japan for the diagnosis of human or avian influenza, in the detection of EIV in nasopharyngeal swabs from both experimentally and naturally infected horses
Summary
Equine influenza (EI) is caused by equine influenza A virus (EIV) and is one of the most important respiratory diseases of horses due to its highly contagious nature.[1,2] EIV is a member of the family Orthomyxoviridae of the genus Influenza virus A.3 two subtypes of EIV have been recognized (H7N7 and H3N8), viruses of the H7N7 subtype have not been isolated for the last three decades and may be extinct.[4]. Equine influenza (EI) is caused by equine influenza A virus (EIV) and is one of the most important respiratory diseases of horses due to its highly contagious nature.[1,2] EIV is a member of the family Orthomyxoviridae of the genus Influenza virus A.3. Two subtypes of EIV have been recognized (H7N7 and H3N8), viruses of the H7N7 subtype have not been isolated for the last three decades and may be extinct.[4] In contrast, viruses of the H3N8 subtype are a major cause of respiratory disease in horses throughout the world with the exception of the equine population in New Zealand and Iceland where EI has never been recorded.[5,6] Horses infected with EIV exhibit the acute onset of pyrexia, associated with depression and anorexia, nasal discharge and coughing.[1,2] EIV infection occurs via the inhalation of aerosolized virus particle in the same way as human seasonal influenza.[1,5]. Equine influenza (EI) is a highly contagious disease caused by viruses of the H3N8 subtype. Many rapid antigen detection (RAD) tests for diagnosing human influenza are available, but their ability to diagnose EI has not been systematically evaluated
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