Asian Research Thesis Index

Abstract

Birds living in densely-populated (urban) areas are exposed to different environmental challenges. One of them is an exposure to a vast range of environmental pathogens simply due to lack of appropriate biosafety and biosecurity measures in hospitals and research centers. Therefore, wild/feral birds living in close vicinity to urban settings are hypothesized to be more immunocompetent and/or resistant to different pathogens than are birds living in rural settings. This hypothesis of varying immunocompetence in birds originating from rural and urban setting was evaluated using an endemic pathogen of birds, the Newcastle disease virus (NDV).The virus was isolated from migratory bird, the mallard (Anas platyrhynchos), at Chashma barrage and was found to be virulent on the basis of genomic (typical F protein cleaving motif: 112R-R-Q-K-R↓F117) and biological characteristics (EID50 =108.5 mL-1 and MDT= 49.5-50 hrs). Immunocompetence among individual group of each of 20 feral birds (pigeon, mynah, sparrow, crow and quail), both from urban and rural settings (n=10), were administered 0.1mL of a mitogen (1mg/mL), the phytohemagglutinin (PHA) and thickness of patagium at different time intervals as 12, 24, 36, 48 and 60hr of post injection was measured through digital caliper. Post administration of PHA, all studied birds’ species showed a similar pattern of increase in web-thickness by the timer interval of 48 hours followed by a decline by 60 hr. Though variations in magnitude of swelling were observed among and/or within birds’ specie group, compared to their respective rural counterparts, birds originating from urban setting showed an enhanced swelling response (e.g., 1.26 2 mm ±0.03 vs 0.980 mm ±0.04 for pigeon, 0.235 mm ±0.02 vs 0.194 mm ±0.03 for sparrow, and 1.10 mm±0.03 vs 0.855 mm±0.04 crow) by 48 hours. For instance, in case of rural and urban pigeon, difference in thickness was continuous for each of the time interval (p < 0.05) whereas, in case of crow, this difference between birds in rural and urban setting was limited to time interval of 24 hrs (95% CI: 0.024-0.082; p < 0.05), 36 hrs (95% CI: 0.026-0.085; p < 0.05), 48 hrs (95% CI: 0.052-0.110; p < 0.05) and 60 hrs (95% CI: 0.036-0.097; p < 0.05). On the other hand, a lack of significant difference was found between urban and rural groups of sparrow, mynah and quail birds (p > 0.05). Following comparative immunocompetence evaluation, all birds were acclimatized for two weeks to diminish the effect of PHA and then challenged with Newcastle disease virus (1mL of 10-8 EID50/mL) isolated from mallard. The results of this study indicated that the urban birds were more resistant as evidenced by increased morbidity and mortality pattern, tissue tropism and virus shedding from 3rd dpi by 9th dpi among birds group. The study birds showed an equal potential to disseminate the virus in apparently healthy chicken where 100% mortality was observed in broiler by 6th dpi. The study outcome ascertains a need for continuous monitoring and surveillance of wild/migratory birds for NDV and also implementation of strict biosecurity measures not only in commercial setting but also in public sectors to control the spillover of pathogen to environment and wild birds.

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