Detection of Low Pathogenicity Influenza A(H7N3) Virus during Duck Mortality Event, Cambodia, 2017

Abstract

In January 2017, an estimated 3,700 (93%) of 4,000 Khaki Campbell ducks (Anas platyrhynchos domesticus) died in Kampong Thom Province, Cambodia. We detected low pathogenicity avian influenza A(H7N3) virus and anatid herpesvirus 1 (duck plague) in the affected flock; however, the exact cause of the mortality event remains unclear.

Emergence of Influenza A(H7N4) Virus, Cambodia

“…Avian influenza virus (AIV) subtype A(H7) is of concern because it has been a leading cause of zoonotic infections over the past 2 decades ( 1 ). The A/Anhui/1/2013-lineage A(H7N9) viruses, a leading cause of zoonotic infections in Asia since 2013, have not been detected in the Greater Mekong Subregion, but independent H7 lineages, including H7N3, H7N7, and H7Nx, have been detected occasionally in Cambodia since 2009 ( 2 – 4 ). H7N3 virus was detected from a duck mortality event in Kampong Thom during January 2017 ( 2 ), and H7N7 virus was detected in a live-bird market (LBM) in Takeo in September 2017 ( 4 ).…”

“…The A/Anhui/1/2013-lineage A(H7N9) viruses, a leading cause of zoonotic infections in Asia since 2013, have not been detected in the Greater Mekong Subregion, but independent H7 lineages, including H7N3, H7N7, and H7Nx, have been detected occasionally in Cambodia since 2009 ( 2 – 4 ). H7N3 virus was detected from a duck mortality event in Kampong Thom during January 2017 ( 2 ), and H7N7 virus was detected in a live-bird market (LBM) in Takeo in September 2017 ( 4 ). Furthermore, highly pathogenic avian influenza (HPAI) A(H5N1) and low-pathogenicity avian influenza (LPAI) A(H9N2) are endemic in Cambodia ( 5 ); 59 poultry outbreaks of AIV and 56 human HPAI A(H5N1) cases have occurred since 2006.…”

“…Furthermore, highly pathogenic avian influenza (HPAI) A(H5N1) and low-pathogenicity avian influenza (LPAI) A(H9N2) are endemic in Cambodia ( 5 ); 59 poultry outbreaks of AIV and 56 human HPAI A(H5N1) cases have occurred since 2006. Although the exact ecologic links are unknown, serologic studies suggest that AIVs of multiple subtypes are frequently introduced into poultry in Cambodia, possibly through cross-border trade or through wild birds ( 2 , 6 , 7 ).…”

The evolution and genetic diversity of avian influenza A(H9N2) viruses in Cambodia, 2015 – 2016

“…In 2016, collections targeted periods known for having high levels of AIV circulation: Lunar New Year (February), Khmer New Year (April) and Pchum Ben (October). Oropharyngeal and cloacal samples from individual birds were pooled and screened for A(H9) AIVs with qRT-PCR assays sourced from the International Reagent Resource (https://www.internationalreagentresource.org/Home.aspx) as described previously [27,28].…”

Avian influenza virus detection, temporality and co-infection in poultry in Cambodian border provinces, 2017–2018

“…Border regions display variable AIV prevalence and diversity, possibly due to poultry movement across borders. While A/H7 was detected previously in Cambodia [4,7], subtype A/H7N4 presents concern due to the human case in nearby China at a similar time period [8]. In addition, detection of co-infections in 3.2% of AIV positive poultry, especially with A/H9, raises concerns about reassortment and emergence of novel viruses with epizootic or pandemic potential [9].…”