Abstract

Feline calicivirus (FCV) is a common cause of upper respiratory and oral disease in cats. Highly virulent systemic strains of FCV (vs FCV) have been described. These vs FCV isolates cause characteristic edema, cutaneous ulcers and other clinical signs typically associated with FCV infection. Vs FCV isolates also cause high mortality even in previously vaccinated cats. We reported previously that the FCV serum cross-neutralization profile of cat serum generated using the oralnasal route of administration is broader than with subcutaneous administration (SC), as measured with a 26-FCV viral panel (Rong et al., Virus Research 122:95-108, 2006). In this report, we tested the in vivo ef- ficacy of the FCV vaccine, in a 4-way (FCV-FHV-FPV-FCp) format, by using a highly virulent vs FCV- 33585 as the challenge virus. Vaccines were administered as 2-dose subcutaneouly (SC/SC), or subcutaneously followed by orally (SC/Oral). The mortality induced by vs FCV-33585 in unvaccinated control cats was 78% (7 out of 9 cats). The mortality decreased to 44% (4 out of 9 cats) with cats vaccinated with the 4-way vaccine given SC/SC. However, when this vaccine was given SC/Oral, the mortality decreased to 10% (1 out of 10 cats). The clinical scores, calculated based on frequency and severity of various clinical signs, correlated with mortality data. These results demonstrated that oral administration of FCV vaccines, as the second dose following the first dose of subcutaneious administration, ehances FCV efficacy against challenge of a highly virulent vs FCV. We propose that not only oral vaccination offers convenience and needle-free inoculation, it also enhances FCV vaccine efficacy.

Highlights

  • Caliciviruses are a family of small viruses that possess a positive-strand, non-segmented, polyadenylated RNA genome of about 7.5 kb

  • Using 23 as the cut-off value for neutralization titers, ON vaccination resulted in 26% of the 26 feline calicivirus (FCV)-panel members neutralized, while subcutaneous administration (SC) vaccination resulted in only 16% neutralized

  • We hypothesize that the results suggest possible enhanced FCV vaccine efficacy with ON administration when compared with SC administration

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Summary

Introduction

Caliciviruses are a family of small viruses that possess a positive-strand, non-segmented, polyadenylated RNA genome of about 7.5 kb Members of this family include feline calicivirus (FCV), rabbit hemorrhagic disease virus (RHDV), San Miguel sea lion virus (SMSV), vesicular exanthema virus of swine (VEV) and many human caliciviruses [1] [2]. The signs of illness produced by FCV infections in the cat vary markedly, depending on the strain involved, the severity of the exposure and the resistance of the host [2]. Strains of low virulence produce moderate pyrexia and can produce ulcers of the tongue, hard palate and nose. In addition to pneumonic signs produced by vsFCV isolates, ulcers of the tongue, hard palate and nose may occur. US, UK, as well as France and Germany, all reported vs FCV outbreaks [15] [16]

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