Biometrical and genetical characterization of large Babesia ovis in Iran.

One species of Babesia was identified on the blood smear of 20 different naturally infected sheep in the Northwest of Iran. It was polymorphic, including double pyriform with acute or obtuse angle, single pyriform, and ring form. The size of typical paired pyriforms with acute angle was 2.7 x 0.4 microm (n=10) and with obtuse angle was 3.5 x 0.6 microm (n=10). Although the morphological and biometrical parameters resembled the Babesia motasi, the results of seminested polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism using primers specific for small subunit of 18S rRNA confirmed this species as Babesia ovis. Furthermore, the sequence analysis of hypervariable region of small subunit of 18S rRNA revealed the corresponding sequences for B. ovis as well. Experimental infection of healthy lambs with the morphological larger B. ovis showed a milder clinical signs compared to the small one.