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Sri Venkateswara Veterinary University, Tirupati


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  • ThesisItemOpen Access
    (Sri Venkateswara Veterinary University, TIRUPATI – 517 502,A.P, 2011) SARITHA, G; SHOBHAMANI, B (Major); SREEDEVI, B; SREENIVASULU, D
    Abstract: Peste des petits ruminants (PPR) is an acute highly contagious and rapidly spreading transboundary viral disease of sheep and goats. The disease is associated with high morbidity and mortality in susceptible animals. It causes severe losses to small ruminant production. Hence a modest attempt has been made to study PPR in Andhra Pradesh with respect to epidemiological status, sero-prevalence, antigen detection and evaluation of efficacy of PPR live attenuated vaccine. The sero-prevalence of PPR was studied by screening 803 sera samples from sheep (398) and goats (405) belonging to 5 different districts of Andhra Pradesh during the period from December 2010 to April 2011. The overall sero-prevalence of PPR in sheep and goat of the present study was 67.87 per cent. Among the districts sero-prevalence ranged from 49.25 to 89.07 per cent. Species wise sero-prevalence of PPR in sheep and goats was 65.32 and 70.37 per cent, respectively. The sero-prevalence was higher (80.65%) in 13-45 months old followed by 4-12 months (67.83%) old sheep and goat. Out of 195 clinical samples (nasal swabs and tissues) tested, the PPR antigen was detected in 66 samples with an overall prevalence of 33.84 per cent. The antigen prevalence (tissues and swabs) was relatively higher (34.52%) in goats than in sheep (33.33%). In the present study 47 flocks (94%) were found positive for PPR antibodies out of 50 flocks (sheep and goats) screened, whereas both the antigen and antibody were detected in 29 flocks (69.04%) out of 42 flocks tested. However in 3 flocks neither antigen nor antibody was detected. Reference vaccine virus as well as clinical samples, including nasal swab and liver tissue showed amplification of approximately 351 bp which is specific to PPRV. However no amplification was observed in the nasal swab collected from apparently healthy sheep. Antibody response to PPR live-attenuated vaccine was studied at Livestock Research station, Palamaner. Results showed that mean PI values in all age groups (G-I, G-II and G-III) gradually increased until 90 days (maximum period of observation) of post immunization, indicating initiation of antibody response to vaccine in field condition. Further studies are required to determine the duration of immunity of PPR live attenuated vaccine.
  • ThesisItemOpen Access
    (Sri Venkateswara Veterinary University, TIRUPATI – 517 502,A.P, 2009-12) VIJAYA SAILAJA, A; SREEDEVI, B (Major); SHOBHAMANI, B; SREELATHA, Ch
    ABSTRACT : Newcastle disease (ND) is one of the devastating poultry diseases which cause great economic loss to the rural poultry production. In the present study, the prevalence of the Newcastle disease antibodies in the rural poultry flocks was estimated by employing a single serum dilution Enzyme Linked Immuno Sorbent Assay (ELISA) kit. A total of 383 serum samples were collected from village chicken from different districts of Andhra Pradesh from both vaccinated and unvaccinated birds. The overall prevalence of ND in village flocks was found to be 77.81%. Out of 169 serum samples collected from vaccinated birds 91.72% were found to have antibody titres above protective levels. In the unvaccinated flocks, out of 214 samples 66.82% were found to have protective titres. Age wise analysis of the data showed maximum prevalence of the ND antibody levels in the 12-18 months age group. Sex wise analysis of the data revealed that there was no significant difference in the prevalence of ND in males and females. The present study indicated a higher prevalence of ND in the rural poultry flocks of Andhra Pradesh. 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. Hence, in the present study an attempt was made to develop thermostable mutants from the lentogenic ND vaccine strains. Lasota and F strains were cultured in the embryonated eggs and they were subjected to different heat treatments for thermostabilisation. Two different procedures were adopted for thermostabilisation, one is stepwise exposure to different temperatures for defined periods of time and the other is direct exposure to 56°C for different time intervals. In the stepwise procedure the Lasota and F strains were kept at 25°C, 37°C and finally at 56°C. Lasota strain could survive for 120 min after 11 successive cycles of heating whereas F strain could survive for 105 min after 11 successive cycles of heating at 56°C. Direct exposure of the strains to 56°C also yielded better results. The Lasota strain could withstand for 135 min after 19 successive heat treatments and F strain could withstand for 90 min after 16 successive thermal cycles. The 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 stability of these mutant strains was checked by incubating the infectious allantoic fluids at 37°C for 35 days with and without addition of the stabilizers. The thermoresistant mutants were found to be more stable and addition of stabilizers improved the keeping quality of the strains. Further, these thermoresistant mutant strains were administered to experimental chicken to evaluate their immunogenicity. A control group of birds vaccinated with the parent strains were also maintained. The results of the experiment revealed that the heat treated mutants were also equally immunogenic as they produced similar Haemagglutination Inhibition (HI) titres as that of the parent vaccine strains. The infected allantoic fluids were titrated and checked for sterility. In the present study an attempt was made to develop thermostable mutants from the conventional lentogenic ND vaccine strains. These mutants were found to be highly stable and equally immunogenic in eliciting immune response to ND. As these vaccines can withstand high environmental temperatures, they can be used successfully under village conditions without 63 any need for cold chain facilities. However, a thermostable food pellet vaccine prepared from locally isolated strains of ND would be a better alternative for the control of the disease in village flocks.
  • ThesisItemOpen Access
    (Sri Venkateswara Veterinary University, TIRUPATI – 517 502,A.P, 2009-10) KANAKA SWARNA LATHA, K; SHOBHAMANI, B (Major); SREEDEVI, B; SREENIVASULU, D
    ABSTRACT : The present investigation was taken up to ascertain the prevalence of brucellosis in bovines and ovines in various districts of Andhra Pradesh. Of the 1856 bovine and 700 ovine sera samples tested 13.36 percent and 11.00 percent respectively were positive to brucella antibodies. The influence of epidemiological factors like species, breed, sex, age, management and breeding systems were studied on the prevalence of brucellosis. Results of the study showed that cattle (14.69%) were more prone to the disease than buffaloes (11.29%). The indigenous breeds (11.91%) of cattle were more resistant compared to the crossbred cattle (16.79%). In sheep, the prevalence of brucellosis did not vary significantly (P>0.05) among Nellore (11.59%), Deccani (10.92%) and non-descript breeds (9.4%). The female animals (13.92%, 13.04%) in both bovines and ovines were comparatively more susceptible than the male animals (7.14%, 7.08%) respectively. Bovines between 3-6 years (15.53%) and ovines between 2-4 53 years (13.93%) of age were more susceptible compared to other age groups. The animals maintained under organized farming conditions showed lesser prevalence than rural areas. A higher prevalence was noticed in the artificially inseminated animals (14.11%) compared to naturally served ones (9.82%). Among the 1856 sera tested, Avidin-Biotin Enzyme Linked Immuno Sorbent Assay (A-B ELISA) detected higher (248) number of positives followed by Rose Bengal Plate Test (RBPT) (92) and Standard Tube Agglutination Test (SAT) (68) in bovines. However in ovines, RBPT could detect 11.00 percent and SAT 8.86 percent positivity. When the Milk Ring Test (MRT) and RBPT were compared, MRT showed a sensitivity of 52.77 percent compared to RBPT. Of the 1806 pooled milk samples collected from milk co-operative societies, 30 samples from 6 villages were found to be positive by MRT. Thus the present study revealed that brucellosis is widespread in bovine and ovine population in different districts of Andhra Pradesh. Furthermore, suitable remedial measures have been suggested for the control of this disease.
  • ThesisItemOpen Access
    ABSTRACT The present study was taken up to evaluate the efficacy of different Infectious Bursal Disease (IBD) vaccines using different vaccination schedules employing different strains of IBD vaccines. The response to vaccination in terms of sero conversion, the extent of bursal damage and immunosuppression caused by these vaccines were studied. A total of 280 layer chicks were randomly divided into seven groups each consisting of 40 chicks. Six different IBD vaccination schedules were tested using different combinations of IBD vaccines. Group I was maintained as a control without giving any IBD vaccination. All the birds including control received Newcastle Disease (ND) vaccination as per the standard schedule. The serum samples were collected from all the groups at weekly intervals for 20 weeks (maximum period tested). The IBD antibodies were estimated using IDEXX - ELISA (Flockcheck) kit. A gradual decline of IBD maternal antibodies was noticed in the control group and the samples were found to be negative by sixth week of age. Vaccination of birds with IBD vaccines did not interfere with the decay of maternal immunity. In group II which received IBD vaccines at day old age, the immediate sero conversion was absent and the antibody titres raised only after subsequent vaccinations. The results of ELISA in other groups showed that, lowest titres were recorded during the third week after which the titres increased gradually reaching peak between eight to twelve weeks of age and a slight decline was observed by the end of 20th week. But they were all found to be above protective levels till 20 weeks of age. No significant difference was noticed between the titres of different treatment groups. The titres in group III which received an oil emulsion IBD vacccine after initial live virus priming also showed similar response in comparison to other groups. Significant difference was noticed in the bursa body weight (B-BW) ratios of IBD vaccinated groups in comparison with the control group. During third week of age, the B-BW ratios recorded were more in vaccinated birds while reduced B-BW ratios were recorded during fourth and fifth weeks in comparison with the control. Histopathology of the bursal sections revealed varying degrees of bursal damage in the vaccinated groups while the bursae collected from the control group were normal. Bursal lesion scores were calculated in terms of the lymphoid depletion in the follicles and were graded between 0 to 4. Highest bursal lesion scores were noticed in groups vaccinated with intermediate plus strain of IBD vaccines. The immunosuppressive effect of different IBD vaccines was evaluated in terms of response to ND vaccination. The results revealed that there was a gradual increase in the NDV-HI titres from third week onwards in all the groups including the control. But a moderate suppression of vaccine response was noticed in groups V, VI and VII which received either one or few doses of intermediate plus vaccines. But all the HI titres were found to be well above the protective level. Based on the results obtained in the present study it is concluded that even though live IBD vaccines caused significant bursal damage, the immunosuppression caused by these vaccines was only moderate. Hence, they can be used at the field level by selecting a least immunosuppressive strain. Vaccination of day old birds with IBD vaccines and usage of an oil emulsion vaccine in the early days of life did not confer any special advantage. Also no additional advantage was observed by giving a third dose of IBD vaccine after fourth week of age.