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20131
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Author: REVATHI, PAGADALA × Thesis Type: M.V.Sc. ×
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    ThesisItemOpen Access
    DEVELOPMENT AND EVALUATION OF THERMOSTABLE NEWCASTLE DISEASE VACCINE STRAINS
    (SRI VENKATESWARA VETERINARY UNIVERSITY , TIRUPATI – 517502. (A.P.) INDIA, 2013-01) REVATHI, PAGADALA; SREEDEVI, B (Major); SHOBHAMANI, B; SREENIVASULU, D
    ABSTRACT : New Castle disease (ND) is an infectious, highly contagious and destructive viral disease of poultry causing serious constraint to poultry rising and has a devastating effect on the productivity and survival of commercial and village poultry. The circulating strains of ND in the village chicken act as source of infection to the commercial poultry flocks. Vaccination is the only strategy for the control of the NewCastle disease in the poultry flocks. However, the presently available ND vaccines though they are effective in eliciting good immune response, they require maintenance of a cold chain from the point of production until they are delivered in the field which is very difficult under the village conditions. Administration of vaccines for the rural scavenging birds and in commercial poultry where the chickens are housed, it is difficult to catch individual bird for vaccination which leads to stress. Hence, in the present study an attempt was made to develop thermostable mutants from the ND vaccine strains and the delivery of these vaccines through different routes. In the present study, lentogenic strains Lasota and F, and mesogenic strains R2B and K were cultured in the embryonated eggs and they were subjected to different heat treatments for thermostabilisation. Vaccine strains were subjected to 56°C directly for different time intervals in the current study. The mesogenic R2B and K could withstand 180 minutes after 21 and 20 successive thermal cycles. The thermostable mutants of Lasota (135 minutes, 19 Thermal cycles) and F (90 minutes, 16 Thermal cycles) which were developed previously in the department were given further thermal treatments. Then the Lasota strain could withstand for 165 minutes after a total of 21 thermal cycles and F strain could withstand for 150 minutes after a total of 20 thermal cycles at 56°C. Mesogenic strains were found to be more thermostable than Lentogenic strains. The thermostable mutants were found to have better thermostability than the parent viruses and they did not revert back to original even after back passages in the embryonated eggs. The infected allantoic fluids were titrated and checked for sterility. The thermostable mutant strains K and Lasota were administered to experimental chicken to evaluate their immunogenicity and efficacy in comparison with conventional vaccines. Further, these thermostable vaccines were administered through different routes to know the comparative efficacy. The control group of birds were vaccinated with the conventional parent strains were also maintained. The results of the experiment revealed that there was no significant difference between thermostable vaccines and the conventional vaccines. Further, there was no significant difference between different routes of administration (ANOVA). The stability of thermostable mutant strains of K and R2B were checked by incubating the infectious allantoic fluids at 25°C and at 37°C for 80 days with and without addition of the stabilizers. The thermostable mutants were found to be more stable in the presence of stabilizers which improved the keeping quality of the strains. In the present study, an attempt was made to develop thermostable mutants from the conventional ND vaccine strains. These mutants were found to be highly stable and equally immunogenic in eliciting immune response to ND when administered through different routes. As these vaccines can withstand high environmental temperatures, they can be used successfully under village conditions without any need for cold chain facilities with great ease of administration. Further administration of thermostable protective nanoencapsulated vaccine tablet and drinking water methods were found to be easy for the use in rural and commercial poultry flocks.