Hosts: Ox, zebu, water buffalo.
Location: Small intestine.
Geographic Distribution: North America, Europe (Austria, Spain), USSR.
Prevalence: This species is common in cattle. Boughton (1945) found it in 45% of 2492 bovine fecal samples from southeastern United States and remarked that its oocysts comprised 40 to 50% of the total oocyst population in 959 samples from over 100 calves 3 to 12 weeks old. Christensen (1941) found its oocysts more frequently than those of any other species in the feces of healthy calves in Alabama during early natural infection. Hasche and Todd (1959) found it in 43% of 355 cattle in Wisconsin. Supperer (1952) found it in 15% of 130 cattle in Austria. Yakimoff, Gousseff and Rastegaieff (1932) found it in 23% of 126 oxen in Uzbekistan. Yakimoff (1933) found it in 27% of 41 oxen, 6% of 17 zebus and 52% of 21 water buffaloes in Azerbaidzhan. Marchenko (1937) found it in 16% of 137 cattle in the North Caucasus. Ruiz (1959) found it in 3% of 100 adult cattle in the San Jose, Costa Rica abattoir.
Morphology: The oocysts have been described by Becker and Frye (1929) and Christensen (1941), among others. They are 12 to 27 by 10 to 18 u with a mean of 17 by 13 u. Their length-width ratio is 1.0 to 1.6 with a mean of 1.30. They are predominantly ellipsoidal, but vary in shape from spherical to almost cylindrical, the spherical and subspherical oocysts occurring in the smaller size range. The oocyst wall is thin, smooth, presumably composed of a single layer, homogeneous, transparent, colorless to pale lavender or pale yellowish, and slightly thinner and paler at one end, suggesting a possible micropyle. A true micropyle is apparently absent, however. An oocyst residuum and polar granule are absent. A sporocyst residuum is present. The sporocysts were illustrated by Becker and Frye (1929) without a Stieda body. The sporocysts (in the zebu) measure 13 to 14 by 4.5 u according to Yakimoff (1933). The sporozoites were illustrated by Becker and Frye (1929) without clear globules. The sporulation time is 2 to 3 days.
Life Cycle: Unknown. The endogenous stages occur in the epithelial cells of the small intestine mucosa, according to Boughton (1945).
Pathogenesis: According to Boughton (1945), this species often causes nonbloody diarrhea in calves 1 to 3 months old.