Isospora Sp

Hosts: Ox and ox-zebu hybrids.

Location: Unknown. Oocysts found in feces.

Geographic Distribution: North America (Illinois).

Prevalence: Levine and Mohan (1960) found this form in 6 out of 54 beef cattle on 3 farms in central Illinois.

Morphology: The oocysts are usually subspherical, occasionally spherical, 21 to 33 by 20 to 32 u with a mean of 27 by 25 u. The oocyst wall is smooth, colorless, pale lavender or pale yellowish, composed of a single layer about 1 u thick. In some oocysts, the wall appeared to be lined by a thin membrane. A micropyle and oocyst residuum are absent. Several oocyst polar granules are present. The sporocysts are lemon-shaped, quite thick-walled, 14 to 20 by 10 to 12 u with a mean of 17 by 11 u. The sporocyst Stieda body is a button-shaped cap, with a dependent, globular hyaline mass protruding into the interior of the sporocyst. The sporocyst residuum is finely granular. The sporozoites are sausage-shaped, not arranged in any particular order in the sporocyst. The sporocyst residuum and sporozoites are enclosed in a membrane, forming more or less of a ball within the sporocyst.

Life Cycle: Unknown.

Pathogenesis: Unknown.

Remarks: Levine and Mohan (1960) compared this form with I. lacazei of the English sparrow, which they redescribed. They found that the 2 forms were practically indistinguishable and concluded that the oocysts found in bovine feces were most likely those of I. lacazei and were pseudoparasites of cattle. They calculated that, in a steer which produced about 20 pounds of feces per day, the presence of 1 oocyst per gram of feces would represent contamination of the feed with about 9000 oocysts, assuming that the oocysts were mixed uniformly with the ingesta and passed thru the animal unchanged. Assuming again that a flotation was carried out with about 2 g of feces and that about 10% of the oocysts present were recovered, they calculated that every oocyst found might represent an initial contamination of a day's feed with about 45,000 oocysts. Since Boughton (1933) quite frequently obtained counts of 200,000 to 2 million oocysts per gram of dried sparrow feces, they considered it quite likely that sparrow coccidia could be detected in a calf's feces if it ingested only a single fecal deposit from a single sparrow in the course of a day.