CMAH genotyping survey for blood types A, B and C (AB) in purpose‐bred cats

Summary In domestic cats, the AB blood group system consists of the three types A, B and C (also called AB). Mismatches can cause acute hemolytic transfusion reactions and hemolysis of the newborn (neonatal isoerythrolysis, NI). As blood types B and C are inherited recessively to A, breeders need to know the genotype to predict blood types in offspring and avoid NI. Several CMAH variants have been described as being associated with the b and ac alleles, and different genotyping schemes exist. Here, we genotyped 2145 cats with the original SNV panel, including SNVs c.142G>A and ∆‐53, and our new scheme, with SNVs c.179G>T, c.268T>A and c.1322delT, to differentiate types A and B and added the SNV for the common ac (c.364C>T). Based upon the new scheme, all samples were assigned the correct genotype. No discordances appeared for the A allele, and new breed‐specific SNVs (c.179G>T, c.1322delT) for the b allele were discovered. Furthermore, the genotypes A/ac (type A), ac/ac (C) and ac/b (C) could be detected. We found the variant c.179G>T in additional breeds: Ragdoll, Siberian, Scottish Fold, Chartreux, Neva Masquerade, British Shorthair and Highlander. Also, the variant c.364C>T was detected in additional breeds: Bengal, British Shorthair, Maine Coon, and Scottish Fold. We conclude that our new SNV panel is superior in genotyping cats than the original SNV panel and assures correct assignments of types A, B and C to assist veterinary clinicians and breeders to recognize, confirm and avoid blood incompatibilities such as acute hemolytic transfusion reactions and NI.