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Subject: Veterinary Epidemiology and Preventive Medicine × Author: Sharma, Abhilasha × End date: 2023 × Start date: 2020 × Thesis Type: M.V.Sc. ×
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    ThesisItemOpen Access
    Transmission of Newcastle disease virus at domestic-wild bird interface
    (College of Veterinary Science, Assam Agricultural University, Khanapara Campus, 2022-09) Sharma, Abhilasha; Dutta, Jyoti B
    Wild birds have been known to be reservoirs of Newcastle disease virus and the disease has been identified as one of the endemic diseases in India despite vaccination. Moreover, wildlife-livestock interfaces have come into light as the most overlooked areas of disease emergence. In that context, to demonstrate and establish spillover and spillback of Newcastle disease virus in wild and domestic birds as well to identify epidemiological means facilitating transmission at interface areas, a study was undertaken to detect and characterize NDV in the pool maintained in wild and domestic birds along with some epidemiological studies. Samples were collected from a total of 321 birds, both wild (n=81) and domestic (n=240) and subjected to haemagglutination inhibition (HI) and RT-PCR. The apparent prevalence of NDV in wild birds was found to be 22.2% (95% CI: 13.2-31.3%) and 14.6% (95% CI: 10.1-19.1%) in domestic birds at the sampled areas in this study from April, 2021 to August, 2022 revealing that wild birds had a higher likelihood of being affected with NDV than that of domestic (OR=1.67, 95% CI: 0.89-3.16, P=.101). The highest proportion of NDV positive wild birds were from the interface areas of Kaziranga National Park (32.21%) and in domestic birds from the interface areas of Assam State Zoo (25%). The study revealed that NDV positive cases in were highest among the raptors in wild (56.3%) and granivores (7.78%) in case of domestic birds. 14.3% and 4% of the sampled swabs collected from wild (n=56) and domestic birds (n=151) respectively to be positive for NDV thereby illuminating the dominant shedding nature of the virus. Similarly, 23.9% and 12.6% of the sampled tissues collected from wild (n=67) and domestic birds (n=261) were found to be positive for the virus. Additionally, it was found that in wild birds, highest proportion of NDV detection was seen in winter (44.44%) whereas in domestic birds, it was seen highest in pre-monsoon season (31.42%). Furthermore, detection of NDV was found to be significantly correlated with species and colony of birds as well as with the type of samples collected. A total of 11 NDV isolates from wild (n=6) and domestic birds (n=5) were subjected to biological and molecular pathotyping on the basis of MDT and FPCS respectively. MDT for NDV isolates of wild birds ranged between 31.02±2.98 to 48.56 ±2.79 and 40.67±2.03 to 59.01±0.77 for NDV isolates of domestic rendering them to be of velogenic nature. Molecular pathotyping based on F protein cleavage site motif revealed the 11 isolates from both wild and domestic birds to be of the virulent nature with 112RRQKRF117 amino acid sequence at their F protein cleavage site. Representative NDV isolates from wild (n=6) and domestic (n=5) were sequenced and subjected to phylogenetic analysis which revealed all the wild isolates to be clustered under genotype VII in class II NDV, whereas isolates from wild birds were grouped under both genotype VII and XIII. A questionnaire survey was conducted to evaluate the risk factors enabling transmission of Newcastle disease virus at interface areas. Analysis of risk factors associated with NDV transmission showed that change in weather had 37 times significantly higher risk of mass mortality of Newcastle disease than that of no changes in weather, OR=37 95% CI :9.34- 146.65, P<.001. Similarly, farms in close proximity significantly had higher chances of ND affection, OR=3.96 95% CI :1.38-11.36, P=.008. The presence of waterbody nearby had a 5.11 times higher risk of being exposed to NDV than absence of waterbody nearby, OR=5.11 95% CI :1.78-14.67, P=.002. Other animals housed in the premises was also a significant risk factor, OR=3.87 95% CI :1.45-10.33, P=.006. Linear regression analysis revealed risk factors including mortality after weather change, presence of water body nearby, unavailability of clean drinking water, unavailability of chlorinated water, not practising all-in-all-out system; not practising down-time, interaction of other birds while feeding, mixing with neighbourhood ducks and geese, being housed with pigeons, deworming not carried out, no use of foot-baths, biosecurity not followed, being housed with pigeons, presence of bamboo groves in the farm, crows visiting the farm, predation by rodents, wild birds interacting while feeding and seasonal migration of wild birds observed nearby to be significant risk factors at flock level. Knowledge and attitudes were found to have positive correlations with practices adopted by bird owners. A statistically insignificant link was found between knowledge and attitudes, but a positive trend line was observed between the two. The derived data base regression explained about 36.82% of total variation in practice.