Immunosuppression by Babesia bovis against its tick vector, Boophilus microplus

INFECTION with protozoan parasites may interfere with the immune response to a variety of agents including bacteria 1 , other protozoans 2–5 and helminths 6–8 . In two recent studies of immunosuppression by a rodent piroplasm 8,9 , the likely, veterinary importance of the effect was suggested. We have now verified this possibility by showing that Babesia bovis , a pathogenic piroplasm of cattle causes immunosuppression against its natural tick vector, Boophilus microplus . The observation seems to be the first of immunosuppression caused by a protozoan against a parasitic arthropod.