Eimeria Magna

Synonyms: Eimeria per forans var. magna.

Hosts: Domestic rabbit, California jack rabbit (Lepus californicus), varying hare (L. timiclus), European hare (L. europaeus), cottontail (Sylvilagus floridanus) (experimental).

Location: Jejunum, ileum.

Geographic Distribution: Worldwide.

Prevalence: This species is quite common. Kessel and Jankiewicz (1931) found it in 19% of over 2000 rabbits in California.

Morphology: The oocysts are ovoid or ellipsoidal, becoming subspherical toward the end of the patent period, smooth, orange-yellow or brownish, and 27 to 41 by 17 to 29 u with a mean of 35 by 24 u. The micropyle is large and surrounded by prominent shoulders. An oocyst polar granule is absent. An oocyst residuum is present. The sporocysts are elongate ovoid, with a Stieda body. A sporocyst residuum is present. The sporulation time is 2 to 3 days. Oocyst variation was studied carefully by Kheisin (1947).

Life Cycle: Rutherford (1943) described the life cycle of this species. The endogenous stages are found below the epithelial cell nuclei of the villi and also in the submucosa. There are 2 asexual generations of merozoites followed by microgamete and macrogamete production. It takes 7 days for completion of the endogenous cycle, and the prepatent period is 6 to 8 days. According to Kheisin (1947), E. magna produces 800,000 oocysts per oocyst fed.

Pathogenesis: This is one of the most pathogenic of the intestinal coccidia of the rabbit. Only a few hundred oocysts of some strains may produce symptoms, and 300,000 may cause death (Lund, 1949). Other strains are less pathogenic, 1 million oocysts not causing death. The principal signs are loss of weight, inappetance and diarrhea. A good deal of mucus may be passed. The animals lose their appetites and grow thin. The intestinal mucosa is hyperemic and inflamed, and epithelial sloughing may occur.