Evaluation of the stability of rabies vaccine baits – field trial

Abstract

Objective: To analyse the stability of oral rabies virus vaccine baits in terms of virus titre and physical stability of the bait casing over a two week observation period in relation to air temperature, sunlight and rainfall. Materials and Methods: Two batches of Lysvulpen vaccine produced by Bioveta (Czech Republic) were tested. The vaccine titre indicated by the producer was not less than 107,0 TCID50/dose. A 100 vaccine baits each were distributed by hand in the forest and in the outskirts of the forest in spring and autumn. Air temperature, precipitation and sunlight were daily recorded and the shape and consistency of the vaccine bait casing was documented. Vaccine titration ws conducted at the Lithuanian National Veterinary Laboratory, Kaunas. Results: The mean air temperature during the spring test period was 10,0 ºC (10,0 ºC ±1,1 ºC) and 18,9 ºC (18,9 ºC ±3,5 ºC) during night and day, respectively. It was sunny, no rainfall. The baits, distributed in the forest, were totally covered by the casing for 12 days of the two observation period. On day 3 and 6 the bait casing of 23% and 19% of the tested baits became soft and sticky. On day 6 and 9 one and two baits were disintegrated, respectively, and the vaccine capsule was visible. The vaccine titre on day 9 was 105.6 TCID50/dose. The casing of baits distributed in the outskirts of the forest became soft and sticky on day 3. On day 9 all tested vaccine baits were deformed and 17 out of 27 baits were disintegrated with the vaccine capsules visible. The vaccine titre on day 9 was 103.75 TCID50/dose. The mean air temperature during the autumn test period was 1,5 ºC (1,5 ºC ± 0,8 ºC) and 2,5 ºC (2,5 ºC ± 1,0 ºC) during night and day, respectively. It was heavy... [...].