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Psittacine
Beak and Feather Disease
- Part of a new family of viruses known as
circoviridae, PBFD virus is the smallest known virus capable of
causing disease. The actual host range is not yet clear but it appears
that most psittacines (parrots and parakeets) are susceptible. Incubation
periods for PBFD vary from 21 days to a maximum of about 18 months.
Clinical signs include rapid weight loss, depression, shedding of
developing feathers, development of abnormal feathers, beak elongation
and abnormal growth leading to eventual death. Viral transmission
is possible through direct contact with infected feces, crop secretions,
infected materials and surfaces, and feather dust. Transmission
may also be possible to a developing egg. PCR testing allows Avian
Biotech to identify, with extreme accuracy, those birds infected
with PBFD virus as well as environmental contamination of incubators,
brooders, veterinarian offices etc.
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Typical
appearance of
feather shafts showing
PBFD symptoms
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 PBFD
has been around for a long
time but is on the increase. It is a disease that has come from the
wild but is far more effective at spreading itself around among captive
birds. Import quarantine sheds, bird rooms, baby rearing rooms, etc.
are perfect situations for this terrible virus to get a foothold.
Young birds (nestlings and juveniles) are especially prone to this
virus as their immune system is not strong enough to fight off the
invasion. For young birds, PBFD infection will almost always lead
to death. The young ring-necked parakeet pictured is showing advanced
stages of the virus. This poor little scrap died two weeks after these
pictures were taken. Note the
absence of most feathers. If feathers did grow, they were deformed
and would break off. The shafts of the feathers showed splits and
fractures in them and the wing tips would bleed where the feathers
broke off. The beak and claws grew abnormally long and out of shape
and were "softer" than a normal beak or claws. The general
health of the bird was extreme depression, lethargy and weakness. |
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This terrible disease has a wide
species range although parrots and parrot like seem to be top of
the list. PBFD naturally occurs in the wilds of Australasia, therefore
Cockatoos are wide open to infection. Cockatiels and budgerigars
are among the commonly infected.
Old World parrots that succumb to this disease include the African
Greys. New World parrots such as Macaws and Amazons seem to show
less of the disease and are more resilient to it, but will become
infected if placed into a situation of PBFD contamination.
Older parrots that are in good health and become infected with this
virus can fight off the attack using their own immune system. We
cannot assume that those birds that recover are virus free, but
the levels of PBFD are so low that they fall below detection levels.
Avian
Biotech International is actively researching a DNA based
vaccine to inoculate your birds against PBFD.
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PBFD infected
feather.
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Note split
shaft and dried blood.
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PBFD is a deadly disease,
mostly for young pisttacines. The older the bird is when it becomes
infected, the less the chance is that the bird really gets sick and
dies. Older birds (as well as less susceptible young ones) can develop
a transient viraemia, in which birds which initially tested positive
for PBFD by DNA testing, gradually become less and less positive (the
viral levels go down) until, after time, one cannot detect any virus
anymore. This does not mean that the bird is really virus free, for
all tests have a limit to their sensitivity. In my mind, the immune
system of such birds can cope with the infection and can either get
rid of the viral infection altogether or keep the infection at such
low levels that one cannot detect the virus and that the bird does
not show any symptoms of the disease. Young birds with not yet fully
developed immune systems or older bird with some immune deficiency
are more prone to develop the disease and ultimately die.
Over the last years we have acquired a large number of birds, mostly
lovebirds and cockatiels from people who had PBFD in their collections.
We wanted to find out a) how much virus remained in recovering individuals
and b) whether there were strain (DNA-sequence) differences between
the viruses infecting these birds. We found that indeed when birds
recovered, their viral levels went down from very high to undetectable.
Birds with obvious clinical signs like feather loss etc. never recovered,
eventually died and always showed readily detectable viral levels,
even though they sometimes lived
without feathers for about two years. They may well have died from
causes other than PBFD. The young which we got out of the recovered
birds never
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PBFD Infected
Feather
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showed any signs of the disease, but
we have to add that we did not have many offspring, since
we do not have a setup to really raise lovebirds. The finding indicates
that under the conditions in
which we kept the birds, there is not enough virus anymore around
to infect the neonates.
Avian Biotech have sequenced the DNA of a number of isolates and found
some significant sequence differences with strains described by others,
but as of yet, we do not know the effect of the sequence difference
on the virulence of the disease. Such differences can be used,
however, to track the spread of the
disease, which would be interesting in itself. |
Clinical
Description
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PO Box
107, Truro, Cornwall, TR1 2YR England
Tel: (44) 01872 262737, Fax: (44) 01872 262737
info@avianbiotech.co.uk
WebMaster: Rockin@avianbiotech.co.uk
Copyright © 1995-2004
Animal Genetics, Inc. All rights reserved.
Avian Biotech and Avian Connection are ™ of Animal Genetics, Inc.
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