Blood typing prior to canine blood transfusions minimizes the risk of transfusion reaction due to blood type incompatibility. Information on the prevalence of different blood types in various breeds aids the selection of blood donors for inclusion in a blood donor program . This study showed a similar prevalence of DEA 1, 7 and 4 to that reported in previous studies in the same, and in different, geographic areas [16, 17, 19, 22].
Canine blood groups have been reported to vary geographically and between breeds [11,12,13], and the recognition of new canine blood groups, such as Dal and Kai 1 and Kai 2 antigens, demands further epidemiological studies to provide new information about the prevalence of these blood groups [4, 25]. In the USA, Dalmatians and Doberman Pinschers were identified as breeds with a high prevalence of Dal negative dogs . However, Dal negative Beagles, Shih Tzus and Lhasa Apsos were also identified .
In the present study, using gel column technology and polyclonal anti-Dal antibodies, seven Dal negative blood donor dogs were identified from Italy and Spain with no significant difference between this population and the prevalence of Dal negative blood donor dogs in the population previously analyzed in USA .
The scarcity of Dal negative dogs among blood donors raises a concern that Dal negative dogs receiving an incompatible transfusion risk being sensitized. The Dal blood group is not, as previously hypothesized, a high-frequency antigen such as DEA 4, but seems to be missing in some dogs within certain breeds. There are also some breeds where > 10% of the dogs are Dal negative . The identification of breeds with a high prevalence of Dal negative subjects would be advantageous to improve guidelines for blood donor dogs recruitment, until a commercial test is developed for Dal blood typing during routine clinical testing.
The Dal group seems to have an autosomal dominant mode of inheritance similar to that previously identified in other canine blood groups . Furthermore, Dal positive parents usually produce only Dal positive offspring, and Dal negative offspring are uncommon if both parents are Dal positive.
Although, only a small number of Doberman Pinschers were typed (n = 46) in our study compared to the study in the USA (n = 432), we confirmed a high percentage of Dal negative dogs in this breed, although numbers were significantly lower than those found in the study from the USA .
The Dal blood group in Doberman Pinschers may have clinical importance, given the high prevalence of von Willebrand disease (vWD) in this breed . Affected dogs have a high risk of bleeding and may need multiple transfusions , increasing their risk of being sensitized to the Dal antigen, developing Dal alloantibodies and experiencing a transfusion reaction.
The risk of an acute transfusion reaction linked to the Dal group, would most likely be confined to dogs receiving multiple transfusions as previous studies have shown that dogs have no naturally occurring anti-Dal antibodies [4, 16].
As there is no relationship between the DEA blood types tested and Dal positivity [19, 22], and because Dal testing is not currently routinely available, the only way to evaluate transfusion compatibility for the Dal group is by cross-matching. Cross-matching must always be carried out in dogs receiving further transfusions 4 days after the first. Our study also identified Dal negative dogs in the Cane Corso breed. This finding is of particular interest because the Cane Corso dog is an ancient Italian large breed dog that makes a very good blood donor for a number of reasons: large size (> 25 kg bodyweight), good temperament, easy and readily accessible jugular veins and significant higher DEA 1 and DEA 7 negative prevalence than most of the canine populations previously surveyed [7, 9, 11]. Our study also confirms the high prevalence of DEA 1 and DEA 7 negative subjects in this breed.
In this study, we typed only a small number of blood donor dogs, and further studies are required to estimate the real prevalence of Dal negative dogs in Doberman Pinschers, Cane Corsos and other blood donor breeds in Europe. Furthermore, the findings in the Cane Corso breed, which is classified in the Molossoid group, might prompt testing of other Molossoid breeds for identification of those with a higher prevalence of Dal negative individuals. As relevant antisera are not commercially available, it was not possible to assay DEA 3, 5 and Kai 1 and Kai 2 blood types [21, 22, 25], so the relationship of these with the Dal blood type could not be investigated.