Adventure Doc
Erik McLaughlin MD, MPH
Affiliates
AMEBIASIS
Basics:
Entamoeba Histolytica is a parasite with 2 forms, cyst and trophozoite. The cyst form is very difficult to kill and is the infective stage. The trophozoite is more fragile and causes the majority of symptoms. This protozoan can cause intestinal (dysentery) or extra intestinal disease. Intestinal manifestations include pain, bloody diarrhea and colitis. Liver or brain abscess can occur with serious consequences in extra intestinal disease. Often seen Europe or America as an illness of hikers/campers.
AMEBIASIS
Location:
Worldwide
Transmission/ Incubation:
Acquired through ingestion of cyst-contaminated water. Cysts are ingested and maturation to trophozoite occurs in intestinal lumen. Incubation is generally 2-3 weeks but patients can be a symptomatic for months to years.
Prevention:
Water sanitation/purification is key. Boiling for at least one minute is advised to kill cysts (infective form). Iodine tablets can be used with a contact time of 30 minutes. Micropore filtration has been effective as well. Avoid fecal contamination of water supply.
PRODUCT REVIEWS
Diagnosis:
Demonstration of cysts or trophozoites in fecal smear. ELISA is helpful in invasive (extra intestinal) disease. Use serology to differentiate from identically appearing and non-pathologic E. Dispar on microscopy. Try to test 3 separate samples.
Treatment:
Metronidazole 750 mg TID for 10 days
Entamoeba Histolytica Trophozoite with ingested erythrocyte
Entamoeba Histolytica Trophozoite
Entamoeba Histolytica Cyst
Entamoeba Histolytica Cyst
Purify your water to avoid this! E. Hystolytica cysts are tough to kill. Boiling is probably best and the one minute rule applies to sea-level. More time is required at higher elevations. Symptoms can vary from mild gastroenteritis/diarrhea to full-blown dysentery (bloody stools) as the parasite invades the lining of the intestine. Possible severe consequences include formation of liver abscesses (surgical aspiration is sometime required). Skin ulcers in the peri-anal region are thankfully rare. This is rare in kids less than 5 years old and very rare in kids less than 2 years old. Shigella is far more common in this age group. Chronic cyst carriers are possible, without symptoms.
