Life Cycle of Isospora canis Nemeséri, 1959 in the Dog*

Abstract

SYNOPSIS The life cycle of I. canis Nemeséri, 1959 was studied in experimentally infected dogs. Freshly sporulated oocysts were ovoid and 34–40 × 28–32 μm. The endogenous stages were found directly beneath the epithelium of the distal portion of the small intestinal villi. Most of the endogenous stages were in the lower 1/3 of the small intestine, but occasionally they were found in other portions of the small intestine. Three asexual generations were present. First‐generation schizonts were 16–38 × 11–23 μm and contained 4–24 merozoites; mature 1st‐generation merozoites were 8–11 × 3–5 μm. First‐generation schizogony lasted up to 7 days after inoculation. Second‐generation schizonts were 12–18 × 8–13 μm and contained up to 12 merozoites which were 11–13 × 3–5 μm. Second‐generation schizogony was present on postinoculation days 6 and 7. Third‐generation schizonts were formed by nuclear division of 2nd‐generation merozoites. Most 2nd‐generation merozoites underwent nuclear division without leaving the parasitophorous vacuole of the 2nd‐generation schizont. Mature 3rd‐generation schizonts were 13–38 × 8–24 μm and contained 6–72 merozoites. Third‐generation merozoites were 8–13 × 1–3 μm. Third‐generation schizogony was present on days 6–8 after inoculation. Mature macrogametes were 22–29 × 14–23 μm. Mature microgametocytes were 20–38 × 14–26 μm. Gametes were present on postinoculation days 7–10. Oocysts were present in tissue sections on postinoculation days 8–10 and 12. The prepatent period was 9–11 days.

Cystoisospora Canis Nemeséri, 1959 (Syn. Isospora Canis), Infections in Dogs: Clinical Signs, Pathogenesis, and Reproducible Clinical Disease in Beagle Dogs Fed Oocysts

“…Nemeséri (1960) found that 5 ϫ 10 3 oocysts of a Hungarian isolate of C. canis were not pathogenic for dogs, but an inoculum of 5 or 8 ϫ 10 4 oocysts produced clinical coccidiosis. In contrast, severe clinical disease was not produced in 25, 6-wk-old or 6, 8-wkold pups inoculated with 1-1.5 ϫ 10 5 C. canis oocysts (Lepp and Todd, 1974) isolated in dogs from Illinois. The pathoge-FIGURE 5.…”

“…Sporulation time: Sporulation is complete in 48 hr at 20 C and 16 hr at 30 or 35 C (Lepp and Todd, 1976).…”

“…Prepatent period: From 9 to 11 days (Nemeséri, 1960;Lepp and Todd, 1974; present study) if oocysts are used as inoculum. The prepatent period is 8-9 days in dogs fed C. canis-infected mice (Dubey, 1975b).…”

“…Severe clinical disease was not produced in 25, 6-wk-old or 6, 8-wk-old dogs inoculated with 1-1.5 ϫ 10 5 C. canis oocysts of an Illinois isolate of the parasite (Lepp and Todd, 1974). Nemeséri (1960) found that 5 ϫ 10 3 oocysts of a Hungarian isolate of C. canis were not pathogenic for dogs, but an inoculum of 5 or 8 ϫ 10 4 oocysts produced clinical coccidiosis.…”

“…The oocysts of these 3 similarsized coccidial species are often grouped together and termed C. ohioensis-like oocysts because detailed structural examinations and life-cycle studies are needed before a definitive diagnosis can be made. The life cycle and transmission of C. canis has been examined by several groups of researchers (Nemeséri, 1960;Lepp andTodd, 1974, 1976;Dubey, 1975bDubey, , 1982Hilali et al, 1979;Becker et al, 1981). The life cycles and transmission of C. ohioensis, C. neorivolta, and C. burrowsi, have also been examined (Dubey, 1975a(Dubey, , 1978a(Dubey, , 1978bDubey and Mahrt, 1978;Dubey and Mehlhorn, 1978;Dubey et al, 1978;Trayser and Todd, 1978;Becker et al, 1981;Rommel and Zielasko, 1981.…”