Development and application of a dual ERA method for the detection of Feline Calicivirus and Feline Herpesvirus Type I

Feline calicivirus (FCV) and feline herpesvirus type I (FHV-1) are the most common viral pathogens responsible for cat respiratory diseases, and coinfection with these two pathogens is often found. In veterinary clinics, the main diagnostic methods for FCV and FHV-1 are test strips and polymerase chain reaction (PCR). However, the sensitivity of test strips are not sufficient, and PCR is time-consuming. Therefore, developing a rapid and high-performance clinical diagnostic test is imperative for the prevention and treatment of these diseases. Enzymatic recombinase amplification (ERA) is an automated isothermal nucleic acid amplification technique that maintains a constant temperature, and is both rapid and highly accurate. In this study, a dual ERA method was developed using the Exo probe for a differential detection of FCV and FHV-1. This dual ERA method demonstrated high performance with the detection limit of 101 copies for both viruses, and no cross-reactions with feline parvovirus virus and F81 cells. To test the utility of the method for clinical applications, 50 nasopharyngeal swabs from cats with respiratory symptoms were collected and tested. The positive rates of FCV and FHV-1 were 40% (20/50, 95% confidence interval [CI], 26.4 to 54.8%) and 14% (7/50, 95% CI, 5.8 to 26.7%), respectively. The rate of coinfection with FCV and FHV-1 was 10% (5/50, 95% CI, 3.3 to 21.8%). These results were in agreement with those found using quantitative real-time PCR. Therefore, this dual ERA method is a novel and efficient clinical diagnostic tool for FCV and FHV-1 detection.