Determination of Efficacy of Thermostable PPR Live Homologous Vaccine Incubated at Room Temperature for 14 Days

Abstract

The study was undertaken during the period from July to November 2005, for the first time, to determine the efficacy of thermostable PPR vaccine incubated at -20°C and room temperature (RT) for 14 days which was developed by Bangladesh Livestock Research Institute (BLRI), Savar, Dhaka, in collaboration with and Livestock Research Institute (LRI), Mohakhali, Dhaka. A total of 80 healthy goats of both sexes, aged between 8 to 36 months were divided into three groups as A, B and C. Group A and B comprised of 30 goats each and received thermostable PPR vaccine kept at -20°C and at room temperature (RT) respectively for 14 days, at a dose rate of 1 ml (4 Log₁₀ TCID₅₀ / ml) per goat subcutaneously while group C comprising 20 goats served as non-vaccinated control. At 30 days postvaccination, 3 goats from each vaccinated and non-vaccinated group were challenged with 1 ml (5 GID₅₀) of virulent PPR virus per goat subcutaneously in the mid cervical region. Sera samples were collected from all the groups at pre- and post-vaccination (15 and 30 days postvaccination) and were tested for anti-PPR antibody by competitive enzyme linked immunosorbent assay (C-ELISA). In case of group A, average percent inhibition (PI) values of the sera samples at prevaccination and at 15- and 30 days post vaccination were 11.0 ± 5.7, 62.8 ± 9.9 and 81.5 ±5.9 respectively and in case of group B, were 10.0 ± 4.1, 60.7 ± 9.4 and 79.3 ± 7.2 respectively, which were significantly (p < 0.01) higher than those of non-vaccinated control goats (6.3 ± 3.4, 10.2 ± 3.3 and 13.6 ± 3.7 respectively). The titres of vaccinated goats gradually increased until 30 days postvaccination. The challenge test with virulent PPR virus at 30 days post vaccination showed that the thermostable PPR vaccine with both incubation temperatures at -20°C and RT for 14 days protected all the goats (100%) of groups A and B respectively while all the non-vaccinated control goats were not protected after challenge showing clinical signs of PPR and / or mortality. From the above findings it may be concluded that the thermostable PPR vaccine can be kept at normal environmental temperature (25°-30°C) as long as 14 days without loss of its potency and may be used to prevent PPR in goats in field condition.

Key Words: Thermostable PPR vaccine, efficacy, C-ELISA

doi:10.3329/bjvm.v4i1.1524

Bangl. J. Vet. Med. (2006). 4 (1): 43-46