[Amebiasis--a differential diagnosis from inflammatory bowel disease]

Entamoeba histolytica is a very uncommon etiology of travelers diarrhoea, but may be an important differential diagnosis to inflammatory bowel disease. A misdiagnosis of amoebic colitis as inflammatory bowel disease followed by inadvertent treatment with corticosteroids may be fatal. Current techniques for the diagnosis of amoebiasis include stool studies, endoscopic biopsy and serology. Demonstration of haematophagous trophozoites in feces or in tissue biopsy is the definitive method for diagnosis. Unfortunately both methods have many drawbacks. If the specimens are negative, serology can support the diagnosis especially in a non-endemic area where a positive test is highly predictive of current disease.

The bactericidal activity of blood platelets in patients infested with Entamoeba histolytica/Entamoeba dispar

Blood platelets participate actively in organism defensive reactions and particularity in antiparasitic immunity. Platelets stimulation can be the result of contact with a parasite, the presence of immunoglobulins, complement and lymphokines. The aim of the study was to evaluate the blood platelets bactericidal activity in the course of amoebiasis. The examination was carried out in the group of 22 patients with E. histolytica/E. dispar, diagnosed on the basis of cyst forms presence in faeces. The results show that blood platelets bactericidal activity is significantly impaired in the course of amoebiasis.

Secnidazole vs. paromomycin: comparative antiprotozoan treatment in captive primates

The antiprotozoan activity of secnidazole was studied in Cercocebus t. torquatus, Cercopithecus campbelli, Erythrocebus patas (Cercopithecidae), and Gorilla gorilla (Pongidae) compared with that of paromomycin in Cercocebus t. lunulatus (Cercopithecidae), E. patas, and G. gorilla (Pongidae) by coprological analysis. The antiprotozoan activity of both drugs depended on the parasite species and the host species. The drugs acted in a similar way on Entamoeba coli parasitising C. t. torquatus, and E. patas. This activity was different from that observed on I. buestchlii from the same host species. Nevertheless, E. coli parasitising cercopithecids and pongids responded to drugs differently.

Metronidazole relieves symptoms in irritable bowel syndrome: the confusion with so-called 'chronic amebiasis'

BACKGROUND

Metronidazole is often administered to patients with irritable bowel syndrome with an erroneous diagnosis of 'chronic amebiasis'.

AIMS

To assess how patients with irritable bowel syndrome respond to metronidazole in the absence of amebae in their stools.

METHODS

We randomly allocated 45 patients (35 men; aged 15-59 years) with irritable bowel syndrome to receive isapghul (10 g bid x 60 days), metronidazole (400 mg tid X 10 days, followed by placebo x 50 days), or placebo (1 capsule bid x 60 days). Symptoms were evaluated and scored on days 0, 15, 30, 45 and 60. Rectosigmoid manometry was performed in 5 of 15 patients in each group on days 0 and 60.

RESULTS

There was a significant time effect and treatment effect on the symptom scores in all groups (isapghul > metronidazole > placebo); total score decreased from mean 25.8, 24.0 and 24.6 on day 0 to 7.2, 10.9 and 18.1 on day 60, respectively. Severity, duration and frequency of pain; and mucus in stool were all significantly reduced in all treatment groups (p < 0.001 for each). Treatment with isapghul increased the mean amplitude of propagated activity from 26.2 mmHg to 30.1 mmHg at 20 cm (p < 0.025) and from 23.1 mmHg to 27.4 mmHg at 10 cm (p < 0.05) from the anal verge, as well as the total duration of propagated activity at both sites (p < 0.05), with decrease in number of propagated contractions per 10 min (p < 0.025). Metronidazole and placebo had no effect on manometric findings.

CONCLUSIONS

Metronidazole provides symptom relief in irritable bowel syndrome, without affecting rectosigmoid motility. This symptom response may be misinterpreted as supporting a diagnosis of 'chronic amebiasis'.

Waterborne protozoan pathogens

Protozoan parasites were the most frequently identified etiologic agents in waterborne disease outbreak from 1991 to 1994. The waterborne parasites Giardia lamblia, Naegleria fowleri, Acanthamoeba spp., Entamoeba histolytica, Cryptosporidium parvum, Cyclospora cayetanesis, Isospora belli, and the microsporidia are reviewed. For each parasite, the review includes history, life cycle, incidence, symptoms, and therapy. Clinical detection methods are compared, and emerging technologies are discussed. Information on the association of these parasites with waterborne outbreaks is reviewed. Current information on protozoan parasites identified as etiological agents in waterborne outbreaks is discussed. Water industry issues related to recent disease outbreaks are examined in the context of water quality testing regulations for G. lamblia and those proposed for C. parvum. The review identifies the limitations of the American Society of Testing and Materials water-testing method for these parasites. An overview of federal regulations affecting the water industry and laboratories that test for water quality is also provided. The article highlights the importance of the clinical laboratory as a frontline defense for the detection of infectious organisms. The review points to the need for clinical laboratories, physicians, and public health personnel to cooperatively plan and assess the challenge of meeting this potential public health threat.

Protozoa. Amebiasis

The intestinal protozoan parasite Entamoeba histolytica causes amebic dysentery and amebic liver abscess, and ranks third worldwide among parasitic causes of death. The application of molecular techniques to the study of this organism have led to major advances in understanding the pathophysiology of amebic infection. This article reviews what is currently known about the pathogenesis, clinical manifestations, diagnosis, and treatment of amebiasis.

Does anti-parasitic treatment normalize platelets morphology in patients infested with Entamoeba histolytica?

Platelets are part of body defence system, especially the anti-parasite immunologic response. Platelets manifest their functions only after their activation. Thrombine activates platelets inducing change of their shape and causing secretion of certain substances. This study was designed to estimate platelet morphology as an indicator of their activation and effectiveness of anti-parasite therapy. The study was conducted in group of 30 patients infested with E. histolytica before treatment (A) and group of 23 patients after 2-week treatment course (B). The diagnosis of amoebiasis was based on detection of cyst forms in faeces. During the course of amoebiasis increase of platelets count and platelet crit (PCT) was observed. Mean platelet volume (MPV) in both groups (A and B) was decreased as compared with control group. We suggest that E. histolytica activates platelets, and the degree of their activation determines their morphologic parameters, and these changes come back to normal values during anti-parasite treatment.

Transmission of Entamoeba histolytica within a family complex

A limited outbreak of symptomatic intestinal and extraintestinal amoebiasis within a family complex is described. The infection was almost certainly transmitted by a Philippino housemaid, who was an asymptomatic carrier of Entamoeba histolytica infection acquired in her native country. Starch-gel electrophoresis showed isoenzyme patterns characteristic of pathogenic zymodeme XIX in all the amoebic isolates.

A comparative study of experimental caecal amoebiasis and the evaluation of amoebicides

Caecal amoebiasis models (mouse, hamster and rat) were compared for amoebic infection and chemotherapeutic evaluation using a pathogenic strain of Entamoeba histolytica of human origin. Caecal infection in the hamster was of the acute type, with a large number of amoebae in the caecal tissue, whereas the amoebae in rats were seen in the lumen, on the mucosal surface. Amoebic lesions in the mouse caecum were of moderate severity. The mouse model responded to both metronidazole (tissue amoebicide) and diloxanide furoate (luminal amoebicide), whereas the hamster model only responded well to metronidazole and the rat model only to diloxanide furoate. Using the mouse as a primary screening model, a new oxadiazole compound, BTI 2405E, was found to have tissue and luminal amoebicidal activity. In rodent caecal models, a single dose of BTI 2405E was found to be more effective than one of metronidazole or diloxanide furoate. The mouse model appears to be the most useful for primary screening of anti-amoebic compounds.

The antiamoebic effect of a crude drug formulation of herbal extracts against Entamoeba histolytica in vitro and in vivo

The antiamoebic effect of a crude drug formulation against Entamoeba histolytica was studied. In the traditional system of medicine in India, the formulation has been prescribed for intestinal disorders. It comprises of five medicinal herbs, namely, Boerhavia diffusa, Berberis aristata, Tinospora cordifolia, Terminalia chebula and Zingiber officinale. The dried and pulverized plants were extracted in ethanol together and individually. In vitro amoebicidal activity was studied to determine the minimal inhibitory concentration (MIC) values of all the constituent extracts as well as the whole formulation. The formulation had a MIC of 1000 micrograms/ml as compared with 10 micrograms/ml for metronidazole. In experimental caecal amoebiasis in rats the formulation had a curative rate of 89% with the average degree of infection (ADI) reduced to 0.4 in a group dosed with 500 mg/kg per day as compared with ADI of 3.8 for the sham-treated control group of rats. Metronidazole had a cure rate of 89% (ADI = 0.4) at a dose of 100 mg/kg per day and cured the infection completely (ADI = 0) when the dosage was doubled to 200 mg/kg per day. There were varying degrees of inhibition of the following enzyme activities of crude extracts of axenically cultured amoebae: DNase, RNase, aldolase, alkaline phosphatase, acid phosphatase, alpha-amylase and protease.

Frequency of Entamoeba gingivalis among periodontal and patients under chemotherapy

This study was carried out to investigate the frequency of E. gingivalis in the gingival crevices of patients with periodontitis compared to normal subjects. Flagyl therapy was tried in cases with periodontitis. Also the frequency of this amoeba was investigated in patients receiving chemotherapy to be compared to normal subjects. The results revealed that higher frequency was observed in patients with periodontitis and flagyl therapy reduced this frequency. Cases under chemotherapy showed higher frequency than the normal control. Histopathological sections from the gingiva of periodontitis patients did not show any amoeba invading the tissue.

[Gnathostomiasis after a stay in Thailand]

During a 4-week holiday in Thailand a 13-year-old boy from Germany briefly fell ill with diarrhoea without blood-tinged stools and fever. 5 months later oedematous, reddish swellings occurred, at first on the right upper arm, later over the right side of the chest. Especially at night these swellings were associated with severe local and generalized itching. Bilaterally the axillary lymph-nodes were hard and slightly enlarged. There was a marked eosinophilia of 56%, the white count was 22,700/microliters and the serum level of IgE was raised to 1777 IU/ml. No worm eggs or larvae were found in the stool. Enzyme-linked immunosorbent assay, using larvae of Gnathostoma spinigerum as antigen, demonstrated antibodies against this nematode. Gnathostomiasis having been diagnosed treatment was started with albendazole (200 mg twice daily for 21 days), after which the boy was symptom free. After 2 months the eosinophilia had regressed to 10%, the white cell count was normal and the antibody titre had fallen.

Monoclonal antibody-based immunohistochemical demonstration of Entamoeba histolytica in liver tissues of experimentally infected hamster (Mesocricetus auratus)

Histopathological changes and the presence of Entamoeba histolytica trophozoites was sequentially followed after intrahepatic inoculation of the parasites in 42 hamsters, 35 of which received no treatment whereas the remaining seven were treated with metronidazole. The liver tissues were examined for amoebic trophozoites by a monoclonal antibody (mAb)-based immunofluorescence assay (IFA), a mAb-based immunoperoxidase (IPx) and H & E staining. The number of hamsters developing abscesses was increased with time and was highest on day 30. Cellular infiltration with inflammatory cells and glycogen depletion were observed as early as day 5, followed thereafter by more intense inflammation of portal canals, periportal fibrosis, bile duct proliferation and hepatocyte degeneration. In 7 metronidazole-treated hamsters, no obvious pathological damage was seen. In a group of seven hamsters each, both IPx and IFA were positive in 3, 3, 4, 5 and 4 hamsters and in 3, 4, 3, 3 and 5 hamsters on days 5, 10, 15, 20 and 30, respectively. In 18 control hamsters, IPx, IFA and H & E were all negative. If the result from H & E was used as a gold standard, agreement between H & E and IFA and H & E and IPx were 91.4%, and 88.6%, respectively. Sensitivity and specificity were 93.8% and 89.5%, respectively for IFA, and 93.8% and 84.2%, respectively for IPx.

Control of an amoebiasis outbreak in the Philippi area near Cape Town

Previous studies in Durban have shown that serological investigations, in combination with iso-enzyme electrophoresis, are invaluable for monitoring the endemicity of pathogenic strains of Entamoeba histolytica. We therefore proposed that antibody profiles could be used to detect epidemic situations. An outbreak of amoebiasis in the normally non-endemic Philippi area near Cape Town provided an opportunity for testing this hypothesis. Seven of 9 patients presenting at a district hospital with invasive amoebiasis originated from a single farm in Philippi. Iso-enzyme electrophoresis and serological investigations were used to monitor the endemicity of amoebiasis on 16 of the 49 farms in this district. In an attempt to contain disease transmission all inhabitants on farms from which patients came (including those where cyst-passers were identified) and all seropositive subjects were treated. The antibody profiles proved invaluable for confirming that the farm from which the hospitalised patients originated was the central focus of the outbreak, and also identified subjects infected with pathogenic zymodemes of E. histolytica on the adjacent 4 farms. On all 5 of these farms, 62.5-100% of seropositive subjects were strongly positive. In contrast weak to negative serological responses occurred on the remaining 11 farms. In addition the success of treatment was indicated by a notable drop in strong seropositive responses on the affected 5 farms to 11.5% within 9 months. The infection pathways implied that the pathogenic strain of E. histolytica was introduced into this non-endemic area by a foreigner from an endemic area; this suggests that the pathogenicity of E. histolytica is an immutable stable feature.

Cutaneous amebiasis in children

A 7-month-old girl developed cutaneous amebiasis of the perianal and genital areas in association with amebic dysentery. The diagnosis was based on the identification of Entamoeba histolytica by skin biopsy. She was treated with dehydroemetine and metronidazole with excellent results. This is only the eighth reported case of this disease in a child.

Amebiasis and "nonpathogenic" intestinal protozoa

Infection with single or multiple species of intestinal protozoa is common in humans and can result in either asymptomatic colonization or symptoms of intestinal disease. Entamoeba histolytica serves as a paradigm for invasive colonic protozoal infection. The key to diagnosis and treatment of amebiasis is knowledge of the epidemiologic risk factors and clinical manifestations, a rational approach to diagnosis, and an understanding of the sites of action and uses of anti-amebic drugs. This knowledge of treatment provides a context for consideration of intestinal infection with less common protozoan pathogens such as Dientamoeba fragilis and Balantidium coli and 'nonpathogenic' protozoa such as Blastocystis hominis and Entamoeba coli.

Concurrent parasitic infections in onchocerciasis and the occurrence of adverse reactions after ivermectin treatment

Ivermectin is a safe, effective, and relatively well-tolerated drug for the treatment of human onchocerciasis. However, due to side effects of the drug, large-scale ivermectin distribution without medical supervision is not recommended. The mechanisms involved in the pathogenesis of ivermectin-induced adverse reactions are not yet known. Since onchocerciasis patients are likely to have concurrent parasitic infections, we investigated whether side effects that occur after ivermectin treatment could be related to the presence of parasite eggs and cysts in stool samples prior to treatment. One hundred twenty-nine onchocerciasis patients were treated with a single dose of ivermectin (150 micrograms/kg) and side effects were graded according to the classification of Greene and others. Stool samples were collected before and three days after treatment. A high percentage (80.5%) of the patients reported adverse effects (57% mild, 14.1% moderate, and 9.4% severe reactions). Most (95.1%) of the patients had one or more concurrent parasitic infections. No relationship could be found between the occurrence and extent of side effects and the severity of concurrent intestinal parasitic infections. However, side effects were significantly correlated with pretreatment microfilarial counts. Ivermectin treatment did not induce significant short-term changes in Trichuris trichiura or Schistosoma mansoni egg counts. However, a significant reduction in Ascaris lumbricoides egg counts and Entamoeba coli cyst loads was observed; a cure rate of 46% for cysts was reached. In contrast, hookworm egg production increased after ivermectin treatment. Further studies are required to verify ivermectin-induced changes in cyst and hookworm loads as well as the significance of these findings.

[Amebic brain abscess. Apropos of a case]

We report a case of double primary amoebic brain abscess in a 22 year old man, with signs of intracranial hypertension and deficit. Computed tomography found two hypodense lesions, not suggestive of pyogenic abscesses. Aspiration of one of the two abscesses, revealed the organism, and the two abscesses regressed in response to medical treatment. The authors insist on the rarity of these abscesses, their gravity, and the difficulty of the diagnosis.