Hosts: Domestic goose, blue goose (Anser caerulescens).
Location: Posterior part of small intestine.
Geographic Distribution: Europe, North America.
Prevalence: E. nocens has been reported from the domestic goose only in Europe (Kotlan, 1933; Cerna, 1956), and is apparently not particularly common there. Hanson, Levine and Ivens (1957) found it in blue geese from Ft. Severn and Weenusk, Ontario.
Morphology: The sporulated oocysts were described by Hanson, Levine and Ivens (1957). They are ovoid but flattened at the micropylar end, 29 to 33 by 19 to 24 u with a mean of 31 by 22 u (25 to 33 by 17 to 24 u according to Kotlan, 1933). The oocyst wall is smooth and composed of 2 layers, the outer one 1.3 u thick and pale yellow, the inner one 0.9 u thick and almost colorless. A prominent micropyle is present. A true micropylar cap is absent, but the micropyle appears to be present only in the inner wall and is covered by the outer wall. An oocyst polar granule and oocyst residuum are absent, but part of the oocyst wall often forms one or more roundish protuberances just below the micropyle. The sporocysts are broadly ellipsoidal, with a thin wall and sometimes with a very small Stieda body. The sporocysts are 10 to 14 by 8 to 10 u with a mean of 12 by 9 u. The sporozoites usually lie head to tail in the sporocysts and contain 2 or more large, clear globules which almost obscure their outline. The sporocyst residuum fills the space between sporozoites.
Life Cycle: According to Kotlan (1933), the endogenous stages are found primarily in the epithelial cells at the tips of the villi, but they may also occur beneath the epithelium. The younger developmental stages lie near the host cell nuclei, but as they grow they not only displace the nuclei but also destroy the host cell and come to lie free and partly beneath the epithelium. The schizonts are spherical, 15 to 30 u in diameter, and contain 15 to 35 merozoites. The macrogametes are usually ellipsoidal or irregularly spherical, uniformly coarsely granular, and measure 20 to 25 by 16 to 21 u. The microgametocytes are spherical or ellipsoidal and measure 28 to 36 by 23 to 31 u.
Pathogenesis: Kotlan (1933) described 2 outbreaks of intestinal coccidiosis in goslings in Hungary in which he found both E. nocens and E. anseris. Since the latter is apparently non-pathogenic, the disease was presumably due to E. nocens.