Investigation of the epidemiology of calicivirus infection of cats using molecular and virus isolation techniques

Abstract

Feline calicivirus (FCV) an important and widely detected upper respiratory system agent in cats. Being genetically diverse, FCV can cause different symptoms, such as pneumonia, oral lesions, conjunctivitis, arthritis, and, recently, virulent systemic disease. The present study first determined the presence/prevalence of FCV infection in sampled vaccinated/unvaccinated cats with suspected FCV and/or clinically healthy. Second, it compared PCR and virus isolation (VI) in detecting FCV in these cats. It also aimed to diagnose FCV, and evaluate the advantages/disadvantages of the region and primers used for PCR. Third, it genetically characterized the FCV strains, targeting the VP1 (A-B and E) gene region. A total of 331 diagnostic materials (conjunctival, nasal, oropharyngeal swab samples, and EDTA-containing blood samples) were obtained from 107 cats and checked using PCR and VI. Including both tests, the overall FCV positivity rate was 43.93 % (47/107). The FCV positivity rate was 35.99 % (21/59)/53.33 % (24/45) in vaccinated/unvaccinated and 58.06 % (18/31)/38.16 % (29/76) in clinically infected/clinically healthy cats, respectively. As a result of direct nested RT-PCR, FCV positivity was detected in 23.08 % of oropharyngeal swabs, 15.24 % of nasal swabs and 14.02 % of conjunctival swabs based on diagnostic material. FCV was also detected in 19.63 % (21/107) of the cats after virus isolation. Those samples that were FCV positive for VP1 A-B and VP1 E were subjected to sequence and phylogenetic analysis. Regarding many of the detected viruses were similar to the viruses in Genogroup I, while two viruses (ANK111OSW and ANK113OSW) were phylogenetically similar to both Genogroup I and Genogroup II at the same rate (74.30 %). The findings indicate a, higher overall FCV detection rate than in previous studies in Türkiye. Molecular diagnostic methods are not always sufficient for diagnosing infection due to FCV’s genetic diversity from mutation and, recombination. Hence, including VI techniques in FCV evaluation will help prevent false negative results. Furthermore, testing oropharyngeal, nasal and conjunctival swabs together for FCV is believed to provide more accurate results.