3 research outputs found
Isolation of avian influenza H5N1 virus from vaccinated commercial layer flock in Egypt
Uninterrupted transmission of highly pathogenic avian influenza virus (HPAIV)
H5N1 of clade 2.2.1 in Egypt since 2006 resulted in establishment of two main
genetic clusters. The 2.2.1/C group where all recent human and majority of
backyard origin viruses clustered together, meanwhile the majority of viruses
derived from vaccinated poultry in commercial farms grouped in 2.2.1.1 clade.
In the present investigation, an HPAIV H5N1 was isolated from twenty weeks old
layers chickens that were vaccinated with a homologous H5N1 vaccine at 1, 7
and 16 weeks old. At twenty weeks of age, birds showed cyanosis of comb and
wattle, decrease in egg production and up to 27% mortality. Examined serum
samples showed low antibody titer in HI test (Log2 3.2 ± 4.2). The
hemagglutinin (HA) and neuraminidase (NA) genes of the isolated virus were
closely related to viruses in 2.2.1/C group isolated from poultry in live bird
market (LBM) and backyards or from infected people. Conspicuous mutations in
the HA and NA genes including a deletion within the receptor binding domain in
the HA globular head region were observed. Despite repeated vaccination of
layer chickens using a homologous H5N1 vaccine, infection with HPAIV H5N1
resulted in significant morbidity and mortality. In endemic countries like
Egypt, rigorous control measures including enforcement of biosecurity, culling
of infected birds and constant update of vaccine virus strains are highly
required to prevent circulation of HPAIV H5N1 between backyard birds,
commercial poultry, LBM and humans
Surveillance on A/H5N1 virus in domestic poultry and wild birds in Egypt
The endemic H5N1 high pathogenicity avian influenza virus (A/H5N1) in poultry
in Egypt continues to cause heavy losses in poultry and poses a significant
threat to human health. Here we describe results of A/H5N1 surveillance in
domestic poultry in 2009 and wild birds in 2009-2010. Tracheal and cloacal
swabs were collected from domestic poultry from 22024 commercial farms, 1435
backyards and 944 live bird markets (LBMs) as well as from 1297 wild birds
representing 28 different types of migratory birds. Viral RNA was extracted
from a mix of tracheal and cloacal swabs media. Matrix gene of avian influenza
type A virus was detected using specific real-time reverse-transcription
polymerase chain reaction (RT-qPCR) and positive samples were tested by RT-
qPCR for simultaneous detection of the H5 and N1 genes. In this surveillance,
A/H5N1 was detected from 0.1% (n = 23/) of examined commercial poultry farms,
10.5% (n = 151) of backyard birds and 11.4% (n = 108) of LBMs but no wild bird
tested positive for A/H5N1. The virus was detected from domestic poultry year-
round with higher incidence in the warmer months of summer and spring
particularly in backyard birds. Outbreaks were recorded mostly in Lower Egypt
where 95.7% (n = 22), 68.9% (n = 104) and 52.8% (n = 57) of positive
commercial farms, backyards and LBMs were detected, respectively. Higher
prevalence (56%, n = 85) was reported in backyards that had mixed chickens and
waterfowl together in the same vicinity and LBMs that had waterfowl (76%, n =
82). Our findings indicated broad circulation of the endemic A/H5N1 among
poultry in 2009 in Egypt. In addition, the epidemiology of A/H5N1 has changed
over time with outbreaks occurring in the warmer months of the year. Backyard
waterfowl may play a role as a reservoir and/or source of A/H5N1 particularly
in LBMs. The virus has been established in poultry in the Nile Delta where
major metropolitan areas, dense human population and poultry stocks are
concentrated. Continuous surveillance, tracing the source of live birds in the
markets and integration of multifaceted strategies and global collaboration
are needed to control the spread of the virus in Egypt
Isolation of avian influenza H5N1 virus from vaccinated commercial layer flock in Egypt
Abstract Background Uninterrupted transmission of highly pathogenic avian influenza virus (HPAIV) H5N1 of clade 2.2.1 in Egypt since 2006 resulted in establishment of two main genetic clusters. The 2.2.1/C group where all recent human and majority of backyard origin viruses clustered together, meanwhile the majority of viruses derived from vaccinated poultry in commercial farms grouped in 2.2.1.1 clade. Findings In the present investigation, an HPAIV H5N1 was isolated from twenty weeks old layers chickens that were vaccinated with a homologous H5N1 vaccine at 1, 7 and 16 weeks old. At twenty weeks of age, birds showed cyanosis of comb and wattle, decrease in egg production and up to 27% mortality. Examined serum samples showed low antibody titer in HI test (Log2 3.2± 4.2). The hemagglutinin (HA) and neuraminidase (NA) genes of the isolated virus were closely related to viruses in 2.2.1/C group isolated from poultry in live bird market (LBM) and backyards or from infected people. Conspicuous mutations in the HA and NA genes including a deletion within the receptor binding domain in the HA globular head region were observed. Conclusions Despite repeated vaccination of layer chickens using a homologous H5N1 vaccine, infection with HPAIV H5N1 resulted in significant morbidity and mortality. In endemic countries like Egypt, rigorous control measures including enforcement of biosecurity, culling of infected birds and constant update of vaccine virus strains are highly required to prevent circulation of HPAIV H5N1 between backyard birds, commercial poultry, LBM and humans.</p