Abstract:
In an outbreak of Babesia bovis in a large herd of Friesian x Malawi Zebu cattle, which occurred after
an interruption of intensive dipping, clinical or fatal babesiosis occurred in 54/299 (18,1 %) animals which
had never been vaccinated, as compared to 9/153 (5 ,9 %) vaccinated animals. Eight of the nine affected
vaccinates had been vaccinated more than 27 months previously.
Sera were collected every 3-4 months from 33 Friesian x Malawi Zebu heifers maintained with intensive
dipping and vaccinated with trivalent B. bovis, Babesia bigemina and Anaplasma centrale vaccine.
After 2 years, 25% had become seronegative for B. bovis by indirect immunofluorescence, as
compared to 97% for B. bigemina and 46% for A. centrale.
Because of the evidence that immunity following vaccination against B. bovis declines after 2 years in
the absence of tick challenge, it is recommended that tick control should be relaxed after immunity has
been established, in order to save acaricide, reinforce immunity and avoid any need for revaccination.
