The Life Cycle of Isospora felis Wenyon, 1923, a Coccidium of the Cat*

Abstract

SYNOPSIS. A pure strain of Isospora felis derived from a single oocyst was used to study the endogenous cycle. One and a half to two‐month‐old laboratory‐reared, coccidia‐free kittens were used thruout the study. The endogenous stages occurred in the epithelial cells of the distal parts of the villi in the ileum and occasionally duodenum and jejunum. All stages lay above the host cell nucleus. There were 3 asexual generations. The 1st generation schizonts were 11–30 by 10–23 μ when mature and contained 16–17 banana‐shaped merozoites 11–15 by 3–5 μ. They became mature in 96 or sometimes in 120 hours. The 1st generation merozoites entered new host cells, rounded up and formed 2nd generation schizonts. These formed within themselves 2–10 or more spindle‐shaped bodies resembling 1st generation merozoites in shape and size. These were 2nd generation merozoites. They were uninucleate 120 hours after inoculation, but by 144 hours they became larger, multinucleate and some lost their elongate shape and became ovoid. They were then 3rd generation schizonts. They were 12–16 by 4–5 μ. Each formed up to 6 or more banana‐shaped merozoites 6–8 by 1–2 μ. The 3rd generation schizonts and merozoites developed within the same host cell and parasitophorous vacuole as the 2nd generation schizonts and merozoites. Mature schizonts containing only 3rd generation merozoites appeared 144 hours after inoculation, were most abundant 168 hours after inoculation, and might be present as late as 216 hours after inoculation. They were 14–36 by 13–22 μ and contained 36 to more than 70 merozoites. The 3rd generation merozoites entered the sexual cycle. The mature microgametocytes were 24–72 by 18–32 μ and contained a central residuum and a large number of microgametes 5–7 by 0.8 μ with 2 posteriorly‐directed flagella. The mature macrogametes were 16–22 by 8–13 μ. Gametogony occurred 144–216 hours after inoculation. The prepatent period was 168–192 hours and the patent period 10–11 days. Peak oocyst production occurred on the 6th day of the patent period.

The coccidian parasites (Protozoa, Apicomplexa) of carnivores

“…16-20 days (Tomimura, 1957); 16 days (Chessum, 1972); 10-11 days with peak oocyst production on day 6 (Shah, 1971). …”

“…felis is 2. Wenyon (1923) (Tomimura, 1957;Chessum, 1972;Dubey, 1976); 7-8 days (Lickfeld, 1959;Shah, 1971 .…”

“…The following description, based primarily on Wenyon (1923) and Shah (1969Shah ( , 1970, is taken from Levine (1973 Shah (1969Shah ( , 1970a Shah (1969Shah ( , 1971 According to Walton (1959), the haploid number of chromosomes in /. felis is 2.…”

Pleomorfismo de oocistos de Cystoisospora felis (Wenyon, 1923) Frenkel, 1977 (Apicomplexa: Cystoisosporinae) induzido por differentes fontes de infecção

“…Para análise e caracterização dos oocistos (Figura 1) são necessários conhecer os aspectos taxionômicos que, nesses protozoários, se apoiado nas características morfológicas dos oocistos (Tenter et al, 2002) e biológicas, algumas vezes estas podem ser utilizadas como meio de diagnóstico de rotina na identificação da espécie estudada.…”

Efficacy of Emodepside/Toltrazuril Suspension (Procox® Oral Suspension for Dogs) against Mixed Experimental Isospora felis/Isospora rivolta Infection in Cats

“…Cats developed immunity to infection, but it was not complete as some oocysts were shed after challenge (Dubey 1979). Isospora felis (I. felis) develops in the enterocytes of the small intestine and occasionally in the caecum (Shah 1971). Experimental studies indicate that I. felis is non-pathogenic for cats over 1 month of age (Shah 1971).…”