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Diarrhoea in a Returning Traveller


McGoran J, Ferguson C, Bhat S

Departments / Institutions

Altnagelvin Hospital

Publication Date

Spring 2014


Amoebic colitis is an uncommon condition in the UK which usually presents with diarrhoea, with or without bleeding. Severity can range from mild diarrhoea to amoebic dysentery requiring hospitalisation. Treatments are however much different so it is important to make a correct diagnosis early in the course of the illness. The adverse effects of steroids and disease modifying agents for Crohn’s disease are such that making this diagnosis rather than amoebic colitis potentially carries significant harm. In addition, given the potential infectivity of carriers of Entamoeba Histolytica cysts it is of interest to diagnose and treat this early.

A 43 year old woman presented to the gastroenterology clinic with resurgent complaints of unremitting diarrhoea, without features of PR bleeding or abdominal pain. At that time she had a three year history of diagnosed Crohn’s disease affecting the colon. Her original presenting symptoms were of profuse diarrhoea which had been refractory to antimotility agents. She was in Thailand and had been there for some months during the onset of these complaints. Her condition was diagnosed on return to Northern Ireland, where she attended a clinic and proceeded to colonoscopy. This revealed skip ulceration throughout the colon. Histological analysis of biopsies indicated variable degrees of inflammation with focal cryptitis and crypt abscess formation with the absence of goblet cell depletion. The inflammatory infiltrate appeared to extend deep into the muscularis mucosa. There was no evidence of dysplasia or malignancy and a diagnosis of Crohn’s disease was suggested. As a result of this diagnosis, the patient was commenced on mesalazine 2grams twice daily. She experienced rapid resolution of her symptoms thereafter and did not require steroid therapy. Nine months after the initial diagnosis the patient elected to cease 5-aminosalicylic acid therapy and remained completely page 17 symptom free for 18 months. She then experienced recurrence of diarrhoea without cramps or rectal bleeding and given the atypical nature of the history of these complaints a colonoscopy was arranged to reassess her disease. This demonstrated ulceration confined to the caecum, in keeping with localised Crohn’s disease (Figure 1/Figure 2). Biopsies were taken from the caecum and sent for analysis. This revealed an aggregate of rounded bodies, some containing red blood cells, which stained with Periodic Acid Schiff (Figure 3), giemsa and trichrome. This challenged the presumed diagnosis of Crohn’s disease and stated that the findings were very suggestive of amoebiasis. In response to this finding, we arranged for stool analysis which demonstrated Entamoeba Histolytica cysts in concentrated samples. Serological tests (antibody detection) confirmed recent amoebic infestation with systemic involvement. Once the diagnosis of amoebic colitis had been established the patient was commenced on appropriate treatment and on follow up she had reported a complete resolution of her symptoms.


Amoebiasis (Entamoeba Histolytica) is a parasitic infection that is endemic in many areas of the developing world, including rural Thailand where our patient spent time. It is the second leading cause of death from parasitic disease worldwide after malaria.1 Transmission is via the faecal-oral route with ingestion of cysts and as such the majority of cases arise from food or water contamination. Most patients are asymptomatic but remain carriers. As such it is a matter of public health concern to prevent this in travellers through sound advice and to promptly diagnose the condition in those returning from endemic areas. Invasion of the intestinal lining leads to amoebic dysentery or amoebic colitis. Formation of lytic lesions in the colon and immune modulation by the parasite are the means by which this takes hold.2 Worldwide incidence of amoebiasis has been reported at 50 million cases per year and incidence of acute amoebic diarrhoea in travellers returning from South-East Asia is estimated at 1.5%.3 Cases of amoebic colitis are much less common. Diagnosis is usually made by stool microscopy, with serological tests a useful means of detecting extra-intestinal disease. Positive serological markers are raised in cases of amoebic liver abscess. Recommended treatment is with a nitroimidazole derivative, followed by a luminal agent e.g. paromomycin, to eradicate colonisation. Tinidazole has been shown to result in less clinical failure than metronidazole, which remains the most commonly used drug. Such trials testing this have however had poor methodological quality and it is recommended that further studies be undertaken to determine optimal treatment regimens.4 Asymptomatic patients with positive findings should not generally receive pharmacological treatment, according to WHO guidelines.3 Adherence to these guidelines may differ between countries and regions, reflective of a difference in overall prevalence.


We strongly recommend the inclusion of a detailed travel history for all patients who present with altered bowel habit. If a travel history suggests exposure to areas of high prevalence for infective gastroenterological disease, investigations such as stool analysis and serology can be tailored to the presumptive diagnosis before proceeding to invasive tests. It is also important for matters of public and environmental health to make sure that those in close proximity to patients are not suffering from similar symptoms and that any particular source is identified if possible.


1. Stanley Jr, Samuel L. Amoebiasis. Lancet, 3/22/2003, Vol. 361 Issue 9362, p1025 2. Espinosa-Cantellano, M. Martinez-Palomo, A. Pathogenesis of intestinal amebiasis: from molecules to disease. [Review] Clinical Microbiology Reviews. 13(2):318-31, 2000 Apr. 3. World Health Organization. Amoebiasis. Weekly Epidemiological Record. 1997; 72: 97-99. 4. Gonzales, Maria Liza M. Dans, Leonila F. Martinez, Elizabeth G. Antiamoebic drugs for treating amoebic colitis. [Review] Cochrane Database of Systematic Reviews. (2):CD006085, 2009.

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