Protective effect of the paramunity inducer Parapoxvirus ovis (Zylexis) in kittens experimentally infected with Calicivirus (strain FCV-KS 20).

摘要

The protective effect of a paramunity inducer and the prophylactic use of Zylexis was tested though a feline Calicivirus challenge in specific pathogen free raised kittens aged 11-12 weeks. 12 cats were administered oronasally with 107.5 KID50 feline Calicivirus (field isolate FCV-KS 20) on day 0. The successful experimental challenge infection was examined by seroconversion. After challenge infection by feline Calicivirus (strain FCV KS 20), the animals showed marginal to moderate typical acute symptoms of disease with fever, sneezing and ulceration of the oral cavity. The average rectal temperature of Zylexis-treated cats remained 85% below the value of the controls during the trial period. Clinical symptoms like sneezing occurred more frequently in the controls than in the Zylexis-treated group. Ulcerations of the oral mucous membrane were observed over a considerably shorter period in less animals of the vaccinants (3/6) than in the placebos (5/6). The protective efficacy of Zylexis was also shown for the total clinical index. A significant reduction (p=0.039) of symptoms was shown during day 5 to 13 in the Zylexis-treated kittens. The lymphocyte values of the Zylexis-treated group decreased significantly (p=0.003) compared to the animals of the control group throughout the observation period. Thus, the kittens of the control group developed leukopenia. The initial percentage of the lymphocytes in the total number of leukocytes was 31%, but it decreased up to 16% three days after the challenge infection. The lymphocyte number of the Zylexis-treated animals could be nearly kept continuously at 32%. Seven days after the application of Zylexis, an increase in the percentage part of 44.67% of the total number of lymphocytes could be determined. Three routine Zylexis treatments at 2-day intervals significantly reduced the clinical symptoms of an experimental challenge with the Calicivirus (strain FCVKS 20) and stimulated the lymphocyte proliferation. The stimulation of the unspecific immune system could be recommended due to the study results performed with cat populations of different origin (i.e. animal refuge) as prophylactic measures against Calicivirus infections.