Detection of Low Pathogenic Avian Influenza Virus Subtype H10N7 in Poultry and Environmental Water Samples During a Clinical Outbreak in Commercial Free-Range Layers, Netherlands 2017.

Evelien A Germeraad,Marc Y Engelsma,Naomi D De Bruijn,Armin R W Elbers,Renate Hakze-Van Der Honing,Wim H M Van Der Poel,Saskia A Bergervoet,Rene Heutink,Wendy Van Voorst,Nancy Beerens

doi:10.3389/fvets.2020.00237

Abstract

Wild birds are the natural reservoir of the avian influenza virus (AIV) and may transmit AIV to poultry via direct contact or indirectly through the environment. In the Netherlands, a clinically suspected free-range layer flock was reported to the veterinary authorities by the farmer. Increased mortality, a decreased feed intake, and a drop in egg production were observed. Subsequently, an infection with low pathogenic avian influenza virus was detected. This study describes the diagnostic procedures used for detection and subtyping of the virus. In addition to routine diagnostics, the potential of two different environmental diagnostic methods was investigated for detecting AIV in surface water. AIV was first detected using rRT-PCR and isolated from tracheal and cloacal swabs collected from the hens. The virus was subtyped as H10N7. Antibodies against the virus were detected in 28 of the 31 sera tested. An intravenous pathogenicity index (IVPI) experiment was performed, but no clinical signs (IVPI = 0) were observed. Post-mortem examination and histology confirmed the AIV infection. Multiple water samples were collected longitudinally from the free-range area and waterway near the farm. Both environmental diagnostic methods allowed the detection of the H10N7 virus, demonstrating the potential of these methods in detection of AIV. The described methods could be a useful additional procedure for AIV surveillance in water-rich areas with large concentrations of wild birds or in areas around poultry farms. In addition, these methods could be used as a tool to test if the environment or free-range area is virus-free again, at the end of an AIV epidemic.

Highlights

In recent decades, the avian influenza virus (AIV) has caused many infections in poultry worldwide, leading to significant economic and animal welfare implications [1, 2]
Outbreak Description In September 2017, the veterinary authorities received a report of clinical signs in hens of a commercial free-range layer farm
It is not likely that the virus was present in the flock for more than 8 weeks, because the flock had tested negative for antibodies against AIV during the national serological screening for AIV in poultry at 74 weeks of age [40]

Summary

Introduction

The avian influenza virus (AIV) has caused many infections in poultry worldwide, leading to significant economic and animal welfare implications [1, 2]. Viruses of the H5 and H7 AIV subtypes can evolve to highly pathogenic avian influenza viruses (HPAIVs), which cause severe systematic infections and high mortality rates in poultry [4, 5]. These severe clinical signs of these HPAIVs are the reason that prevention of AIV infections in poultry is required. Because the virus is often shed in aquatic environments by wild birds, the detection of AIV in water is relevant. Several studies have reported methods to detect AIV in surface water during field infections of AIV [12,13,14,15], most of these studies only showed the efficiency of their methods under laboratory circumstances [16,17,18,19,20,21,22,23,24]

Methods

Results

Conclusion