Synonym: Eimeria ildefonsoi Torres and Ramos, 1939.
Hosts: Ox. In addition, Bohm and Supperer (1956) reported finding this species in a wild roe deer in Austria, but gave no morphological information on it.
Location: Unknown. Oocysts found in feces.
Geographic Distribution: North America, South America (Brazil), Europe (Austria, Spain, England).
Prevalence: E. auburnensis is one of the commonest coccidia of cattle in North America. Davis and Bowman (1952) found it in all of 20 calves in Alabama. Hasche and Todd (1959) found it in 45% of 355 cattle in Wisconsin. Torres and Ramos (1939) found it in 32% of 146 cattle in Brazil. Supperer (1952) found it in 3% of 130 cattle in Austria. According to Lapage (1956), Watkins found it in 91% of the calves he examined in Devonshire.
Morphology: The oocysts have been described by Christensen and Porter (1939) and Christensen (1941). They measure 32 to 46 by 20 to 26 u with a mean of 38.4 by 23.1 u. Their length-width ratios range from 1.32 to 2.08 with a mean of 1.67. They are typically elongate ovoid, but vary between sub-ellipsoidal and markedly tapered. The micropyle appears as a thin, pale area at the small end in unstained specimens, but when stained with iodineeosin in physiological salt solution, a definite gap covered by a narrow black line which may be a flat operculum is seen. A membrane lines the oocyst wall, which is illustrated as composed of a single layer. The oocyst wall is 1 to 1.5 u thick, typically smooth, homogeneous, transparent and yellowish brown; relatively rarely it may be semi-transparent and heavily mammillated, and all gradations between these two conditions occur. The smooth-walled forms are more common than the rough.
The sporulation time at room temperature in Alabama is 2 to 3 days. There is no oocyst residuum or polar granule. The sporocysts were illustrated by Christensen and Porter (1939) as elongate with one end pointed. The sporozoites lie lengthwise, head to tail, in them and contain 3 clear globules, 1 of which may be the nucleus. The sporocyst residuum consists of rounded masses or individual granules between the sporozoites.
Christensen and Porter (1939) showed that the rough and smooth forms were the same species by infecting a calf with rough oocysts and recovering all types, but predominantly smooth ones, from it.
Life Cycle: The endogenous stages of this species are unknown. Christensen and Porter (1939) found that the prepatent period in one calf was 24 days. Large numbers of oocysts were discharged for 3 days, and small numbers for the next few weeks.
Pathogenesis: Christensen and Porter (1939) produced a profuse, watery, green diarrhea accompanied by slight apathy in a 2-week-old calf following administration of 8000 sporulated oocysts. The signs appeared 9 days after infection (i.e., 15 days before the first oocysts appeared in the feces) and continued for 5 days. According to Davis and Bowman (1952), infections with E. auburnensis are usually accompanied by straining and the passing of visible blood and mucus, especially following experimental inoculation with large numbers of oocysts or in natural outbreaks where contamination is heavy.