V. Zaman, J. Howe, M. Ng, T.K. GohUltrastructure of the Endolimax nana cyst. Parasitol Res, 86 .. Tratamiento de las enfermedades causadas por parásitos. Although much literature cites this parasite as a non-pathogen, there is much reason to believe that in some cases these “non-pathogenic” agents actually cause. It has been established that the invasive and noninvasive forms represent two separate species, respectively E. histolytica and E. dispar.

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Of the so-called nonpathogenic intestinal protozoa, Endolimax nana belongs to the ones least well described.

Most data on E. Hence, the genus of Endolimax remains largely unexplored in terms of morphology, taxonomy, genetic diversity, host specificity, and epidemiology. In this review, we seek to provide an overview of the work that has been performed on the parasite since the genus Endolimax was described by Kuenen and Swellengrebel in and suggest activities that may pave the way for a better understanding of E.

The genus Endolimax appears to consist of a large number of species based on its reported occurrence in a vast range of mammals, and it has moreover been described in birds, reptiles, and amphibians. Descriptions have been based on morphology and sometimes limited to identification of a cyst stage. Analyzed specimens have been recovered from stool samples or directly from the intestinal lumen if the animal was necropsied.

Recently, an ameba closely related to Endolimax was also recovered from various tissues of a fish Solea senegalensis. An overview of fundamental information such as host specificity, pathogenicity, and epidemiology is unavailable at present. In reality, much more work than this has been carried out on Endolimaxbut most of the literature is relatively old and might not be indexed in the aforementioned search engines; this could also be the reason why such articles are not cited in the more recent literature.

In this study, older articles were identified mainly by backtracking using already available articles, and it turned out that Endolimax research has been carried out by many groups that have been debating issues that can be resolved with modern day technologies. The goal of this review is therefore to provide an overview of some of the work that has been performed on Endolimax nana since the genus Endolimax was described by Kuenen and Swellengrebel[ 2 ] in and the species E.

Central topics such as morphology, taxonomy, host specificity, epidemiology, pathogenicity, diagnosis, and treatment are reviewed and discussed.

Where applicable, emphasis is given on how previous discussions in the scientific community might be elucidated and resolved using state-of-the-art technology. They feed exclusively on bacteria and divide by binary fission.

The nucleus is vesicular and spherical, measuring 2. At first, the cyst contains one nucleus that divides twice by mitotic division. The cyst wall appears thin 80 nmcolorless, and smooth on the outside. In the cytoplasm, no mitochondria, Golgi apparatus, rough endoplasmic reticulum, centrioles, or microtubules are present.

Uniquely among intestinal amebae, E. The nucleus has a thin nuclear membrane with chromatin deposits and no pores. Infection may last for many years exemplified by the experimental infection that Dobell performed on himself, which had been lasting for 17 years at the time of his last publication on Endolimax. It is noteworthy that this sequence is still the only available sequence of E.

Compared with other amoebozoa, the SSU rRNA gene of Endolimax is relatively long more than baseswhich is in part due to AT-rich expansion regions, with no evidence of introns. To clarify the phylogenetic position of Endolimaxthere was a clear need for further studies on intrageneric diversity. SSU rRNA gene sequences were recently obtained from a new species identified in a sole that was named Endolimax piscium ;[ 1 ] while these sequences did cluster specifically with E.

This is mostly due to the fact that general eukaryotic primers are prone to amplifying ribosomal genes that comprise fewer bases than that of Endolimax ; for instance, Blastocystis has a SSU rRNA ribosomal gene of about bp, and since Blastocystis is very often present in stool samples positive for Endolimaxgeneral primers tend to amplify Blastocystis preferentially over Endolimax when applied to genomic DNA extracted from stool. Moreover, sequences derived from Endolimax -positive polymerase chain reaction products often turn out to be more or less unreadable, probably for the same reasons as for Iodamoeba.


The host specificity of Endolimax has been debated in the older literature. Among such studies, Dobell[ 6 ] is the only person to date to have performed experimental infections on humans, namely on himself.

He had examined his own feces for many years and found it to be negative for Endolimax before experimentally infecting himself with Endolimax from what was called a Macacus sinicus.

The infection established, he was later able to infect a so-called M. Some believed in a limited host range and proposed new species names for the isolates of different animals [ Table 1 ], whereas others[ 18 ] believed that E. Dobell[ 6 ] was more cautious in drawing conclusions before having more evidence. This confusion is also evident from the great number of Endolimax species described. Arguments have been made against some of these species names, including the possibility that some were in fact Iodamoeba as in the case of E.

Species of Endolimax reported to date modified from Constenla et al. There might be a need to revise the taxonomy of Endolimax. Yarinsky and Burrows[ 34 ] observed general differences in the size of trophozoites between infected individuals suggesting the existence of at least two lineages of Endolimax based on this morphological characteristic.

To investigate the host specificity and classification of Endolimax spp. Endolimax is transmitted through fecal-oral contamination of food or water.

The scientific literature abounds with studies that have surveyed the prevalence of Endolimax in human stools samples. This can be explained by its inclusion in studies that investigate the prevalence of intestinal parasites in general, based on for instance microscopy of fecal concentrates.

Due to the overwhelming number of studies, an overview of the prevalence, study groups, and methods have been included in Supplementary Table 1. We tried to estimate the global prevalence based on data from healthy individuals and including articles that were only 20 years old or less. These studies were mainly performed on schoolchildren, minority groups, or controls. By calculating weighted averages, we estimated the global prevalence in healthy individuals to be Based on patient samples or reports in articles older than 20 years, the global prevalence is estimated to about 3.

In general, apparently most carriers of E. A relatively low prevalence is generally observed in studies from Asia, but the very low prevalence estimate in symptomatic patients compared with controls is mainly due to the inclusion of a large study carried out in Israel. It is expected that the prevalence be overestimated from articles available due to publication bias, since it is unlikely that E. On the other, it is expected that some studies have not included findings of Endolimax because it was considered unimportant in relation to the study aim.

Endolimax is considered a nonpathogenic commensal protozoon parasitizing the human colon;[ 69 ] this or a similar description is given in most textbooks.

CDC – DPDx – Amebiasis

Dobell[ 6 ] performed postmortem rndolimax of infected monkeys and endllimax to discover any amebic lesions of the intestine. Some authors have argued that Endolimax can cause irritation of the crypts of the intestinal mucosa, referring to observations by Swerdlow and Burrows;[ 48 ] the empirical data to support such a statement are endoliimax, however, since this report is on Dientamoeba fragilis and only one case was co-infected with Endolimax.

It is common to find reports on associations between diarrhea and Endolimax infections. In a couple of case studies, Endolimax was associated with chronic diarrhea;[ 525354 ] all cases responded well to treatment, and it was not possible to detect other infections except in the study by Shah et al.

Twelve cases were described in the study by Sanchez[ 55 ] who concluded that E. There are also case studies that associate E.

Intestinal Amebae

The objections included that no trahamiento of reactive arthritis were performed, that Endolimax is presumably noninvasive, and that the treatment with metronidazole could eradicate other disease-causing organisms; in addition, no efforts were made to investigate whether any such organisms were present.


The reply stated that testing did not reveal any other pathogenic organisms, but that such organisms could possibly be present. There is some evidence that Endolimax may give rise to an immunological response, including eosinophilia.

The authors of this review are of the opinion that the sporadic articles on E. The clinical picture may be subtle, however, and it has been suggested that ttatamiento may develop if a heavy infection is present[ 54 ] or that the pathogenicity might be limited to particularly virulent strains.

The diagnosis of Endolimax traditionally relies on microscopy of cysts, which can be direct or coupled with a concentration procedure and different stains prior to analysis.

Concentration can be formalin-based [ Figure 1a ], and when the fecal concentrate is stained with iodine, cysts of E. This gibbous appearance is however not always present and almost absent when cysts are concentrated using a sucrose gradient and stained with iodine [ Figure 1c ]. The cysts of Endolimax and E. A large number of cysts may be excreted compared with other amebae Entamoeba coliE.

Cysts of Endolimax nana in direct smear aconcentrated with formalin and ethyl acetate and stained with iodine showing the characteristic gibbous appearance band isolated on a sucrose gradient and stained with iodine, respectively c. Image d shows a Endolimax nana trophozoite. It was from sequences generated using these primers that the high variation in the SSU rRNA genes mentioned previously was observed.

Meanwhile, DNA from microscopy-positive samples have sometimes failed to show amplification with these primers. Due to the high variation in Ehdolimax rDNA unpublished observationsdesigning genus-specific primers based on a single sequence or only a few sequences is problematic. There is a need for more reference sequences to develop better diagnostic primers that also eliminates selection for specific Endolimax strains.

It is currently unknown whether the primers included in Table 3 will also amplify Endolimax from hosts other than humans. Endolimax appears to respond well to both metronidazole and diphetarsone treatment.

Stauffer and Levine[ 54 ] were able to treat two cases with metronidazole, although it appears that two courses of treatment were necessary in one of the cases.

The same treatment with metronidazole was successful in a single case in the study by Burnstein and Liakos. In a study by Keystone et al. endollimax

In vitro studies have revealed little effect of streptomycin[ 64 ] and emetine[ 6 ] on Endolimax. Treatment of concurrent pathogenic parasites revealed little effect on Endolimax using emetine[ 6 ] or mebendazole.

Based on available data, the global prevalence of E. Very little research has been performed on Endolimax since the s, 30s, and enodlimax.

With the availability of DNA-based detection methods, resolving major issues such as host specificity, diversity, and which Endolimax species that can infect humans should be straightforward.

Infección por blastocystis hominis – Síntomas y causas – Mayo Clinic

In addition, the development of diagnostic primers will allow Endolimax to be detected with high sensitivity using fecal DNAs and distinguished easily from other amebae. The clinical significance of Endolimax is still an unresolved issue.

Prior exposure immunityparasite load, and genetic variability might influence clinical presentation. Little evidence points toward Endolimax being pathogenic, but a few articles provide data on Endolimax -based stimulation of the immune system; whether this is a harmful or beneficial modulatory effect remains unknown. Hopefully, the present review will stimulate interest in Endolimax research, which may eventually render Endolimax a not so inconspicuous companion. National Center for Biotechnology InformationU.

Tratamientp List Trop Parasitol v. Author information Article notes Copyright and License information Disclaimer. Address for correspondence Dr. Received Nov 4; Accepted Jan This article has been cited by other articles in PMC. Summary of prevalence articles used to estimate the global prevalence. Abstract Of the so-called nonpathogenic intestinal protozoa, Endolimax nana belongs to the ones least well described.

Diagnosis, epidemiology, infectious diseases, protozoon, public health.