Type host: Myotis californicus (Audubon and Bachman, 1842), California myotis.

Other hosts: None reported to date.

Type locality: NORTH AMERICA: USA, California, Humboldt Co., 12.8 km N, 2.4 km E of Arcadia.

Geographic distribution: NORTH AMERICA: USA, California.

Description of oocyst: Oocyst shape: spheroidal to subspheroidal; number of walls: 2; wall thickness: 1.5; wall characteristics: outer, rough, ~2/3 of total thickness; inner, dark; L x W: 23.1 x 20.7 (20-26 x 19-23); L/W ratio: 1.1 (1.0-1.3); M: absent; OR: present; OR characteristics: a large globule <9, but sometimes 2-3 smaler globules ~3 each: PG: 1. Distinctive features of oocyst: rough outer wall combined with presence of OR and PG.

Description of sporocysts and sporozoites: Sporocyst shape: ovoidal; L x W: 12.5 x 7.2 (11-14 x 7-8); L/W ratio: 1.7 (1-5-2.0); SB: present; SSB: absent; PSB: absent; SR: present; SR characteristics: composed of small granules or globules, often as a compact mass, but sometimes dispersed along edge of sporocyst; SP: with 1 posterior RB. Distinctive features of sporocyst: none.

Prevalence: 1/5 (20%).

Sporulation: Exogenous. Oocysts sporulated in 2% aqueous (w/v) potassium dichromate solution in the field.

Prepatent and patent periods: Unknown.

Site of infection: Unknown. Oocysts recovered from feces.

Materials deposited: Symbiotype host (Myotis californicus) in the Museum of SW Biology, UNM, MSB 40676 (NK 623, 13 June 1979). Photosyntypes of sporulated oocysts in the USNPC No. 88100.

Remarks: Sporulated oocysts of E. humboldtensis are most similar to those of E. redukeri from a pipistrelle from Japan in size and in that they both have a rough outer wall, OR, PG, and SB. They differ, however, in host and geographic distribution and because the oocyst wall in E. redukeri is heavily mammillated, causing a striated appearance, whereas the wall of E. humboldtensis, although rough, is not striated looking. Also, the OR of E. redukeri is one globule, ~2-4, whereas in E. humboldtensis it is larger, ~9, or as 2-3 globules ~3 each. This species differs from other Eimeria species described from Myotis as follows: E. catronensis is ellipsoidal and smaller and has a M; E. pilarensis (15 x 14) and E. kunmingensis (17.5 x 16) are smaller and both have smooth outer oocyst walls; and E. californicensis lacks an OR.

References: Duszynski et al. (1999).