Synonyms: Babesiella major, Francaiella colchica.
Geographic Distribution: Europe, USSR.
Morphology: The trophozoites resemble those of B. bovis, but are larger. The piriform, paired forms measure 2.6 ju by 1.5 u, and the round ones are 1.8 u in diameter. The parasites lie in the center of the host erythrocyte.
Life Cycle: Similar to that of B. bovis. The vector in the USSR is Boophilus calcaratus.
Pathogenesis: This species is considerably less pathogenic than B. bovis. There is little fever, relatively slight anemia, and experimentally infected animals show no clear clinical signs of illness.
Immunity: This species can be differentiated from B. bigemina and B. berbera by cross-immunity studies.
Treatment: Same as for B. bovis. Trypan blue is ineffective against B. major.