Risk Factors Associated with Avian Influenza Subtype H9 Outbreaks in Poultry Farms of Central Lowland Nepal

Deepak Subedi; Parshuram Phuyal; Suman Bhandari; Milan Kandel; Shambhu Shah; Gaurav Rawal; Surendra Karki; Santosh Dhakal

doi:10.3390/idr14040056

Risk Factors Associated with Avian Influenza Subtype H9 Outbreaks in Poultry Farms of Central Lowland Nepal

Infect Dis Rep. 2022 Jul 18;14(4):525-536. doi: 10.3390/idr14040056.

Authors

Deepak Subedi¹, Parshuram Phuyal², Suman Bhandari¹, Milan Kandel³, Shambhu Shah¹, Gaurav Rawal⁴, Surendra Karki⁵, Santosh Dhakal⁶

Affiliations

¹ Paklihawa Campus, Institute of Agriculture and Animal Science (IAAS), Tribhuvan University, Siddharthanagar 32900, Nepal.
² National Avian Disease Investigation Laboratory, Bharatpur 44200, Nepal.
³ Faculty of Animal Science, Veterinary Science and Fisheries (FAVF), Agriculture and Forestry University, Bharatpur 44200, Nepal.
⁴ Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
⁵ Food and Agriculture Organization of the UN (FAO), Emergency Center for Transboundary Animal Diseases (ECTAD), Kathmandu 44600, Nepal.
⁶ W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.

Abstract

Low pathogenic avian influenza (LPAI) of subtype H9 outbreaks have been frequently occurring in major commercial hubs of Nepal including Chitwan, a central lowland area, causing substantial economic losses to the farmers. However, the risk factors associated with these outbreaks have been poorly understood, and hence, this case-control study was conducted in Chitwan, Nawalpur, and Makawanpur districts of Nepal from October 2019 to March 2020. A total of 102 farms were selected in which 51 were case farms, and 51 were controls. Case farms were avian influenza (AI)-subtype-H9-confirmed farms through polymerase chain reaction (PCR) assays on poultry samples. Control farms included farms that were AI-negative in the antigen test brought to the National Avian Disease Investigation Laboratory, Chitwan, for diagnosis during the study period. Each farm was visited to collect information using a semi-structured questionnaire. A total of 25 variables representing farm characteristics and biosecurity measures were considered as potential risk factors. The final multivariable model showed that distance of less than 0.5 km from the main road (OR = 4.04, 95% CI = 1.20-13.56, p = 0.023), distance of less than 1 km from a nearest infected farm (OR = 76.42, 95% CI = 7.17-814.06, p = 0.0003), and wild birds coming around the farm (OR = 6.12, 95% CI = 1.99-18.79, p = 0.0015) were risk factors for avian influenza type H9, whereas using apron or separate cloth inside the shed (OR = 0.109, 95% CI = 0.020-0.577, p = 0.0092) was shown to reduce the risk of farms being positive for AI subtype H9. These findings suggest that due consideration should be given to site selection while establishing the farms and the importance of implementing appropriate biosecurity measures, such as using separate cloth inside the shed and preventing the entry of wild birds inside the farm to reduce the potential risk of introduction of avian influenza type H9 to their poultry farms.

Keywords: Nepal; avian influenza; poultry farms; risk factors.

Grants and funding

This work is part of an internship research of DS. Survey expenses were funded through the IAAS, TU internship stipend to DS. Laboratory works were carried out as part of routine tests in the National Avian Disease Investigation Laboratory, Bharatpur, Nepal, supervised by PP.