Dientamoebiasis
Encyclopedia
Dientamoebiasis is a medical condition caused by infection with Dientamoeba fragilis
. Dientamoeba fragilis
is a single celled parasite that infects the lower gastrointestinal tract of humans. It is an important cause of travelers diarrhea, chronic abdominal pain, chronic fatigue and failure to thrive in children.
. This initial report may still be contributing to the reluctance of physicians to diagnose the infection.
A study of Dientamoeba fragilis
isolates from 60 individuals with symptomatic infection in Sydney Australia found that all were infected with the same genotype. which differed from the North American genotype.
The true extent of disease has yet to emerge as most laboratories do not use techniques to adequately identify this organism. An Australian study identified a large number of patients considered to have Irritable bowel syndrome
who were actually infected with Dientamoeba fragilis
.
Although Dientamoeba fragilis
has been described as an infection that is "emerging from obscurity," it has become one of the most prevalent gastrointestinal infections in industrialized countries, especially among children and young adults. A Canadian study reported a prevalence of approximately 10% in boys and girls aged 11–15 years, a prevalence of 11.5% in individuals aged 16–20, and over 20 had a lower incidence of 0.3%-1.9%.
include abdominal pain (69%) and diarrhea (61%). Diarrhea may be intermittent and may not be present in all cases. It is often chronic - over two weeks in duration. The degree of symptoms may vary from asymptomatic to severe, and can include weight loss, vomiting, fever, and involvement of other digestive organs.
Researchers have reported that symptoms may be more severe in children. Additional symptoms reported have included:
are known to produce a cyst stage which is able to survive outside of the host and facilitate infection of new hosts. However, the exact manner in which Dientamoeba fragilis
is transmitted is not yet known, as scientists have reported that the organism is unable to survive outside its human host for more than a few hours after excretion, and no cyst stage has been found.
Early theories of transmission suggested that Dientamoeba fragilis
was unable to produce a cyst stage in infected humans, but some animal existed that in which it did produce a cyst stage, and this animal was responsible for spreading it. However, no such animal has ever been discovered. A later theory suggested the organism was transmitted by pinworms, which provided protection for the parasite outside of the host. Experimental ingestion of pinworm eggs established infection in two investigators. Numerous studies reported high rates of co-infection with helminths http://books.google.com/books?id=fMqLmPrsAQEC&pg=PT155&lpg=PT155&dq=d+fragilis%2Bnon+pathogenic&source=bl&ots=b2Xxnpg8HB&sig=sSaZrkdPxze2wu9iDSplZbT-21c&hl=en&ei=iF1gS4_9A9CGkAXlzMXuCw&sa=X&oi=book_result&ct=result&resnum=5&ved=0CCwQ6AEwBA#v=onepage&q=d%20fragilis%2Bnon%20pathogenic&f=false However recent study has failed to show any association between Dientamoeba fragilis
infection and pinworm infection. Parasites similar to Dientamoeba fragilis
are transmitted by consuming water or food contaminated with feces. The high rate (40%) of concomitant infection with other protazoa reported by at St. Vincent's Hospital, Sydney, Australia. supports the oral fecal route of transmission.
.
A minimum of three specimens (stool) should be submitted having been immediately fixed in polyvinyl alcohol fixative, sodium acetate-acetic acid-formalin fixative, or Schaudinn's fixative as the protozoan does not remain morphologically identifiable for long. Further, all specimens, regardless of consistency, should be permanently stained prior to microscopic examination with an oil immersion lens. The disease may remain cryptic due to the lack of a cyst stage if these recommendations are not followed. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1580247/ Dientamoeba fragilis detection methods and prevalence: a survey of state public health laboratories.
J H Grendon, R F Digiacomo, and F J Frost
Office of Toxic Substances, Washington State Department of Health, Olympia 98504.
The trophozoite forms have been recovered from formed stool, thus the need to perform the ova and parasite examination on specimens other than liquid or soft stools.
DNA Fragment Analysis provides excellent sensitivity and specificity when compared to microscopy for the detection of D. fragilis and both methods should be employed in laboratories with PCR capability.
The most sensitive detection method is parasite culture, and the culture media require the addition of rice starch.
An indirect fluorescent- antibody (IFA) for fixed stool specimens has been developed.
infection should also be excluded although the association has not been proven.
Successful treatment of the infection with Iodoquinol, Doxycycline
, Metronidazole
, Paromomycin, and Secnidazole
have been reported. Resistance requires the use of combination therapy to eradicate the organism.
All persons living in the same residence should be screened for D. fragilis as asymptomatic carriers may provide a source of repeated infection.
Paromomycin is an effective prophylactic for travellers who will encounter poor sanitation and unsafe drinking water.
Dientamoeba fragilis
Dientamoeba fragilis is a single celled parasite found in the gastrointestinal tract of some humans, pigs and gorillas. In some people it causes gastrointestinal upset while in others it does not...
. Dientamoeba fragilis
Dientamoeba fragilis
Dientamoeba fragilis is a single celled parasite found in the gastrointestinal tract of some humans, pigs and gorillas. In some people it causes gastrointestinal upset while in others it does not...
is a single celled parasite that infects the lower gastrointestinal tract of humans. It is an important cause of travelers diarrhea, chronic abdominal pain, chronic fatigue and failure to thrive in children.
History
Early microbiologists reported that the organism was not pathogenic, even though six of the seven individuals from whom they isolated it were experiencing symptoms of dysentery. Their report, published in 1918, concluded the organism was not pathogenic because it consumed bacteria in culture, but did not appear to engulf red blood cells as was seen in the most well known disease causing amoeba of the time, Entamoeba histolyticaEntamoeba histolytica
Entamoeba histolytica is an anaerobic parasitic protozoan, part of the genus Entamoeba. Predominantly infecting humans and other primates, E. histolytica is estimated to infect about 50 million people worldwide...
. This initial report may still be contributing to the reluctance of physicians to diagnose the infection.
Genetic diversity
As many individuals are asymptomatic carriers of D. fragilis it is proposed there exist a pathogenic and non-pathogenic variants.A study of Dientamoeba fragilis
Dientamoeba fragilis
Dientamoeba fragilis is a single celled parasite found in the gastrointestinal tract of some humans, pigs and gorillas. In some people it causes gastrointestinal upset while in others it does not...
isolates from 60 individuals with symptomatic infection in Sydney Australia found that all were infected with the same genotype. which differed from the North American genotype.
Epidemiology
It increases in conditions of crowding and poor sanitation. Rates of infection in military personnel and mental institutions is higher.The true extent of disease has yet to emerge as most laboratories do not use techniques to adequately identify this organism. An Australian study identified a large number of patients considered to have Irritable bowel syndrome
Irritable bowel syndrome
Irritable bowel syndrome is a diagnosis of exclusion. It is a functional bowel disorder characterized by chronic abdominal pain, discomfort, bloating, and alteration of bowel habits in the absence of any detectable organic cause. In some cases, the symptoms are relieved by bowel movements...
who were actually infected with Dientamoeba fragilis
Dientamoeba fragilis
Dientamoeba fragilis is a single celled parasite found in the gastrointestinal tract of some humans, pigs and gorillas. In some people it causes gastrointestinal upset while in others it does not...
.
Although Dientamoeba fragilis
Dientamoeba fragilis
Dientamoeba fragilis is a single celled parasite found in the gastrointestinal tract of some humans, pigs and gorillas. In some people it causes gastrointestinal upset while in others it does not...
has been described as an infection that is "emerging from obscurity," it has become one of the most prevalent gastrointestinal infections in industrialized countries, especially among children and young adults. A Canadian study reported a prevalence of approximately 10% in boys and girls aged 11–15 years, a prevalence of 11.5% in individuals aged 16–20, and over 20 had a lower incidence of 0.3%-1.9%.
Symptoms
The most commonly reported symptoms in conjunction with infection with Dientamoeba fragilisDientamoeba fragilis
Dientamoeba fragilis is a single celled parasite found in the gastrointestinal tract of some humans, pigs and gorillas. In some people it causes gastrointestinal upset while in others it does not...
include abdominal pain (69%) and diarrhea (61%). Diarrhea may be intermittent and may not be present in all cases. It is often chronic - over two weeks in duration. The degree of symptoms may vary from asymptomatic to severe, and can include weight loss, vomiting, fever, and involvement of other digestive organs.
Researchers have reported that symptoms may be more severe in children. Additional symptoms reported have included:
- Weight loss
- Fatigue
- Nausea and vomiting
- Fever
- Urticaria (skin rash)
- Pruritis (itchiness)
- Biliary infection
Transmission
Organisms similar to Dientamoeba fragilisDientamoeba fragilis
Dientamoeba fragilis is a single celled parasite found in the gastrointestinal tract of some humans, pigs and gorillas. In some people it causes gastrointestinal upset while in others it does not...
are known to produce a cyst stage which is able to survive outside of the host and facilitate infection of new hosts. However, the exact manner in which Dientamoeba fragilis
Dientamoeba fragilis
Dientamoeba fragilis is a single celled parasite found in the gastrointestinal tract of some humans, pigs and gorillas. In some people it causes gastrointestinal upset while in others it does not...
is transmitted is not yet known, as scientists have reported that the organism is unable to survive outside its human host for more than a few hours after excretion, and no cyst stage has been found.
Early theories of transmission suggested that Dientamoeba fragilis
Dientamoeba fragilis
Dientamoeba fragilis is a single celled parasite found in the gastrointestinal tract of some humans, pigs and gorillas. In some people it causes gastrointestinal upset while in others it does not...
was unable to produce a cyst stage in infected humans, but some animal existed that in which it did produce a cyst stage, and this animal was responsible for spreading it. However, no such animal has ever been discovered. A later theory suggested the organism was transmitted by pinworms, which provided protection for the parasite outside of the host. Experimental ingestion of pinworm eggs established infection in two investigators. Numerous studies reported high rates of co-infection with helminths http://books.google.com/books?id=fMqLmPrsAQEC&pg=PT155&lpg=PT155&dq=d+fragilis%2Bnon+pathogenic&source=bl&ots=b2Xxnpg8HB&sig=sSaZrkdPxze2wu9iDSplZbT-21c&hl=en&ei=iF1gS4_9A9CGkAXlzMXuCw&sa=X&oi=book_result&ct=result&resnum=5&ved=0CCwQ6AEwBA#v=onepage&q=d%20fragilis%2Bnon%20pathogenic&f=false However recent study has failed to show any association between Dientamoeba fragilis
Dientamoeba fragilis
Dientamoeba fragilis is a single celled parasite found in the gastrointestinal tract of some humans, pigs and gorillas. In some people it causes gastrointestinal upset while in others it does not...
infection and pinworm infection. Parasites similar to Dientamoeba fragilis
Dientamoeba fragilis
Dientamoeba fragilis is a single celled parasite found in the gastrointestinal tract of some humans, pigs and gorillas. In some people it causes gastrointestinal upset while in others it does not...
are transmitted by consuming water or food contaminated with feces. The high rate (40%) of concomitant infection with other protazoa reported by at St. Vincent's Hospital, Sydney, Australia. supports the oral fecal route of transmission.
Diagnosis
Diagnosis is usually performed by submitting a stool sample for examination by a parasitologist in a procedure known as an Ova and Parasite (O&P) Examination. Approximately 30% of children with D. fragilis infection exhibit peripheral blood eosinophiliaEosinophilia
Eosinophilia is a condition in which the eosinophil count in the peripheral blood exceeds 0.45×109/L . A marked increase in non-blood tissue eosinophil count noticed upon histopathologic examination is diagnostic for tissue eosinophilia. Several causes are known, with the most common being...
.
A minimum of three specimens (stool) should be submitted having been immediately fixed in polyvinyl alcohol fixative, sodium acetate-acetic acid-formalin fixative, or Schaudinn's fixative as the protozoan does not remain morphologically identifiable for long. Further, all specimens, regardless of consistency, should be permanently stained prior to microscopic examination with an oil immersion lens. The disease may remain cryptic due to the lack of a cyst stage if these recommendations are not followed. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1580247/ Dientamoeba fragilis detection methods and prevalence: a survey of state public health laboratories.
J H Grendon, R F Digiacomo, and F J Frost
Office of Toxic Substances, Washington State Department of Health, Olympia 98504.
The trophozoite forms have been recovered from formed stool, thus the need to perform the ova and parasite examination on specimens other than liquid or soft stools.
DNA Fragment Analysis provides excellent sensitivity and specificity when compared to microscopy for the detection of D. fragilis and both methods should be employed in laboratories with PCR capability.
The most sensitive detection method is parasite culture, and the culture media require the addition of rice starch.
An indirect fluorescent- antibody (IFA) for fixed stool specimens has been developed.
- One researcher investigated the phenomenon of symptomatic relapse following treatment of infection with Dientamoeba fragilisDientamoeba fragilisDientamoeba fragilis is a single celled parasite found in the gastrointestinal tract of some humans, pigs and gorillas. In some people it causes gastrointestinal upset while in others it does not...
in association with its apparent disappearance from stool samples. The study found that the organism could still be detected in patients through colonoscopyColonoscopyColonoscopy is the endoscopic examination of the large bowel and the distal part of the small bowel with a CCD camera or a fiber optic camera on a flexible tube passed through the anus. It may provide a visual diagnosis and grants the opportunity for biopsy or removal of suspected...
or by examining stool samples taken in conjunction with a saline laxative. - A study found that trichrome staining, a traditional method for identification, had a sensitivity of 36% (9/25) when compared to stool culture.
- An additional study found that the sensitivity of staining was 50% (2/4), and that the organism could be successfully cultured in stool specimens up to 12-hours old which were kept at room temperature.
Treatment
Concomitant PinwormPinworm
The pinworm , also known as threadworm or seatworm, is a nematode and a common human intestinal parasite, especially in children...
infection should also be excluded although the association has not been proven.
Successful treatment of the infection with Iodoquinol, Doxycycline
Doxycycline
Doxycycline INN is a member of the tetracycline antibiotics group, and is commonly used to treat a variety of infections. Doxycycline is a semisynthetic tetracycline invented and clinically developed in the early 1960s by Pfizer Inc. and marketed under the brand name Vibramycin. Vibramycin...
, Metronidazole
Metronidazole
Metronidazole is a nitroimidazole antibiotic medication used particularly for anaerobic bacteria and protozoa. Metronidazole is an antibiotic, amebicide, and antiprotozoal....
, Paromomycin, and Secnidazole
Secnidazole
Secnidazole is a nitroimidazole anti-infective. Effectiveness in the treatment of dientamoebiasis has been reported. It has also been tested against Atopobium vaginae....
have been reported. Resistance requires the use of combination therapy to eradicate the organism.
All persons living in the same residence should be screened for D. fragilis as asymptomatic carriers may provide a source of repeated infection.
Paromomycin is an effective prophylactic for travellers who will encounter poor sanitation and unsafe drinking water.
External links
- http://emedicine.medscape.com/article/997239-treatment complete diagnostic workup and treatment protocols for adult and pediatric patients; David R Mack, MD, FRCPC, Professor, Departments of Pediatrics and Biochemistry, Microbiology, and Immunology, University of Ottawa Faculty of Medicine
- http://www.dpd.cdc.gov/dpdx/HTML/Dientamoeba.htm