Increased numbers of strahlenkörper in Boophilus microplus ticks ingesting a blood-passaged strain of Babesia bigemina.

Observations were made on the morphology and infectivity of Babesia bigemina parasites in the gut of Boophilus microplus ticks. The babesia parasites were derived from stabilates of a laboratory strain, prepared at intervals during several years of blood-passaging in cattle. Increased numbers of a particular developmental stage of the parasite, considered to be a type of strahlenkörper, were observed in ticks ingesting parasites derived from the latter stages of passaging. The presence of large numbers of these parasites was associated with reduced infectivity of the strain for ticks.