Studies on Dientamoeba fragilis (Protozoa). I. Observations with Special Reference to Nuclear Structure

Description of Dientamoeba fragilis Cyst and Precystic Forms from Human Samples

“…Cyst forms of D. fragilis were also described from Argentina in 1928 (23). Another study conducted in 1936 on the morphological observations of the parasite from 70 infected patients reported the absence of cysts (21). While no true cyst forms were described in this study, the author did describe what he thought was a precystic or pseudocyst stage of Dientamoeba.…”

“…Putative precystic or pseudocyst forms (as per the studies by Wenrich [21], Kofoid [20], and Kudo [22]) were found in a total of 163 of the 500 slides, giving a prevalence of 32.6% per patient sample.…”

“…Special care was taken to identify forms bearing a strong resemblance (or considered identical) to the cysts described by Munasinghe et al (11). Care was also taken to make note of forms bearing a morphology between that of D. fragilis trophozoites and cysts as these were likely to represent the precystic or pseudocyst forms previously described (and illustrated) by pioneering investigators (20)(21)(22). At the same time in the United States, a total of 47 Wheatley's trichrome permanently stained smears positive for D. fragilis trophozoites were reexamined for forms consistent with the prior description of the cyst stage (11).…”

Dientamoeba fragilis, One of the Neglected Intestinal Protozoa

“…Precysts have recently been described by Stark et al (10); however, previous publications have described these stages in the past (2,11,12). These stages range from 3.5 to 5 m in diameter, have one or two nuclei, and contain finely granular and uniform cytoplasm (12).…”

“…While D. fragilis was first thought to be an ameba, after many years of study using light microscopy, the organism was placed into a new family with Histomonas in 1953, the Dientamoebidae (4,12,17). With the introduction of electron microscopy studies, confirmation was obtained that D. fragilis was closely related to flagellates (18).…”