CASE 2 - PARASITOLOGY ENTAMOEBA HISTOLYTICA DR. SALAMA ABD MEGUID

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1 CASE 2 - PARASITOLOGY ENTAMOEBA HISTOLYTICA DR. SALAMA ABD MEGUID G/D Host Reserv Infect Stage MOT Division Diagnos Stage Life Cycle Worldwide but especially Africa, China, Latin America and South East Asia Man Monkey, dogs, rat Mature quardri nucleated cyst Ingestion of water, food and raw vegetables contaminated by stool contain mature cyst Direct feco oral contamination (auto infection) Mechanical transmission of cyst by flies and cockroaches Simple binary fission Mature cyst in stool examination / thropozoite in aspirate at ulcer part or in diarrhea. 1. Man acquire the infection by ingestion of mature quadri nucleate cyst 2. Excystment occurs in the small intestine, liberating a single trophozoite with 4 nucle 3. The trophozoite undergoes a series of cytoplasmic and nuclear divisions to form 8 small meta cystic trophozoites 4. The trophozoite passed to the lumen ofthe large intestine (ileo caecal area) where they multiply by simple binary vision 5. They colonize on the mucosal surface of the large intestine 6. After colonization, they may show one of the following routes a. Encystment in the lumen and formed cyst passed to outside with the stool (diagnostic stage) b. Trophozoites may invade the wall of the large intestine (tissue or pathogenic form) resulting in necrosis and ulcer formation. Trophozoites will be excreted with blood nd mucus in the stool (diagnostic stage) c. Trophozoites gain access into the portal vein, to the extra intestinal tissues (liver, lung and brain ) where they multiply 7. The mature quadri nucleate cyst excreted in the stool presents the infective stage 8. Cysts cause infection in other susceptible persons through faecal contamination and the cycle is repeated MORPHOLOGY Trophozoite Pre-cyst Cyst Size Shape Irregular Oval Rounded Nucleus Cytoplasm N/B Single, vesicular and rounded. Has small central karyosome, lined by peripheral chromatin granules Single nucleus similar to throphozoite Mature: quadri nucleated Immature: mono or bi nucleated Lumen and wall of large intestine Lumen, mucosa and Lumen of the sub mucosa of large large intestine intestine with extra intestinal metastases (liver, lung, brain) Ectoplasm: clear, provided with pseudopodia Endoplasm: granular, vaculated and contains RBCs It is the active invasive form of the parasite Granular and contains rod like bars and glycogen mass. The chromatoid bodies are consumed with repeated nuclear division It is an intermediate stage between trophozoite and cyst Morphological characteristics of that of the trophozoite

2 Causative Agent Stages Limits Prevention and Control Entamoeba Histolytica 1. Adherence of trophozoite to the surface of the intestinal mucosa a. The slow passage of intestinal contents in the caeum and sigmoid colon helps the trophozoites to invade these sites b. The intestinal bacterial flora affects the invasiveness of the trophozoites to a great extent c. Adherence of the trophozoites to the intestinal mucosa is mediated by a surface lectin ( Gal/GalNec lectin) 2. Invasion of the intestinal mucosa a. After adherence, the trophozoites kill a target cell in the intestinal mcosa by Direct contact Amoeba pore peptides Proteolytic enzymes b. Only 10% cases, the trophozoites invades the mucous membrane of the large intestine and live as tissue forms and are responsible for the clinical picture of acute amoebic dysentery 3. The secreted entero toxins can cause diarrhea in intestinal amoebiasis Pathogenic activities of E. Hystolytica depends upon a. The resistance of the host; hosts immunity and state of nutrition b. Virulence and invasiveness of amoebic strain and the number of amoeba c. Local conditions of the intestinal tract: invasion is facilitated by carbohydrate diet, physical or chemical injury of the mucosa, food stasis and type of bacterial flora 1. Avoid fecal contamination of water supplies, food and vegetables 2. Boiling or filtration of drinking water 3. Treating of raw vegetables with acetic acid (5%) or vinegar for 30 minutes before consumption as salad to kill the cyst 4. Avoid the use of untreated human faeces as an agricultural fertilizer 5. Improved personal hygiene as washing hands before eating and after defecation 6. of infected patients specially carriers ( food handlers and cyst passers ) 7. Sanitary disposal of human stool 8. Control of house flies and cockroaches 9. Health education 10.Development of protective vaccine AMOEBIASIS Type Diagnosis Pathology Intestinal Amoebiasis Most common: caecum, ascending colon Less common: sigmoido rectal region Parasitic examination : Stool examination, sigmoidoscopic examination of rectal ulcers Sero diagnosis: IHA, IFA, ELISA Luminal amoebicide: diloxanide furoate, furamide Tissue amoebicides: metronidazole, tinidazole Extra-Intestinal Amoebiasis Liver: amoebic liver abscess Lung: pleuro pulmonary amoebiasis Brain: cerebral amoebiasis Rare: splenic, cutaneous, genito urinary Parasitic diagnosis Sero diagnosis Biochemical diagnosis Haematological diagnosis Sputum exam CSF exam Radio diagnosis PCR Metronidazole Broad spectrum antibiotic Luminal agent Items of Difference Amoebic Bacillary Dysentery Dysentery A. Clinical Picture Incubation period Long Short (< 7 days) Onset Gradual Acute Abdominal Localized Generalized tenderness (caecum & sigmoid colon) Tenesmus Moderate Severe Fever _ + Stool contents Blood, mucus and faecal matter Blood and mucus. faecal matter Frequency of Defecation 6-8 times/day > 10 times/day B. Stool Examination : Pus cells Few Numerous RBCs. In clumps Scattered (rouleaux) Haematophagous + - trophozoites Bacilli (On culture) - + Charcot-Leyden + - Crystals PH Acidic Alkaline C. Differential Blood Count (Leukocytosis) - Marked

3 Clinical Manifest PATHOLOGY OF INTESTINAL AMOEBIASIS Acute intestinal amoebiasis Very small, pin head to an inch in diameter Round or oval, flask shaped with broad base narrow neck The inflammatory cells are numerous Trophozoites are usually found in large numbers at the periphery of the ulcer They heal completely w/o scar Chronic intestinal ameobiasis Small and shallow, only in the mucosa Generalized thickening of the intestinal wall makes it palpable per abdomen Diffuse mass of granulomatous tissue (amoebic granuloma) is formed without any evidence of ulceration Scarring of the intestinal wall is marked Asymptomatic cyst passer Symptomatic 1) n dysenteric colitis It is characterized by chronic intermittent diarrhea with mucus, abdominal pain, flatulence and loss of weight. The patient respond well to treatment with anti amoebic drugs 2) Acute amoebic dysentery It is characterized by presence of blood and mucus in the stool, abdominal pain, tenderness and rectal tenesmus. Fever is uncommon. The condition must be differentiated from that of bacillary dysentery by the demonstration of RBCs, Charcot Layden crystals and haematophagus amoebic trophozoites in the amoebic dysenteric stool. 1. Fulminant amoebic colitis: common in pregnancy, malnutrition, corticosteroids therapy 2. Amoeboma: contains active trophozoites. Common in colon, caecum, rectum. Rare. Except in central and south America. 3. Thick mega colon: it is resistant to anti amoebic drugs 4. Colonic stricture 5. Appendicitis and peritonitis 6. Haemorrhage: due to erosion of intestinal blood vessels 7. Peri anal ulceration A) Luminal amoebicides : Act on lumen parasite mainly cysts B) Tissue amoebicides Act on invasive or tissue forms C) Asymptomatic intestinal infection (cyst passers) Diloxanide furoate (Furamide): 500 mg tds for 10 days Iodoquinol, Paromomycin Characteristics Complication of Symptomatic Diagnosis Precaution for stool exam Parasitic Diagnosis A) Stool Examination i. Direct stool examination: Trophozoites and cysts are demonstrated in saline, eosine (0.5 %) and Iodine (1%) smears. Permanent staining of the stool smear by iron-haematoxlin or trichrome stains allows the best identification of haematophagous trophozoites ii. Concentration technique: Zinc sulfate centrifugal flotation method is used to concentrate amoebic cysts in chronic method is available for concentration of trophozoites. iii. Stool culture: It is helpful in chronic and asymptomatic This is performed on an artificial media which may be mono-phasic (serum or albumin and saline) or bi-phasic ( monophasic medium on a solid egg or agar slant). iv. Detection of copro-antigens: Detection of amoebic antigen in the stool by CIEP and ELISA. This method differentiates the pathogenic E. histolytica from the non-pathogenic E. dispar. B) Sigmoidoscopic examination of rectal ulcers for trophozoites. Sero-diagnosis Serum amoebic antibodies are detected by IHA, IFA and ELISA in the invasive intestinal Substances that interfere with stool examination should not be given at least 10 days before the collection of the stool for examination, e.g. kaolin, barium, liquid paraffin. Since excretion of cysts in the stool is intermittent, so at least 3 consecutive specimens should be examined. Trophozoites are easily detected if the stool is examined within 15 minutes of the passage, while cysts can be detected in 3 days-old formed stool specimen. D) n dysenteric colitis 1. Metronidazole (Flagyl): 750mg tds for 10 days + diloxanide furoate(furamide): 500mg tds for 10 days 2. Furazole: 2 tablets tds for 5 10 days 3. Tinidazole (Fasigen): 2g once a day for 3 days in an alternative to metronidazole E) Dysenteric colitis 1. Bed rest + fluid and electrolytes replacement therapy 2. Flagyl or fasigen 3. Furamide

4 PATHOLOGY OF EXTRA-INTESTINAL AMOEBIASIS Amoebic liver abscess Emboli of EH trophozoites reaching the liver via portal blood, leads to a number of necrotic foci, which if untreated, coalesce to form an abscess and continue to enlarge as the trophozoites destroy and ingest liver cell. The abscess contains lysed Hepatocytes erythrocytes bile fat reddish to chocolate brown (anchovy sauce) single or multiple commonly in the postero superior surface of the right lobe semi fluid a. n-suppurative amoebic hepatitis: Tender hepatomegaly, fever and leukocytosis in patients with amoebic dysentery. b. Amoebic liver abscess: Fever, sweating, stabbing pain, tender hepatomegaly with loss of weigh, marked intercostal edema over the site of liver affection. Amoebic plueritis, amoebic pericarditis, amoebic peritonitis amoebic pus is thick and chocolate brown in color, it is bacteriologically sterile It may contain E. histolytica trophozoites in the necrotic or in the degenerated liver tissues. Pleuro pulmonary amoebiasis Primary direct extension from amoebic liver abscess through the diaphragm Secondary embolization from the intestinal wall Single or multiple Lower lobe of the right lung Reddish brown sputum Trophozoites Cough, plueritic pain and dyspnea Cerebral Amoebiasis Secondary to amoebic liver or pulmonary amoebiasis Secondary amoebic meningo encephalitis Small Single Acts like a brain tumor in sign and symptom; space occupying lesions It usually a haematogenous spread from colon. CSF and abscess contain trophozoites but never cyst form Parasitic Sero-dx Patho Color Consistency Compli -cation n/b Causes Sputum Causes Result Size Biochemical dx Hematological dx Sputum Exam Cutaneous amoebiasis Lesions have a wet glandular, necrotic surface with prominent borders and can be highly destructive Genito urinary amoebiasis in recto vaginal fistula, in females, the trophozoites can spread into the genito urinary tract Diagnostic Test Detection of trophozoites in the aspirated pus of amoebic liver/lung abscess Circulating amoebic antigens or Ab are demonstrated by IHA, IFA or ELISA In amoebic liver abscess a. Serum alkaline phosphatase, transaminase level are increased b. Decrease serum albumin In amoebic liver abscess a. Leukocytosis: 2ry bacterial infection b. Mild normocytic, normochromic anemia c. Elevated ESR To demonstrate trophozoites in pulmonary amoebiasis Use in cerebral ameobiasis CSF Exam Radio-dx Use in amoebic liver, lung or brain abscess : Ultra sonography, CAT scan or MRI PCR To detect parasite DNA in liver abscess and stool Metronidazole (Flagyl) + chloroquine phosphate or Emetine hydrochloride Aspiration of large abscess Broad spectrum antibiotic, Luminal agent

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