Here is a compilation of term papers on ‘Entamoeba Histolytica’. Find paragraphs, long and short term papers on ‘Entamoeba Histolytica’ especially written for college and medical students.
Term Paper on Entamoeba Histolytica
Term Paper Contents:
- Term Paper on the Historical Background of Entamoeba
- Term Paper on the Distribution of Entamoeba
- Term Paper on the Habits and Habitat of Entamoeba
- Term Paper on the Physiology of Entamoeba
- Term Paper on the Reproduction in Entamoeba
- Term Paper on the Pathogenicity of Entamoeba
- Term Paper on the Diagnosis and Treatment of Entamoeba
- Term Paper on the Prevention (Prophylaxis) of Entamoeba
- Term Paper on the Life Cycle of Entamoeba
- Term Paper on the Other Species of Entamoeba
Term Paper # 1. Historical Background of Entamoeba:
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Entamoeba Histolytica is an amoeba-like microscopic disease-producing (pathogenic) endoparasite of human beings. It habits colon of man and produces the disease called amoebiasis or amoebic dysentery.
Entamoeba Histolytica was first of all reported by a Russian Zoologist, Losch (1875), as Amoeba coli from the faeces of a patient suffering from dysentery. The genus Entamoeba was established by Cosagrandi and Barbagallo (1895); it should not be confused with the genus Endamoeba which was established by Leidy (1879).
Concilman and Loffteur (1901) worked out the pathogenicity of amoebiasis and amoebic ulcers. The species Entamoeba histolytica was established by Schaudinn (1903) and he differentiated the pathogenic and nonpathogenic types. But, Walker and Sellards (1930) are credited for attributing pathogenic effects of this parasite. Craig (1962) has estimated that more than 10 per cent of world population is suffering from the infection of this parasite.
Term Paper # 2. Distribution of Entamoeba:
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Entamoeba histolytica has a world-wide distribution. It is especially prevalent in the tropical and subtropical countries, where sanitary conditions are poor. It occurs, on an average, in 5-10% population of civilized countries and 50-60% population of backward countries.
The incidence is high in Mexico, China, India and parts of South America. Infections are higher in populations with shabby standards of living and under unhygienic conditions Infants below the age of one year are rarely infected, while children and young adults are very susceptible to the parasite.
Term Paper # 3. Habits and Habitat of Entamoeba:
Entameoba histolytica lives in the lumen of the lower portion of small intestine and the entire large intestine (colon) of humans. It may invade the lining (i.e., mucosa and sub-mucosa) of the host’s large intestine.
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There it feeds on tissues and red blood corpuscles of intestinal wall and produces ulcers and dysentery which involve inflammation of intestine, loose stools or diarrhoea and 6 to 10 blood-stained painful mucus motions per day. In chronic cases, it may enter the blood circulation and may infect liver, lungs, kidneys, testes and even the brain. It proves fatal when it produces large abscesses in liver or perforates the intestinal wall of the host.
Term Paper # 4. Physiology of Entamoeba:
(i) Locomotion:
Entamoeba hystolytica performs locomotion by the help of a single, large, thick and blunt pseudopodium called lobopodium. It is called monopodial locomotion. Lobopodium is formed largely of ectoplasm and protrudes at the advancing end of body.
(ii) Nutrition:
Trophozoite has holozoic nutrition. It dissolves the intestinal mucous membrane of the host and phagocytosis the debris, i.e., blood and epithelial cells, at the level of its plasma membrane. Food is digested intracellularly inside the food vacuoles by the help of lysosomal enzymes.
(iii) Respiration:
Trophozoite is a facultative anaerobe, i.e., it requires very little oxygen for the breathing and can survive without oxygen. It is an adaptation for its endoparasite mode of existence inside the colon.
(iv) Excretion:
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Trophozoite excretes its nitrogenous metabolic wastes in the form of ammonia. The ammonia is got rid of by diffusion through general body surface into the surrounding medium.
Term Paper # 5. Reproduction in Entamoeba:
The trophozoite of Entamoeba histolytica reproduces normally by a process of simple binary fission in the intestinal wall and by a modified form of mitosis. The exact nature of the division of the nucleus is controversial but it is believed by many authors that it is probably a modified type of mitosis.
Kofoid and Swezy observed six chromosomes in it. Entamoeba histolytica also, has the capacity to encyst. In fact, the nucleus divides by mitosis but without the disappearance of the nuclear membrane.
It is, then, followed by the division of the cytoplasm (cytokinesis) resulting into two daughter entamoebae. These start feeding upon bacteria and host tissues, grow in size and again multiply by binary fission. Some of these forms may invade fresh intestinal tissues, while some of them become pre-cystic or minuta form.
Term Paper # 6. Pathogenicity of Entamoeba:
Every harmful parasite causes some disease to its host and also brings some destruction and injury to its tissues. These effects or symptoms are called the pathological effects, such a parasite is known as pathogenic, the phenomenon is known as pathogenicity or pathogenesis, and their study is known as pathology.
Entamoeba histolytica causes amoebic dysentery, abscesses in liver, lungs and brain and non-dysenteric infections.
i. Amoebic Dysentery:
Entamoeba histolytica secretes a tissue dissolving enzyme (probably of histolysis nature) that destroys the epithelial lining of the colon and causes its necrosis and forms the abscesses (small wounds) which later become flask-shaped bleeding ulcers.
The cavity of these ulcers is generally filled with mucus, bacteria, amoeba and cell debris. The abscesses pour their contents into the lumen of the intestine. The ulcers vary greatly in number and size; in severe cases almost the entire colon in undermined.
The ulceration of colon may produce severe dysentery. In amoebic dysentery the stools are acidic and contain pure blood and mucus, in which swarms of amoeba and blood corpuscles, are usually present.
ii. Abscesses in Liver, Lungs and Brain:
Sometimes Entamoeba histolytica may be drawn into the portal circulation carried to the liver. In liver the parasites settle, attack the liver tissue and form abscesses. The patient has pain in liver region, fever and high leucocyte number, a condition referred to as amoebic hepatitis.
Lung abscesses are fairly frequent; these are usually caused by direct extension from a liver abscess through the diaphragm. The lung abscesses usually rupture into a bronchial tube and discharge a brown mucoid material which is coughed out with the sputum. Sometimes the parasite also forms abscesses in the brain.
Term Paper # 7. Diagnosis and Treatment of Entamoeba:
Diagnosis:
Presence of ‘Charcot-Leyden Crystals,’ in stool suggests infection by E. histolytica. These are diamond or white-stone-shaped crystals varying in size from 5 to 50 microns. Microscopical examination of fresh stoll shows presence of motile trophozoites and cysts. The trophozoites are easily recognized by their characteristic movement and presence of ingested red blood corpuscles.
Treatment:
Metronidazole, Emetin, iodine compounds (Yatren, Diodoquin) and arsenic compounds (Carbarsone, Thiocarbarsone) are used in amoebic dysentery. Bismuth substrate is found beneficial in controlling amoebic dysentery. Certain antibiotics, such as, Fumagillin, Erythromycin, Terramycin and Auromycin have proved to be more effective in case of severe infection. In case of secondary infection, i.e., infection of liver, lungs, etc., Chloroquine is given.
Term Paper # 8. Prevention (Prophylaxis) of Entamoeba:
Following measures may be applied for the prevention of the disease:
(i) Sanitary disposal of faecal matter.
(ii) Perfect sanitation and protection of water and vegetables from pollution.
(iii) Washing of hands with antiseptic soap and water before touching the food.
(iv) Cleanliness in preparing the food.
(v) Protection of foods and drinks from houseflies, cockroaches, etc.
(vi) Raw and improperly washed and cooked vegetables should be avoided.
Term Paper # 9. Life Cycle of Entamoeba:
E. histolytica is a monogenetic parasite, i.e., its life cycle involves only one host, the host being the man.
Its life cycle includes the following steps:
(i) Encystment:
Some of the precystic minuta forms exist in intestinal lumen and undergo encystment or encystation. However, before the encystment, they become round, eliminate food vacuoles and accumulate considerable amount of reserve food materials in the form of glycogen granules and chromatoids.
Soon each parasite secretes a thin, rounded, resistant, colourless and transparent cyst wall around it. The cysts of Entamoeba histolytica have average size of 12mm (or 12 microns). Each cyst has a clear cytoplasm and single nucleus and is called mononucleate cyst. Ultimately, the nucleus of the cyst divides twice so that each cyst becomes tetranucleate or quadranucleate. At this stage the cysts are infective to new hosts.
(ii) Infection of New Hosts (Transmission):
The nature quadrinucleate cysts are the most resistant and infective forms of the parasite. They are unable to develop in the host in which they are produced. This necessitates their transference to fresh susceptible hosts.
Infection of fresh human hosts occurs by taking food, vegetables or drinking water contaminated with faecal matter containing mature quadrinucleate cysts. The untreated human faeces in open grounds, or crop and vegetable fields, are a common source of infection. Unhygienic food-handlers, flies, cockroaches, birds, etc. carry viable cysts on their body or in their intestine and convey the infection to unprotected food stuffs.
(iii) Excystment:
The excystment of cysts and metacystic development have been observed and studied specially by Dobell (1924) and Cleveland and Sanders (1930) in cultures. According to Dobell, in the process of excystation a single tetranucleate amoeba (metacystic form) emerges from a cyst through a minute pore in the cyst wall.
The tetranucleate metacystic form produces a new generation of trophozoites by a diverse series of nuclear and cytoplasmic divisions which result in the production of eight uninucleate amoebulae. These are called metacystic trophozoites. They feed on the contents of the intestine and grow in size to form the trophozites of the next generation. The trophozoites stay in the lumen of the intestine for a particular period when they may attack the wall of the intestine and start the life cycle again.
Term Paper # 10. Other Species of Entamoeba:
i. Entamoeba Gingivalis:
Entamoeba gingivalis is a nonpathogenic human parasite. It was first parasite amoebae reported from man and was discovered by Gross in 1849.
E. gingivalis is commonly known as mouth amoeba. It lives in the cavities of teeth, in the tarter and plaque deposited around the base of teeth. It may also live in the abscesses of gums and pus-pockets of tonsils.
The sub-spherical trophozoite of E. gingivalis measures 12 to 20 mm in diameter. It bears 2 or 3 small and blunt (i.e., broad and rounded) pseudopodia, called lobopodia. The cytoplasm is divisible into a clear homogeneous peripheral ectoplasm and central, granular, highly vacuolated endoplasm. Endoplasm contains a vesicular nucleus with central endosome and several food vacuoles.
Trophozoites have pseudopodial locomotion. It feeds mainly on bacteria present in the cellular debris around the roots of teeth and also on white blood cells (WBC) by phagocytosis.
Trophozoite reproduces only by asexual means, i.e., by binary fission. It does not form cysts and is transmitted from mouth to mouth of persons either by contact during kissing or while eating or drinking by same utensils.
E. gingivalis is found in about 70 per cent of human population. Its occurrence is more common in mouth of persons suffering from pyorrhea. It was believed in the past that pyorrhoea was caused by E. gingivalis. However, it is now certain that pyorrhoea is caused by infection of bacteria. E. gingivalis is known to aggravate pyorrhoea disease by destroying the gum tissues.
ii. Entamoeba Coli:
Entamoeba coli are the commonest species of Entamoeba found in the colon and has been stated to occur probably in 50% of human population. This amoeba lives in the lumen of the colon and does not enter the tissues of the wall. It is a harmless species (non-pathogenic) feeding on bacteria, particles of undigested food and other debris but never on blood cells or other lining tissues of the host, therefore, considered as endocommensal.
The trophozoite measures 15 to 40 microns (average individuals 20 to 35 microns) in diameter. The cytoplasm is not well differentiated into ecto-and endoplasm. The endoplasm is granular and contains bacteria, faecal debris of various sizes in food vacuoles. Nucleus is 5 to 8 microns in diameter containing a comparatively larger nucleolus which is not placed in the centre.
The cyst is spherical or often ovoid, highly refractile; 10 to 30 microns in diameter. Immature cyst contains 1, 2 or 4 nuclei, one or more large glycogen bodies and small number of filamentous chromatoid bodies with sharply pointed ends. Mature cyst contains 8 nuclei and a few or not chromatoid bodies. Nothing is known about its life cycle in lumen intestine. According to Hegner, the cysts hatch as entire 8-nucleated amoeba.
iii. Entamoeba Hartmanni:
This species closely resembles the minute form of E. histolytica. It also inhabits the colon, invades the intestinal tissues and causes amoebic dysentery; but is less harmful that E. histolytica. The trophozoites measure 9 to 14µ in diameter and the mature cysts are less than 10µ in diameter. The nucleus is more compact.