Is predisposition to giardiasis associated with the ABO groups?

Since an excess of blood group A in giardiasis has been repeatedly reported, we studied 190 patients with parasitologically confirmed giardiasis. Their blood group distribution did not differ from that of the Finnish population, and the statistically insignificant deviations were a surplus of group B and a shortage of group A. Among 85 participants of four travel groups which experienced an epidemic of giardiasis, the blood group distributions of the infected and the noninfected persons were not different. Thus, blood group A did not predispose to the acquisition of Giardia lamblia infection. To disclose an impact on the course of the disease, the patients were classified according to symptoms or duration of infection, but the ABO distributions did not differ from the expected. Our patients were adults, probably contracting giardiasis for the first time during a trip abroad, while the excess of group A has been reported in children in enedemic areas.