Introduction:
In 1917, the genus Endolimax was described by Kuenen and Swellengrebel. The genus Endolimax appears to consist of various species, and its occurrence has been reported in a variety of mammals. The global prevalence of Endolimax nana is estimated to be 13.9 percent on average in healthy individuals. It has also been found in birds, reptiles, and amphibians. Endolimax has been described based on its morphology, and sometimes identification is limited to a cyst stage. The samples for analysis have been obtained from stool or from the intestinal lumen directly if the animal was necropsied.
What Is Endolimax Nana Cyst?
Endolimax nana is an intestinal protozoan that thrives in the colon and has also been reported in the appendix. Dobell demonstrated that this infection might last for many years.
Trophozoites feed primarily on bacteria and it grows through division by binary fission. They are eight to ten micrometers in size and move with the help of pseudopodia, and may reach a size of up to 30 micrometers during movement. The nucleus of Endolimax nana is vesicular and spherical and measures around two micrometers with a polymorphic karyosome. The trophozoite divides before excystation (emerging from a cyst) and leads to the production of stages with smaller nuclei of the same size. Initially, Endolimax nana contains one nucleus that is divided twice through mitotic division. When cysts of Endolimax nana are matured, they are oval and very small in comparison to other intestinal amebae cysts.
Endolimax nana shows elongated tubular structures made up of ribosome-like particles, a unique feature among intestinal amebae. The cyst is usually made up of four nuclei. However, it is possible that Endolimax nana might produce super nucleate cysts. These cysts might undergo additional division leading to the production of cysts containing five to eight nuclei.
The ameba undergoes excystation after ingestion by escaping through a pore in the cyst wall. They divide into uninucleate amebae by successive cytoplasmic bipartition, leading to the formation of the trophic stage.
A thin nuclear membrane encompasses the nucleus with chromatin deposits and no pores.
The typical features of the cyst are:
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Thin wall (80 nanometers).
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Colorless.
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Smooth on the outside.
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In the cytoplasm, no mitochondria, rough endoplasmic reticulum, Golgi apparatus, centrioles, or microtubules are present.
These cysts are excreted in feces and might thrive for up to two weeks if they are incubated at room temperature and for up to two months at lower temperatures. Trophozoites can survive in stool for up to one day if the feces is incubated at room temperature.
What Are the Clinical Features of Endolimax Nana Infection?
The Endolimax nana cyst can lead to irritation of the crypts of the intestinal mucosa. In certain cases, it has been associated with diarrhea. This association is explained by Endolimax nana being an indicator of fecal contamination that is related to co-infection by other organisms that can cause diarrhea.
In a number of cases, Endolimax nana was associated with chronic diarrhea, and all cases responded well to the treatment. There are also cases that associate Endolimax nana with urticaria (a rash-causing intense itching) and polyarthritis (pain and inflammation in multiple joints). However, in most cases, Endolimax nana is considered noninvasive, and the treatment with Metronidazole helps to combat or eradicate other disease-causing organisms.
Most of the research shows that there is very less evidence in favor of the assertion that Endolimax should be considered a pathogenic agent that can cause diarrhea or intestinal inflammation. The clinical features are usually subtle. However, it has been suggested that symptoms might be present in case of a heavy infection or that the pathogenicity can be confined to a particularly virulent strain.
There is some data that reveals that Endolimax nana might lead to an immunological response, like eosinophilia. Currently, there are no known cases of Endolimax nana crossing the intestinal barrier in humans.
How Is the Infection Diagnosed?
Endolimax nana is diagnosed based on the microscopy of the cysts, involving concentration procedures (usually formalin-based) and different stains before the analysis is initiated. The cysts of Endolimax nana appear gibbous when the fecal concentrate is stained with iodine. The cysts are not always gibbous in appearance and are almost absent if the cysts are concentrated using a sucrose gradient iodine stain.
Endolimax nana also is stained with the following stains:
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Ziehl–Neelsen.
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Trichrome.
The cysts of Endolimax nana and Entamoeba hartmanni have to be differentiated as they both have four nuclei. Endolimax nana has a larger punctuate karyosome and peripheral chromatin. However, both these features are quite difficult to detect.
Other identifying features include that cysts of Endolimax nana are one of the smallest among the amebas. Therefore, it is recommended to use a microscope with at least 400x magnification to avoid missing these minute details and to differentiate them from E. hartmanni.
With the advancement in DNA-based detection methods, the following issues can be resolved:
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Host specificity.
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Diversity.
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Endolimax species that can infect humans
Further, with the development of diagnostic primers, Endolimax nana can be detected with high sensitivity with the use of fecal DNAs (deoxyribonucleic acid) and can be differentiated easily from other amebae.
How Is the Endolimax Nana Infection Treated?
Endolimax nana is usually treated with
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Metronidazole.
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Diphetarsone.
Based on different studies, Graczyk et al. recommended the following dosage of Metronidazole for Endolimax nana infection treatment:
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250 milligrams thrice daily for ten days.
Further, a study by Keystone et al. recommended the following dosage of Diphetarsone
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500 milligrams thrice daily for ten days.
For the treatment of concurrent pathogenic parasites, little effect was seen on Endolimax nana with the use of Emetine or Mebendazole.
Certain in vitro studies have shown little effect of Emetine and Streptomycin on Endolimax nana.
Conclusion:
The clinical significance of Endolimax nana still remains an unresolved problem. The clinical presentation can be influenced by the parasite load, prior exposure or immunity, and genetic variability. There is very little data available that proves that Endolimax nana is pathogenic. However, few studies provide information on Endolimax nana-based stimulation of the immune system, which may be harmful or beneficial. Hopefully, further research on Endolimax nana will help explore the aspects of the infection that still need to be answered.
