Andy Pachikerl, Ph.D
Like humans, cats have blood grouping. However, cats do not have the blood-type O positive. The blood type classification of cats, however, is currently based on the AB system, but like dogs, there are other antigens besides the AB system , such as the Mik blood type.
The blood type of cats is composed of mainly A, B, and AB. Type A is the most common, type B is rarer, and type AB is rarest. About 95% of domestic cats are type A blood, and some varieties such as exotic short-haired cats, British short-haired cats, Persian cats, and Scottish folds have a higher percentage of type B blood.
As mentioned, the blood-type of cats is mainly A, B, or AB. Peculiarly for AB type, other blood types have innate antibodies. Unlike dogs, cats have antibodies against “non-self” or foreign erythrocytes that can cause lethal immuno -reaction. Therefore, cats cannot obtain a “wrong” blood of different blood types. Before any blood transfusion clinically, cat blood typing is extremely important. Incompatibility of blood type can lead to fatal acute hemolysis reaction, particularly, the blood of a type A cat was given to a type B cat. The anti-type B antibodies found in type A cats have weaker affinity towards each other, causing a mild immune response. However, type B cats have a strong affiliated anti-type A antibody, which can cause a strong immune response. Once type B cat transfuses A-type blood, the red blood cells are rapidly destroyed,resulting in intravascular hemolysis. As little as 1 ml of type A cat blood, it is enough to cause a serious immune reaction in type B cat and then causes absolute lethality.
Keep in mind that blood typing is not only extremely vital prior a blood transfusion, but also for cat breeding!
Neonatal isoerythrolysis (NI) occurs when a mommy cat with type B blood gives birth to kittens with type A or AB blood and breast-feed them with a high chance of having antigens of type A blood antibodies in the milk, which can cause a severe hemolysis reaction in the kittens. There are no obvious clinical signs to severe hemolytic anemia, but only subtle symptoms such as hemoglobinuria and jaundice. Therefore, we must pay attention to the blood type of the parent before breeding.
Despite the best of efforts to prevent them, transfusion reactions may still happen. Depending on the severity, therapy can include glucocorticoids, epinephrine, IV fluids, and discontinuing the transfusion. Fever is usually mild, requiring no treatment. Furosemide should be administered if volume overload occurs. The blood product can be warmed to no more than 37 ° C if hypothermia occurs. Crossmatching blood is the best means of preventing immune-mediated transfusion reactions even if the blood type is known for both cats. It is also imperative blood be collected and administered as aseptically as possible and cats receiving blood products are monitored carefully.
The distribution of feline blood types varies by geographic region and breed (Table 1) 1-2. Type-A is the most common type among most cats. There is, however, geographic variation in the prevalence of type-B domestic shorthaired cats. Over 10% of the domestic shorthair cats in Australia, Italy, France and India are type- B. Breed distribution does not vary as much by location because of the international exchange of breeding cats. Over 30% of British Shorthair cats, Cornish and Devon Rex cats, and Turkish Angora or Vans have type-B blood. In contrast, Siamese and related breeds are almost exclusively type-A. Ragdoll cats appear to be unique regarding blood types. Approximately 3.2% of Ragdoll cats are discordant for blood group when genotyping is compared to serology, necessitating further investigation in this breed.
Table 1: Selected Blood Type A and B Frequencies in Cats (ignoring AB blood types)
The AB blood type is very rare while the frequency of the MiK blood type is unknown. The presence of red blood cell antigens in addition to the AB group may explain why transfusion compatibility is not guaranteed by blood typing; crossmatching is recommended prior to any transfusion 3. Breeding queens, along with blood donors and, if possible, blood recipients should be blood typed.
Feline blood-typing methods
There are various methods are that can be used to determine blood type, both in a laboratory and veterinarian clinic. Usually in a diagnostic laboratory, they would use various serological methods by adding reagents to samples of blood and observe for any agglutination reactions marking a positive result. In addition, genetic testing is now available to identify blood types A and B using buccal swabs, although it cannot distinguish between A and AB blood groups. In veterinarian clinics, testing may be performed using a card typing system (BIOGUARD® Feline blood -typing kit, New Taipei City, Taiwan and Rapid Vet-H®, Flemington, NJ). If the card-typing system is used, type-AB and type-B results should be confirmed by a referral laboratory as some cross-reactions have been known to occur. Recently,there was an introduction to an alternative novel method for blood typing ie using the gel column agglutination test (DiaMed-Vet® feline typing gel, DiaMed, Switzerland). This test is easier to interpret than the card method, although it requires a specially designed centrifuge that may be cost-prohibitive in some settings. An evaluation of various blood typing kits and methods revealed that accuracy of blood type must be high and working hand in hand with time efficiency. A complete comparison of kits and methods for blood typing is as follow.An evaluation of various blood typing kits and methods revealed that accuracy of blood type must be high and working hand in hand with time efficiency. A complete comparison of kits and methods for blood typing is as follow.An evaluation of various blood typing kits and methods revealed that accuracy of blood type must be high and working hand in hand with time efficiency. A complete comparison of kits and methods for blood typing is as follow.
Pros and cons of commercially available feline blood-typing kits
In felines, blood types are categorized into the existing types A, B and AB blood groups based on the three alleles ( a , ie dominant, a ab and b ) inherited, which is different from the human ABO system. Type A cats have been proven to have weak naturally occurring anti-B alloantibodies, whereas type B have strong naturally occurring anti-A alloantibodies. 4–6 The antigens of A and B red blood cells are sialic N -glycolyl- and N -acetyl-neuraminic acids, respectively . 4 There have been known genetic mutations identified in the antigens of feline blood; however, their precise functional effects are yet to be uncovered. 7–9
Blood-typing in cats are only tested when there is a need for blood transfusion or before breeding. Usually, blood transfusions are required because of anaemias that can lead to blood loss (mostly acute, rarely chronic). The decision whether a blood transfusion should be done depends on the ratio of red blood cells (RBC) to whole blood volume ie haematocrit (Hct). A RBC transfusion is recommended for critically ill cats if the Hct falls below 10-15%. It is equally important to observe the condition of the cat: parameters like tachycardia, weak pulse, prolonged capillary refill time, lethargy, and weakness are also indicators hinting a transfusion. In cases of acute anaemia or if the animal needs surgery, blood transfusions are given at higher Hct values. Cats with a chronic anaemia tolerate a low Hct better than those with an acute anaemia.7 In case of breeding, neonatal erythropoiesis or haemolysis can occur if cat having one blood group is mated with another cat having another blood group.
Methods of blood typing and various known brands
There are two methods in identifying blood types in feline and they are: polymerase chain reaction (PCR) using antigen specific primers along sequencing the products and rapid kits. The most widely used method in veterinarian clinics is rapid kits since it is both cost efficient and less time consuming. The top consuming brands of feline blood typing rapid kits are from: Alvedia®, Rapid VetH® and BIOGUARD® (Fig. 1). Alvedia® uses murine antibodies for testing both type A and B blood in feline on a lateral flow test strip, which are generated from a female Cmah-/-knocked-out mouse to prevent endogenous murine blood antigens being extracted. Rapid VetH® rapid kit uses an antibody for type A blood and a wheat-extracted peptide known as lectin (WGA) for type B blood and their method slightly differs to that of Alvedia. Instead of a strip showing a single test line and a single control line, Rapid VetH® uses the hemagglutination observable on the sheet of paper they provided with blood dilution buffers. Last but not the least, BIOGUARD® uses almost the same type of sheet used by Rapid VetH® but with a variation in that testing type B blood, they use an antibody instead of WGA. With all things considered, veterinarians would consider the use of rapid blood typing kit for a much time and cost -efficient method of identifying the blood type before a feline blood transfusion,rather than using PCR method if identifying the antigens in the sampled blood and would take hours until the results are in.
Figure 1. Various feline blood-typing kits. (A) Alvedia ® (b) Rapid Vet-H ® and (c) BIOGUARD ®.
Pros and Cons
Alvedia® blood typing kit
If the blood typing is done as part of a blood transfusion, this sometimes involves a hectic situation where time is of key importance and many activities are happening at the same time. To aid the user in making the correct transfusion decisions, the analyser offers optional clinical advice based on the test result at the end of the test. This is where Alvedia® gains the advantage with its strikingly high antigen to antibody specificity and simplicity to read. Alvedia® blood typing kits only require a mere four minutes in distinguishing the feline’s blood type with high accuracy due to the specific antibodies on both the test and control line. Despite being one of the most expensive kits, with one set (10 pieces) costing roughly $ 250.00 USD or € 228.00 to test for feline blood,many veterinarians still recommend the use of Alvedia® blood typing kit prior to blood transfusion and / or breeding.
One other pro of Alvedia® would be its capability of identifying blood groups from cats that are anaemic or having lesser RBC than the norm. Lastly, Alvedia® blood typing kit uses a unique specific membrane technology, the agglutinated red blood cells (RBCs) will be retained at the bottom of the membrane whereas non agglutinated RBCs will continue to migrate to the top of the membrane. Even though Alvedia® blood typing kit has plenty of pros, it does have its downfall in an additional feature that Rapid VetH® and BIOGUARD ® have in detecting auto-hemagglutination and hemagglutination inhibition in blood. Even though these cases are rare to encounter, but cats possessing these traits may cause great complication after blood transfusion.
Rapid VetH® and BIOGUARD®
These two brands for rapid blood typing are known for their assays being carried out on a test card. They can be easily observed and quite readily fast (1 – 3 minutes). What make them popular is their reasonable with one set (10 pieces) price of $ 240.00 USD or € 228.00 (Rapid VetH®) and $ 220.00 USD or € 200.50 (BIOGUARD ®). Both antibody-antigen binding specificity is comparable to that of Alvedia’s; however, when it comes to anaemic cats, Rapid VetH and BIOGUARD will have a problem in detecting the blood type. Thus, both requires normal whole blood samples with enough RBC. Additionally, Rapid VetH® has a higher chance of false positive compared to Alvedia and this is caused by variant concentration of the WGA peptide dried unto the test card. If the volume of the buffer were mistakenly added lesser than it should,a false positive of hemagglutination could occur, since WGA in higher concentration can cause agglutination in any blood type. However, as much as specificity and buffer volume is concerned, VetH® and BIOGUARD® both have an advantage in identifying cats with auto-hemagglutination and hemagglutination inhibition of blood. This additional pro can help veterinarians prevent blood transfusion that could cause complications in cats later on.
- Knottenbelt C. The feline AB blood group system and its importance in transfusion medicine. J Fel Med Surg 2002; 4: 69-76.
- Bighignoli B, Owens SD, Froenicke L, et al. Blood types of the domestic cat In: August J, ed. Consultations in feline internal medicine. 6 ed. St. Louis: Saunders Elsevier, 2010; 628-638.
- Weinstein NM, Blais MC, Harris K, et al. A newly recognized blood group in domestic shorthair cats: the Mik red cell antigen. J Vet Intern Med 2007; 21: 287-292.
- Griot-Wenk ME, Callan MB, Casal ML, et al. Blood type AB in the feline AB blood group system. Am J Vet Res 1996; 57: 1438–1442.
- Giger U, Bücheler J, Patterson DF. Frequency and inheritance of A and B blood types in feline breeds of the United States. J Hered 1991; 82: 15–20.
- Knottenbelt CM, Day MJ, Cripps PJ, et al. Measurement of titers of naturally occurring alloantibodies against feline blood group antigens in the UK. J Small Anim Pract 1999; 40: 365–370.
- Kehl A, Heimberger K, Langbein-Detsch I, et al. Molecular characterization of blood type A, B, and C (AB) in domestic cats and a CMAH genotyping scheme. PLoS One 2018; 13.
- Gandolfi B, Grahn RA, Gustafson NA, et al. A novel variant in CMAH is associated with blood type AB in Ragdoll cats. PloS One 2016; 11.
- Giger U. Blood typing and crossmatching to ensure blood compatibility. In: Bonagura JD, Twedt DC, editors. (Eds). Current veterinary therapy. St Louis, MO: Saunders, 2014, e143.