This species was described from the deermouse, Peromyscus maniculatus, in Idaho by Frenkel (1955). He transmitted it by intraperitoneal or intravenous inoculation of peritoneal fluid from acutely ill animals or by trophozoites from cysts of chronically affected animals to white mice, rats, hamsters, voles (Microtus), ground squirrels (Citellus) and chicken embryos, but not to guinea pigs, rabbits, the ox, rhesus monkey, baby chick, canary or pigeon (Frenkel, 1956a). Jellison, Fullerton and Parker (1956) transmitted it to mice by feeding trophozoites from cysts or peritoneal fluid of affected animals.
The cysts occur in the connective tissue and on the serosae of many of the viscera organs, including the intestine, liver, spleen, heart, testes, etc. They are spherical, up to 1 mm in diameter, with thick walls containing giant nuclei. The wall is positive to the periodic acid-Schiff reaction and is unaffected by salivary digestion.
The trophozoites are crescent-shaped, with a central nucleus. According to Goldman, Carver and Sulzer (1957, 1958), who studied them after staining with Bodian silver stain, they have a truncated, caplike cone at the anterior end with 1 or more rod- or fibril-like structures extending posteriorly from it, a dark-staining posterior granule and a nucleus consisting of a larger, less dense portion and a smaller, more compact structure. They reproduce by endodyogeny.
B. jellisoni may cause an acute, fatal disease or a chronic one.
B. jellisoni is serologically and immunologically distinct from Toxoplasma and also from B. besnoiti. Goldman, Carver and Sulzer (1957) found that fluorescein-labelled Toxoplasma antibody did not stain B. jellisoni, and Frenkel (1955) found that sera from cows naturally infected with B. besnoiti did not react with B. jellisoni in the dye test.