Can cattle ticks spread the vaccine organisms to other cattle?
This depends on the tick fever vaccine strain. With Babesia bovis, yes. However, most properties in cattle tick infested areas are already infected. Cattle can remain carriers of tick fever for life, so the greatest risk is from the introduction of disease-carrying animals, not use of the vaccine. With Babesia bigemina, unlikely. It is very unlikely that ticks will become infected if they feed on cattle vaccinated with this strain. With anaplasmosis, no. The strain used in the vaccine (Anaplasma centrale) is not transmitted by Australian ticks.
