Introduction: Significant geographical variation of AB feline blood type has been described in the world. Risks of life-threatening acute immune-mediated hemolytic reactions due to mismatched transfusion (MT) and neonatal isoerythrolysis (NI) depend on proportion of anti-A and anti-B alloantibodies and on the respective prevalence of blood types.

Background: The most described erythrocyte antigens system in cats is the AB system. Strong anti-A antibodies are responsible for acute hemolytic reaction whereas weak anti-B antibodies produce milder reactions such as shorten survival of red blood cells transfused.

Objectives: Aims of this study were to update the prevalence of feline blood types in Lyon (France) area and to determine the risk of MT and NI in kittens with unknown blood-type parents, compared with other geographical regions.

Methods: Blood samples were obtained from feline blood donors and cats admitted in the intensive care unit. AB blood typing was performed using an immunochromatographic strip (CHROM Method, Lab Test A+B, Alvedia). Risk of MT was estimated by adding the risk of a major transfusion reaction and the risk of a minor transfusion reaction. Risk of NI was estimated according the equation (p²)(q²)+2pq(q²) with q the B allele frequency and p=1-q. Results were analyzed by absolute and relative frequency and multivariate analysis.

Results: Cohort-study population included 320 non-pedigreed cats and 37 pedigreed cats from Lyon (France) area. Prevalence of blood types A, B and AB were 83.2%, 13.7%, and 1.7%, respectively. Considering non-pedigreed cats, prevalence of types A, B and AB were 83.8%, 14.4%, and 1.9%, respectively. Based on these percentages, the risks of MT and NI in non-pedigreed cats were 24.3% and 12.3%, respectively.

Discussion: Regarding previously published data on prevalence of AB blood type, the five countries where risks of MT and NI are the most elevated are Australia, England, Turkey, Greece and Ireland. France appears to be the sixth country at risk.

Conclusions: Prevalence of type B cats is high in France and associated with high risks of MT and NI. These results confirm the importance of performing blood typing prior to any blood transfusion or mating.