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ENTAMOEBA HISTOLYTICA

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Symptoms
Transmission
Detection (testing for)
Experiences with E.histolytica (updated March 2005)

E.histolytica is an invasive protozoal organism capable of causing life-threatening intestinal and extra-intestinal disease. E.histolytica can invade the liver, lung and other bodily sites by penetrating the intestinal mucosal barrier.

It has a worldwide distribution and is the third leading cause of death by parasitic infection. It was first documented in 1875 and is estimated to cause between 50,000 and 100,000 deaths every year. Ninety percent of those infected have no symptoms.

 SYMPTOMS:
Symptoms range from mild diarrhoea to hemorrhagic dysentery.
Cases of mild diarrhoea caused by E.histo. are often misdiagnosed as Irritable Bowel Syndrome.

Many infected individuals are asymptomatic but can infect others via intermittent shedding of cysts in the stool.

Symptoms may include:
Fever (in approx. 10-30% of patients)
Weight loss
Tenesmus (straining to pass stool, a feeling of imcomplete evacuation)
Abdo. pain, including tenderness.
Stools which are loose, watery.
Constipation
Passing of blood, mucous
Dehdyration

Rare complications:
Amoebic colitis
including necrotising (fulminant) colitis (approx. 0.5% of patients) which has a mortality rate of 40%. Nectrotising colitis can occur in the malnourished, during corticosteroid use (steroids used to suppress inflammatory response), in young children & during pregnancy.

Liver abscess
Symptoms:
Upper quadrant abdo. pain and fever.
A prior history of dysentery
Weight loss
Jaudice

Individuals with liver abscess may not excrete the organism in the stool, in these cases stool antigen tests may not be suitable for the diagnoses of amoebic liver abscess.
Although blood tests for antibodies against E histolytica are approx. 80% accurate, the detection rate drops dramatically after treatment with metrondazole. In one study of 75 patients all positive for amoebic liver abscess, only 15% tested positive after treatment with metronidazole (Flagyl).(J Clin Microbiol. 2000;38:3235-3239).

Vaginal infection:
"Genital amebiasis is a rare complication of infection with Entamoeba histolytica, even in areas where the pathogen is endemic. We describe a patient who apparently contracted intestinal amebiasis on a trip to Mexico and who presented with ulcerative vulvovaginitis 2 months later. Her condition rapidly progressed to severe necrotizing vulvovaginitis that required a radical vulvectomy. Histopathologic examination of the surgical specimen revealed the presence of E. histolytica trophozoites. The patient recovered after surgery and antiamebic therapy."
Clin Infect Dis 1995 Mar;20(3):700-2
Severe vaginal infection with Entamoeba histolytica in a woman who recently returned from Mexico: case report and review.
Citronberg RJ, Semel JD. Section of Infectious Disease,
Rush Medical College, Chicago, Illinois, USA.

TRANSMISSION:
Exposure to E.histolytica cysts can occur via:
Contaminated water and food — spread by direct contact with an infected person’s hands or with contaminated surfaces.
Consuming food grown in feces-contaminated soil, fertilizer, or water.
E.histolytica cysts can survive for weeks under moist conditions.
Swimming pools are a possible source of contamination because E.histo. survives chlorine levels sufficient to kill bacteria.

DETECTION:
Stool testing:
Examination of a single stool specimen is approx. 33% sensitive.
Because the cysts of E.histolytica shed intermittently in the stool and may not be present at the time of testing at least three to six stool examinations are recommended (read individual experiences here.

"Over the years I've tested positive for Giardia, B. Hominis, E. Nana, many different species of yeast and bacteria. On my last test, E. Histolytica turned up. I've had no fewer than ten stool tests by very reputable labs (Diagnos-Techs, Great Smokies) and this is the first time E. Histolytica has shown up."
emailed by C. 21 April 2003

The following can interfere with the recovery of the parasite:
Antibiotics, antacids, antidiarrheals, drugs, anti-parasitic herbs, enemas.

STOOL TEST: ELISA (Enzyme-Linked Immunosorbent Assay):
Parasites are composed of cell surface molecules called lectins, which enable the parasite to adhere to the bowel. ELISA detects the lectins specific to E.histolytica and is performed on fresh, unfixed samples.
The labs on the "Where to find help/labs" section of this site use ELISA & other antibody tests to detect E.histolytica.

Colonoscopy
"An increased risk of intestinal perforation exists in fulminant (necrotising) colitis, .
The appearance of amebic colitis may resemble that of inflammatory bowel disease, with a friable and diffusely ulcerated mucosa. In addition, an ameboma may be present in the form of an annular lesion, which usually occurs in the cecum and ascending colon and often is visually indistinguishable from colonic carcinoma". (Robert Swords, MD. Feb 2002)

TREATMENT

METRONIDAZOLE/TINIDAZOLE
"In a small pilot study the parasite cure rate (PCR) of non-invasive amoebiasis was compared after treatment with metronidazole 800 mg three times daily or tinidazole 600 mg twice daily for five days. Both treatment regimens were found to be highly unfavourable with PCRs of 44 and nil respectively, in contrast to previous published results showing PCR over 80%".
Treatment of non-invasive amoebiasis--a comparison between tinidazole and metronidazole.
Pehrson P, Bengtsson E. Ann Trop Med Parasitol 1984 Oct;78(5):505-8

Email me me for an effective treatment.

NITAZOXINIDE
"nitazoxanide was more toxic than
metronidazole and albendazole against E. histolytica"
In vitro effect of nitazoxanide against Entamoeba histolytica, Giardia intestinalis and Trichomonas vaginalis trophozoites.
J Eukaryot Microbiol 2002 May-Jun;49(3):201-8
Cedillo-Rivera R, Chavez B, Gonzalez-Robles A, Tapia A, Yepez-Mulia L.

"Thirty-eight (81%) of 47 patients in the nitazoxanide treatment group resolved diarrhea within 7 days (median, 3 days) after initiation of treatment, versus 17 (40%) of 42 in the placebo group (P=.0002).
Treatment of diarrhea caused by Giardia intestinalis and Entamoeba histolytica or E. dispar: a randomized, double-blind, placebo-controlled study of nitazoxanide.
J Infect Dis 2001 Aug 1;184(3):381-4
Rossignol JF, Ayoub A, Ayers MS.

(Note: Nitazoxanide is undergoing trials both here in Australia & in the US

More info.on symptoms & treatment is available on the Merck Manual site.
An study in Africa compared four amoebicide drugs treatments on 300 symptomatic patients over a 5 month period. Seventy-six percent submitted 3 follow up stool samples.
The results were:
Metronidazole + Oxytetracycline (tetracycline) - 10.9% continued to excrete E.histo. cysts.
Di-iodohydroxyquinoline (an older, more toxic version of Iodoquinol/Yodoxin) and Oxytetracycline: 25.5% continued to excrete E.histo. cysts.
This figure fell to 20% when *Dehydroemetine was added.
Clioquinol and Oxytetracycline - 27.5% continued to excrete the parasite.

*Dehydroemetine - this drug can cause serious side effects and is usually reserved for dangerously ill patients

Therapeutic trial of four amoebicide regimes in rural Zaire. Masters DK, Hopkins AD. A prospective comparative trial of four amoebicide regimes was carried out with protozoological control using 300 patients presenting with symptomatic intestinal amoebiasis at a tropical rural hospital during a five month period.
J Trop Med Hyg 1979 May;82(5):99-101

Personal experiences with E.histolytica:

During 4 years of chronic digestive symptoms Gary had been diagnosed with the parasite Entamoeba histolytica twice - once by stool antigen and once by saliva antibody testing. Ova and parasite, stool antibody, saliva antigen, stool antigen and a blood antibody test had all been negative.

As the negative results outweighed the positive, and drs questioned the results of
saliva antibody testing, finding a doctor who believed he was actually infected with E.histolytica proved a challange. In an effort to find an answer to his illness Garey consulted more than ten doctors over four years. Despite a number of Flagyl treatments his symptoms remained unchanged. (cont. below)

Some therapeutic failures with metronidazole in patients with invader amebiasis and some reports of resistance to it
In vitro sensitivity of Entamoeba histolytica to metronidazole
Aguirre-Cruz ML, Valadez-Salazar A, Munoz O.
Arch Invest Med (Mex). 1990;21 Suppl 1:23-6
Unique in that it is effective both in the bowel lumen and in tissues, metronidazole has been reported to eradicate only up to 50% of luminal infections
This statement has support from a study of 36 patients with amoebic liver abscess for whom the hepatic lesions were cleared; but 20 were recolonized in the intestine, 16 asymptomatically. This was ascribed to the pharmacokinetics of metronidazole cycling in the liver and the action of metronidazole against trophozoites but not invariable eradication of cysts, creating E. histolytica carrier states.

Current recommendations suggest the use of metronidazole or tinidazole PLUS the luminal amoebicide diloxanide furoate or iodoquinol, with other combinations (including paromomycin, tetracycline, and chloroquine) depending on the severity of the infection and site, i.e., whether it is intraluminal, invasive, or abscessed.
Drug Targets and Mechanisms of Resistance in the Anaerobic Protozoa
Peter Upcroft* and Jacqueline A. Upcroft
Queensland Institute of Medical Research and The Tropical Health Program, Australia
(italics & caps added by author of this site)
full text here

Garey managed to keep the worst of the symptoms at bay with anti-parasitic herbs. In hindsight he realises this may have contributed to the negative results because some herbs and drugs not only reduce the number of parasites colonising the bowel, but may also alter the appearance of the parasite. This change in appearance makes it more difficult for the lab technician to identify the parasite microscopically. Drugs can also alter sensitivity of stool antigen testing during and after drug treatment.

Keeping the symptoms under control did not always work in Garey's favour: "We have a fairly sophisticated infectious disease clinic at the medical school complex here in Portland. At one point I tried to make an appointment about my infection via a naturopathic doctor based on a positive lab test through Great Smokies Diag. I was refused to be seen. The reason given was that I was not thought to be sick enough to require the services of a specialist".

After four years of searching Garey eventually found a specialist endocrinologist with an interest in treating parasites, who "thought outside the square" and was willing to taking into consideration Garey's positive result for E.histolytica combined with chronic health problems. The specialist agreed to treat Garey with a combination of Humatin and Nitazoxinide resulting in a complete recovery.

Garey wrote to his first primary care physician outlining the extent of his search for a treatment, enduring misdiagnosis and inadequate treatment for four years until he finally found a dr who would help him. The doctor replied, by registered mail, informing Garey he "would no longer be willing to see me for any reason".

Garey wrote: "I can corroborate about the lack of knowledge doctors often have about parasites, symptoms, testing and treatment. I have heard many times that Eh is not pathological. I saw about 10 different doctors. It is remarkable the ignorance of this very serious infection."

Garey took Nitazoxanide 600mg 4 x daily for four days and Paromomycin 250mg 3 x daily for five days. If this treatment helps you please drop me a line. Your experience will help others make an informed decision about their own treatment.
March 2004

P was diagnosed with E.histolytica and Blasto. hominis. Despite two Flagyl treatments his symptoms remained unchanged. He has tested negative to E.histolytica twice since the Flagyl. Apart from a hiatus hernia, other testing (colonoscopy, barium meal x-ray) have been inconclusive. P. broached with his clinician whether he could still be infected. The clinician advised that "the amoebic dysentry could not be still be around in my gut". Full story here

In 2001 S. wrote contacted me after being diagnosed with E.histolytica. Stool testing by ELISA antigen (a stool test considered gold standard for detection of E.histolytica) was negative. She was eventually diagnosed by bowel biopsy with Entamoeba histolytica.

S. described her symptoms as "severe, excrutiating pain at times, in my back. A constant lower back pain, which eventually became debilitating. I could barely walk, and could not lift my son. I also had extremely heavy period, later becoming irregular. Fatique, sleeplessness, frequent urination, skin rashes, as well as extreme itching of my skin. Alternating bouts of diarrhea and constipation. Constant feeling of bloating and gas."

My husband, after the inital "food poisoining" incident, had the extreme back
pain and was misdiagnosed with sciatica. He was given pain medication for
approximately three months until the symptoms subsided.

Every doctor we saw, always quickly dismissed our suspicions of acquiring a
parasite from shrimp we had from Ecuador, as impossible. Finally, one doctor
decided to test for it by ELISA but the test was negative.

Finally, a rheumatologist who I went too, talked to me for 45 minutes and
recognized my symptoms as being the same as his wifes. She recently had been
diagnosed with an amoeba.(Little did he know we were infected with the exact
same bug.) He sent me to a parasitologist on fith avenue in NYC., NY.
Within two days, after biopsy, he had a diagnosis! The medicine, humatin and
doxycyline, had to be shipped from the city, but three months later we are
negative and on the road to recovery!
received from S, 3 Sept 02

D. had been ill for 6 years after returning from Mexico with symptoms of chronic fatigue, and digestive symptoms severe enough to interfere with D's ability to work. He had previously never been tested for parasitic infection until 3 stool samples recently revealed infection with E.histolytica:

"First let me thank you profusely for your very informative page on parasites and IBS, CFS, etc.. I came across it while doing a search on parasites and CFS. I've suffered from CFS for four+ years, and am getting so bad I'll have to quit work soon. Like you, I've been to a zillion doctors, and tried a zillion things, with temporary, but never lasting success. I am currently waiting for word back on a three-sample ova and parasite test. I called this morning, they said it was being cultured, and would take a couple weeks to hear back."
received 6 Feb 02
My CFS symptoms are pretty constant now, but for years (5 or so) they've come and gone. Actually, they've never gone away, but have lessened to where I'm feeling better for 2, 3, or 4 months, then I slowly get worse. Now the periods of fatigue have increased, and the periods of "energy" (Ha!) are relegated to basically to some evenings, or late afternoons, when I tend to feel a little better. I do have digestive symptoms, the loose, poorly formed stools, and then every once in awhile, bad constipation. Plus, usually a lot of gas, depending on the food combinations, but no cramping. My CFS symptoms are of course always worse when the digestive symptoms are worse. Eating carbs, (and I never eat plain white sugar, always more complex, oats, dates, figs, etc.,) gives me what little energy I have, although if I don't eat protein, then I get very relaxed and sleepy. I've had blood sugar tests, celiac, thyroid, iron storage, CBC, all the usual suspects, which of course come out "normal". This is the first time I've been tested for parasites. Besides the irregular bowel habits, for parasitical symptoms, I have at times (although not right now) had a very itchy anal area. Recently, I've had very itchy ear canals, and also some bad TMJ symptoms, including problems with my bite lining up correctly (I noticed that bruxism, teeth grinding, can be a symptom of parasites.)
e-mailed by 6th Feb 02
Good news -- in a way, anyway. I just found out that my stool tested positive for entamoeba histolytica! Probably from a trip to Mexico almost 6 years ago.Doc is recommending flagyl, but I'm trying to see if she'll go for tinidazole, as there is a pharmacist (outside the HMO system) close to Seattle, that is authorized to compound it, even though it is not available generally, in the US.
8th Feb. 02
"I have been researching parasites today and came across your web site. For the last 2 months I have been suffering from nausea and just feeling ill. I have had so many test done the doctors are running out of options.( CT scan, ultrasound, Upper and lower GI, chest exams, blood test, stool test- negative. I recently went to a alternative medical doctor who ordered a more detailed stool analyst. The test also checked saliva. The saliva test came back positive for Ameba histolytica, and Toxoplasma."
S. August 2002
" My symptoms are upper bloating, reflux, heartburn, bad taste in mouth, and sinus trouble. I have been to many docs and have tried many meds. I even had surgery for the reflux which did not work. I have been dealing with this for 4 years. I probably burp 100 times a day. Well last week I decided to see a tropical disease expert in NYC. He did a sigmoinoscopy( I think that is what it is called). He called me today to tell me that he found mucous, inflamation, and charcoal crystals??? He says that these are signs of parasitic infection and he is 99% sure I have an ameba called Histelica? He wants to treat me with a 2 week dose of flagyl. I think I may go back for another sig, to see if he can find the bug for sure. Any opinions or advice is greatly appreciated.
P. 13 March 02
Further investigation by sigmoidoscopy confirmed E.histolytica infection.
Another example of Entamoeba histolytica infection misdiagnosed as IBS can be found at the following site.
Chronic Illness Support and Research Association (CISRA):
Synergy Health Newsletter site
(The lab which uses salivary testing mentioned in this story can be found here:
Diagnos-Techs, Inc)
References:
Entamoeba histolytica Schaudinn, 1903 and Entamoeba dispar Brumpt, 1925: differences in their cell surfaces and in the bacteria-containing vacuoles.
J Eukaryot Microbiol 2002 May-Jun;49(3):209-19
Pimenta PF, Diamond LS, Mirelman D.

Amebiasis, Robert Swords, MD
eMedicine Journal, February 22 2002, Volume 3, Number 2 on-line

Molecular cloning of a 30-kilodalton lysine-rich surface antigen from a nonpathogenic Entamoeba histolytica strain and its expression in a pathogenic strain.
Infect. Immun. 63: 917-925.
Bracha, R., Nuchamowitz, Y. and Mirelman, D. (1995)