Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

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Chapter | 28 Avian Clinical Biochemistry
will precipitate at 56°C, while the other plasma proteins
remain in solution. EDTA rather than heparin should be used
as an anticoagulant when this test is performed ( Hawkey and
Hart, 1988 ; Schlam et al. , 1975). Protein concentrations can
be estimated in the plasma column of two hematocrit tubes,
one of which has been placed in a water bath at 56°C to 58°C
for 3 min. Fibrinogen concentration is the difference between
the protein concentration of the two plasma columns ( Schalm
et al ., 1975 ). See also Section IV.B.
Because the difference between plasma and serum
is the absence of fibrinogen in the latter, it is possible to
locate the fibrinogen fraction in the electrophoretic gel of
a particular species by performing a comparative protein
electrophoresis in serum and plasma from the same sample
of this particular avian species ( Roman et al ., 2006 ).
D . Hemostatic Disorders
1 . Bacterial and Viral Infections
A variety of bacterial and viral diseases in a variety of
avian species have caused hemostatic disorders. Examples
are circovirus and polyomavirus in psittacines. Reasons for
the increased bleeding tendency seen with these infections
may include thrombocytopenia, liver failure leading to a
lack of clotting factors, vasculitis, and disseminated intravascular
coagulation (DIC). In DIC, the chain of events
is initiated by exogenous or endogenous procoagulants,
which stimulate the formation of fibrin, which is followed
by fibrinolysis. The combination of consumption of thrombocytes
and clotting factors and the inhibition of fibrin
formation by fibrin degradation products may result in
consumptive coagulopathy.
2 . Vitamin K Defi ciency
Because vitamin K is essential for the formation of prothrombin
and factors VII, IX and X, both the extrinsic and
the common coagulation pathway is affected in vitamin K
deficiency, leading to a prolonged PT in birds. Vitamin K
deficiency is well known in birds and has been reported in
chickens fed a diet low in fat ( Dam, 1935 ). A syndrome
resembling the disease in chickens has been reported in a
pigeon with exocrine pancreatic insufficiency by Amann
et al . (2006) , supposedly because of malabsorption of the
fat-soluble vitamin K. Intoxication with anticoagulant rodenticides
interferes with the formation of active vitamin K and
produces similar clinical effects. Clinical signs are widely
reported ( Powers, 2000 ) but depend on species, susceptibility
and the type of anticoagulant used, poultry being 10-fold
more sensitive than pigeons and quail (Towsend and Tarrant,
1997) . History, clinical signs, prolonged PT, and toxicological
investigation of gastrointestinal contents can confirm
the diagnosis. It has also been suggested that Vitamin
K deficiency in birds is caused by oversupplementation
with vitamin E, causing a competitive inhibition of vitamin
K by α -tocopherol ( Nichols et al ., 1989 ). A similar antagonism
has been reported with the use of sulphonamides in
birds (Griminger and Donis, 1960).
3 . Fatty Liver Hemorrhagic Syndrome
It has been suggested that alterations in the composition of
the phospholipids that are essential cofactors in the thrombin
formation may be a contributing factor in the development
of fatty liver hemorrhagic syndrome (FLHS) in
laying hens ( Thomson et al. , 2003 ).
4 . Afl atoxicosis
Aflatoxins originating from Aspergillus fungi can be found
on moldy feed and are a well-known cause of fatty liver
degeneration and bile duct proliferation in poultry. In experimental
aflatoxicosis, the increase of the PT was dependent
on the aflatoxin dose. The specific activity of clotting factors
I, II, V, VII, and X was reduced ( Fernandez et al. , 1995 ) .
ACKNOWLEDGMENTS
The author is grateful to the publishers of the journals
Avian Diseases, Avian Pathology, Seminars in Avian and
Exotic Pet Medicine, and The Veterinary Quarterly for
permission to use illustrations that were published previously
in these journals and to Wingers Publishing Inc. (Lake
Worth, Florida) for using material previously published in
Avian Medicine: Principles and Application (B. W. Ritchie,
G. J. Harrison, and L. R. Harrison, Eds.), 1994. The respective
sources have been indicated in the text were appropriate.
The critical remarks on the draft document from various
diplomats of the European College of Avian Medicine
and Surgery were highly appreciated: Dr. Med. Vet. Petra
Zsivanovits, MRCVS; Brian Coles, BVSc, FRCVS; Brian
Speer, DVM, Dip ABVP-certified in avian practice; Prof.
Dr Med. Vet. Marina Krautwald-Junghanns and Frank
Verstappen, DVM.
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