Docstoc

Entamoeba histolytica

Document Sample
Entamoeba histolytica Powered By Docstoc
					GIT protozoa
Ameba:
Entamoeba histolytica         INTESTINAL PROTOZOA
Entamoeba dispar
Entamoeba coli                 unicellular eukaryotic organisms
Entamoeba hartmanni
Endolimax nana
Iodamoeba bütschlii
Flagellates:
• Giardia lamblia
• Dientamoeba fragilis
• Chilomastix mesnili
• Trichomonas hominis
• Trichomonas vaginalis
    •(other body sites)
• Enteromonas hominis
• Retortamonas intestinalis
Apicomplexa:
• Cryptosporidium hominis
• Cryptosporidium parvum
Other:
• Blastocystis hominis
• Balantidium coli
     Fecal-Oral Transmission Factors
• poor personal hygiene
   • food handlers                Control/Prevention
   • institutions                 • improve personal hygiene
   • children in day care centers    • especially institutions
• developing countries            • treat asymptomatic carriers
   • highly endemic                  • eg, family members
   • poor sanitation              • health education
   • travelers diarrhea              • hand-washing
• water-borne epidemics              • sanitation
                                     • food handling
• zoonosis                        • protect water supply
   • Entamoeba = no
                                  • treat water if questionable
   • Cryptosporidium = yes
                                     • boiling
   • Giardia = controversial
                                     • iodine
                                     • not chlorine
Amoebiasis
 Amoebiasis is caused by Entamoeba histolytica .
 The organism formerly known as E. histolytica is now
  known to consist of two distinct species :E. histolytica ,
  which is pathogenic, and E. dispar ,which is non-
  pathogenic.
 Cysts of the two species are identical, but can be
  distinguished by molecular techniques after culture of
  the trophozoite .E. histolytica can be distinguished
  from all amoebae except E. dispar ,and from other
  intestinal protozoa, by microscopic appearance.
 Amoebiasis occurs world-wide, although much higher
  incidence rates are found in the tropics and
  subtropics .
Cont.
 The organism exists both as a motile
  trophozoite and as a cyst that can survive
  outside the body.
 Cysts are transmitted by ingestion of
  contaminated food or water, or spread
  directly by person-to-person contact.
 Trophozoites emerge from the cysts in the
  small intestine and then pass on to the
  colon, where they multiply .
Clinical features
 Many individuals can carry the pathogen
  without obvious evidence of clinical disease
  (asymptomatic cyst passers).
 This is may be due in some cases to the
  misidentification of non-pathogenic E.
  dispar as E. histolytica, and it is not clear
  how often true E. histolytica infection is
  symptomless.
 In affected people E. histolytica
  trophozoites invade the colonic epithelium,
  probably with the aid of their own
  cytotoxins and proteolytic enzymes.
Cont.
 The parasites continue to multiply
  and finally frank ulceration of the
  mucosa occurs.
 If penetration continues, trophozoites
  may enter the portal vein, via which
  they reach the liver and cause
  intrahepatic abscesses.
 This invasive form of the disease is
  serious and may even be fatal .
• ulcers with raised borders
• little inflammation between lesions
Incubation period
 The incubation period of intestinal amoebiasis is
  highly variable and may be as short as a few days or
  as long as several months.
 The usual course is chronic, with mild intermittent
  diarrhoea and abdominal discomfort. This may
  progress to bloody diarrhoea with mucus, and is
  sometimes accompanied by systemic symptoms such
  as headache, nausea and anorexia.
 Less commonly, infection may present as acute
  amoebic dysentery, resembling bacillary dysentery or
  acute ulcerative colitis.
Complications
 Complications are unusual, but include toxic
  dilatation of the colon, chronic infection with
  stricture formation, severe haemorrhage,
  amoeboma, and amoebic liver abscess.
 Amoebomas, which develop most commonly in the
  caecum or rectosigmoid region, are sometimes
  mistaken for carcinoma. They may bleed, cause
  obstruction or intussuscept.
 Amoebic liver abscesses often develop in the absence
  of a recent episode of colitis. Tender hepatomegaly, a
  high swinging fever and profound malaise are
  characteristic, although early in the course of the
  disease both symptoms and signs may be minimal.
Diagnosis
 Microscopic examination of fresh stool or colonic
  exudate obtained at sigmoidoscopy is the simplest
  way of diagnosing colonic amoebic infection.
 To confirm the diagnosis motile trophozoites
  containing red blood cells must be identified: the
  presence of amoebic cysts alone does not imply
  disease. Sigmoidoscopy and barium enema
  examination may show colonic ulceration but are
  rarely diagnostic.
 The amoebic fluorescent antibody test is positive in at
  least 90% of patients with liver abscess and in 60-
  70% with active colitis. Seropositivity is low in
  asymptomatic cyst passers.
Management
 Metronidazole 800 mg three times daily for
  5 days is given in amoebic colitis; a lower
  dose (400 mg three times daily for 5 days)
  is usually adequate in liver abscess.
 Tinidazole is also effective: dehydroemetine
  and chloroquine are alternative drugs, but
  are rarely used. After treatment of the
  invasive disease, the bowel should be
  cleared of parasites with a luminal
  amoebicide such as diloxanide furoate.
prevention
 Amoebiasis is difficult to eradicate
  because of the substantial human
  reservoir of infection. The only
  progress will be through improved
  standards of hygiene and better
  access to clean water.
 Cysts are destroyed by boiling, but
  chlorine and iodine sterilizing tablets
  are not always effective.
     Thank you
Dr. Ayham Abulaila

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:0
posted:3/7/2013
language:Latin
pages:25