New attenuated strains of apicomplexa and their use as antigen vectors for the prevention of infectious diseases

The present invention concerns a mutant strain of Sarcocystidae in which the two genes mic1 and mic3 are deleted, containing two specific recombination sites of an enzyme enabling a specific recombination in particular Cre recombinase, said specific recombination sites being at the respective locus of each of the above-said deleted genes, the specific recombination site of the enzyme enabling a specific recombination, in particular of Cre recombinase, at the locus of the deleted mic1 gene being different from that at the locus of the deleted mic3 gene.