Recurring and spontaneously curing spring haemoglobinuria was recently reported in a small sheep flock in a selenium deficient area of northern Hungary. In blood smears of two animals showing clinical signs, Anaplasma-like inclusion bodies were seen in erythrocytes. To extend the scope of the study, 156 sheep from 5 flocks and 26 cattle from 9 farms in the region were examined serologically with a competitive ELISA to detect antibodies to Anaplasma marginale, A. centrale and A. ovis. The seropositivity in sheep was 99.4%, and in cattle 80.8%. A. ovis and A. marginale were identified by PCR and sequence analysis of the major surface protein (msp) 4 gene in sheep and cattle, respectively. Haemoglobinuria, an unusual clinical sign for anaplasmosis might have been a consequence of transient intravascular haemolysis facilitated by selenium deficiency in recently infected sheep, as indicated by the reduction of mean corpuscular haemoglobin concentration (MCHC). Membrane damage was also demonstrated for parenchymal cells, since their enzymes showed pronounced elevation in the plasma. Ticks collected from animals in the affected as well as in neighbouring flocks revealed the presence of Dermacentor marginatus, Ixodes ricinus and D. reticulatus, with the dominance of the first. The present data extend the northern latitude in the geographical occurrence of ovine anaplasmosis in Europe and reveal the endemicity of A. ovis and A. marginale in Hungary.