Stool analysis for protozoa

Detection and differentiation of protozoa in the analysis of stool (the difference of pathogenic forms from nonpathogenic ones) is a rather difficult task. Most unicellular organisms in feces are found in two forms: vegetative (the trophozoite stage) - active, mobile, vital, easily susceptible to harmful effects (in particular, cooling) and therefore rapidly dying after isolation from the intestine, and in the form of cysts resistant to external influences oocyst). In the decorated feces the protozoa are usually found only in the incised state; for detection of vegetative forms it is necessary to investigate feces still in a warm state. This is due to the fact that in the cooled feces the vegetative forms of the protozoa quickly die and the dead quickly succumb to the action of proteolytic enzymes, as a result of which they lose their characteristic features of their structure. In addition, during cooling, the mobility of protozoa decreases, and then disappears - an important auxiliary factor in their differentiation.

[1], [2], [3], [4], [5]

Types of parasites in feces

Basic types of parasites and optimal methods for their detection

Type of parasite	Often affected organs	Diagnostic method
Leishmania donovani	Spleen, liver, lymph nodes	Detection of parasites in punctata of spleen, liver, bone marrow, affected skin, detection of specific ATs in the blood
Trypanosoma rhodesiense and T. Gambiense	Lymph nodes and brain	Detection of parasites in the affected skin, lymph nodes, liquor
Echinococcus granulosus or Echinococcus multilocularis	Liver, lungs, brain	Detection of specific AT in the blood
Schistosoma haematobium, S. Mansoni, S. Japonicum and others.	Urinary tract, liver, portal vein	Detection of eggs of parasites in urine, feces, a biopsy of the rectum, liver tissue or specific AT in the blood
Fasciola hepatica	Liver	Detection of eggs of parasites in feces or specific ATs in the blood
Clonorchis sinensis, Opisthorchis felineus, Opisthorchis viverrini	The biliary system	Detection of eggs of parasites in feces or bile
Trichostrongylus capricola, T. Vitrinus	Small intestine	Detection of parasite eggs in feces
Echinostoma ilocanum	Small intestine	Detection of parasite eggs in feces
Angiostrongylus costaricensis	Thin and large intestine	Detection of eggs In the intestinal biopsy
Dipylidum caninum	Thin and large intestine	Detection of eggs or parasite swallowing in feces

In feces it is possible to identify 20 species of protozoa (8 pathogenic and conditionally pathogenic and 12 commensals). The simplest intestines live in the small or large intestine in the stage of trophozoite and / or cyst. They belong to one of 4 groups: amoebas, flagella, ciliated and coccidia.

Dysenteric amoeba in feces

Entamoeba histolytica (dysentery amoeba) causes amoebiasis in a person. It is localized in the large intestine, it is released in the form of trophozoite (with liquid feces) and / or cysts (in a decorated stool). Due to the fact that most species of amoebas (intestinal, Hartmann, Buçli) are not pathogenic for humans, caution should be exercised when assessing the results of a study of faeces. Only detection of trophozoites-hematophagous (fabric form E. Histolytica forma magna ) may serve as a reliable indication of the presence in a patient amoebic dysentery and / or amoebic ulcerative colitis. The presence of erythrocytes in the protoplasm is a very important diagnostic feature, since the non-pathogenic forms of amoebas never contain them. Detection in all other cases E. histolytica-like forms of trophozoites that do not contain red blood cells, is not a basis for the diagnosis of amoebiasis as a disease. Similarly, the results of detection of only cysts E are evaluated . histolytica (luminal form), which can be found in people recovering from acute amebiasis, in patients with chronic amoebiasis and in carriers.

[6], [7], [8], [9]

Giardia in feces

Lamblia intestinalis (lamblia) belongs to the class of flagella. Lamblias are parasitic in the small intestine, mainly in the duodenum, as well as in the gallbladder. The existence of trophozoites (vegetative form of lamblia) requires a liquid medium, therefore, when entering the large intestine, the lamblia are encysted, and only the cysts are found in the stool. Only with profuse diarrhea or after the action of laxatives in feces can you find vegetative forms.

Balantidia in feces

Balantidium coli is the only ciliated infusoria that parasitizes the human intestine and causes diseases of varying severity - from mild colitis to severe ulcerative lesions. The causative agent is found in feces in the form of trophozoites or cysts. Perhaps the carriage in healthy people.

[10], [11], [12]

Cryptosporidia in feces

Representatives of the genus Cryptosporidium are now considered to be the most important pathogens of diarrhea. Cryptosporidia (from the Greek "hidden dispute") - obligate parasites that infect the microvilli of the mucous membranes of the gastrointestinal tract and the airways of humans and animals. GI infections caused by cryptosporidia are registered in all countries of the world. Such a wide distribution of cryptosporidiosis is associated with a large number of natural reservoirs of infection, a low infectious dose and high resistance of the pathogen to disinfectants and antiparasitic drugs.

Among the cryptosporidia, Cryptosporidium parvum and Cryptosporidium felis are potentially pathogenic for humans (identified in HIV-infected individuals). The most typical localization of infection in humans is the distal parts of the small intestine. In patients with severe immunodeficiency, the entire gastrointestinal tract can be infected - from the oropharynx to the rectal mucosa.

Diagnosis of cryptosporidiosis in most cases is based on the detection of cryptosporidia oocysts in feces and / or (significantly less often) in the biopsy specimen of the small intestine mucosa in the syndrome of watery diarrhea. Use microscopy of prepared preparations stained by Gram. In most cases, this method of coloring does not allow the identification of oocysts, due to their weak ability to retain the dye and the inability to distinguish them from yeast-like fungi. Therefore, apply the coloration to acid resistance. With this method of coloring, the cryptosporidia oocysts are painted red or pink and are clearly visible on a blue-violet background in which other microorganisms and intestinal contents are stained.

In acute cryptosporidiosis, the number of oocysts in the feces is large, which makes it easy to detect them with microscopy of stained preparations. However, in chronic cryptosporidiosis with a light course, when the amount of oocysts in the feces is small, in order to increase the probability of their detection it is necessary to use enrichment techniques. In recent years, serological methods have often been used to diagnose cryptosporidiosis.

Cryptosporidiosis of the biliary tract can be manifested by cholecystitis, much less often with hepatitis (with an increase in bilirubin concentration, ACT activity, ALT, alkaline phosphatase in the blood) and sclerosing cholangitis. For the diagnosis of biliary cryptosporidiosis, liver and bile biopsy specimens are examined, where cryptosporidia can be detected at various stages of development.

To control the effectiveness of treatment of protozoal intestinal lesions, the feces are examined depending on the detected disease: in amebiasis, balantidiasis - immediately after treatment, with giardiasis - after 1 week. After treatment of invasions of biliary tract, control of efficacy can be carried out both in the study of stool and bile.

[13], [14]

Scraping from perianal folds to enterobiasis

Scraping from perianal folds to enterobiosis is a purposeful study for the detection of pinworm eggs ( Enterobius vermicularis ). Due to the fact that mature female pinworms crawl to lay eggs in the folds around the anus, eggs of pinworms in feces are rarely found, they are easier to detect in scrapings from folds around the anus or in rectal mucus.