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Life-Cycle of Entamoeba histolytica
Quadrinucleated cysts (Infective stages)
Contamination of food & H2O
Excystation in Small / large Intestine
4 Metacyclic Forms (Amoebules)
Life-Cycle of Entamoeba histolytica
Amoebules in Intestinal lumen
Binary Fission 8 Amoebae
Invade intestinal tissues (Trophozoites)
Asexual reproduction by binary fission(Colonies of Amoebae:Increase in Population)
Life-Cycle of Entamoeba histolytica
Asexual reproduction by binary fission ( Increase in Population)
Last generation before encystment:Precystic stage Trophozoites Round up, Expel food particles
Encystment & Cysts in lumen
Cysts in faeces Environmental contamination (Soil/Ground) (PP : Man- 4days;Dogs-8-10Days)
Pathogenesis of E. histolytica
Attributed to Invasive natureInvasion of tissues : (?) Secretion of proteolytic enzymes Phosphohydrolase Viruses : Icosahedral & Filamentous Bacteria
Pathogenesis of E. histolytica
Invasion of Intestinal mucosa
Multiply asexually: Binary fission
Invasion in deeper layers (Submucosa)
Spread laterally
Flask shaped ulcers:Caecum & Ascending Colon
Pathogenesis of E. histolytica
Pathogenesis of E. histolytica
Flask Shaped Ulcers in Colon
Pathogenesis of E. histolytica Invasion in intestinal mucosa/submucosa
Spread to other organs via circulation
Right lobe of liver via portal circulation
Trapped in interlobular venules
Lytic necrosis Hepatic Amoebic Abscess Other organs : Lungs & Brain
Hepatic Amoebic Abscess
Pathogenesis of E. histolytica
Chronology : Sequence of events
Noninvasive colonization in Int. lumen
Invasion in Int. mucosa / submucosa ( Flask shaped ulcers)
Extraintestinal invasion: Liver/Lung/Brain
Pathogenesis of E. histolytica in Animals ( Dogs & Cats)
Dogs :Natural infections Source: Man Intestinal Disease : Caecum
Cats : Highly susceptible Acute Disease : Ulcerative lesions Organisms Fail to encyst Cat Borne Infection ?
Clinical Signs of Amoebic Dysentery
Influenced by severity of infection : Acute Amoebiosis : Severe dysentery Dehydration (Anorexia) Blood & Mucus in faeces Intense griping pain,frequently visits latrines straining blood & mucus
Prolapse of rectum
Clinical Signs of Amoebic Dysentery
Chronic Amoebiosis : Recurrent GI symptoms Viz. Diarrhoea or Dysentery Abdominal Pain (Abdominal discomfort) Nausea Flatulence Anorexia
Clinical Signs of Amoebic DysenteryExtra intestinal Phase
Liver : Pain on right side of abdomen Enlarged tender liver Fever, Vomiting, Anorexia.
Lungs : Chest Pain & Respiratory Distress.
CNS : Epilepsy & Nervous signs.
Epidemiology of Amoebiosis. Zooanthroponosis Ubiquitous : Common in tropical &
subtropical countries India; Densely populated cities Delhi- 20%; Kolkata- 24%; Mumbai- 27% & Chennai-37%. (Survey 1972)
Epidemiology of Amoebiosis
Longevity of Cysts Tetranucleated cysts: Infective stages Survive for two weeks in wet surrounding. No effect of water chlorination- viable for
several weeks Very susceptible to desiccation Thermal death point – 500C
Epidemiology of Amoebiosis Other Vital Factors : Flies
Vegetables
Food Handlers
Faulty Plumbing (Metropolitan Cities)
Epidemiology of Amoebiosis
Human & Cats suffer more severely Human Beings : Travelers disease Complete elimination is difficult &
relapses are common Cats : Organisms do not encyst
Diagnosis of Amoebiosis
Intestinal Disease Stool Sample Examination
Demonstration of cysts (tetranucleated). Differential diagnosis(1% Lugols Iodine) Trophozoites in loose stools. Immunodiagnosis: Invasive disease
Diagnosis of Amoebiosis
Intestinal Disease: SSE : Cysts
DD : Entamoeba coli
Diagnosis of Amoebiosis Extraintestinal Disease: Immunodiagnosis
Radiology
MRI
CT scan
Diagnosis of Amoebiosis
Extraintestinal Disease:
Treatment of Amoebiosis
Intestinal Disease: Metronidazole: Drug of choice. Acute : 800mg tid for 5 days. Chronic : 400mg tid for 5 days.
Treatment of Amoebiosis Extraintestinal disease: Tinidazole- 200mg bid - 5 days. Chloroquine: 150 mg bid - 10 days. Diloxanide furoate-500mg tid-10 days. Di-iodohydroxyquinoline-600mg bid-21 days Supportive : Gut acting antibiotics Anticoagulants, Astringents.
Control of Amoebiosis
Good Sanitation.
Proper sewage system.
Avoidance of contamination of food & H2O.
Health Education & Personal Hygiene.