Rajbhandari, U. | Search bioRxiv

bioRxiv2022

Screening Avian Pathogens in Eggs from Commercial Hatcheries in Nepal- an Effective Poultry Disease Surveillance Tool

BackgroundCommercial hatcheries play an important role in the overall poultry value chain-providing small to large poultry farmers with day old chicks. Any outbreak in such hatcheries can spread diseases to other farms. Regular screening of major avian pathogens, along with strict bio-security measures, can prevent spread of diseases in hatcheries. Newcastle Disease Virus (NDV), Infectious Bronchitis Virus (IBV), Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS), Infectious Bursal Disease Virus (IBDV) and Influenza A Virus (IAV) are among the most prevalent poultry diseases which can be detected in egg albumin. MethodWe retrospectively (August 2020-August 2021, except October 2020) analyzed diagnostic results for six selected avian pathogens (NDV, IBV, MS, MG, IBDV and IAV) on eggs (n=4343) received from eleven major commercial poultry hatcheries located in the five adjoining districts of Kathmandu, Nepal. Albumin from 10% randomly selected eggs from each hatchery were tested for the six avian pathogens using multiplex PCR. ResultMajority (7/11, 64%) of the poultry hatcheries had at least one of the six pathogens present. We detected at least one avian pathogen in nine out of eleven months (82%) of screening. Except for IBDV, we found one or more of the other major avian pathogens-Influenza A (IAV) (n=4 times) and Mycoplasma gallisepticum (MG) (n=4 times) were detected the most, followed by Newcastle Virus (NDV) (n=3 times). Infectious bronchitis virus (IBV) were detected twice, and Mycoplasma synoviae (MS) was detected once. ConclusionIn a resource strapped country like Nepal, poultry disease outbreak investigation in particular and surveillance in general are challenging. Meanwhile, poultry production is highly impacted by disease outbreaks often triggered by poor bio-security and lack of pathogen screening practices. Our molecular screening tests have picked up major poultry pathogens present throughout the year in eggs collected from hatcheries. Influenza A was detected at 4 different incidences throughout the year, which is of concern to both human and animal health. Quick systematic screening of eggs at key distribution points (hatcheries) for major avian pathogens is an effective surveillance tool for early disease detection and containment of outbreaks.

microbiology↗

bioRxiv2022

Newcastle disease burden in Nepal and efficacy of Tablet I-2 vaccine in commercial and backyard poultry production

Poultry (Gallus domesticus) farming plays an important role as an income generating enterprise in a developing country like Nepal, contributing more than 4% to the national GDP. It is also one of the major sources of protein for growing population. Newcastle Disease (ND) is a major poultry disease affecting both commercial and backyard poultry production worldwide. There were more than 90 reported cases of ND outbreaks in Nepal in 2018, with over 74,986 birds being affected. ND might be responsible for over 7% of total poultry mortality in the country. Recent outbreak of ND in 2021 affected many farms throughout Nepal, and caused massive poultry production loss. ND is caused by a single stranded RNA virus which presents very similar clinical symptoms as Influenza A (commonly known as Bird flu), adding much complexity to clinical disease identification and intervention. We conducted a nationwide ND and Influenza A prevalence study, collecting samples from commercial and backyard poultry farms from across the major poultry production hubs of Nepal, and conducted both serological and molecular assessments-giving us disease exposure history and identification of floating strains of ND Virus (NDV). Of 600 commercial chickens tested from various farms, both NDV (n=381, 64%) and IA (n=125, 21%) antibodies were detected in the majority of the samples. In backyard chicken (n=108, 39 farms), sero-prevalence was also relatively high for both NDV (n=38, 35%) and IA (n=17, 16%). Out of the 40 commercial farms, majority had detectable NDV (n=31, 78%) and IA (n=15, 38%) virus present. In backyard farms (n=36), we also detected NDV (n=6, 16%) and IA (n=1, 3%) virus. We Genotyped (strain) detected NDV, and found Genotype II to be present in most of the commercial farms (which might be coming from live vaccine usage) and Genotype I in some backyard poultry samples. The identified Genotype I strain is reported for the first time, and hence could be an endemic NDV strain found in Nepal. Our 2021 ND outbreak investigation identified Genotype VII c as the causative strain. Additionally, we have developed a thermostable I-2 NDV vaccine (Ranigoldunga) in tablet formulation and tested on various (mixed) breeds of chicken (G. domesticus). This vaccine seems to be highly effective against NDV, including a virulent 2021 outbreak strain (Genotype VII c). The I-2 Tablet ND vaccine showed more than 85% efficacy when administered either ocularly or in water, and has a stability of 30 days in room temperature.

microbiology↗