Efficacy of Intranasal Administration of a Modified Live Feline Herpesvirus 1 and Feline Calicivirus Vaccine against Disease Caused by Bordetella bronchiseptica after Experimental Challenge

Background Studies suggest that intranasal vaccination can stimulate nonspecific immunity against agents not contained within the vaccine, but this effect is not reported for cats. Hypothesis A modified live feline herpesvirus-1 (FHV-1) and feline calicivirus (FCV) intranasal vaccine will reduce clinical signs of disease caused by experimental infection with Bordetella bronchiseptica. Animals Twenty specific pathogen-free 12-week-old kittens. Methods Experimental study. Cats were randomized into 2 groups of 10 cats each. The vaccinated group was administered a single intranasal dose of a commercially available vaccine containing modified live strains of FHV-1 and FCV, and the control group remained unvaccinated. All 20 cats were administered B. bronchiseptica by nasal inoculation 7days later and were observed daily for clinical signs of illness for 20days. Results In the first 10days after B. bronchiseptica challenge, vaccinated cats were less likely to be clinically ill than control cats with a median clinical score of 0/180 (range 05) versus 2/180 (range 08) (P=.01). Nine of 10 control cats and 2 of 10 vaccinated cats were recorded as sneezing during days 110 after challenge (P=.006). Conclusions and Clinical Importance Intranasal vaccination against FHV-1 and FCV decreased signs of illness due to an infectious agent not contained in the vaccine. This nonspecific immunity could be beneficial for protection against organisms for which vaccines are not available and as protection before development of vaccine-induced humoral immunity.