or H7 strains were identi;ed in 7,478 cloacal
were tested for the two receptors. The results
of the study suggest varying expression of the
two receptors among the wild birds tested. In
addition, various species expressed human-type receptors, suggesting the ability to bind
human in;uenza type viruses. The result
of this research adds to the knowledge and
understanding of the different receptors present on cells for AI viruses to bind to before
entering a cell.
Increased understanding of AI
Avian in;uenza varies in pathogenicty.
Low pathogenic strains can cause mild, if any,
clinical signs or mortality. High pathogenic
strains of AI are capable of causing severe
clinical signs and extremely high mortality. The H5N1 highly-pathogenic AI has
been reported to have increasing virulence
M. Pantin-Jackwood, from the Southeast
Poultry Research Laboratory reported on a
research study addressing the pathogenicity
of the highly-pathogenic H5N1 AI virus in
domestic ducks. The study examined the
virulence of single-gene reassortants in an effort to determine which viral genes contribute
to increased pathogenicity.
produced were inoculated into two-week-old Pekin ducks. The ducks exhibited more
severe clinical signs than the less virulent
parent but not the high mortality of the highly-virulent parent virus.
The results indicated that more than
one gene is involved in the pathogenicity
of the Egyptian H5N1 AI virus. Increased
understanding of the genes of the AI virus
is of tremendous bene;t in understanding
the effects of genetic mutations and how
these changes can impact the host range and
virulence of the virus.
Virus receptors give clues about
transmission between species
Research by M. França of the University
of Georgia should be of value in understanding the transmission of AI between species.
AI viruses bind to speci;cally linked recep-
Avian influenza facts
✔ Commonly referred to as “bird flu”
✔ Historically know as “fowl plague”
✔ Viral disease caused by an RNA virus
✔ Affects respiratory, nervous, digestive systems of birds
✔ Virus shed in the feces, eye and nose discharges from infected birds
✔ Readily mutates and can change from low to high pathogenicity
✔ Good biosecurity reduces disease risk
tors on cells as part of virus entry into the cell,
and these linkages are different for avian and
human in;uenza viruses.
França presented results of a study look-
ing at the prevalence of two In;uenza A
virus receptors in tissues. Various wild bird
species from nine different orders of birds
Reverse genetics was used to produce
the single-gene reassortant virus from two
Egyptian H5N1 AI viruses that had shown
different pathogenicity. One of these AI
viruses was highly virulent in ducks and the
other was less virulent in ducks.
Vaccine research shows
Many infectious diseases of poultry have
been dramatically reduced by the use of vaccination programs. Prevention and control
of avian in;uenza requires a multifaceted
program, but vaccination has been used and
can be used as one tool in that program.
Research into use of various AI vaccine
delivery systems and variants continues to
enhance methodologies for controlling and/or
preventing outbreaks of avian in;uenza.
Virosomes are a method of delivering
a vaccine. They consist of a phospholipid
bilayer vesicle and viral-derived protein.
Virosomes are not able to replicate but are
capable of fusing with the target cells. They
have been used in humans as a vaccination
method for in;uenza but have not been used
as a vaccination method for poultry.
S. Sharif of the University of Guelph
reported on avian in;uenza virosome-based
vaccine research in poultry. The project involved infecting chickens with an H4H6 AI
virus then vaccinating them with a virosome-based vaccine. The virosome-based vaccine
was used alone or in combination with
interferon-gamma or synthetic DNA CpG
ODN expressed by a recombinant baculovirus. The vaccinated birds all seroconverted;
the highest antibody titers were observed in
those birds vaccinated with the virosome-based vaccine and the CpG ODN.
Sharif’s research demonstrated that
virosome-based vaccines against AI would