ENTAMOEBA HISTOLYTICA

PARASITOLOGY

1. ENTAMOEBA HISTOLYTICA Man Bahadur Rana,BPH,ACAS,Nepal

2. INTRODUCTION kingdom : Protista sub kingdom: protozoa Phylum: Sarcomastigophora Sub phylum: Sarcodina Class: Lobosea Sub class: Gymnamoebia Order: Amoebida Sub order: Tubulina Genus: Entamoeba Species: histolytica

3. INTRODUCTION - Lambl (1859) first discovered the parasite. - Losch (1875) prove its pathogenic nature. - Schaudinn (1903) differentiated pathogenic and non pathogenic types of amoebae. The amoeba infecting man may be classified according to their pathogenecity and habitat as follows:

4. Contd… A. PATHOGENIC: Intestinal Amoeba : E. histolytica B. Non Pathogenic ( Harmless commensals) 1. Mouth Amoeba : E. gingivalis 2. Intestinal Amoeba : E. coli, E. nana, I. butschlii

5. Geographical Distribution - World wide - More common in tropics and sub tropics than in temprate zone. Habitat: Trophozoites of E. histolytica live in the mucous and submucous layers of the large intestine of man.

6. Histology of large intestine

7. MORPHOLOGY The morphology of E. histolytica shows three different stages. 1. Trophozoite (the growing or feeding stage). 2. Pre- cystic stage. 3. Cystic stage.

8. Contd.. Trophozoite: Shape: not fixed because of constantly changing position. Size: Average being 20-30 um. Cytoplasm: divisible into two portion, - a clear translucent ectoplasm. - a granular endoplasm. - Red blood cells, occasionally leucocytes and tissue debris are found inside the endoplasm .

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10. Contd… Nucleus: shape – spherical size – 4-6um In stained preparation, the nuclear structure shows, i ) karyosome- a small dot like, central in position and surrounded by a clear halo ii) nuclear membrane .iii) the space between the karyosome and the nuclear membrane is traversed by a fine thread of linin network.

11. Pre-cystic stage Size – 10-20um shape – round or slightly ovoid with a blunt pseudopodium projecting from the periphery. Endoplasm is free of red blood cells and other food particles. Nuclear structure is same as that of trophozoite.

12. Cystic stage The cyst varies greatly in size: - the small race being 6to9um. - the large race being 12-15um. During encystment, the parasite becomes rounded and is surrounded by a highly refractile little membrane, called the cyst wall. A mature cyst is a quqdrinucleate spherical body. The cyst begins as a uninucleate body but soon divides by binary fission and develops into binucleate and quadrinucleate bodies.

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14. Contd… - The single nucleus multiplies by two successive divisions into 2 and ultimately to 4 daughter nuclei. During the process of division the nuclei undergo gradual reduction in size becoming 2 um in diameter. - In early stage of development, the cytoplasm of the cyst shows the following.

15. Contd.. i ) chromatoid or chromidial bars: - These do not stain with iodine - seen as refractile oblong bars with normal saline preparation. ii) glycogen vacuole: stains brown with iodine. - As the cyst matures (passing from the uninucleate to the quadrinucleate stage), both the chromatoid bars and glycogen mass gradually disappear .

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18. Reproduction The reproduction occurs in three stages : . Excystation . Encystation . Multiplication Excystation : This is the process of transformation of cyst to trophozoites. During excystation a quadrinucleate cyst give rise to eight amoebulae each one of which is being capable of developing into a trophozoite.

19. Contd… Encystation : This is the process of transformation of trophozoite to cyst and occurs inside the lumen of the intestine of an infected individual. Multiplication : This occurs only in the trophozoite forms of Entamoeba histolytica, growing and multiplication takes place inside the tissue . Reproduction of trophozoites occurs by simple binary fission.

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21. Life Cycle - E. histolytica passes its life cycle in only one host. - The mature quadrinucleate cysts are the infective forms. These infective cyst are passed in the faeces of carriers.

22. Contd… - Man acquires the infection by ingestion of water and food containing these cyst. - When the cyst reaches the caecum or the lower part of the ileum, the excystation occurs (due to lysis of cyst wall by trypsin in the small intestine).

23. Contd… - During this process, each mature cyst liberates a single amoeba with four nuclei, a tetranucleate amoeba which eventually produce eight metacystic trophozoites by the division of nuclei by binary fission. - The metacystic trophozoite ultimately lodge in the submucous tissue of the large intestine, their normal habitat. Here they grow and multiply by binary fission.

24. Contd… - During growth, E. histolytica secretes a proteolytic enzyme which cause destruction and necrosis of tissue leading to flask shaped ulcer. - Sometimes the trophozoite enter into deeper layer and may gain entry into deep layers into the radicals of portal vein to be carried away to liver producing amoebic liver abscess.

25. Contd… - When the effect of the parasite on the host is toned down and there is increase in the tolerance of the host, the lesion start healing . The trophozoites, in the lumen of large intestine occurs encystation. - These quadrinucleate cyst again pass into the faeces and continued their life cycle.

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27. MODE OF TRANSMISSION - Transmission of E. histolytica from man to man is effected through its encysted stage and infection occurs through the ingestion of these cyst. - Faecal contamination of drinking water, vegetables, and food are the primary causes. - Eating of uncooked vegetables and fruits which have been fertilised with infected human faeces has often lead to occurrence of disease.

28. Pathogenicity - Incubation period : 4-5 days. - Clinical features or Symptomatology : The term amoebiasis is used to denote all those condition which are produce in the human host by infection with E. histolytica. - Amoebic dysentry : is a condition in which the infection is confined to the intestinal canal and is characterised by the passage of blood and mucus in the stool.

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35. Contd… Secondary or metastatic lesion: Some individual with intestinal amoebiasis develop hepatic amoebiasis. Amoebic liver abscess is formed. It is the most common form of hepatic amoebiasis and accounts for upto 10% of all intestinal amoebiasis. It may occur in any part of liver but is generally confined to posteriosuperior surface of right lobe of liver.

36. Contd… Clinical features of Amoebic Liver abscess: - Onset is insidious - Pain and tenderness in the right hypochondrium. - Shoulder pain due to the irritation of phrenic nerve - Fever. - Jaundice is an unusual manifestation. - The patient becomes emarciated ( excessively thin)

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39. Contd… Metastatic lesions in other organs: The various extra hepatic amoebiasis include: - Pulmonary Amoebiasis - Cerebral Amoebiasis - Cutaneous Amoebiasis - Splenic Amoebiasis - Vaginal and Penile Amoebiasis.

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42. LABORATORY DIAGNOSIS

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44. Contd… Specimen : The various sample collected for laboratory investigation include stool, swabs, aspirated pus, blood, CSF, biopsied and autopsied material.

45. Contd… 1.Examination of Stool: a) Naked eye or Macroscopic appearance: - An offensive dark brown semi-fluid stool - Acid in reaction - Admixed with blood and mucus.

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47. Contd… b) Microscopical Character:

48. Contd… 2. Examination of Blood : - Shows moderate leucocytosis. 3. Serological Test: - In early cases it is always negative. ELISA, Indirect haemagglutination, Dot ELISA, latex agglutinatio n test are in use.

49. Contd… Extra intestinal amoebiasis: 1. Parasitological: wet (saline and iodine) and permanent preparation of clinical material obtained from lesion. 2. Serological: CFT ( Complement Fixation Test) ELISA, Dot ELISA, IFA test are in use.

50. Contd… 3. Biochemical Test: Liver Function Test shows raised alkaline phosphatase level and SGOT level. 4. Intradermal Skin Test: In an infected individual injection of 0.1ml of an antigen prepared from a culture of E. histolytica produces at the site of injection, an erythema which manifest after 3 hrs (9-10cm) in diameter and disappearing in another 24-48hrs.

51. Contd… 5. Radiological Examination: - USG of upper abdomen - CT-Scan of liver. - MRI scan of liver may be found useful for detection of Amoebic liver abscess.

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53. Contd… 6. Histopathological: Typical cellular architecture at the site of lesion (liver abscess) is seen. 7 . Detection of antibodies in liver pus: Gel diffusion and Counter Current Immuno Electrophoresis (CCIEP) test are commonly used.

54. CULTURE Cultures are not done routinely. Boeck and Drbohlavs medium modified by Laidlaw extensively used for isolation and maintenance of E. histolytica . Diamonds axenic medium used in studies on Pathogenecity, antigenic characterization, and drug sensitivity test.

55. Treatment

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57. Prophylaxis

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