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Abstract

Objective

To evaluate duration of immunity in cats vaccinated with an inactivated vaccine of feline panleukopenia virus (FPV), feline herpesvirus (FHV), and feline calicivirus (FCV).

Animals

17 cats.

Procedure

Immunity of 9 vaccinated and 8 unvaccinated cats (of an original 15 vaccinated and 17 unvaccinated cats) was challenged 7.5 years after vaccination. Specific-pathogen-free (SPF) cats were vaccinated at 8 and 12 weeks old and housed in isolation facilities. Offspring of vaccinated cats served as unvaccinated contact control cats. Virus neutralization tests were used to determine antibody titers yearly. Clinical responses were recorded, and titers were determined weekly after viral challenge.

Results

Control cats remained free of antibodies against FPV, FHV, and FCV and did not have infection before viral challenge. Vaccinated cats had high FPV titers throughout the study and solid protection against virulent FPV 7.5 years after vaccination. Vaccinated cats were seropositive against FHV and FCV for 3 to 4 years after vaccination, with gradually declining titers. Vaccinated cats were protected partially against viral challenge with virulent FHV. Relative efficacy of the vaccine, on the basis of reduction of clinical signs of disease, was 52%. Results were similar after FCV challenge, with relative efficacy of 63%. Vaccination did not prevent local mild infection or shedding of FHV or FCV.

Conclusions

Duration of immunity after vaccination with an inactivated, adjuvanted vaccine was > 7 years. Protection against FPV was better than for FHV and FCV.

Clinical Implications

Persistence of antibody titers against all 3 viruses for > 3 years supports recommendations that cats may be revaccinated against FPV-FHV-FCV at 3-year intervals. (Am J Vet Res 1999;60:652–658)

Free access
in American Journal of Veterinary Research

Summary

Feline sera were submitted to the Cornell Feline Health Center (n = 497) or to the New York State Diagnostic Laboratory (n = 1,565) for feline immunodeficiency virus (fiv) testing. Some sera (n = 166) were submitted for confirmation of previous fiv-positive results; 151 of these sera had been tested at the referring veterinary practice or laboratory, using an in-house elisa. Excluding the samples submitted for confirmation, a total of 173 samples (9.1%) were fiv-positive; 11.6% of the clinically ill or high-risk cats and 0.49% of the healthy, low risk cats were positive for fiv antibody.

A commercially available elisa for detection of antibody to fiv was evaluated in relation to the immunofluorescent antibody (ifa) test and the immunoblot assay. The elisa was interpreted according to the manufacturer's instructions, with the ratio of sample optical density to positive control optical density (s/p) determining a positive or negative result. The elisa results based on the s/p interpretation were compared with a kinetics-based (kela) interpretation of the elisa. The kela values were reported as positive, negative, or equivocal.

Using the immunoblot as the standard, elisa (s/p interpretation) had sensitivity of 0.93 and specificity of 0.98, whereas the ifa test had sensitivity of 0.95 and specificity of 0.98. However, the sensitivity and specificity of the elisa (s/p interpretation) were markedly reduced for sample results falling in the kela equivocal range, indicating that equivocal results were valid interpretations for some sera.

A high number (22.5%) of the samples submitted for confirmation of a positive result from use of the in-house elisa were determined to be negative for fiv antibody. Operator error or incorrect interpretation of the in-house elisa were thought to be the cause of most of these false-positive test results.

Free access
in Journal of the American Veterinary Medical Association