Prevalence and incidence of Entamoeba histolytica infection in South Africa and Egypt

Gastrointestinal parasites in Africa: A review

Data on human gastrointestinal parasites (GIP) infections in the african sub-regions and countries are mainly lacking in terms of prevalence and population stratification by afflicted age group, symptomatology, multi-parasitism, and diagnostic methods. This study aims to describe the GIP reported in african countries and discuss the extent of the burden in the african context. Only 68.42% (39/57) of african countries reported human cases of GIP with helminths (45%, CI: 40-50%, I²: 99.79%) as the predominant parasitic group infecting the african population. On a regional scale, Central Africa had the highest pooled prevalence for GIP (43%, CI: 32-54%, I²: 99.74%), while the Central African Republic led all countries with a pooled prevalence of 90% (CI: 89-92%, I²: 99.96%). The vulnerable population (patients who are minorities, children, old, poor, underfunded, or have particular medical conditions) was the most affected (50%, CI: 37-62%, I²: 99.33%), with the predominance of GIP in the 6 to <20 years age group (48%, CI: 43-54%, I²: 99.68%). Reports on multi-parasitism (44%, CI: 40-48%, I²: 99.73%) were almost double the reports of single infections (43%, CI: 27-59%, I²: 99.77%) with combined molecular and non-molecular techniques demonstrating the best performance for GIP identification. The current review spans more than 40 years of GIP reports from the african continent. Geographical characteristics, environmental factors, habits of its inhabitants, and their health status play a crucial role in GIP modulation and behaviour in its captive hosts. Strategies for regular and enhanced surveillance, policy formation, and high-level community awareness are necessary to identify the true incidence in Africa and the transmission of the pathogens via water and food.

Updates on the worldwide burden of amoebiasis: A case series and literature review

BACKGROUND

Amoebiasis is an intestinal and tissue parasitic infection caused by the protozoan Entamoeba histolytica. Despite significant medical importance and worldwide dispersion, little is known about the epidemiology and distinct geographical distribution of various clinical forms of amoebiasis in the world. In this study, we present an amoebiasis case series referred to Avicenne Hospital (Bobigny, France) from 2010 to 2022 followed by an overview of the released literature to explore diverse clinico-pathology of amoebiasis and to update the actual epidemiological situation of this parasitosis worldwide.

METHODS

The referred patients underwent a combination of clinical and parasitological examinations and imaging. The study was followed by an overview of released literature performed based on PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guideline.

RESULTS

A total of 15 patients with amoebiasis were diagnosed with an average age of 48.5 years old at the occurrence time of infection. Men (78%) were the most affected patients. Most of the cases were reported following a trip to endemic regions, such as Mali, India, Nepal, Algeria, Cameroon or Congo. All of the processed patients exhibited a hepatic amoebiasis. Amoebic abscess was observed in all cases with an average size of 6.3 cm. Of these patients, seven cases (46.7%) benefited from drainage following a risk of rupture or superinfection of the abscess. A compilation of findings extracted from 390 scientific publications via seven major medical databases, allowed us to update the main epidemiological and clinical events that has led to the current worldwide expansion of amoebiasis. We presented a clinical and epidemiological overview of the amoebiasis accompanied with a worldwide illustrative map displaying the current distribution of known amoebiasis foci in each geographical ecozone of Asia, Europe, Africa, Americas, and Australia.

CONCLUSIONS

Although Metropolitan France is not known as an endemic region of amoebiasis, amoebic liver abscess was the most frequent clinical form observed among our 15 patients processed. Most of infected patients had a history of travel to or lived-in endemic areas before arriving in France.

Development of diffractive optics technology-based immunoassay protocol and its application in the detection of Entamoeba histolytica infections

Amebiasis due to infection with Entamoeba histolytica is a problematic parasitic disease in many countries. By means of a novel technology developed by Axela Biosensors, Inc., the dotLab™ system, a rapid immunoassay was developed to detect at least 5.45 cells/mL of E. histolytica, the causative agent of amebiasis, in spiked stool samples in 66 min. Regeneration of the dotLab™ sensor using 0.1 M glycine (pH 2.5) solution was established, enabling the assessment of multiple stool samples (up to 8 X) using a single sensor. This developed assay was applied to assess the health status of a community in relation to E. histolytica infections of relocated families in San Isidro, Rodriguez, Rizal, Philippines. The community was found to be 15.6% and 26.1% positive for E. histolytica using real-time polymerase chain reaction (real-time PCR) and dotLab™ methods, respectively. Compared to real-time PCR, the dotLab™ method is 94.74% sensitive and 74.79% specific. The agreement of the two methods was tested using Kappa coefficient test and it showed that dotLab™ is a reliable alternative to real-time PCR. The optimized dotLab™ assay did not cross-react with stool samples containing Escherichia coli, Blastocystis sp., Cryptosporidium sp. and Giardia intestinalis. The community had 17 X to 24 X higher infection rate than previous reports in the Philippines. Sex, age, and duration of settlement in the relocation area were not related to the rate of infection. This increase may be due to improper hygiene and sanitation in the community.

Decreasing trend of seroprevalence of hepatic amoebiasis in tertiary care hospital of North India: 2010-2015

BACKGROUND:

Globally, amoebic liver abscess, a common extraintestinal complication of intestinal amoebiasis. Diagnosis of hepatic amoebiasis is based on the detection of anti-Entamoeba histolytica immunoglobulin G (IgG) antibody using enzyme-linked immunosorbent assay (ELISA), because of its technique's relatively higher sensitivity and specificity (90%).

AIM:

The aim of the present study was to determine the seroprevalence of hepatic amoebiasis in a referral tertiary care hospital in North India.

MATERIALS AND METHODS:

The blood samples were tested specifically for anti-E. histolytica IgG antibody using commercially available ELISA kit (RIDASCREEN^®E. histolytica IgG [K1721] kit).

RESULTS:

A total of 879 patients (n = 879) were evaluated, of which 78.49% (690/879) were positive for anti-E. histolytica IgG antibody. The seroprevalence rates showed a declining trend from 2010 to 2015 with rates falling from 91.4% to 66.7%. He present a study showed the decreasing trend of seroprevalence of hepatic amoebiasis from 2010 to 2015.

CONCLUSIONS:

This decrease may be attributed to several factors such as increase in awareness, improved hygienic practices, use of safe drinking water, better socioeconomic condition, and perhaps early treatment sought for intestinal amoebiasis.

Epidemiological Prevalence of Entamoeba histolytica Infections Among the Patients Attending Nyanza District Hospital, Rwanda in 2018

Background and aims: Entamoeba histolytica is an intestinal parasite and a causative agent of amoebiasis which is a common life-threatening parasitic disease. This study was intended to determine the prevalence of E. histolytica and to provide the primary data about its infections among the patients attending Nyanza District Hospital in Rwanda. Methods: Bottles were used to collect 138 stool specimens from patients. All the samples were physically analyzed based on their colors, states, and the presence of blood or mucus. The wet preparation method and zinc sulphate floatation technique were used to concentrate the parasites. Microscopic analysis was done to examine the presence of cysts and trophozoites. Data were statistically analyzed by SPSS using chi-square test and independent t test. Results: The prevalence of E. histolytica was 15.94%. The sex distribution of infections revealed that males (21.54%) were more infected than females (10.95%). The highest prevalence of E. histolytica was found in the age group of 1-19 years old (27.11%) and the lowest prevalence was observed in the age group of 20-39 years old (6.89%). A prevalence of 33.33% was reported among the people who directly drink tap water and 40% of infections among the patients who did not wash their hands before eating and after using latrines. Conclusion: Overall, E. histolytica is still considered as a health burden in Nyanza District Hospital. Therefore, it is vital to control direct exposure to its risk factors for mitigating the occurrence of amoebiasis.

Successful Diagnosis of a Longstanding Giant Amoebic Liver Abscess Using Contrast-Enhanced Ultrasonography (CEUS): A Case Report in a Western Country

BACKGROUND E. histolytica liver abscess results from extra-intestinal diffusion of amebiasis, which is responsible for up 100 000 deaths per annum, placing it second only to malaria in mortality. Currently, the criterion standard for the diagnosis of liver abscesses is ultrasound, but CEUS (contrast-enhanced ultrasound) is emerging as a more accurate method for liver study, and it could be more accurate than ultrasound and non-invasive compared to CT. CASE REPORT A white man (59 years old) with a 2-day history of dyspnea, acute abdominal pain in right upper quadrant, and raised inflammatory markers was admitted to a second-level Emergency Department in Rome (Italy). He reported several trips to tropical areas many years before, during which he ingested non-potable water and became infected with Entamoeba histolytica. This was treated medically with success. After administration of antibiotics (meropenem and metronidazole), a liver CEUS (contrast-enhanced ultrasonography) with administration of SonoVue (sulphur hexafluoride microbubbles) confirmed a giant liver abscess (15×16 cm). One day later, CT-guided drainage was performed without complications and the patient was discharged on the 25th post-procedure day, with improved blood results. CONCLUSIONS Acute abdominal pain can be caused by a variety of diseases, but a diagnosis of parasitic abscess should not be overlooked in non-endemic Western countries. CEUS is a new, promising, and more accurate technique that can be utilized to recognize liver abnormalities, including abscesses; however, retrospective population-wide studies are necessary to define the differential diagnoses.

Use of shotgun metagenomics for the identification of protozoa in the gut microbiota of healthy individuals from worldwide populations with various industrialization levels

Protozoa have long been considered undesirable residents of the human gut, but recent findings suggest that some of them may positively affect the gut ecosystem. To better understand the role and ecological dynamics of these commensal and potentially beneficial protozoan symbionts, we need efficient methods to detect them, as well as accurate estimates of their prevalence across human populations. Metagenomics provides such an opportunity, allowing simultaneous detection of multiple symbionts in a single analytical procedure. In this study, we collected fecal samples of 68 individuals from three Cameroonian populations with different subsistence modes and compared metagenomics-based and targeted methods of detection for two common protozoan genera: Blastocystis and Entamoeba. In addition, we analyzed our data along with publicly available fecal metagenomes from various worldwide populations to explore the prevalence and association patterns of ten protozoan genera. Regarding the detection method, microscopy was much less sensitive than metagenomics for Entamoeba, whereas qPCR was at least as sensitive as metagenomics for Blastocystis sp. However, metagenomics was more likely to detect co-colonizations by multiple subtypes. Out of the ten examined genera in 127 individuals from Cameroon, Tanzania, Peru, Italy or USA, only three (Blastocystis, Entamoeba and Enteromonas) had an overall prevalence exceeding 10%. All three genera were more common in less industrialized populations and their prevalence differed between continents and subsistence modes, albeit not in a straightforward manner. The majority (72.5%) of colonized individuals carried at least two protozoan species, indicating that mixed-species colonizations are common. In addition, we detected only positive and no negative association patterns between different protozoa. Despite the pitfalls of the metagenomic approach, ranging from the availability of good-quality sequencing data to the lack of standard analytical procedures, we demonstrated its utility in simultaneous detection of multiple protozoan genera, and especially its ability to efficiently detect mixed-species colonizations. Our study corroborates and expands prevalence results previously obtained for Blastocystis sp. and provides novel data for Entamoeba spp. and several other protozoan genera. Furthermore, it indicates that multiple protozoa are common residents of the healthy human gut worldwide.

Clinical and microscopic predictors of Entamoeba histolytica intestinal infection in travelers and migrants diagnosed with Entamoeba histolytica/dispar infection

Background

Amebiasis is a protozoal infection caused by Entamoeba histolytica, while the morphologically indistinguishable E. dispar is considered as non-pathogenic. Polymerase chain reaction (PCR) assays are necessary to differentiate both species. The most common clinical presentations of E. histolytica disease are amebic colitis and amebic liver abscess, but asymptomatic infection is also possible. We assessed the frequency and pattern of clinical symptoms and microscopic features in travelers/migrants associated with E. histolytica intestinal infection and compared them to those found in individuals with E. dispar infection.

Methods

We conducted a retrospective study at the travel clinic of the Institute of Tropical Medicine, Antwerp, Belgium on travelers/migrants found from 2006 to 2016 positive for Entamoeba histolytica/dispar through antigen detection and/or through microscopy confirmed by PCR. All files of individuals with a positive PCR for E. histolytica (= cases) and a random selection of an equal number of Entamoeba dispar carriers (= controls) were reviewed. We calculated the sensitivity, specificity and likelihood ratios (LRs) of clinical symptoms (blood in stool, mucus in stool, watery diarrhea, abdominal cramps, fever or any of these 5 symptoms) and of microscopic features (presence of trophozoites in direct and in sodium acetate-acetic acid-formalin (SAF)-fixed stool smears) to discriminate between E. histolytica and E. dispar infection.

Results

Of all stool samples positive for Entamoeba histolytica/dispar for which PCR was performed (n = 810), 30 (3.7%) were true E. histolytica infections, of which 39% were asymptomatic. Sensitivity, specificity and positive LRs were 30%, 100% and 300 (p 0.007) for presence of blood in stool; 22%, 100% and 222 (p 0.03) for mucus in stool; 44%, 90% and 4.7 (p 0.009) for cramps and 14%, 97% and 4.8 (p = 0.02) for trophozoites in direct smears. For watery diarrhea, fever and for trophozoites in SAF fixated smears results were non-significant.

Conclusions

E. histolytica infection was demonstrated in a small proportion of travelers/migrants with evidence of Entamoeba histolytica/dispar infection. In this group, history of blood and mucus in stool and cramps had good to strong confirming power (LR+) for actual E. histolytica infection. Trophozoites were also predictive for true E. histolytica infection but in direct smears only.

In the present work, we found that E. histolytica intestinal infections are rarely diagnosed among travelers and migrants presenting in a national reference travel clinic in Europe. Microscopic finding of cysts or trophozoites and antigen testing cannot discriminate between Entamoeba histolytica/dispar infection, which leads to overdiagnosis of E. histolytica infections in low resource settings where PCR is not available. We found visualization of trophozoites under the microscope helpful in discriminating between E. histolytica and E. dispar infection in direct smears. Hematophagy is a very rare finding but in our experience was always associated with E. histolytica infection. In a context where only microscopy is available, a patient presenting with blood or mucus in stool or cramps should anyhow be treated as amoebiasis if Entamoeba histolytica/dispar cysts/trophozoites are found. Nevertheless it is worth noting that a sizeable proportion of E. histolytica cases were asymptomatic. Last, our study suggests that E. dispar might be pathogenic but symptoms in E. histolytica infected patients were clearly more often suggestive of intestinal tissue invasion.

When IBD is not IBD

Entamoeba histolytica colitis can mimic Crohn's disease. However, a fulminant infection can be life-threatening, especially after exposure to systemic steroids. We present a case of the patient who was initially diagnosed with ileocolonic Crohn's disease, but developed a hepatic E histolytica abscess while undergoing anti-TNF therapy. After revision of the initial diagnostic biopsies, the diagnosis was questioned and E histolytica was confirmed using PCR and histopathology. As intestinal amoebiasis is the most common form of amoebic infection, care should be taken in case of refractory IBD or at initial diagnosis in patients who travelled to endemic areas. We therefore discuss the epidemiology, clinical features, diagnostic tools and pathophysiology of E Histolytica in order to raise awareness among gastroenterologists treating patients with inflammatory bowel disease.

Detection and differentiation of Entamoeba histolytica and Entamoeba dispar in clinical samples through PCR-denaturing gradient gel electrophoresis

Amebiasis is one of the twenty major causes of disease in Mexico; however, the diagnosis is difficult due to limitations of conventional microscopy-based techniques. In this study, we analyzed stool samples using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) to differentiate between Entamoeba histolytica (pathogenic) and E. dispar (non-pathogenic). The target for the PCR amplification was a small region (228 bp) of the adh112 gene selected to increase the sensitivity of the test. The study involved 62 stool samples that were collected from individuals with complaints of gastrointestinal discomfort. Of the 62 samples, 10 (16.1%) were positive for E. histolytica while 52 (83.9%) were negative. No sample was positive for E. dispar. These results were validated by nested PCR-RFLP (restriction fragment length polymorphism) and suggest that PCR-DGGE is a promising tool to differentiate among Entamoeba infections, contributing to determine the specific treatment for patients infected with E. histolytica, and therefore, avoiding unnecessary treatment of patients infected with the non-pathogenic E. dispar.

Increases in Entamoeba histolytica Antibody-Positive Rates in Human Immunodeficiency Virus-Infected and Noninfected Patients in Japan: A 10-Year Hospital-Based Study of 3,514 Patients

Serological evidence of the epidemiological trends in Entamoeba histolytica infection is scarce, especially in nonendemic countries. We aimed to determine the antibody-positive rates over a 10-year period, and compare the trends between human immunodeficiency virus (HIV)–infected and –noninfected patients. We reviewed 3,514 patients who underwent antibody testing during the study periods, which were divided into five annual categories: 2004–2005, 2006–2007, 2008–2009, 2010–2011, and 2012–2013. Anti-E. histolytica antibody was assessed by indirect immunofluorescence assay. The antibody-positive rate increased yearly from 2004–2005 to 2012–2013 (P < 0.001), although there was no increase in the annual number of antibody tests. This trend was seen among males (18.6–28.3%; P < 0.01), females (5.4–28.2%; P < 0.01), HIV-infected patients (18.4–26.9%; P < 0.001), and non-HIV-infected patients (14.6–36.8%; P < 0.001), and HIV-infected men who have sex with men (19.4–29.1%; P < 0.001). Among antibody-positive patients, there was a significant increase in the proportion of patients with high (≥ 1,600) titers (0.7–12.9%; P < 0.001), whereas this trend was not seen in patients with low (100) or intermediate (200–800) titers (P = 0.282 and 0.409, respectively). This large hospital-based study demonstrated that positive anti-E. histolytica antibody rates increased over 10 years, even though the annual number of antibody tests remained constant. Moreover, this trend was identified in non-high-risk patients (females and non-HIV-infected patients) as well as in high-risk patients. The proportion of patients with high antibody titers significantly increased among the antibody-positive patients.

Risk Factors Associated with Parasitic Infection Among Municipality Solid-Waste Workers in an Egyptian Community

Solid-waste management is associated with several health hazards, particularly parasitic infection. The objective of the study was to determine the association between risk factors and the occurrence of intestinal parasitic infections (potentially pathogenic) among municipal waste collectors in Alexandria, Egypt. A cross-sectional survey was conducted in the main municipality company in Alexandria. A total of 346 municipality solid-waste workers (MSWWs) was interviewed using an in-depth questionnaire. The type of parasitic infections among waste handlers was determined using formol-ether concentration and modified Ziehl-Neelsen technique. About half of the workers were infected with parasites. The profile of parasitic infection revealed 12 parasitic species. These were comprised of the following helminths: Schistosoma mansoni (13.3%), Enterobius vermicularis (1.7%), Ascaris lumbricoides (1.4%), and Hymenolepis nana ova (0.6%). Among protozoa were pathogenic Entamoeba histolytica (3.2%), Giardia intestinalis (2.9%), nonpathogenic protozoa such as Entamoeba coli (1.7%), and potentially pathogenic or opportunistic ones as Cryptosporidium (23.4%), Microsporidia (20.25%), Cyclospora (2.0%), Blastocystis hominis (1.7%), and Cystoisospora belli (1.2%). About 1.4% of MSWWs have pediculosis and phthiriasis in their scalp and eyelashes respectively. Risk factors for infection were associated with direct exposure to solid fecal waste (odds ratio [OR] = 1.8, confidence interval [CI] = 1.1-3.0) and occupational activities that allowed for direct exposure to solid fecal waste (OR = 2.3, CI = 1.4-4.0). Logistic regression model has revealed that educational level and residence were the factors that contribute to parasitic infection among MSWWs (P < 0.05). MSWWs are at high risk of acquiring parasitic infections. Data of the present study highlighted the need for greater biomonitoring of MSWWs and the improvement of environmental conditions and health care in such marginalized communities to prevent parasitic infection and associated morbidities.

Simultaneous detection of Entamoeba histolytica/dispar, Giardia duodenalis and cryptosporidia by immunochromatographic assay in stool samples from patients living in the Greater Cairo Region, Egypt

Gastrointestinal infection due to intestinal parasites is an enormous health problem in developing countries and its reliable diagnosis is demanding. Therefore, this study aimed at evaluating a commercially available immunochromatographic assay (ICA) for the detection of cryptosporidia, Giardia duodenalis, and Entamoeba histolytica/dispar for its usefulness in the Greater Cairo Region, Egypt. Stool samples of 104 patients who presented between October 2012 and March 2013 with gastrointestinal symptoms or for the exclusion of parasites at Kasr-Al-Ainy University Medical School were examined by light microscopy of wet mounts and the triple ICA. Microscopy revealed in 20% of the patients [95% confidence interval (CI), 13.5-29.0%] parasites with Hymenolepis nana, E. histolytica/dispar and Blastocystis hominis being the most frequent ones, but was not able to detect G. duodenalis and cryptosporidia, whereas ICA was positive in 21% (95% CI, 14.3-30.0%) and detected E. histolytica/dispar in 12.5% (95% CI, 7.3-20.4%), cryptosporidia in 6.7% (95% CI, 3.1-13.5%) and G. duodenalis in 15.4% (95% CI, 9.6-23.6%) of the patients. Detection of one or more pathogens was associated with access to water retrieved from a well or pump (p = 0.01). Patients between 20 and 29 years of age (p = 0.08) and patients with symptoms of 5 days or longer (p = 0.07) tended to have a higher risk to be infected than patients of other age groups or with shorter-lasting symptoms. In conclusion, the ICA was easy to perform and timesaving. Importantly, it enabled the detection of cryptosporidia, which cannot be found microscopically in unstained smears, demonstrated a higher sensitivity for the detection of G. duodenalis than microscopy, and was more specific for distinguishing E. histolytica/dispar from apathogenic amoeba.

Entamoeba dispar: Could it be pathogenic

Amebiasis is a disease caused by the protozoan parasite Entamoeba histolytica. This ameba can colonize the human intestine and persist as a commensal parasite, similar to Entamoeba dispar, an ameba considered to be non-pathogenic. The similarities between E. histolytica and E. dispar make the latter an attractive model for studies aimed at clarifying the pathogenesis of amebiasis. However, in addition to being an interesting experimental model, this relative of E. histolytica remains poorly understood. In the 1990, it was believed that E. dispar was unable to produce significant experimental lesions. This scenario began to change in 1996, when E. dispar strains were isolated from symptomatic patients in Brazil. These strains were able to produce liver and intestinal lesions that were occasionally indistinguishable from those produced by E. histolytica. These and other findings, such as the detection of E. dispar DNA sequences in samples from patients with amebic liver abscess, have revived the possibility that this species can produce lesions in humans. The present paper presents a series of studies on E. dispar that begin to reveal a new facet of this protozoan.

The intestinal protozoa: emerging impact on global health and development

PURPOSE OF REVIEW

To highlight new findings on the relevance of gastrointestinal protozoan infections to global public health in low-income and middle-income countries and suggest new large-scale interventions.

RECENT FINDINGS

New disease burden assessments and epidemiological studies highlight the role of the major intestinal protozoa as important etiologic disease agents in low-income and middle-income countries. Despite their prevalence and adverse health impact, such information has not yet translated to the implementation of large-scale interventions as exist for helminth infections and other neglected tropical diseases. There are also several key research and development questions that must be addressed for intestinal protozoan infections and the potential need for new tools, for example, drugs, diagnostics, and vaccines. Additional studies have identified new and emerging species of intestinal protozoa relevant to global public health such as Dientamoeba fragilis and Blastocystis hominis and how they too might emerge as important gastrointestinal pathogens in the coming years.

SUMMARY

New and emerging information on intestinal protozoa are reviewed with emphasis on aspects considered relevant to global health policymakers including prospects for scaling up interventions against intestinal protozoan infections in resource-poor countries.

Comparison of microscopic and immunoassay examination in the diagnosis of intestinal protozoa of humans in Mansoura, Egypt

Protozoal diseases are prevalent globally and especially in developing countries that have relatively lower socioeconomic populations such as Egypt. Direct microscopic examination (DME) is used for the detection and identification of protozoa but lacks sufficient reliability, and thus may be detrimental in obtaining accurate diagnostic or epidemiological data. In this study, we determine the prevalence of infections by Giardia intestinalis, Cryptosporidium sp., and Entamoeba histolytica in humans in Egypt. Furthermore, we determine the reliability of DME in determining infections caused by these protozoa and compare the results to enzyme linked Immunosorbent assays (ELISA). Our results indicate that the prevalence of giardiasis, cryptosporidiosis, and entamoebiasis is 38, 22, and 16 %, respectively. The sensitivity and specificity of DME for detection of G. intestinalis is 45 and 99 %, for Cryptosporidium 66 and 99 %, and for Entamoeba 45 and 100 %, respectively. Our findings demonstrate that ELISA is more reliable for diagnostic and epidemiologic study purposes.

Review of parasitic zoonoses in egypt

This review presents a comprehensive picture of the zoonotic parasitic diseases in Egypt, with particular reference to their relative prevalence among humans, animal reservoirs of infection, and sources of human infection. A review of the available literature indicates that many parasitic zoonoses are endemic in Egypt. Intestinal infections of parasitic zoonoses are widespread and are the leading cause of diarrhea, particularly among children and residents of rural areas. Some parasitic zoonoses are confined to specific geographic areas in Egypt, such as cutaneous leishmaniasis and zoonotic babesiosis in the Sinai. Other areas have a past history of a certain parasitic zoonoses, such as visceral leishmaniasis in the El-Agamy area in Alexandria. As a result of the implementation of control programs, a marked decrease in the prevalence of other zoonoses, such as schistosomiasis and fascioliasis has been observed. Animal reservoirs of parasitic zoonoses have been identified in Egypt, especially in rodents, stray dogs and cats, as well as vectors, typically mosquitoes and ticks, which constitute potential risks for disease transmission. Prevention and control programs against sources and reservoirs of zoonoses should be planned by public health and veterinary officers based on reliable information from systematic surveillance.

Blastocystis spp., Cryptosporidium spp., and Entamoeba histolytica exhibit similar symptomatic and epidemiological patterns in healthcare-seeking patients in Karachi

In this study, we collected data on the incidence of enteric parasites in healthcare-seeking individuals along with their symptoms to quantify the potential roles of factors such as age, sex, and seasonality in infection. We performed analysis to identify factors which could help differentiate parasitic infection from other causes of gastrointestinal illness in a community. The size of the patient population (n = 339), patient selection methodology, collection methods, and statistical analysis followed approaches from similar studies in core clinical journals. Ethical approval was obtained from the University of Karachi's Ethical Review Board. Fecal specimens (n = 339) submitted by symptomatic patients were collected from two clinical laboratories, along with information about the patients' age, sex, and symptoms. We found that symptoms of fever, vomiting, and constipation were 100 % predictive of finding a parasitic infection, while diarrhea was 88 % predictive of a parasitic infection. Gastrointestinal parasite-positive patients reported diarrhea (~60 %), vomiting (~30 %), fever (~25 %) and constipation (~25 %), while parasite-negative patients exhibited a symptomatic profile without fever, vomiting, and constipation. The distribution of symptoms in parasite-positive patients remained relatively invariant regardless of the parasite identified. Blastocystis spp.-mono-infected patients reported a similar profile to patients positive for Entamoeba histolytica/Entamoeba dispar and Cryptosporidium spp. Most parasitic infections exhibited a strong seasonal pattern, with a peak incidence in summer months. Infection by Blastocystis spp. was the most prevalent, and it was the only infection mathematically correlated to rainfall by Pearson's method. We observed no increase in healthcare-seeking behavior following a stressful community event, namely, the attempted assassination of Benazir Bhutto in Karachi. The data suggest that parasitological testing would produce a high yield of positive results when performed on healthcare-seeking patients in Karachi in 2007 with symptoms of fever, vomiting, or constipation and a low yield when performed on patients noting only abdominal pain. Parasitological testing also produces a higher yield on patients seen in summer months.

Seroprevalence of Entamoeba histolytica infection in China

The seroprevalence of Entamoeba histolytica infection in the residents of seven provinces in China was examined by using an enzyme-linked immunosorbent assay with a crude antigen and a recombinant surface antigen, C-Igl, of the parasites. A total of 1,312 serum samples were investigated. The positivity rates for these two antigens were 11.05% and 6.25%, respectively. There was no significant difference in the seropositivity to E. histolytica between men and women. We used a logistic regression model and maximal-likelihood methods to estimate the prevalence of E. histolytica infection from sequential serologic data. Seropositivity in Sichuan, Guizhou, and Sinkiang Provinces was higher than that in Beijing, Shanghai, and Qinghai Provinces. The present study provides an overview of seropositivity to E. histolytica infection in seven provinces in China and use the logistic regression model estimation method to achieve a more accurate measure of amebiasis prevalence.

Human immunodeficiency virus-related gastrointestinal pathology: a southern Africa perspective with review of the literature (part 1: infections)

CONTEXT

Human immunodeficiency virus infection is rife in sub-Saharan Africa and in southern Africa in particular. Despite the increasing availability of antiretroviral therapy in this region, opportunistic infections remain common and frequently involve the gastrointestinal tract.

OBJECTIVE

To review the histopathologic findings and distinguishing features of human immunodeficiency virus-associated gastrointestinal infections in southern Africa and relate those findings to the documented international literature.

DATA SOURCES

The available literature on this topic was reviewed and supplemented with personal experience in a private histopathology practice in South Africa.

CONCLUSIONS

In southern Africa, the range of gastrointestinal, opportunistic infectious pathology in human immunodeficiency virus afflicted patients is diverse and includes viral, bacterial, fungal, and parasitic infections. This infectious pathology is sometimes a manifestation of systemic disease. In profoundly immunocompromised patients, unusual histologic features, involvement of uncommon gastrointestinal tract sites, and more than one pathogen may be seen.

Vaccines to combat the neglected tropical diseases

The neglected tropical diseases (NTDs) represent a group of parasitic and related infectious diseases such as amebiasis, Chagas disease, cysticercosis, echinococcosis, hookworm, leishmaniasis, and schistosomiasis. Together, these conditions are considered the most common infections in low- and middle-income countries, where they produce a level of global disability and human suffering equivalent to better known conditions such as human immunodeficiency virus/acquired immunodeficiency syndrome and malaria. Despite their global public health importance, progress on developing vaccines for NTD pathogens has lagged because of some key technical hurdles and the fact that these infections occur almost exclusively in the world's poorest people living below the World Bank poverty line. In the absence of financial incentives for new products, the multinational pharmaceutical companies have not embarked on substantive research and development programs for the neglected tropical disease vaccines. Here, we review the current status of scientific and technical progress in the development of new neglected tropical disease vaccines, highlighting the successes that have been achieved (cysticercosis and echinococcosis) and identifying the challenges and opportunities for development of new vaccines for NTDs. Also highlighted are the contributions being made by non-profit product development partnerships that are working to overcome some of the economic challenges in vaccine manufacture, clinical testing, and global access.

A morphological approach to the diagnosis of protozoal infections of the central nervous system

Protozoal infections, though endemic to certain regions, can be seen all around the world, because of the increase in travel and migration. In addition, immunosuppression associated with various conditions, particularly with HIV infection, favors the occurrence of more severe manifestations and failure to respond to treatments. The CNS may be the only affected system; when not, it is often the most severely affected. Despite information obtained from clinical, laboratory, and imaging procedures that help to narrow the differential diagnosis of intracranial infections, there are cases that need confirmation with biopsy or autopsy. Predominant presentations are meningoencephalitis (trypanosomiasis), encephalopathy (cerebral malaria), or as single or multiple pseudotumoral enhancing lesions (toxoplasmosis, reactivated Chagas' disease). The immune reconstitution disease, resulting from enhancement of pathogen-specific immune responses after HAART, has altered the typical presentation of toxoplasmosis and microsporidiosis. In this paper, a morphological approach for the diagnosis of protozoal infections affecting the CNS (amoebiasis, cerebral malaria, toxoplasmosis, trypanosomiasis, and microsporidiosis) is presented.

Evaluation of multiplex tandem real-time PCR for detection of Cryptosporidium spp., Dientamoeba fragilis, Entamoeba histolytica, and Giardia intestinalis in clinical stool samples

The aim of this study was to describe the first development and evaluation of a multiplex tandem PCR (MT-PCR) assay for the detection and identification of 4 common pathogenic protozoan parasites, Cryptosporidium spp., Dientamoeba fragilis, Entamoeba histolytica, and Giardia intestinalis, from human clinical samples. A total of 472 fecal samples submitted to the Department of Microbiology at St. Vincent's Hospital were included in the study. The MT-PCR assay was compared to four real-time PCR (RT-PCR) assays and microscopy by a traditional modified iron hematoxylin stain. The MT-PCR detected 28 G. intestinalis, 26 D. fragilis, 11 E. histolytica, and 9 Cryptosporidium sp. isolates. Detection and identification of the fecal protozoa by MT-PCR demonstrated 100% correlation with the RT-PCR results, and compared to RT-PCR, MT-PCR exhibited 100% sensitivity and specificity, while traditional microscopy of stained fixed fecal smears exhibited sensitivities and specificities of 56% and 100% for Cryptosporidium spp., 38% and 99% for D. fragilis, 47% and 97% for E. histolytica, and 50% and 100% for G. intestinalis. No cross-reactivity was detected in 100 stool samples containing various other bacterial, viral, and protozoan species. The MT-PCR assay was able to provide rapid, sensitive, and specific simultaneous detection and identification of the four most important diarrhea-causing protozoan parasites that infect humans. This study also highlights the lack of sensitivity demonstrated by microscopy, and thus, molecular methods such as MT-PCR must be considered the diagnostic methods of choice for enteric protozoan parasites.

Seroprevalence of Entamoeba histolytica in the context of HIV and AIDS: the case of Vhembe district, in South Africa's Limpopo province

In a recent study in northern South Africa, the seroprevalence of Entamoeba histolytica infection among 257 HIV-positive and 117 HIV-negative individuals was determined, using an ELISA for the detection of antibodies reacting with the parasite's galactose/-acetyl-D-galactosamine(Gal/GalNAc)-inhibitable adherence lectin. Overall, 34.0% of the 374 participants (36.1% of the females and 28.1% of the males) were found seropositive for E. histolytica. Although all age-groups were affected by the amoebic pathogen, the subjects aged 50-59 years had the highest seroprevalence (69.2%). The seroprevalence of E. histolytica was also significantly higher among the HIV-positive subjects than among the HIV-negative (42.8% v. 14.5%; chi(2)=28.65; P<0.0001). Among the HIV-positive subjects, those with fewer than 200 CD4+ cells/microl were relatively more likely to be seropositive for E. histolytica (60.3% v. 43.8%; chi(2)=4.016; P=0.045). This is the first report indicating a positive association between E. histolytica infection and HIV in South Africa. Further studies, for example to determine the occurrence of diarrhoea or liver abscess in the study area, in relation to seropositivity for E. histolytica and/or HIV, are now needed.

Clinical significance of enteric protozoa in the immunosuppressed human population

Globally, the number of immunosuppressed people increases each year, with the human immunodeficiency virus (HIV) pandemic continuing to spread unabated in many parts of the world. Immunosuppression may also occur in malnourished persons, patients undergoing chemotherapy for malignancy, and those receiving immunosuppressive therapy. Components of the immune system can be functionally or genetically abnormal as a result of acquired (e.g., caused by HIV infection, lymphoma, or high-dose steroids or other immunosuppressive medications) or congenital illnesses, with more than 120 congenital immunodeficiencies described to date that either affect humoral immunity or compromise T-cell function. All individuals affected by immunosuppression are at risk of infection by opportunistic parasites (such as the microsporidia) as well as those more commonly associated with gastrointestinal disease (such as Giardia). The outcome of infection by enteric protozoan parasites is dependent on absolute CD4(+) cell counts, with lower counts being associated with more severe disease, more atypical disease, and a greater risk of disseminated disease. This review summarizes our current state of knowledge on the significance of enteric parasitic protozoa as a cause of disease in immunosuppressed persons and also provides guidance on recent advances in diagnosis and therapy for the control of these important parasites.

Neglected tropical diseases in sub-saharan Africa: review of their prevalence, distribution, and disease burden

The neglected tropical diseases (NTDs) are the most common conditions affecting the poorest 500 million people living in sub-Saharan Africa (SSA), and together produce a burden of disease that may be equivalent to up to one-half of SSA's malaria disease burden and more than double that caused by tuberculosis. Approximately 85% of the NTD disease burden results from helminth infections. Hookworm infection occurs in almost half of SSA's poorest people, including 40-50 million school-aged children and 7 million pregnant women in whom it is a leading cause of anemia. Schistosomiasis is the second most prevalent NTD after hookworm (192 million cases), accounting for 93% of the world's number of cases and possibly associated with increased horizontal transmission of HIV/AIDS. Lymphatic filariasis (46-51 million cases) and onchocerciasis (37 million cases) are also widespread in SSA, each disease representing a significant cause of disability and reduction in the region's agricultural productivity. There is a dearth of information on Africa's non-helminth NTDs. The protozoan infections, human African trypanosomiasis and visceral leishmaniasis, affect almost 100,000 people, primarily in areas of conflict in SSA where they cause high mortality, and where trachoma is the most prevalent bacterial NTD (30 million cases). However, there are little or no data on some very important protozoan infections, e.g., amebiasis and toxoplasmosis; bacterial infections, e.g., typhoid fever and non-typhoidal salmonellosis, the tick-borne bacterial zoonoses, and non-tuberculosis mycobaterial infections; and arboviral infections. Thus, the overall burden of Africa's NTDs may be severely underestimated. A full assessment is an important step for disease control priorities, particularly in Nigeria and the Democratic Republic of Congo, where the greatest number of NTDs may occur.

C1q- and collectin-dependent phagocytosis of apoptotic host cells by the intestinal protozoan Entamoeba histolytica

BACKGROUND

Entamoeba histolytica, the cause of invasive amebiasis, phagocytoses apoptotic host cells during tissue invasion. In mammals, collectin family members (e.g., mannose-binding lectin [MBL]) and the structurally related protein C1q bind to apoptotic cells and stimulate macrophage phagocytosis via a conserved collagenous tail domain. The collectins also bind to bacteria, the usual source of nutrients for E. histolytica.

METHODS

To test the possibility that the collectins are ligands that stimulate E. histolytica phagocytosis, we used a flow cytometry-based assay for amebic phagocytosis, a method for making single-ligand particles to delineate a given ligand's ability to initiate phagocytosis, and purified human C1q, MBL, and collagenous collectin tails.

RESULTS

Apoptotic lymphocytes opsonized with serum or human C1q were phagocytosed more efficiently than control cells, an effect that was dependent on ligand density. C1q and the collectins alone were adequate to trigger amebic phagocytosis, because single-ligand particles coated with C1q, MBL, or purified collectin tails were phagocytosed more efficiently than control particles. Furthermore, C1q, MBL, and the tail domain of C1q were all chemoattractants for E. histolytica.

CONCLUSIONS

C1q and MBL can serve as opsonins on apoptotic cells that stimulate E. histolytica phagocytosis, an effect mediated at least in part by the collagenous collectin tail domain.

Evidence for a link between parasite genotype and outcome of infection with Entamoeba histolytica

The factors determining whether a person infected with Entamoeba histolytica develops disease remain obscure. To investigate whether the parasite genome contributes to the outcome, we have investigated the distribution of parasite genotypes among E. histolytica-infected individuals in Bangladesh. Samples were obtained from individuals who either were asymptomatic, had diarrhea/dysentery, or had developed a liver abscess. Genotypes were determined by using six tRNA-linked polymorphic markers, and their distributions among the three sample groups were evaluated. A significant population differentiation in the genotype distribution was found for four of the six individual markers as well as for the combined genotypes, suggesting that the parasite genome does contribute in some way to the outcome of infection with E. histolytica. The markers themselves do not indicate the nature of the underlying genetic differences, but they may be linked to loci that do have an impact on the outcome of infection.

Irritable bowel syndrome: a review on the role of intestinal protozoa and the importance of their detection and diagnosis

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder in which abdominal pain is associated with a defect or a change in bowel habits. Gut inflammation is one of the proposed mechanisms of pathogenesis. Recent studies have described a possible role for protozoan parasites, such as Blastocystis hominis and Dientamoeba fragilis, in the etiology of IBS. Dientamoeba fragilis is known to cause IBS-like symptoms and has a propensity to cause chronic infections but its diagnosis relies on microscopy of stained smears, which many laboratories do not perform, thereby leading to the misdiagnosis of dientamoebiasis as IBS. The role of B. hominis as an etiological agent of IBS is inconclusive, due to contradictory reports and the controversial nature of B. hominis as a human pathogen. Although Entamoeba histolytica infections occur predominately in developing regions of the world, clinical diagnosis of amebiasis is often difficult because symptoms of patients with IBS may closely mimic those patients with non-dysenteric amoebic colitis. Clinical manifestations of Giardia intestinalis infection also vary from asymptomatic carriage to acute and chronic diarrhoea with abdominal pain. These IBS-like symptoms can be continuous, intermittent, sporadic or recurrent, sometimes lasting years without correct diagnosis. It is essential that all patients with IBS undergo routine parasitological investigations in order to rule out the presence of protozoan parasites as the causative agents of the clinical signs.

Comparison of a stool antigen detection kit and PCR for diagnosis of Entamoeba histolytica and Entamoeba dispar infections in asymptomatic cyst passers in Iran

The present study was conducted to compare stool antigen detection with PCR for the diagnosis of Entamoeba sp. infection in asymptomatic cyst passers from Iran. Entamoeba dispar and, in one case, E. moshkovskii were the Entamoeba spp. found in the amebic cyst passers. There was a 100% correlation between the results from the TechLab E. histolytica II stool antigen kit and those from nested PCR. We concluded that E. dispar is much more common in asymptomatic cyst passers in Iran and that antigen detection and PCR are comparable diagnostic modalities.