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Tests of annual immunity in foxes after oral immunization against rabies

VRZAL V, MATOUCH O
Veterinarni Medicina 41, 1996, 107-111

Ten young foxes were orally immunized with a ''Rabies vaccine for oral immunization of foxes - LYSVULPEN port a.u.v.'', batch 69 10 93, commercially manufactured by the company Bioveta, s.r.o. at Ivanovice in Hana. The vaccine contained 1.8 x 10(7.5) TKID50 of rabies vaccination virus, strain SAD-Bern, in a vaccination dose. Three foxes were used as control animals without vaccination. Blood samples were taken before the beginning of the experiment in all test foxes, and then in three-month intervals. The last blood samples were taken just before the beginning of a challenge experiment and two months after challenge in the foxes that survived. A challenge test was done in all foxes (vaccinated and nonvaccinated ones) a year after single oral immunization against rabies. Challenge virus was prepared from the salivary gland of a naturally infected fox living in the territory of the Czech Republic. Street virus was applied to each fox i.m. to a great depth to both masticatory muscles (musculus masseter) at a total dose of 10,000 MICLD(50). The experimental animals were 60 days under observation. Tab. I shows the titers of virus-neutralizing rabies antibodies after oral immunization against rabies in all experimental foxes. Except fox no. 8, the formation of specific virus-neutralizing rabies antibodies was recorded in all animals after they had eaten vaccination baits. The antibodies were detected throughout the whole year of observation. Tab. II shows the results of challenge test. Out of the nine vaccinated foxes (fox no. 9 died before infection) only fox no. 8 died from rabies, the other treated foxes were protected from rabies (89% rate of protection). Tab. III presents the results of laboratory examination. Tetracycline was demonstrated in all treated foxes (a vaccination proof). Death due to rabies was demonstrated in control animals without vaccination and in fox no. 8. The results achieved in the Czech Republic for oral immunization of foxes against rabies with the vaccination strain SAD-Bern document very good efficacy of the vaccine manufactured by the company Bioveta, s.r.o., in Ivanovice in Hana since 1992. Oral immunization largely improved the infection situation in the Czech Republic. A total of 1,501 cases of rabies infection were recorded at the start of vaccination in 1989 while it was only 221 cases in 1994 (a decrease in the number of foci by 85%)


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