The Life Cycle of Isospora felis in the Kitten

Abstract

This life-cycle is presented by means of photomicrographs and drawings of the morphological stages in their relative locations in the tissues. Kittens (average age 43 days) were infected with 100,000 sporulated oocysts and sacrificed at daily intervals from 2 to 8 days. Tissues, for microscopic examination, were removed at definite locations from the small intestine, cecum and large intestine. This life-history consisted of 2 asexual cycles and 1 sexual. The 1st asexual phase, described for the 1st time, existed from the 2d to the 4th days, while the 2d asexual phase lasted during the 5th and 6th days, and the sexual cycle remained the 7th and 8th days. Since oocysts were passed on the 7th and 8th days, this presented a prepatent period different from that previously thought to exist. All parasitic stages of L felis found were intracellular. Most of the sexual and asexual stages were found in the small intestine, but a few sexual stages were found in the cecum. A few asexual forms were present in the cecum and, for the 1st time, noted in the large intestine. The majority of the mature 2d generation schizonts contained 12, 14, or 16 merozoites. No pathological conditions or symptoms attributed to this infection were recognized.