Isospora Rivolta

Synonyms: Coccidium rivolta, Lucetina rivoltai.

Hosts: Dog, cat, dingo, and probably other wild carnivores.

Location: Small intestine.

Geographic Distribution: Worldwide.

Prevalence: This species is common in dogs and cats. Gassner (1940) found it in 20% of 320 dogs in Colorado. Catcott (1946) found it in 4% of 113 dogs in Ohio. Ehrenford (1953) found it in 72% of 377 dogs from Indiana and nearby states. Choquette and Gelinas (1950) found it in 13.5% of 155 dogs in Montreal. Hitchcock (1953) found it in 13% of 147 kittens in Michigan.

Morphology: The oocysts are ovoid, 20 to 25 by 15 to 20 u. The oocyst wall is smooth, with a micropyle at the small end. An oocyst polar granule and residuum are absent. The sporocysts are 16 by 10 u. A sporocyst residuum is present. The sporulation time is 4 days.

Life Cycle: The endogenous stages of I. rivolta are poorly known. They are said to resemble those of I. felis but to be smaller. They are found in the epithelial cells and sometimes in the subepithelial tissues of the small intestine. Oocyst development ordinarily takes place outside the body, but occasionally occurs in the subepithelial tissues.

Pathogenesis: Altho experimental studied on I. rivolta alone have apparently not been carried out, it is presumably as pathogenic as I. bigemina and I. felis.

Cross Transmission: Lee (1934) infected a fox with I. rivolta from the dog.