1. Amebiasis

3. 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

4. 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

5. Iodine stain of Entamoeba histolytica trophozoite in stool

7. Entamoeba histolytica tropohozoites in stained stool

8. Life cycle of Entamoeba histolytica

9. 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

10. Amebic liver abscess

11. Amebic pleuro- pericardial abscess

12. AMEBIASIS Symptoms  Incubation period variable, but often 5 to 10 days  Crampy abdominal pain  Dysentery  +/- weight loss  +/- anorexia, nausea  Focal symptoms if complications develop

13. 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 )

14. Sigmoid colon perforation from amebiasis

15. Externally ruptured amebic groin abscess

16. 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

18. Computed tomography scan showing amebic liver abscess

19. Aspirating “anchovy paste” pus from amebic liver abscess

20. 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

21. 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

22. 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

23. 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