Surveillance on respiratory diseases reveals enzootic circulation of both H5 and H9 avian influenza viruses in small‐scale commercial layer farms of Bangladesh

Abstract

Poultry production in Bangladesh has been experiencing H5N1 highly pathogenic avian influenza (HPAI) and H9N2 low pathogenic avian influenza (LPAI) for the last 14 years. Vaccination of chickens against H5 HPAI is in practice since the end of 2012. Subsequently, the official reporting of HPAI outbreaks gradually decreased.However, the true extent of circulation of avian influenza virus (AIV) in commercial poultry production is not clear. To explore this, we conducted active surveillance in 422 small-scale commercial layer farms in 20 villages of Mymensingh and Tangail districts of Bangladesh during 2017 and 2018 for the presence of diseases with respiratory signs. A total of 88 farms with respiratory disease problems were identified and investigated during the surveillance. In addition, 22 small-scale commercial layer farms in the neighbouring areas with respiratory disease problem were also investigated on request from the farmers. Pooled samples of oropharyngeal swabs from live birds or respiratory tissues from dead birds of the farm suffering from respiratory disease problem were tested for molecular detection of avian influenza virus (AIV), Newcastle disease virus (NDV), infectious bronchitis virus (IBV), infectious laryngotracheitis virus (ILTV), Mycoplasma gallisepticum and Avibacterium paragallinarum. A total of 110 farms (88 in the surveillance site and 22 in the neighbouring region) were investigated, and one or more respiratory pathogens were detected from 89 farms.AIV was detected in 57 farms often concurrently with other pathogens. Among these 57 farms, H5, H9, both H5 and H9 or non-H5 and non-H9 AIV were detected in 28, 9, 13 or 7 farms, respectively. Birds of most of the H5 AIV-positive farms did not present typical clinical signs or high mortality. Twenty such farms were observed longitudinally, which had only 1.05%-5.50% mortality but a marked drop in egg production. This widespread circulation of H5 AIV along with H9 AIV and other pathogens in small-scale commercial layer farms, often with low mortality, reaffirms the enzootic circulation of AIV in Bangladesh, which may escape syndromic surveillance focused on unusual mortality only. To reduce public health risks, strengthening of the | 897 RAHMAN et Al.

Patterns and risk factors of avian influenza A(H5) and A(H9) virus infection in pigeons and quail at live bird markets in Bangladesh, 2017–2021

“…Similar results were also found by Guo, Song ( 38 ) in LBMs in China. On the other hand, in 2020, the Government of Bangladesh approved an H9N2 vaccination (CEVAC NEW FLU H9K) ( 39 ). However, pet birds such as pigeons and quails are seldom vaccinated, and vaccination programs typically target layer and breeder chickens ( 40 ).…”

Redesign and Validation of a Real-Time RT-PCR to Improve Surveillance for Avian Influenza Viruses of the H9 Subtype

“…Viruses 2022, 14, 1263 2 of 14 sporadic detections in Eurasia and North America, since the mid-1990s H9 viruses have expanded their geographic range to large territories of Asia, the Middle East and Africa [2][3][4][5] becoming endemic in domestic Galliformes [6][7][8][9][10][11][12]. The dissemination of H9 viruses in different continents resulted in the establishment of two distinct phylogeographic lineages: the American and the Eurasian.…”

Investigation of respiratory disease outbreaks of poultry in Bangladesh using two real-time PCR-based simultaneous detection assays

“…Intensification of commercial farming leads to the accumulation of multiple pathogens at a single site, in particular, a wide range of respiratory viral pathogens cause huge economic losses (3). The presence of more than one pathogen in hosts at the same time causes the complexity of diseases (3)(4)(5)(6)(7)(8). Globally, poultry production encounters more viral infections compared to infections with other pathogens (9).…”

“…The current study emphasizes the prevalence of respiratory viruses in poultry and their early, accurate detection. Several laboratory methods such as virus isolation in embryonated eggs and organ cultures and serological tests are being used for decades for detecting and differentiating avian respiratory viral infections ( 3 , 22 – 24 ). These methods are time-consuming and laborious, particularly when used separately for a single pathogen ( 25 – 27 ).…”

“…Many countries have implemented respiratory disease surveillance, and the use of multiplex real-time PCR assays has aided in detecting circulating viruses and outbreaks, as well as estimating disease burden ( 29 – 32 ). Recently, a PCR-based panel assay for the detection of multiple poultry respiratory pathogens has been established using a real-time PCR system in a single reaction with SYBR Green reagent ( 3 ). A mini version of the Riems Influenza a Typing Array (RITA) assay ( 34 , 35 ) has also been used in the subtype detection of AIVs and identification of other avian viral pathogens in Bangladesh ( 20 , 36 ).…”