Download ID Amebiasis

Amebiasis
AMEBIASIS
Incidence
Possibly 10 % of world's population infected
Prevalence in tropical countries : 30 %
Prevalence in U.S.A. : 1 to 5 %
Man is primary reservoir
Prevalence in U.S. homosexual population :
25 %
Reported epidemic in Grand Junction
Colorado from chiropractic "colonic therapy"
irrigation
AMEBIASIS
Pathophysiology
Two life cycle forms (as for Giardia) :
–Trophozoite : causes illness
–Cysts : passed in stool, are infectious
Transmission by fecal-oral route
Most infections are asymptomatic
Attack rates 5 to 30 %
Cysts can remain viable for months in
moist environment
Cysts sensitive to chlorination, dessication,
boiling
Iodine stain of Entamoeba histolytica trophozoite in stool
Entamoeba histolytica tropohozoites in stained stool
Life cycle of
Entamoeba
histolytica
AMEBIASIS
Pathology
Main pathology is in colon
–Initial mucosal inflammation
–Then mucosal erosions, then ulcers
Extraintestinal spread is hematogenous
Large abscesses can develop in :
–Liver
–Lung
–Brain
–Other tissues
Amebic liver
abscess
Amebic pleuropericardial abscess
AMEBIASIS
Symptoms
Incubation period variable, but often 5 to 10
days
Crampy abdominal pain
Dysentery
+/- weight loss
+/- anorexia, nausea
Focal symptoms if complications develop
AMEBIASIS
Complications
Fatality rate for amebic dysentery is 2 %
Overall complication rate is 3 to 4 %
–Colon perforation
–Toxic megacolon
–Ameboma (abd. mass, bowel obstruction)
–Liver abscess - may rupture into pleural or
pericardial space
–Brain abscess
May cause 40,000 to 75,000 deaths
annually (2nd or 3rd parasitic cause of death in the world after
malaria +/- leishmaniasis )
Sigmoid colon perforation from amebiasis
Externally ruptured
amebic groin
abscess
AMEBIASIS
Diagnosis
Fresh stool or colon mucus shows cysts or
trophozoites
Often 3 or more stool exams required
Serologic tests important to distinguish
amebiasis from ulcerative colitis
Sigmoidoscopy useful to inspect ulcers
and obtain stool or mucus for culture &
stain
Abd. CT needed if liver abscess suspected
Computed tomography scan showing amebic liver abscess
Aspirating “anchovy paste” pus from amebic liver abscess
AMEBIASIS
Treatment
Two general classes of meds used:
–Tissue amebacides : combat invasive
amebiasis in bowel & liver
Metronidazole
Emetine, dehydroemetine
Chloroquine
–Lumenal drugs : kill amebas within colon
Iodoquinol
Paramomycin
Diloxanide
AMEBIASIS
Treatment of Asymptomatic Carriers
Recommended for:
–Food handlers (always)
–All cases in low incidence regions ( U.S.A.,
Europe)
–Not always recommended for asymptomatic
cases in high incidence tropical countries
AMEBIASIS : Treatment Regimens for
Asymptomatic Carriers
Iodoquinol
–650 mg tid x 10 days (40 mg / kg / day )
–Side effects mild : nausea, emesis, rash
Paramomycin
–500 mg tid x 7 to 10 days (30 mg / kg / day)
–OK in pregnancy
Diloxanide furoate (Furamide)
–500 mg tid x 10 days (20 mg / kg / day)
–Only available in U.S.A. by calling CDC in
Atlanta
AMEBIASIS : Treatment of Invasive Disease
Metronidazole 750 mg tid x 10 days, followed
by iodoquinol 650 mg tid x 20 days (or
paramomycin 25 to 30 mg / kg / day in 3
divided doses x 7 days)
Dehydroemetine one to 1.5 mg / kg / day
(max. 90 mg / day) IM up to 5 days following
iodoquinol
Tetracycline 500 mg qid x 10 days (indirect
amoebacidal action)
 Chloroquine phosphate : 2nd line agent for extralumenal infection ;
1gram / day, then 500 mg / day x 2 to 3 weeks