Newcastle and Influenza A Disease Burden in Commercial and Backyard Poultry Farms in Nepal

Newcastle Disease (ND) and Influenza A (IA) are major poultry diseases affecting both commercial and backyard poultry production worldwide1 . We conducted a Nepal’s first nationwide ND and IA prevalence study in 2018, collecting samples from both in commercial and backyard poultry farms. In commercial and backyard farms prevalence of ND was 70% and 17.5% respectively. We also determined the prevalence of IA in these farms (commercial= 27.5%, backyard= 7.5%). Genotype II was the most prevalent strain of ND virus found in the commercial farms, and Genotype I was detected in the backyard samples. We also identified and characterized the ND virus variant (Genotype VIIc) that caused a nationwide ND outbreak in 2021.

Poultry farming plays an important role as an income generating enterprise in a developing country like Nepal2 . There were more than 90 reported cases of ND outbreaks in Nepal in 20181 . In 2019, Nepal reported three highly pathogenic Influenza A (H5N1) outbreaks in commercial layer farms (n=2) and backyard birds (n=1)3 . Although there is an active nationwide IA surveillance, this is a first study that assessed a comprehensive ND and IA prevalence in both commercial and backyard poultry farms in Nepal.

We collected samples (oral, cloacal and blood) from commercial (n=40 farms, total birds= 600) and backyard (n=36 farms, total birds= 108) poultry farms from across the major poultry production hubs of Nepal in 2018. We used commercially available ELISA kits to detect antibodies (Nucleoprotein) against NDV and Influenza A; and conducted PCR and DNA sequencing based molecular assessments to characterize ND virus variants.

Of 40 commercial farms (each farm=15 birds) tested, both ND (n=28, 70%) and IA (n=11, 27.5%) antibodies were detected. In 36 backyard farms, sero-prevalence of ND was 17.5% (n=7) and IA was 7.5% (n=3). In the commercial farms, we were able to detect live ND virus (n=31, 78%) and IA virus (n=15, 38%) by using PCR. We found ND- Genotype II to be most common variant in the commercial farms; and ND-Genotype I was detected in some backyard poultry samples. The identified Genotype I is reported for the first time and could be an endemic ND virus variant found in Nepal. Additionally, ND- Genotype VIIc variant was found to cause 2021 ND outbreak in Nepal.

Prior to this study, there was a limited information on disease burden and epidemiological dynamics of ND and IA in Nepal. We detected higher prevalence rate of ND in commercial farms than in backyard farms. Usage of live virus vaccine for ND probably resulted in a high sero-prevalence of ND in commercial farms. The Government of Nepal has banned vaccination against IA, however, detection of IA virus (Genotype II) in the commercial farms could indicate practice of illegal use of live IA vaccines in the farms.