Babesia is spread to humans via ticks or blood transfusions. Severity of Plasmodium falciparum malaria is strongly correlated to the ABO blood group of the patient. Babesia divergens is an intraerythrocytic parasite with many similarities to malaria, but the impact of ABO on the susceptibility to and progression of the infection in humans is unknown. We have now cultured B. divergens in human group A, B and O erythrocytes in vitro and measured rates of multiplication. The predilection for the different erythrocyte types was also determined using an in vitro erythrocyte preference assay when the parasites were grown in group A, B or O erythrocytes over time and then offered to invade differently stained erythrocytes of all the blood types at the same time. The results showed no difference in multiplication rates for the different blood types, and the parasite exhibited no obvious morphological differences in the different blood types. When cultured first in one blood type and then offered to grow in the others, the preference assay showed that there was no difference between the A, B or O blood groups. In conclusion, this indicates that individuals of the different ABO blood types are likely to be equally susceptible to B. divergens infections.

Babesia is an intraerythrocytic parasite transmitted by ticks or through blood transfusion, and it can cause babesiosis with symptoms such as fever, anemia, and organ failure. The parasite is closely related to the mosquito-borne Plasmodium falciparum, which causes malaria. Several studies have shown that individuals with blood group O have a reduced risk of severe malaria compared to individuals with other ABO blood groups. Whether or not this is also the case for babesiosis has not yet been clearly investigated. In this study, serum samples from over 650 individuals were analyzed using an ELISA assay to detect antibodies against Babesia divergens. The ABO blood groups of the same samples were determined using a conventional method. There was no difference in B. divergens IgG antibody levels between the different ABO blood groups, nor was there any difference in the percentage of positive reactions in the ELISA against B. divergens between the different blood groups. This could indicate that the development and maintenance of B. divergens antibodies are not influenced by ABO blood groups.