Cysts protozoan

Balantidiasis (balantidiosis, balantidial dysentery), an intestinal disease seen almost worldwide, is caused by the large ciUated protozoan, balantidium coll The organism is usually found in the lumen of the large intestine of humans and animals. Cysts formed in the lumen of the colon or in freshly evacuated feces of humans or domesticated and wild animals, can colonize the colon and terminal ileum of new hosts by the latter s ingestion of contaminated food or water. The hog has been found to be the most heavily parasitized host. Its association with the rat may be a means for maintaining a reservoir infection in the two animals. 

Formed specimens, which are likely to contain protozoan cysts or helminth eggs or larvae, can remain satisfactory for a number of... 

The direct wet mount made from unconcentrated fresh feces is most useful for the detection of the motile trophozoites of intestinal protozoa and the motile larvae of Strongyloides spp. It is also useful for the detection of protozoan cysts and helminth eggs. For fixed feces, the direct wet mount may allow the detection of parasites which do not concentrate well. This method is also useful for the examination of specific portions of feces, such as flecks of blood or mucus. 

Permanent stains of fecal smears are most needed for the detection and identification of protozoan trophozoites, but they are also used for the identification of cysts. Wet mounts of fresh feces, even with stains such as methylene blue, are not as sensitive for trophozoites and therefore do not substitute for permanent stains. It is sometimes difficult to identify cysts which are detected in wet mounts thus, for each specimen, regardless of consistency, it may be worthwhile to fix a portion in PVA fixative or to prepare two fecal films fixed in Schaudinn fixative so that permanent stains can be performed if needed. Permanent stains also provide a permanent record and are easily referred to consultants if there are questions on identification. 

The protozoan Entamoeba histolytica causes amebiasis, an infection that is endemic in parts of the United States. The parasite can be present in the host as either an encysted or a trophozoite form. Initial ingestion of the cyst may result either in no symptoms or in severe amebic dysentery characterized by the frequent passage of bloodstained stools. The latter symptom occurs after invasion of the intestinal mucosa by the actively motile and phagocytic trophozoite form of the protozoan. 

Balantidium coli is the largest of the protozoans that infect humans. The trophozoite form is covered with cilia, which impart mobility. Infection is acquired through the ingestion of cyst-contaminated soil, food, or water. The trophozoite causes superficial necrosis or deep ulceration in the mucosa and submucosa of the large intestine. Otherwise healthy persons commonly exhibit nausea, vomiting, abdominal pain, and diarrhea, whereas debilitated or nutritionally stressed patients may develop severe dysentery. 

Fig. 2. Postembedding technique. Section through part of a tissue cyst of the protozoan parasite Toxoplasma gondii immunostained with a rat monoclonal antibody (CC2) which recognizes a molecule located in the cyst wall (CW) and in dense granules within the parasite (for details, see ref. 2). N, nucleus PG, polysaccharide granules. Three-step protocol rat monoclonal followed by rabbit antirat Ig and visualized with goat antirabbit Ig conjugated to 10-nm gold. Bar is 0.5 pm.

IMPORTANCE TO INTESTINAL PARASITES Bile is of particular importance to intestinal parasites, for in many cases it is involved in the trigger mechanisms concerned in the hatching of helminth eggs, excystation of protozoan cysts, evagination of cestode scoleces and excystment of trematode metacercaria. In relation to cestodes, its role in... 

Micro-, ultra-, and nano-filtration can separate smaller particles using media with defined porous sizes (i.e., 10 1—1 pm in microfiltration, 10 2—10 pm in ultrafiltration, and 10 3— 10 2 pm in nanofiltration). Residual colloidal and suspended solids can be removed by microfiltration. Selected salts, most organic compounds, bacteria, protozoan cysts, oocysts and viruses are removed by nanofiltration, so that the treated water will be disinfected. This advanced filtration is used for the treatment of effluents for indirect potable reuse applications such as groundwater injection, water softening, decoloriza-tion, or removal of micropollution. 

Giardia lamblia. Giardia lamblia is a flagellate parasitic protozoan. This parasite is largely confined to the lining of the intestine. It can colonize the lining and feed and grow there. It is shed in feces in the form of cysts. The cyst, however, cannot multiply outside the host. 

Rendtorff, R. C. (1954). The experimental transmission of human intestinal protozoan parasites, II. Giardia lamblia cysts given in capsules. Am. J. Hyg. 59, 209-220. 

Giardiasis results from ingestion of G. lamblia cysts in fecaUy contaminated water or food. The protozoan excysts under the stimulus of low gastric pH to release the trophozoite. Colonization and multiplication of the trophozoite lead to mucosal invasion, localized edema, and flattening of the villi, resulting in malabsorption states in the host. ... 

The asexual developmental cycle of this protozoan occurs within any nucleated cell of warm-blooded animals. This cycle consists of two infective stages tachyzoites, which imdergo fast multiplication in various host cell t)q5es and are t)q5ically present in the acute infection, and bradyzoites, which undergo slow multiplication in latent tissue cysts, have a high affinity for neural and muscular tissues and are located predominantly in the central nervous system, the eye, and skeletal and cardiac muscles. 

Certain treatment processes are less effective in reducing enteric viruses and protozoan cysts than enteric bacteria. Different treatment processes are differently able to remove and to inactivate viruses, bacteria, antinomycetes, algae, protozoa, filamentous fungi and yeasts in drinking water. 

Protozoa may become another problem of water treatment. Usually, removal or inactivation of Entamoeba has been the central problem, but recent investigations also concerns Giardia [43]. Proper coagulation, flocculation, sedimentation, and filtration can remove up to 99% of protozoan cysts slow sand filtration can remove Giardia cysts [16]. Improper operation of treatment facilities can cause outbreaks of water-borne illnesses caused by protozoa [44]. Chlorination and disinfectants such as chloramines and ozone can further reduce levels of protozoa [45-47]. 

In Europe tests with rotifers, cysts from aquatic invertebrates (Calleja et al., 1994), development of onion roots have been tried but none have been accepted (Persoone et al., 1994 Snell and Persoone, 1989 Fresjog, 1985 Gaggi et al. 1995). Jaffe (1995) has proposed a method using the survival of a protozoan. Toxic chemicals kill the protozoa. The test requires a Coulter particle counter to determine the numbers of viable protozoa. 

Giardia lamblia is a flagellated protozoan that has a trophozoite form and a cyst form. The length of the trophozoite form ranges from 9 to 21 pm, the width from 5 to 15 pm and a thickness from 2 to 4 pm. In an unfavorable environment the parasite encysts, and the cysts are characteristically oval or ellipsoid in shape (sUghtly asymmetric) with a length of 8-14 pm and a width of 7-10 um. 

Payment, P. and Franco, E. (1993). Clostridium perfringens and somatic coliphages as indicators of the efficiency of drinking water treatment for viruses and protozoan cysts. Appl. Envir. 

Hijnen WAM, Beerendonk EF, Medema GJ (2006) Inactivation credit of UV radiation for viruses, bacteria and protozoan (oo)cysts in water a review. Water Res 40(1) 3—22 Hildesheim ME, Cantor KP, Lynch CF, Dosemeci M, Lubin J, Alavanja M, Cratm G (1998) Drinking water source and chlorination byproducts 11. Risk of colon and rectal cancers. Epidemiology 9(l) 29-35... 

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