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[Amebiasis and amebic liver abscess in Mexico: a present-day public health problem].

BACKGROUND: Amebiasis still remains as a major public health problem in the world. It is one of the most common reasons for medical consult. There are more than half a million cases of amebiasis just at the Mexican Institute of the Social Security. There is still a lack of epidemiologic information on amebiasis in Mexico. AIM: To describe the secular trend fro amebiasis and for amebic liver abscess in the Mexican population, as well as in those covered by IMSS Solidaridad. METHOD: An ecologic trend study was carried on. Incidence rate of amebiasis in all of its forms of presentation, and of amebic liver abscess, were plotted against each year for the 1986-1994 period. RESULTS: Amebiasis incidence in all of its forms of presentation showed a stable trend in this period, as it was seen with amebic liver abscess. Amebiasis is more common in the first years of life. On the contrary, amebic liver abscess showed an inverted 'J' pattern; its occurrence is higher in the extreme years of life. Fatality rates have shown a descendent trend. CONCLUSIONS: Amebiasis reflects socioeconomic conditions in Mexico and the fact that Mexican is still an endless culture. There is a need to promote health education, better diagnostic procedures and detection of asymptomatic carriers. Health policies for mothers that are asymptomatic carriers should be reviewed, due to the high rates of amebiasis and amebic liver abscess in children under one year of age.

Adolescent↗

Thoracic amebiasis.

Pleuropulmonary amebiasis is the common and pericardial amebiasis the rare form of thoracic amebiasis. Low socioeconomic conditions, malnutrition, chronic alcoholism, and ASD with left to right shunt are contributing factors to the development of pulmonary amebiasis. Although no age is exempt, it commonly occurs in patients aged 20 to 40 years, with an adult male to female ratio of 10:1. Children rarely develop thoracic amebiasis: when it does occur there is an equal sex distribution. The infection usually spreads to the lungs by extension of an amebic liver abscess. Infection may pass to the thorax directly from the primary intestinal lesion through hematogenous spread, however. Lymphatic spread is one possible route. Inhalation of dust containing cysts and aspiration of cysts or trophozoites of E histolytica in the lungs are some other hypothetical routes. The lung is the second most common extraintestinal site of amebic involvement after the liver. Usually the lower lobe, and sometimes the middle lobe of the right lung, are affected, but it may affect any lobe of the lungs. The patient develops fever and right upper quadrant pain that is referred to the tip of the right shoulder or in between the scapula. Hemophtysis is common. The diagnosis of thoracic amebiasis is suggested by the combination of an elevated hemidiaphragm (usually right), hepatomegaly, pleural effusion, and involvement of the right lung base in the form of haziness and obliteration of costophrenic and costodiaphragmatic angles. Infection is usually extended to the thorax by perforation of a hepatic abscess through the diaphragm and across an obliterated pleural space, producing pulmonary consolidation, abscesses, or broncho-hepatic fistula. Empyema develops when a liver abscess ruptures into the pleural space. Rarely, a posterior amebic liver abscess can burst into the inferior vena cava and develop an embolism of the inferior vena cava and thromboembolic disease of the lungs with congestive cardiac failure or corpulmonale. Diagnosis by finding E histolytica in stool specimens is of limited value. In a limited number of cases amebae might be found in aspirated pus or expectorated sputum. "Anchovy sauce-like" pus or sputum may be found. Presence of bile in sputum indicates that the pus is of liver origin. Serological tests are of immense value in diagnosis. Liver enzymes are usually normal and neutrophilic leucocytosis may or may not be found. ESR is invariably elevated. Anti-amebic antibodies can be detected by ELISA, IFAT, and IHA. Amebic antigen can be detected from serum and pus by ELISA. Detection of Entamoeba DNA in pus or sputum may be a sensitive and specific method. Pleuropulmonary amebiasis is easily confused with other illnesses and is treated as pulmonary TB, bacterial lung abscesses, and carcinoma of the lung. A single drug regimen with metronidazole with supportive therapy usually cures patients without residual anomalies. Aspiration of pus from empyema thoracis may be needed for confirmation and therapeutic purposes. The pericardium is usually involved by direct extension from the amebic abscess of the left lobe of the liver, sometimes from the right lobe of the liver, and rarely from the lungs or pleura. An initial accumulation of serous fluid due to reactive pericarditis followed by intrapericardial rupture may develop either (1) acute onset of severe symptoms with chest pain, dyspnea, and cardiac tamponade, shock, and death, or (2) progressive effusion with thoracic cage pain, progressive dyspnea, and fever. Chest radiograph, ultrasound examination, and CT scan usually confirm the presence of a liver abscess in continuity with the pericardium and fluid within the pericardial sac with or without the fistulous tract. Echocardiography may demonstrate fluid in the pericardial cavity. Patients should be cared for in the ICU and ambecides should be started without delay. Pericardiocentesis usually confirms the diagnosis and improves the general condition of the patient. Aspiration of the accumulated fluid should be performed urgently in cardiac tamponade; repeated aspiration may be needed. Surgical drainage should be done if needed. Acanthamoeba, a free-living ameba, may also infect the lungs in the form of pulmonary nodular infiltration and pulmonary edema in association with amebic meningoencephalitis in immunocompromised patients. It usually spreads to the meninges of the brain by way of the blood from its primary lesion in the lung or skin. Early diagnosis and institution of treatment may be life saving for these patients. A literature review shows that HIV/AIDS patients are not prone to infection with E histolytica. It is now clear that there are an increasing number of HIV-seropositive patients among amebic liver abscess patients, however, which suggests that although the incidence of intestinal infection is not high among HIV-seropositive or AIDS patients they are more susceptible to an invasive form of the disease.

Animals↗

Purification and identification of major soluble 40-kDa antigenic protein from Entamoeba histolytica: its application for serodiagnosis of asymptomatic amebiasis.

One of the major soluble antigenic proteins of Entamoeba histolytica was purified to homogeneity and identified on a molecular basis. Its recombinant protein was expressed in Escherichia coli as a fusion protein with Shistosoma japonicum glutathione S-transferase. Apparent molecular weight of the purified antigenic protein was estimated to be 40-kDa and molecular-based analysis indicated that the purified protein was NADP+-dependent alcohol dehydrogenase (EhADH1). The application of the purified protein for the serodiagnosis of amebiasis was evaluated using an enzyme-linked immunosorbent assay applied to sera obtained from patients with amebiasis and healthy human controls. The purified protein was well recognized by the sera from asymptomatic amebiasis humans (22/22, 100%), whereas, it was less recognized by the sera from symptomatic amebiasis patients (5/16, 31%) with amebic colitis or liver abscess. To confirm the antigenicity of EhADH1, the recombinant glutathione S-transferase-EhADH1 fusion protein was also evaluated by the enzyme-linked immunosorbent assay using the same sera. The recombinant protein was also recognized by the sera from asymptomatic amebiasis humans (14/22, 64%) and less recognized by the sera from symptomatic amebiasis patients (2/16, 13%). These results suggest that the purified protein is applicable antigen for serodiagnostic screening of asymptomatic amebiasis humans.

Animals↗

Epidemiologic and clinical features of invasive amebiasis in Bangladesh: a case-control comparison with other diarrheal diseases and postmortem findings.

To describe the epidemiologic and clinical features associated with invasive amebiasis in Bangladesh, 85 hospitalized diarrheal patients with hematophagous trophozoites of Entamoeba histolytica in their stools were compared to a control group of 84 hospitalized diarrheal patients without amebiasis. Postmortem examinations were carried out in 22 deaths due to amebiasis. For the patients with amebiasis, there was a bimodal age distribution with peaks at 2-3 years and greater than 40 years, whereas the control patients had a unimodal distribution with the peak at 0-1 year. The sex distribution was equal in childhood but young adults were predominantly female and older adults predominantly male. The clinical features significantly associated with amebiasis were prolonged dysentery, prior measles rash, malnutrition, hyponatremia, hypokalemia, and hypoproteinemia (all P less than 0.05). The case fatality rate in amebiasis was 29%, which was significantly higher than 11% for the controls (P less than 0.05). Postmortem findings included extensive colitis with deep ulcers and complications, including colonic perforation in 2 cases, peritonitis in 4 cases, pneumonia in 9 cases, and septicemia in 5 cases. These results indicate that invasive amebiasis in this population differs from other diarrheal diseases, affecting mainly children greater than 2 years and adults and causing severe and fatal illness characterized by extensive colitis with diverse systemic consequences.

Adolescent↗

Genital amebiasis.

Five cases of amebiasis of the genital tract involving the cervix, vulva and penis are described. All presented as an ulcerating mass and were clinically suspected to have a tumor. In two cases the amebiasis co-existed with a carcinoma, an association which is extremely rare. The spouse of a patient with penile amebiasis was found to have amebiasis of the cervix suggesting a sexually transmitted mode of infection. The need for histopathological confirmation of all suspected genital malignancies is emphasised due to the striking resemblance of genital amebiasis to a carcinoma. The co-existence of amebiasis with carcinoma is of interest and suggests a possible etiological relationship.

Adult↗

Amebiasis: epidemiologic studies in the United States, 1971-1974.

Seven investigations of suspected foci of amebiasis between October 1971 and June 1974 lead to three conclusions. (1) A number of laboratories have vastly overdiagnosed amebiasis and have reported leukocytes in stools as Entamoeba histolytica. Two laboratories found to be in error were in community hospitals, and one was at a teaching hospital associated with a medical school and a school of public health. These three laboratories had been diagnosing more than 1200 cases of amebiasis a year for 20 years. (2) When amebiasis does occur, it is likely to be misdiagnosed. In one outbreak with four cases and three deaths, amebiasis was not diagnosed until two patients had died and another was critically ill. Sporadic cases may be mistakenly diagnosed as ulcerative colitis and inappropriately treated with steroids. (3) Foci of endemic amebiasis continue to exist in the United States, both in institutions and in noninstitutional settings.

Amebiasis↗

Selective primary health care: strategies for control of disease in the developing world. X. Amebiasis.

The human parasite Entamoeba histolytica has a worldwide distribution. The majority of infected individuals suffer few symptoms; nonetheless, a variable proportion experience dysentery, hepatic abscesses, or invasion of other extraintestinal organs. Invasive amebiasis is a major health problem, particularly in certain developing countries. The aim of this review is to clarify, as much as possible, controversial issues about the biology of the parasite, the clinical features of amebiasis, and the estimations of morbidity and mortality rate as the basis for defining strategies for control of amebiasis by primary health care workers. The eradication of invasive amebiasis lies basically in potentially political and economic actions at the governmental level. Preventive and control measures include (1) provision of water supplies and sanitation, (2) health education, (3) adequate diagnosis and correct treatment of invasive amebiasis, and (4) implementation of surveillance and control programs.

Amebiasis↗

Amebiasis: introduction, current status, and research questions.

This series of five papers on the worldwide problem of amebiasis, its current status, research needs, and opportunities for progress has grown out of a renewal of investigative interest in amebiasis. The recent development of in vitro culture methods and of means to distinguish strain differences and the application of modern tools of cellular biology and biochemistry have raised new questions regarding strain definitions, virulence traits, host defenses, and the mechanism of invasive disease sometimes caused by Entamoeba histolytica. The clinical manifestations of amebic infections range from prolonged asymptomatic carriage to extensive, invasive intestinal and extraintestinal disease. The virulence traits of the parasite, whether stable in each strain or alterable by environmental or genetic factors, and the host factors involved in the development of disease and in protection have been investigated. From this series of reviews on the definition of amebiasis, its manifestations, its global magnitude, the methods for its detection, and the current understanding of its epidemiology, pathogenesis, cellular biology, and host defenses, a list of key questions that can now be addressed in work on amebiasis has been derived. Amebiasis is the third leading parasitic cause of death in the world. The need for work in this field is great, and the time is ripe for the application of new research tools to a better understanding of this remarkable tissue-lysing protozoan parasite and to the control of the disease it causes.

Amebiasis↗

Gender distribution in asymptomatic and invasive amebiasis.

OBJECTIVE: The majority of individuals infected by the protozoan parasite Entamoeba histolytica experience subclinical infections. However, a small proportion of parasitized individuals develop severe invasive disease such as amebic dysentery or amebic liver abscess. Invasive amebiasis affects predominantly men; the usual explanation for this has been that men have a higher rate of asymptomatic infections and therefore experience a higher rate of invasive disease. To date, there is no convincing evidence of an increased rate of asymptomatic infection of men as compared with women. The purpose of this study was to evaluate the evidence supporting the hypothesis that men have higher rates of asymptomatic infection and thus an increased frequency of invasive amebiasis. METHODS: We reviewed published reports of invasive amebiasis and population-based parasitological studies from 1929-1997 to compare the gender ratio of asymptomatic and symptomatic E. histolytica infection. Infections with E. histolytica were differentiated from the nonpathogenic E. dispar whenever possible. RESULTS: The reports of invasive amebiasis (dysentery, liver abscess, colonic perforation, peritonitis, appendicitis, and ameboma) showed a higher proportion of men than women (ratio, male:female = 3.2:1, p < 0.05). This contrasts with the epidemiological surveys, where the rate of asymptomatic infection with E. histolytica was the same (1:1) for both genders (p > 0.05). CONCLUSIONS: Asymptomatic E. histolytica infection is equally distributed between the genders. The high proportion of men with invasive amebiasis may be due to a male-related susceptibility to invasive disease.

Adult↗

Amebiasis: unusual radiographic manifestations.

Unusual radiographic manifestations of amebiasis have not previously been emphasized in the literature. These unusual manifestations often mimic other, more common disease entities. A recent case of urinary bladder-cervical amebiasis prompted a review of other unusual manifestations of amebiasis. Over a 25-year period, unusual cases involving the musculoskeletal, genitourinary, cardiopulmonary, and gastrointestinal systems have been encountered. Primary amebiasis of any organ may occur without clinical evidence of gastrointestinal or hepatic involvement. These unusual cases illustrate the clinical spectrum of amebiasis and will clarify aspects of this interesting disease entity.

Amebiasis↗

Serodiagnosis of invasive amebiasis using a recombinant Entamoeba histolytica protein.

One hundred eight serum samples from 106 patients were examined by Western blot analysis for the presence of antibodies to a recombinant fusion protein containing the sequence of the newly described serine-rich Entamoeba histolytica protein (SREHP). Among patients with invasive amebiasis from Durban, Republic of South Africa; San Diego, Calif; Mexico City, Mexico; and St Louis, Mo, 53 (82%) of 65 had antibodies to SREHP. In contrast, only one patient (2%) of 43 without acute invasive amebiasis had antibodies to SREHP. The predictive value of a positive test for anti-SREHP antibodies in the detection of acute invasive amebiasis was most marked when analyzed in the patients from Durban, where 11 (92%) of 12 patients who were seropositive for SREHP had acute invasive amebiasis vs 17 (65%) of 26 patients who had a positive serologic diagnosis as determined by agar gel diffusion. The use of a serologic test based on the recombinant SREHP fusion protein may be a useful adjunct to the diagnosis of acute invasive amebiasis in endemic regions.

Amebiasis↗

Serology of amebiasis using the FIAX-TM system.

A new fluorescent immunoassay system (FIAX TM) has permitted development of a promising serologic test for amebiasis. The test is similar but far superior to the soluble antigen fluorescent antibody test. The main differences are the unique StiQ TM sampler and the flourometer itself. Quantitative results can be obtained from a single standard dilution of serum. The procedure is simple to perform, gives objective readings, and uses the proven principle of immunofluorescence. It is possible to test for different immunoglobulin classes and to use purified antigen prepared from axenically cultured Entamoeba histolytica. Conservation of reagents is comparable to microplate systems, and results are available in less than two hours. FIAX TM for amebiasis has demonstrated excellent discriminating power between amebic and nonamebic sera. Sensitivity is 100 percent for extra-intestinal amebiasis (33 sera), 90 percent for symptomatic intestinal amebiasis (20 sera), and 43 percent for asymptomatic amebiasis (seven sera). Specificity is 97 percent (158 sera).

Amebiasis↗

Invasive amebiasis as an emerging parasitic disease in patients with human immunodeficiency virus type 1 infection in Taiwan.

BACKGROUND: Whether risk of invasive amebiasis due to Entamoeba histolytica is higher among human immunodeficiency virus (HIV)-infected persons than uninfected persons remains unclear, although intestinal colonization by Entamoeba dispar is common among men who have sex with men. Our objective was to determine the prevalence of invasive amebiasis and intestinal colonization by E histolytica and E dispar in HIV-infected persons and uninfected controls. METHODS: We assessed the prevalence of invasive amebiasis by case review of 951 HIV-infected persons and by serologic studies of 634 of the 951 HIV-infected persons, 429 uninfected controls with gastrointestinal symptoms, and 178 uninfected healthy controls using indirect hemagglutination antibody assay. We assessed the rate of intestinal colonization by E histolytica and E dispar by fecal antigen and polymerase chain reaction tests in 332 asymptomatic HIV-infected persons and 144 of the 178 uninfected healthy controls. RESULTS: Forty-nine (5.2%) of 951 HIV-infected persons had 51 episodes of invasive amebiasis. A high indirect hemagglutination antibody titer was detected in 39 (6.2%) of 634 HIV-infected persons compared with 10 (2.3%) of 429 uninfected controls with gastrointestinal symptoms and 0 of 178 uninfected healthy controls (P<.001). Stool specimens from 40 (12.1%) of 332 HIV-infected persons and 2 (1.4%) of 144 uninfected healthy controls were positive for E histolytica or E dispar antigen (P<.001). Ten (25.0%) of the 40 antigen-positive stool specimens from HIV-infected persons contained E histolytica. CONCLUSION: Persons infected with HIV in Taiwan are at increased risk for invasive amebiasis and exhibit a relatively high frequency of elevated antibody titers and intestinal colonization with E histolytica.

AIDS-Related Opportunistic Infections↗

Hepatic amebiasis.

Amebiasis can be considered the most aggressive disease of the human intestine, responsible in its invasive form for clinical syndromes, ranging from the classic dysentery of acute colitis to extra-intestinal disease, with emphasis on hepatic amebiasis, unsuitably named amebic liver abscess. Found worldwide, with a high incidence in India, tropical regions of Africa, Mexico and other areas of Central America, it has been frequently reported in Amazonia. The trophozoite reaches the liver through the portal system, provoking enzymatic focal necrosis of hepatocytes and multiple micro-abscesses that coalesce to develop a single lesion whose central cavity contains a homogeneous thick liquid, with typically reddish brown and yellow color similar to "anchovy paste". Right upper quadrant pain, fever and hepatomegaly are the predominant symptoms of hepatic amebiasis. Jaundice is reported in cases with multiple lesions or a very large abscess, and it affects the prognosis adversely. Besides chest radiography, ultrasonography and computerized tomography have brought remarkable contributions to the diagnosis of hepatic abscesses. The conclusive diagnosis is made however by the finding of Entamoeba histolytica trophozoites in the pus and by the detection of serum antibodies to the amoeba. During the evolution of hepatic amebiasis, in spite of the availability of highly effective drugs, some important complications may occur with regularity and are a result of local perforation with extension into the pleural and pericardium cavities, causing pulmonary abscesses and purulent pericarditis, respectively The ruptures into the abdominal cavity may lead to subphrenic abscesses and peritonitis. The treatment of hepatic amebiasis is made by medical therapy, with metronidazole as the initial drug, followed by a luminal amebicide. In patients with large abscesses, showing signs of imminent rupture, and especially those who do not respond to medical treatment, a percutaneous drainage must be performed with either ultrasound or computerized tomography guidance. Surgical drainage by laparotomy is reserved to patients with secondary infections.

Animals↗

Amebiasis complicating carcinomas: a diagnostic dilemma.

Two black African women and one black American man had carcinomas of cervix, perineum, and sigmoid colon, respectively. In each of these patients, trophozoites of Entamoeba histolytica had invaded the surface of the tumor, and in some areas had invaded more deeply into the stroma between the tumor cells. Although it is well known that cutaneous amebiasis of anus, penis, vulva, and cervix can mimic squamous cell carcinoma, it may be, perhaps, less well known that carcinomas at these sites may be colonized by trophozoites of E. histolytica. In patients with amebiasis but without an associated carcinoma, a correct diagnosis of amebiasis spares the patient unnecessary and sometimes mutilating surgery. But a diagnosis of amebiasis, when there is an unrecognized underlying carcinoma, delays effective treatment of the carcinoma. A smear that establishes a diagnosis of cutaneous amebiasis, therefore, should be followed by biopsy to exclude or confirm an underlying carcinoma.

Adenocarcinoma↗

Amebiasis at an evacuation site on the Thai-Cambodian border.

Symptomatic intestinal amebiasis was highly endemic among the Cambodians living at Green Hill, an evacuation site on the Thai-Cambodian border between June 1987 through May 1989. Monthly incidence rates of intestinal amebiasis were determined to be inversely proportional to cumulative monthly rainfall. The highest incidence of amebic dysentery was 63/1000 in children 12-23 months old. Behavioral risk factors were investigated by conducting a case-control study. A questionnaire was administered to 73 families, each having at least one member with confirmed intestinal amebiasis within the past 3 months, and to 95 randomly selected control families having no individual with diarrhea for at least 3 months. Individuals from families with greater than 4 members were at higher risk for acquiring intestinal amebiasis. No significant differences in behavioral risk factors were identified between case and control families. Eighty-six percent of 51 water samples drawn from wells where amebiasis patients obtained their drinking water had greater than 10 coliforms/100 ml. The main route of transmission of E. histolytica was not identified, but was most likely via the fecal-oral route.

Adolescent↗

[The morphology of amebiasis].

Amebiasis--a protozoan human disease caused by Entamoeba histolytica--occurs in the USSR sporadically in particular geographic regions and in particular populations. The paper reports morphologic findings made in patients with amebiasis involving the intestine or other organs. In typical cases, amebiasis affects the large intestine, particularly the cecum and ascending colon, and has the development of distinctive ulcers as its characteristic feature. As the disease progresses, these appear in all parts of the large intestine; less commonly, the terminal portion of the small intestine is also involved. The most frequent complications of amebic colitis are perforation and phlegmon, which result in peritonitis. Not infrequently, amebic abscesses arise in the liver or other organs through hematogenous dissemination of amebas. Histologic diagnosis of amebiasis may be difficult. Recommendations on how to detect amebas and the tissue changes peculiar to amebiasis are given.

Adult↗