Biosurveillance of avian orthoavulavirus 1 in multiple avian species in Pakistan from 2011 to 2021.

BACKGROUND

Newcastle disease (ND) is a highly infectious disease affecting multiple avian species worldwide. Repeated ND outbreaks in Pakistan have presented substantial challenges to the poultry sector.

AIM: Extensive surveillance in Pakistan over a decade has revealed a high prevalence of avian orthoavulavirus 1 (AOAV-1), highlighting the need for tailored vaccination approaches and continuous monitoring.

METHODS

This study presented a 10-year biosurveillance (2011-2020) of AOAV-1 across 1083 locations (including commercial farms, backyard poultry, live bird retail stalls, household birds, national zoos, and wild migratory birds), with a total of 5,145 samples (trachea and oropharyngeal swabs) and 822 blood samples collected from 18 avian species. Tracheal and swab samples were inoculated in embryonated chicken eggs, and the positive allantoic fluids were assessed for AOAV-1 prevalence using reverse-transcriptase real-time PCR (rRT-PCR) targeting the fusion (F) gene. Serum samples were evaluated using a hemagglutination inhibition (HI) test to detect AOAV-1 antibodies.

RESULTS

rRT-PCR analysis showed a prevalence of 37.41%, while seroprevalence assessed through the HI assay was 48%. Moreover, over a decade after repeated outbreaks of virulent AOAV-1 that resulted in high morbidity and mortality in Pakistan, the responsible strain was detected in vaccinated chickens across multiple commercial poultry farms, despite the existence of elevated AOAV-1-specific antibody titers (>4.6 log2).

CONCLUSION

The observations suggest a possible role of vaccinated poultry as a reservoir of virulent AOAV-1. These findings contribute to our understanding of the high prevalence of AOAV-1 in Pakistan, emphasizing the need for customized vaccination approaches and continuous monitoring to enable effective management of AOAV-1 in avian species.