NOT PERIPHERAL PARASITEMIA BUT THE LEVEL OF SOLUBLE PARASITE ANTIGEN IN PLASMA CORRELATES WITH VACCINE EFFICACY AGAINST BABESIA-CANIS

Groups of five dogs were vaccinated against Babesia canis using solubl e parasite (SPA) antigens from in vitro cultures. Although vaccination did not significantly alter peripheral parasitaemia upon challenge, p rotected animals had lower levels of SPA in the plasma after a challen ge infection. The severity of anaemia correlated with the SPA-load dur ing the post-challenge period in that high levels of SPA were associat ed with low haematocrit values, In addition, it was found that recover y was associated with the production of antibodies against SPA. The re sults suggest that SPA induce anaemia during B. canis infection, and t hat vaccination with SPA results in antibody protection that can neutr alize the effects of SPA after a challenge infection.