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An Urban Experience
U. Giger1
1University of Pennsylvania, Veterianry Hospital, Philadelphia, USA
FELINE TRANSFUSION MEDICINE – An Update for Your Busy Practice
Urs Giger, Prof. Dr. med. vet. MS FVH
Dipl. ACVIM & ECVIM-CA (Internal Medicine) & Dipl.
ECVCP (Clinical Pathology)
School of Veterinary Medicine, University of Pennsylvania, Philadelphia
Transfusion support is also critical for the feline patient, most commonly to correct anemia and less often bleeding. Nevertheless, blood transfusions are overall still less frequently administered to cats than dogs for a variety of reasons. The peculiarities of feline blood types, blood collection and transfusion will be presented.
Compared to canine transfusion medicine, cats can tolerate anemia better, they still get somewhat less medical attention, except for rodenticide toxicity and hepatopathies they bleed less severely, recruiting healthy donors is more difficult (occult heart disease, viral infections), blood collection requires sedation and special small bag collection systems, component therapy is
less commonly practiced in clinics, cats have important naturally occurring alloantibodies and may experience life-threatening complications with a first transfusion, and the anemic cat is more sensitive to volume overload. There is no specific trigger PCV, but rather the overall clinical picture with a PCV of <20% is used.
Blood Typing: The major feline blood group system is known as the feline AB blood group system and contains 3 alleles: type A, type B, and the extremely rare type AB (except Ragdolls). Type A is dominant over B. Thus, cats with type A blood have the genotype a/a or a/b, and only homozygous b/b cats express the type B antigen on their erythrocytes. In the extremely rare AB cat, a third allele recessive to the a allele and/or codominant to b allele leads to the expression of both A and B substances. AB cats are not produced by mating of a type A to a type
B cat unless the A cat carries the rare AB allele. Cats with type AB blood have been seen in many breeds and domestic shorthair cats.
Most domestic shorthair cats have type A blood, but the proportion of type B cats can be substantial in certain
geographical areas. The frequency of A and B blood types varies greatly between different breeds, but likely not much geographically in purebred cats. Kitten losses due to A-B incompatibility and changes in breeding practices influence the frequency of A and B in various breeds. Most blood donors have type A blood, but some places also keep cats with the rare type B and type AB as donors. All blood donors must be typed. Naturally- occurring alloantibodies have been well documented in type A and type B cats and require that blood typing be performed prior to both blood transfusion and breeding to assure appropriate blood compatibility.
Cats have naturally-occurring alloantibodies. All type
B cats have very strong naturally-occurring anti-A alloantibodies, which can be detected by hemolysis and hemagglutination assays. Kittens receive alloantibodies through the colostrum from type B queens and develop high alloantibody titers (>1:32) after a few weeks of
age. These alloantibodies are strong hemolysins and hemagglutinins, and are of the IgM and, to a lesser extent, IgG classes. They are responsible for serious transfusion reactions and neonatal isoerythrolysis in
type A or AB kittens born to type B queens. Type A cats have weak anti-B alloantibodies, and their alloantibody titer is usually very low (1:2), nevertheless they can also cause hemolytic transfusion reactions, but have not been associated with NI. Type AB cats have no alloantibodies. Furthermore additional blood group systems have been identified such as the common Mik red cell antigen in domestic shorthair cats and Mik-negative cats may also produce naturally occurring alloantibodies.
Serological testing relies on identification of surface antigens, leading to agglutination and hence can distinguish A, AB or B phenotypes. Several different reagents may be used but monoclonal antibodies against the type A and type B antigen are currently used in typing kits. A genetic test is also available for identification of the b allele, allowing identification of type B cats and carriers of this allele, but not distinguishing A or AB phenotypes.

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