Attenuation of a strain of Eimeria mivati of U.S. origin by serial embryo passage.

A strain of Eimeria mivati (FS50) isolated in Georgia was purified and serially passaged in groups of developing chicken embryos. Starch gel electrophoresis using glucose phosphate isomerase and lactate dehydrogenase showed the parasite to be similar to another strain of E. mivati isolated in the U.S. The embryo-passaged line of E. mivati (FS50) was less pathogenic than the parent line but retained its immunogenicity. This strain may be suitable for inclusion in an improved coccidiosis vaccine. The status of E. mivati and E. mitis is discussed.