Evaluation of cobas Influenza A/B & RSV Test for Diagnosis of Equine Influenza

Performance of a microfluidic immunofluorescence assay kit for equine influenza virus antigen detection

Equine influenza virus (EIV) infection is one of the most important respiratory diseases in the equine industry around the world. Rapid diagnosis, facilitated by point-of-care testing, is essential to implement movement restrictions and control disease outbreaks. This study evaluated a microfluidic immunofluorescence assay kit, which detects influenza virus and SARS-CoV-2 antigens in human specimens with a 12 min turnaround time, for its potential use in detecting EIV. The microfluidic immunofluorescence assay kit succeeded in detecting 11 EIV strains. Using the real-time reverse transcription polymerase chain reaction as a reference assay, the microfluidic immunofluorescence assay kit showed a sensitivity of 60.7% when evaluating nasopharyngeal swab samples of three horses experimentally infected with EIV. Comparing with the other two rapid antigen detection kits based on immunochromatography and silver amplification immunochromatography, the microfluidic immunofluorescence assay kit exhibited higher sensitivity than the former assay (53.6%) and the same sensitivity as the latter (60.7%). The microfluidic immunofluorescence assay kit did not detect nine non-EIV viruses including one equine coronavirus strain and seven bacteria, suggesting a high specificity for EIV antigens. Similar to other rapid antigen detection kits, the microfluidic immunofluorescence assay kit could be an effective diagnostic tool to detect EIV in the field.

Outbreak of equine coronavirus infection among riding horses in Tokyo, Japan

In 2020, an outbreak of equine coronavirus (ECoV) infection occurred among 41 horses at a riding stable in Tokyo, Japan. This stable had 16 Thoroughbreds and 25 horses of other breeds, including Andalusians, ponies and miniature horses. Fifteen horses (37 %) showed mild clinical signs such as fever, lethargy, anorexia and diarrhoea, and they recovered within 3 days of onset. A virus neutralization test showed that all 41 horses were infected with ECoV, signifying that 26 horses (63 %) were subclinical. The results suggest that subclinical horses played an important role as spreaders. A genome sequence analysis revealed that the lengths from genes p4.7 to p12.7 or NS2 in ECoV differed from those of ECoVs detected previously, suggesting that this outbreak was caused by a virus different from those that caused previous outbreaks among draughthorses in Japan. Among 30 horses that tested positive by real-time RT-PCR, ECoV shedding periods of non-Thoroughbreds were significantly longer than those of Thoroughbreds. The difference in shedding periods may indicate that some breeds excrete ECoV longer than other breeds and can contribute to the spread of ECoV.