Entamaoeba Histolytica (Exam Point of View)
- 1. ENTAMOEBA HISTOLYTICA (PARASITOLOGY) Sijo.A, M.Sc. Junior Microbiologist DDRC SRL Diagnostics Pvt Ltd, Trivandrum, Kerala, India
- 2. REFERENCE Bailey & Scotts; Diagnostic Microbiology Paniker’s Textbook of Medical Parasitology Apoorba S Sastry & Sandya Bhatt; Essentials of medical microbiology
- 3. Entamoeba histolytica was first discovered by Losch in 1875. It is worldwide distribution. It is prevalent in tropical and subtropical countries where sanitary conditions are poor. In india, it is prevalent in Chandigarh, Tamil Nadu & Maharashtra. It is found in the colon of man. It is monogenetic because the whole life cycle completed within a single host, i.e. man. ENTAMOEBA HISTOLYTICA
- 4. MORPHOLOGY 1. Trophozoite It is small & irregular in shape. The cytoplasm of amoeba is bounded by membrane and it is differentiated into outer ectoplasm and inner endoplasm. The endoplasm contain nucleus, food vacoules, erythrocytes, leukocytes and tissue debris. • It exists in three forms. 1. Trophozoite 2. Precyst 3. Cyst
- 5. The locomotory organ is pseudopodia. The typical amoeboid motility is crawling or gliding movement. The nucleus contain central karyosome surrounded by clear halo and it gives cartwheel appearance. They divide by binary fission. They are killed by drying, heat and chemical sterilisation. 2. Pre-cyst The pre-cyst formation occurs in intestinal lumen. It is oval in shape. It contain glycogen vacoule and two chromatid bar.
- 6. 3. Cyst o It is the mature cyst. o It is spherical in shape. o It contain 4 nuclei, hence it is called quadrinucleate. o Glycogen vacoule and chromatid bars are absent. o It is resistant to gastric juice. Pathogenesis & Clinical Features 1. Intestinal Amoebiasis o Here the infection is limited to large intestine. o The metacystic trophozoites enters the intestinal epithelium through Crypts of Liberkuhn. o The trophozoites releases histolysin enzyme which brings about the destruction, necrosis and abscess of the tissue. o It results amoebic ulcer.
- 7. Clinical features The stool is large, foul-smelling, brownish black with mucus and blood and it is called Amoebic dysentery. The incubation period is 1-4 months. 2. Extra Intestinal Amoebiasis a) Hepatic Amoebiasis o It is the inflammation of the liver. o It occurs due to the repeated invasion of amoeba from ulcerated gut through blood stream. o Liver contain thick chocolate brown pus.
- 8. b) Pulmonary Amoebiasis o It is the inflammation of the right lung. o It occurs due to the repeated invasion of amoeba from liver through blood stream. o It results chocolate brown sputum. c) Metastatic Amoebiasis o It involves kidney, brain, spleen & adrenals. d) Cutaneous Amoebiasis o It involves destruction of skin around anus. e) Genitourinary Amoebiasis o It involves amoebic vaginitis or amoebic ulcer on penis.
- 10. DIAGNOSIS 1. Microscopic examination of stool, pus & sputum. 2. Liver biopsy 3. Serodiagnosis include IHA Test, Latex Agglutination test and ELISA. 4. Demonstration of ghost cells, pyknotic bodies and CL crystals. Their presence indicates that the immune response arised due to parasitic infection. TREATMENT 1. Administration of Metronidazole, Tinidazole, Paromomycin, Iodoquinal. 2. Oral rehydration & electrolyte replacement should be done wherever necessary.