Avian Influenza a H9N2 Viruses in Morocco, 2018–2019

Abstract

Low pathogenic H9N2 avian influenza (LPAI H9N2) is considered one of the most important diseases found in poultry (broiler, laying hens, breeding chickens, and turkeys). This infection causes considerable economic losses. The objective of this work was to monitor and assess the presence of avian influenza virus (AIV) H9N2 in eight different regions of Morocco using real-time RT-PCR, and to assess the phylogenetic and molecular evolution of the H9N2 viruses between 2016 and 2019. Field samples were collected from 108 farms suspected of being infected with LPAI H9N2 virus. Samples were analyzed using H9N2-specific real-time RT-PCR. Highly positive samples were subjected to virus isolation and seven isolates were fully sequenced. Low pathogenic H9N2 avian influenza virus was introduced in Morocco in 2016. We show that in 2018–2019, the virus was still present irrespective of vaccination status. Phylogenetic and molecular analyses showed mutations related to virulence, although our viruses were related to 2016 Moroccan viruses and grouped in the G1 lineage. Specific amino acid substitutions were identified in Moroccan H9N2 viruses that are believed to lead to increased resistance to antiviral drugs.

Antigenic mapping of the hemagglutinin of the H9 subtype influenza A viruses using sera from Japanese quail ( Coturnix c. japonica )

“…Consistent with these observations, a previous report using the strain A/chicken/Shanghai/F/98 (H9N2) determined position 180 as directly responsible for antigenic drift ( 29 ). Variability at position 180 was also reported in field isolates from Morocco between 2018 and 2019, reinforcing a preponderant role of position 180 in evading pre-existing immunity ( 45 ). Consistent with the Morocco study, molecular characterization of H9N2 viruses from local markets in southern China also revealed a potential role of position 180 (and other positions) on antigenic properties ( 27 ).…”

Prevalence of major infectious diseases in backyard chickens from rural markets in Morocco

“…Since its first detection in broiler poultry farms in 2016 [ 28 ], LPAI H9N2 virus has circulated among wild birds and commercial poultry flocks, resulting in substantial economic losses. Despite control efforts, the H9N2 virus continues to spread among commercial poultry in Morocco [ 29 ]. Moreover, the presence of LPAI H9N2 infection among the backyard chicken population reported in our study makes it an additional risk factor for the poultry industry.…”

Evaluation of the Virulence of Low Pathogenic H9N2 Avian Influenza Virus Strains in Broiler Chickens

“…The suspicion of disease was based on severe respiratory signs, and H9N2 virus infection was confirmed via RT-PCR. A few genetic and phylogenetic differences were observed between the isolates in 2016 and 2018, despite vaccination since July 2016 [ 8 , 10 ]. In late 2017, elevated poultry death rates were identified on Algerian farms where H9N2 avian influenza outbreaks had taken place.…”

“…In infected birds, the most common visible defects were the opacity of the thoracic and abdominal air sacs, accompanied by mild congestion of the trachea and lungs. The kidneys were enlarged [ 10 , 15 , 16 ]. In affected flocks, the mortality rates ranged from 10 to 65% within five to seven days of the emergence of clinical symptoms.…”

“…Morbidity and mortality significantly increased in cases of co-infection with other microorganisms that cause respiratory diseases. A disease prevalence of 58% was reported in an epidemiological survey conducted in Morocco [ 10 ].…”