Epidemiological Investigation of Feline Upper Respiratory Tract Infection Encourages a Geographically Specific FCV Vaccine

Abstract

A total of 1158 cats with feline upper respiratory tract infection were incorporated from twenty animal hospitals in Wuhan, China, from April 2019 to April 2022 to investigate the epidemiology of feline calicivirus (FCV), herpesvirus-1 (FHV-1), Mycoplasma felis (M. felis) and Chlamydia felis (C. felis) for the development of a geographically-specific FCV vaccine with reference to prevalence and risk factors for infection. The 871 samples (75.2%) of kittens were younger than 12 months, of which 693 were males, and 456 were females. Among the samples, 443 were British shorthair cats, accounting for 38.3%, and 252 were Chinese rural cats, accounting for 21.8%. PCR/RT-PCR detection of the above four viruses (FCV, FHV-1, M. felis, and C. felis) in the upper respiratory tract of cats showed that the total positive samples were 744 (64.3%), including 465 positive samples of feline calicivirus, accounting for 40.2% of the total 1158 samples. There were 311 positive samples of M. felis, accounting for 26.9% of the total samples, ranked second in clinical practice. The 180 positive samples of feline herpesvirus accounted for 15.5%, and 85 positive samples of Chlamydia felis accounted for 7.3%. Among them, the number of positive samples of single pathogenic infections was 493, accounting for 66.3% of the total 744 positive samples. Double, triple, and quadruple infections accounted for 28.2%, 5.0%, and 0.5%, respectively, with the highest proportion of single infections. The molecular biological characteristics of the 17 isolated FCVd strains in Wuhan were further analyzed. It was found that the F9 vaccine strain and the antigenic epitopes in the 5’HVR of the E region were collated with the F9 vaccine strain. Moreover, phylogenetic tree analysis showed that the strains related to the F9 and 255 vaccines were distantly related, leading to the failure of the vaccine. In addition, the strains associated with the F9 and 255 vaccines were distant, which might lead to vaccine failure in anticipation of the development of a more phylogenetically close FCV vaccine in China and may require the development of a vaccine for a locally related FCV strain.

Epidemiological Surveillance of Respiratory Diseases in Urban Stray Cats in Shanghai

“…In this study, FHV-1 showed a higher positivity rate in winter compared to summer, while FCV exhibited a higher positivity rate in summer than in winter, consistent with the findings reported by Gao et al [ 20 ]. This variation may be related to the physical and chemical properties of the viruses themselves.…”

Biological Characteristics of Feline Calicivirus Epidemic Strains in China and Screening of Broad-Spectrum Protective Vaccine Strains

“…The continuous evolution of FCV viruses poses challenges to vaccine design [ 34 ]. Several studies have indicated that vaccine strains used over decades may have become less effective, and that there are differences in neutralizing titers between FCV epidemic isolates from different regions and vaccine strains, which has also been confirmed by our previous research [ 27 , 29 ]. The FCV-255 inactivated vaccine widely used in China has limited in vitro cross-neutralizing potency against the Chinese epidemic strains, and it may not provide effective protection [ 22 , 30 , 35 ].…”

“…Cats with a history of immunization are still susceptible to new epidemic strains [ 26 ]. The persistent high mutability of FCV epidemic strains has greatly increased the clinical demand for new FCV vaccines [ 27 ]. Therefore, the diversity of FCV genotypes should be taken into account in the development of new FCV vaccines [ 28 ].…”

Drug screening identified that handelin inhibits feline calicivirus infection by inhibiting HSP70 expression in vitro

“…FCV is a nonenveloped, positive-sense, ssRNA virus that belongs to the family Caliciviridae [6,14], and its 7-8 kb RNA genome has three ORFs, ORF1, ORF2 and ORF3 [3,6,15]. Notably, ORF2 encodes the capsid protein VP1, which includes six regions, and regions C and E are variable; thus, new mutated strains are constantly emerging [3,6,9,16]. Although commercial vaccines have been approved for preventing FCV-induced disease, whether the existing commercial vaccines exhibit cross-protection against the newly emerging FCV strains is unknown [3,9].…”

“…Although commercial vaccines have been approved for preventing FCV-induced disease, whether the existing commercial vaccines exhibit cross-protection against the newly emerging FCV strains is unknown [3,9]. Since the prevention and control of the disease are limited, it is necessary to find and develop novel antiviral compounds [16]. Previous studies have discovered that several compounds, including sinefungin, poly (sodium 4-styrenesulfonate), the analogue NITD008, nitazoxanide, mefloquine, copper chloride and mizoribine, have antiviral activities [17][18][19][20][21][22][23].…”