AMOEBIASIS

1
AMOEBIASIS
2
HISTORY

• 2yr 10mo girl
• Main Complaint
• 7 days of loose, bloody diarrhoea and vomiting
• Lethargic and doesnt feed well
• Previous history
• Uneventful perinatal history
• No previous admissions to hospital
• Numerous clinic visits in preceding months for
  diarrhoea
• RVD status unknown
• No TB or other infectious contacts
• No recent travel history / No significant family
  history
• DIET Never breastfed , Feeds on a family diet
  that includes mainly veg protein and
  carbohydrates. Denies traditional medicine
  ingestion.

3
EXAMINATION

• Growth paramoeters
• Weight 11kg - 73 of expected for age
• Length 86cm Below 3rd centile
• Head Circ 48cm On 50th centile
• Weight for height Just below 3rd centile
• Temp 37.1 HR135bpm RR42/m BP70mmHg syst
• Distressed, ill-looking, pale, 7.5 dehydrated
• Chest, CVS CNS Normal

4
EXAMINATION

• Abdomen
• Soft, distended abdomen with decreased bowel
  sounds
• 3cm hepatomegaly Firm, sharp edge, smooth
  surface non-displaced and not
  tender.
• Fullness possibly a mass lesion extending from R
  flank across midline tender to touch.
• Normal hernial orifices and female genitalia
• PR No exterior abnormalities noted
• Irregular rectal mucosa
• Bloody, foul-smelling diarrhoea mixed with pus
  noted

5
SPECIAL INVESTIGATIONS

• FBC
• WCC 3.12
• Hb 9.5
• MCV 80.1
• Platelets 127
• Diff Neut 42.7
• Mono 17.8
• Lymph 35.7
• Eosino 1.8
• Smear Left shift toxic granulation.
• CRP 337

• UE
• 129 / 2.6 / 91 / 24 / 3.4 / 38
• LFT
• Tbili 13 Cbili 1
• TP 46 Alb 17 Glob 29
• ALP 54 GGT 32
• ALT 68 AST81
• Urine culture Negative
• Stool culture Negative
• Blood culture Negative
• RVD Elisa Positive
• CD4 188 (4.62)
• TB W/Up Negative

6
SPECIAL INVESTIGATIONS

• AXR
• Distended loops of large bowel with air fluid
  levels
• No free air noted
• Abd. Sonar
• Aperistaltic thickened loops of bowel in RFI
• No mass seen
• CT Abdomen
• Fluid-filled large small bowel loops
• Closely related bowel loops in RFI bowel wall
  thickening
• No definite mass seen

• Sigmoidoscopy
• Mass seen at recto-sigmoid junction biopsy
  taken
• Histology
• Rectal biopsy with extensive mucosal ulceration.
• Marked inflammatory cell infiltrate composed
  predominantly of chronic inflamm. cells and
  fibrin deposition
• Amoebae noted and confirmed with PAS stain.

7
SUMMARY MANAGEMENT

• 2yr 10mo girl with
• Immunosuppression
• Amoebic proctitis and a chronic inflammatory mass
  at the recto-sigmoid junction consistent with an
  amoeboma.
• Treated with oral Metronidazole
• Optimized general condition in terms of nutrition
• Referred for initiation of HAART

8
AMOEBIASIS
9
The Organism

• 4 species of Entamoeba
• Nonpathogenic E. dispar, E. coli, E. hartmanni
• Pathogenic E. histolytica
• amoebiasis A Parasitic infection caused by the
  protozoon Entamoeba histolytica
• 2nd to Malaria as protozoan cause of death
  worldwide
• 10 of worlds population infected Increased
  prevalence in developing countries (up to 25)
• In SA More common in KZN
• Factors contributing to faecal-oral spread
• Poor education
• Poverty and overcrowding
• Unsanitary conditions
• HIV infection

10
The Life Cycle

• 1. Cyst Stage
• Infective stage
• Survive from 4 to 40 Celcius
• Size 12mm
• Quadrinucleated
• Ingested by contact with fecally contaminated
  food
• Passes through stomach, excysts in lower small
  bowel.
• Metacystic amoeba with four cystic nuclei from
  each cyst
• 8 Small trophozoites from each metacystic amoeba
• Trophozoites carried to cecum

11
The Life Cycle

• The Trophozoite Stage
• 10-40 qm, fragile
• Uninucleate
• Erythrophagocytosis
• Reside, feed and multiply by binary fission in
  lumen of colon
• May invade Lytic physical mechanisms and
  metastasize to liver and other extra-intestinal
  sites
• Galactose-containing molecules receptors
  regulate cyst formation
• Precyst Cyst Uninucleate to Quadrinucleate
  and passed in stool

12
(No Transcript)
13
The Pathogenesis

• 10 of infected individuals develop invasive
  disease
• Factors contributing to developing invasive
  disease
• Pathogenicity of infecting Entamoeba species
• Dose of inoculum
• Host factors Impaired cell-mediated immunity, on
  steroids
• Virulence of infecting species
• Presence of surface adhesion factors
• Release of proteolytic enzymes
• Release of cytotoxins and inflicting of cytolysis

14
The Pathogenesis

• Trophozoites adhere to colonic mucosal
  glycoproteins via a galactose and
  N-acetyl-D-galactosamine-specific lectin.
• (Gal/GalNac) Lectin is 260kD-surface protein
  consisting of a 225kD subunit and a 35kD subunit.
• Adherence results in cell lysis (apoptosis) and
  PMN invasion
• PMNs are then lysed releasing lytic enzymes,
  causing more tissue destruction
• Small foci of necrosis in the intestinal wall
  coalesce to form ulcers (Flask-shaped ulcers)
• Parasites resist destruction by complement arm of
  immune system via Gal/GalNac mediated
  inhibition of the membrane attack complex
• Cell-mediated immunity is important in clearing
  infection through generating ?-INF and TNF-a to
  activate macrophages and neutrophils to kill the
  trophozoite

15
The Pathogenesis

• Area most commonly involved Cecum, then
  Recto-sigmoid area
• May invade blood vessels causing thrombosis,
  infarction and dissemination via portal
  circulation to liver and extra-intestinal sites
  eg. brain, pleura, pericardium and genito-urinary
  system.

• Flask-shaped ulcers

16
The Clinical Features

• Many infections Asymptomatic cyst passers
• Symptomatic infections may have a gradual, acute
  or rapid, fulminant course.
• Clinical incubation period 4 days to several
  months
• Often gradual development of symptoms Irregular
  bouts of diarrhoea, abdominal pain, weight loss,
  nausea, loss of appetite
• (amoebic proctocolitis)
• Less often sudden onset of copious diarrhoea
  containing mucus and blood.
• Findings may include low-grade fever, tenderness
  on palpation of the abdominal wall overlying
  involved large bowel.

17
The Complications

• Complications of Intestinal amoebiasis
• Fulminant Amoebic Colitis with Perforation
• May have a mortality rate of up to 50
• Children less than 2 yrs at increased risk of
  perforation
• Massive Haemorrhage
• Due to vasculitis of large arteries or multiple
  ulcers leading to small arterial leaks
• amoebomas
• A granulomatous thickening of the colon resulting
  from lytic necrosis followed by secondary
  pyogenic inflammation, leading to fibrosis and
  proliferative granulation tissue. Lesions are
  firm, hard, may resemble a carcinoma.
• amoebic Stricture
• Resulting from fibrosis of intestinal wall. Can
  involve rectum, anus or sigmoid.

18
The Complications

• Complications of Extra-Intestinal Amoebiasis
• Amoebic Liver Abcess
• Most frequent complication of amoebiasis
• MaleFemale Ratio 1 in Children and infants
• In adulthood More common in young males
• Third to Half may have no history of diarrhoea
• Commonly found in Right Lobe of liver
• Presents acutely with high fever, RUQ tenderness
• Jaundice an unusual finding
• Have marked leucocytosis and may have XR
  abnormalities in 25 to 90 of patients

19
The Complications

• Complications of Extra-Intestinal amoebiasis
• amoebic Peritonitis
• As a complication of a ruptured hepatic abcess
• Pleuropulmonary amoebiasis
• Caused by rupture of Rt. Lobe Liver abcess in 10
  of patients
• Has cough, pleuritic chest pain dyspnoea
• amoebic Pericarditis
• Rare, but most serious complication in 3 of pts.
  with liver involvement
• Rupture of Left Lobe liver abcess
• Cerebral amoebiasis
• Rare, has altered consciousness and focal neuro
  signs
• CT Irregular lesions without surrounding
  capsule or enhancement
• Genito-Urinary Involvement
• Painful genital ulcers Punched out appearance
  profuse discharge

20
The Diagnosis

• Light Microscopy of Stool
• Identification of trophozoites / cysts in fresh
  stool
• Disadvantages
• Not sensitive (miss up to two thirds of
  infections)
• Cannot distinguish between E.histolytica and E.
  dispar
• Serology
• Anti-amoebic antibodies (IgM) 70 sensitive for
  amoebic colitis and 90 sensitive for amoebic
  liver abcess
• Stool antigen-detection test or PCR
• Sensitive and Specific
• Disadvantages
• Antigen detection test (EIA) only available from
  Blacksburg VA

21
The Diagnosis

• Colonoscopy / Sigmoidoscopy
• Colonoscopy preferable
• Wet preps of material from ulcer-base can show
  trophozoites
• Biopsies should be taken from edge of ulcers
• Recommended to evaluate for amoebic colitis even
  when Ulcerative Colitis considered

22
The Diagnosis

• amoebic Liver Abcess
• Diagnosis relies on
• Detection of risk factors for E.histolytica
  infection
• Positive Serology
• Lesion in Liver
• Abdominal USS
• Abdominal CT Well-rounded, wall enhances
• Aspiration may yield anchovy-paste material
• More often yellow / gray-green
• Often odourless and sterile Highly suggestive
  of amoebic abcess

23
The Management

• Asymptomatic infections
• Luminal agent only recommended but ?not available
  in SA
• In general, not treated in endemic areas
• Symptomatic infections
• Oral Metronidazole for 10 days
• Effective in eradicating amoebae in bowel lumen
  and wall
• Effective in eradicating extra-intestinal disease
• Additional luminal agent not necessary
• E. dispar infection doesnt require treatment

24
Prevention

• Improved sanitation and clean water supply reduce
  fecal-oral transmission
• Boiling water, Washing veg with vinegar
• Vaccination
• None available currently
• Prototype subunit vaccines based on the
  Gal/GalNAc-lectin under study