Type host: Lithobates catesbeianus (Shaw, 1802), American bullfrog.

Other hosts: Lithobates clamitans (Latreille, In Sonnini de Manoncourt and Latreille, 1801), Green frog; Lithobates septentrionalis (Baird, 1854) Mink frog; Lithobates sylvaticus (LeConte, 1825), Wood frog.

Type locality: NORTH AMERICA: Canada: Ontario, Algonquin Park, Lake Sasajewun.

Geographic distribution:NORTH AMERICA: Canada: Ontario.

Description of oocyst: Oocyst shape: spheroidal; number of walls: 1; wall thickness: thin; wall characteristics: smooth; L x W: 15.8 (14.5-16); L/W ratio: 1.0; M: absent; OR: present; OR characteristics: spheroidal, 10 (9-11), composed of coarse granules; PG: absent. Distinctive features of oocyst: colorless, thin, smooth wall and the massive size of the OR which mostly obscures the sporocysts (line drawing).

Description of sporocysts and sporozoite: Sporocyst shape: banana-shaped; L x W: 19.5 x 4.2 (19-20 x 4-5); L/W ratio: 4.6; SB: absent; SSB: absent; PSB: absent; SR: present; SR characteristics: composed of small, coarse granules (line drawing); SZ: elongate, 13.8 x 1.6 (13.5-14 x 1-2), with 2 spheroid RBs present, located on each side of an indistinct N. Distinctive features of sporocysts: very thin wall that is almost invisible (line drawing) and a L/W ratio that is the largest of any amphibian coccidium.

Prevalence: 26 of 162 (16%) Lithobates catesbeianus; 3 of 25 (12%) L. clamitans; 7 of 68 (10%) L. septentrionalis; 3 of 9 (33%) L. sylvaticus.

Sporulation: Presumably exogenous.

Prepatent and patent periods: Unknown.

Site of infection: Unknown, but see Remarks.

Endogenous development: Unknown.

Materials deposited: None.

Remarks: There are four other species of amphibian Eimeria that have spheroidal oocysts similar to those of E. algonquini. Sporulated oocysts of E. belawini, E. laminata, and E. mazzai are smaller, while those of E. streckeri are larger than those of E. algonguini. In addition, sporocyst sizes, hosts and geographical locations are different between these five species. The authors suggested that due to the method of obtaining fecal samples (gently squeezing the abdomen or giving the frog an enema with 85% saline), only moderate to heavy infections were detected, while lighter infections may have been missed. Thus, actual prevalence in examined frogs may have been higher than what they found. Young bullfrogs, based on size, were most frequently infected. This might be due to sporulated oocysts released into the water being ingested by larger invertebrates and, or, tadpoles, the prey of young bullfrogs (Korschgen & Baskett 1963; Fulk & Whitaker 1969). Chen and Desser (1989) reported the site of infection for E. algonquini as the intestine, but oocysts were recovered from the feces and no attempt was made to examine the intestine for developing stages of E. algonquini; therefore, the site of infection for this species is unknown.