Amebiasis: aspectos clínicos, terapéuticos y de diagnóstico de la infección / An update on amebiasis

The description of Entamoeba dispar, and the recovery of Entamoeba moshkovskii from humans had a major impact in the epidemiology and clinical management of amebiasis. Infections range from asymptomatic colonization to hemorrhagic colitis and extra-intestinal diseases. Only a minority of amebiasis patients progress to the development of disease. Recent studies suggest that susceptibility to infection, and its outcome is influenced by the host, parasite genotype, and environment. The identification of Entamoeba histolytica is based on the detection of specific antigens by ELISA and DNA in stool and other clinical samples. Several diagnostic tests have been developed, including polymerase chain reaction, the technique of choice, for the detection and differentiation of E. histolytica, E. dispar, and E. moshkovskii. Combination of serologic tests with detection of the parasite DNA by PCR or antigen by ELISA offers the best approach to diagnosis. However, these techniques are impractical for clinical laboratories of developing countries. Clinicians must follow the guidelines of the World Health Organization to avoid unnecessary treatments. This review describes and discusses recent advances in amebiasis with emphasis in the clinical aspects and management of infection.

Farmacoterapia actual de la amibiasis, avances en nuevas drogas y diseño de una vacuna / Current pharmacotherapy of amebiasis, advances in new drugs, and design of a vaccine

Aunque existe una gran cantidad de fármacos amebicidas que actúan en la luz intestinal, las drogas de acción tisular usadas para tratar la amibiasis invasiva son aún relativamente limitadas. El advenimiento del metronidazol (MTZ), que es el fármaco de elección para la amibiasis invasiva, y otros nitroimidazoles en el tratamiento de la amibiasis, ha simplificado enormemente la quimioterapia de la infección. No obstante, la erradicación de ésta después de la administración del MTZ requiere terapia adicional con un amebicida de acción luminal como la paramomicina. Después de décadas desde la introducción de estas drogas en la terapia de la infección, se han hecho pocas innovaciones. Mientras tanto, esta parasitosis continúa siendo una causa importante de morbilidad y mortalidad en el mundo contemporáneo. Debido a los efectos tóxicos y los recientes fracasos en el tratamiento de algunos protozoos intestinales con el MTZ, es necesaria la búsqueda de nuevos compuestos amebicidas. Un avance reciente es la nitazoxanida que tiene una actividad de amplio espectro contra diversos agentes infecciosos y se ha demostrado recientemente su acción contra E. histolytica. Este fármaco podría ser clave como amebicida por su efectividad contra el parásito en la luz intestinal y en los tejidos. Sin embargo, el diseño de una vacuna protectora contra la infección sigue siendo deseable. Los estudios experimentales recientes en animales modelo son alentadores. El objetivo de esta revisión es examinar y discutir los aspectos más importantes de la farmacoterapia actual de la amibiasis, así como de los prospectos para el desarrollo de nuevas drogas y una vacuna protectora contra la infección.

Although many drugs destroy Entamoeba histolytica within the colonic lumen, the number of tissue amebicides used to treat invasive amebiasis is still relatively limited. Metronidazole (MTZ), which is the drug of choice for invasive amebiasis, and other nitroimidazoles have greatly simplified the chemotherapy of this disease. However, eradication of E. histolytica infection after completion of MTZ therapy requires additional treatment with luminal amebicides, such as paramomycin. After decades of the introduction of MTZ and other nitroimidazoles in the therapy of amebiasis, there have been few innovations in treating amebic infections. Meanwhile, amebiasis remains among the leading causes of morbidity and mortality in the contemporary world. The toxic effects of MTZ and recent failures in the treatment of several intestinal protozoan parasites, has led to a search for other amebicidal drugs. A recent advance is the demonstration of the effect of nitazoxanide, which has broad spectrum of antiparasitic activity, against E. histolytica. This compound could be the key in the therapy of amebiasis by its action against both luminal and invasive parasite forms. However, the design of an effective vaccine against the infection is still being desirable. Work is underway to develop a vaccine and recent experimental studies are promising. The aim of this review is to examine and discuss the most important aspects of current antiamebic pharmacotherapy and the prospects for development of new drugs and a vaccine.

Hepatitis C virus infection in hemodialysis patients in Maracaibo, Venezuela / Infecção pelo vírus da Hepatite C em pacientes em hemodiálise em Maracaibo, Venezuela

Over a two year period, the incidence of hepatitis C virus (HCV) infection was evaluated in 29 hemodialysis patients, aged between 15 and 75 years (mean ± SD: 45 ± 39.5 years), from the University Hospital Hemodyalisis Unit, Maracaibo, Zulia State, Venezuela. Anti-HCV antibodies were determined using a fourth generation ELISA (Innotest HCV Ab IV) kit and positive blood samples were tested using a recombinant assay kit (Inno-LIA HCV Ab III), both kits from Innogenetics N.V., Belgium. The findings indicate a lack of HCV seroconversion in the hemodialysis patients over the study period, confirmed by the recombinant assay. Risk factors for HCV infection were 0.3270 (95 percent confidence interval: 0.01323-8.080) in patients undergoing hemodialysis. The findings suggest a lack of significant sources for HCV infection due to the preventive measures to avoid its transmission in the hemodialysis unit.

Durante período de 2 anos, estudamos a incidência da infecção pelo vírus da hepatite C (VHC) em 29 pacientes em tratamento de diálise, com idades entre 15 e 75 anos (c ± DS; 45 ± 39,5 anos), procedentes da unidade de hemodiálise do Hospital Universitário de Maracaibo, Estado Zulia, Venezuela. Para a detecção dos anticorpos contra o VHC (anti-VHC) utilizamos a técnica de imunoensaio enzimático (ELISA, Innotest HCV Ab IV) e em amostras reativas por ELISA, utilizamos o método de immunoblot recombinante de terceira geração (Inno-LIA HCV Ab III), ambos da casa comercial Innogenetics N.V., Bélgica. Os resultados demonstram ausência de soroconversão ao VHC nos pacientes hemodializados durante o período estudado, o que foi confirmado pelo método de imunoblot recombinante. Os fatores de risco ao VHC foram 0,327 (95 por cento CI: 0,01323 - 8,080) nos pacientes submetidos ao tratamento de diálise. Nossos resultados sugerem ausência de fontes de infecção neste centro de hemodiálise e que as medidas universais de controle de infecção são cumpridas.

Cyclospora cayetanensis: biología, distribución ambiental y transferencia: [revisión] / Cyclospora cayetanensis: biology, environmental distribution and transfer: [review]

Cyclospora cayetanensis es un protozoo apicomplexa que ha emergido como un patógeno importante causante de diarrea endémica y epidémica en el mundo. En los países industrializados, el parásito se ha reconocido como agente causal de diversas epidemias asociadas, principalmente, con alimentos importados de áreas endémicas. En los países en vías de desarrollo, la ciclosporosis humana está ampliamente distribuida y, en la población general, se han descrito tasas de infección que varían de 0 % a 41,6 %. Sin embargo, la epidemiologia, biología y ecología de C. cayetanensis permanecen poco conocidas. Su ciclo de vida no está totalmente caracterizado y parece requerir un huésped único, el humano, para completarse. El papel que los animales puedan desempeñar como reservorios naturales del parásito permanece sin determinar. Se tiene poca información sobre la distribución ambiental de C. cayetanensis y los vehículos de transmisión del ambiente a los humanos. El agua, los alimentos y los suelos contaminados pueden actuar como vehículos de diseminación del coccidio. Permanecen incertidumbres significativas sobre el parásito, que reflejan la necesidad de continuar los esfuerzos de investigación en diversas áreas, incluyendo su biología básica y distribución ambiental.

Cyclospora cayetanensis is an apicomplexan protozoan that has emerged as an important pathogen causing endemic or epidemic diarrheal disease worldwide. In industrialized countries, the parasite has been recognized as the causative agent of several outbreaks of diarrheal illness mostly associated with produce imported from endemic areas. In developing countries, human cyclosporosis is widely distributed. Infection rates from 0% to 41.6% have been described in the general population. However, the epidemiology, biology, and ecology of C. cayetanensis are not fully understood. The life cycle is not completely characterized, although it appears to require a single human host to be accomplished. The role of animals as natural reservoirs of the parasite remains to be determined. Little information is available concerning the environmental distribution and vehicles of transmission of C. cayetanensis. Contaminated water, foods or soil can be vehicles of spread of the parasite. The significant uncertainties that remain in the knowledge of C. cayetanensis highlight the need for continuing research in several areas, including its basic biology and environmental distribution.

Amibiasis: implicaciones del reconocimiento de entamoeba dispar e identificación de entamoeba moshkovskii en humanos: revisión / Amebiasis: implications of the recognition of entamoeba dispar and the identification of entamoeba moshkovskii in humans: revisión

La historia de Entamoeba histolytica es muy confusa y muestra diversos conceptos erróneos acerca del parásito y su relación con el hospedador. La poca correlación entre la prevalencia de la amibiasis asintomática y sintomática originó la propuesta de tres hipótesis explicativas, entre las cuales estaba el concepto de Brumpt de que existían dos especies morfológicamente idénticas, E. dysenteriae y E. dispar. La aplicación de las técnicas moleculares modernas demostró, en forma irrefutable, que lo que se conocía clásicamente como E. histolytica se trataba realmente de dos especies, confirmándose el concepto de Brumpt casi 7 décadas después. Estudios recientes han identificado en humanos E. moshkovskii, morfológicamente indistinguible de E. histolytica y E. dispar, así como una gran diversidad genética de cada una de estas especies y heterogenicidad en virulencia entre las razas de E. histolytica. La redescripción de E. dispar y la identificación de E. moshkovskii en humanos han impactado enormemente el conocimiento de E. histolytica y la amibiasis con importantes implicaciones clínicas y epidemiológicas que han conducido a la necesidad de reevaluar la prevalencia y morbilidad de la infección en la población mundial y estudiar la distribución geográfica, prevalencia y modelo de transmisión de las razas de E. histolytica para detectar aquéllas epidemiológicamente relevantes y predecir el riesgo de la enfermedad amibiana en una población.

The history of Entamoeba histolytica is very confuse and shows several wrong concepts about the parasite and its relationship with the host. The poor correlation between the prevalence of asymptomatic and symptomatic amebiasis originated the proposal of three explicative hypothesis, among them was the concept of Brumpt that E. histolytica comprised two morphologically identical species, E. dysenteriae and E. dispar. The application of modern molecular techniques irrefutably proved that E. histolytica was really a complex of two species, confirming the concept of Brumpt almost 7 decades later. Recent studies have identified in humans E. moshkovskii, morphologically indistinguishable from E. histolytica and E. dispar, a great genetic diversity within each of these species, and heterogeneity in virulence among E. histolytica strains. The redescription of E. dispar, and the recovery of E. moshkovskii from humans have had a major impact in our understanding of E. histolytica and amebiasis with important clinical and epidemiologic implications. This has led to the need of a reevaluation of the infection in terms of prevalence and morbidity in the global population and to study the geographic distribution, prevalence, and transmission pattern of E. histolytica strains in order to detect those with epidemiologic relevance and predict the risk of amebic disease in a population.

Baja prevalencia de la infección por el virus de la hepatitis C en una población de reclusos, Maracaibo, Venezuela / Low prevalence of hepatitis C virus infection in a prisoner population from Maracaibo, Venezuela

Introducción. Las conductas de alto riesgo presentes en los centros de reclusión incrementan la probabilidad de transmisión de la infección por el virus de la hepatitis C. En Venezuela no se han realizado estudios del virus en estos centros, por lo que se desconoce la relevancia de la infección en ellos. Objetivo. Estimar la prevalencia del virus de la hepatitis C y los posibles factores de riesgos involucrados en la transmisión del virus en reclusos de la cárcel de Sabaneta, Maracaibo, Venezuela. Material y métodos. Se seleccionó una población de 200 reclusos de un total de 1.000. Las edades estaban comprendidas entre 18 y 69 años (media ± DE: 31,629,93 a˜os). La detección de anticuerpos contra el virus de la hepatitis C se realizó por duplicado mediante el método inmunoenzimático ELISA de IV generación y por el método de inmunoblot INNO-LIA HCV®, ambos de Innogenetic Lab (Bélgica). El ARN viral se detectó por la técnica de reacción en cadena de la polimerasa, previa transcripción inversa, RT-PCR. Resultados. La frecuencia obtenida con el método ELISA fue de 5% (10/20) y 3/200 (1,5%) individuos fueron positivos, a la vez, con los métodos de INNO-LIA y RT-PCR. Conclusiones. La prevalencia de la infección por el virus de la hepatitis C en esta población fue baja, lo que evidencia la baja circulación del virus en el reclusorio. El principal factor de riesgo para la adquisición de la infección, al parecer, es el uso de drogas intravenosas.

Introduction. The high risk behaviors observed in prison centers have favored the transmission of hepatitis C virus infection. The main risk factor to acquire hepatitis C virus infection seems to be the use of intravenous drugs. In Venezuela, the prevalence of the infection in these centers is unknown since studies of the hepatitis C virus there are lacking. Objective. The aim of this study was to determine the prevalence of hepatitis C virus and the risk factors involved in the transmission in prisoner populations. Material and methods. A sample of 200 prisoners was studied from Sabaneta Jail, Maracaibo, Venezuela. The ages were between 18-69 years (average ± DS: 31.6±9.9 years). Serum samples were tested by a fourth generation enzyme-linked immunosorbent assay ELISA and a confirmatory assay INNO-LIA. Both kits were from Innogenetic Laboratories N.V. (Belgium). Viral RNA was tested by the reverse transcription polymerase chain reaction technique (RT-PCR). Results. The ELISA assay determined a hepatitis C virus prevalence of 5.0% (10/200); 3/200 (1.5%) individuals were positive by both INNO-LIA and RT-PCR tests. Conclusions. The observed prevalence of hepatitis C virus antibodies in this population was very low, suggesting a low circulation of the virus in this environment and a low level of associated risk behaviors.

Criptosporidiosis en pacientes con el virus de la inmunodeficiencia humana / Cryptosporidiosis in patients with the human immunodeficiency virus / Criptosporidiose em pacientes com o vírus da imunodeficiência humana

El alto potencial oportunista de Cryptosporidium y la cronicidad y gravedad eventual de la infección en individuos inmunocomprometidos han acentuado su importancia como un problema de salud pública global. La tasa de infección del parásito en individuos con el Virus de la Inmunodeficiencia Humana (VIH) y diarrea es alta, con promedio de 32%. Estos pacientes son más propensos a la infección y a especies que generalmente no son infecciosas para los humanos. Los pacientes con el Síndrome de Inmunodeficiencia Adquirida son susceptibles a una forma devastadora de la criptosporidiosis, manifestada por diarrea acuosa, voluminosa y crónica, y pueden experimentar infecciones atípicas que afectan tejidos extraintestinales. Sin embargo, existe una marcada variedad en la presentación clínica, incluyendo la asintomática. En general, el riesgo a la infección, a la enfermedad severa y al desarrollo de complicaciones es proporcional a la disminución en el número y la función de los linfocitos CD4+; la forma crónica más severa está limitada a pacientes con cuentas de estas células menores de 150/ml. La variedad genética del parásito también puede afectar la presentación clínica de la infección. No existe una quimioterapia curativa ni inmunoterapéuticos o vacunas aprobados para el tratamiento o prevención de la infección en pacientes infectados con el VIH. Lo mejor para la terapia y prevención de la criptosporidiosis en estos pacientes es el tratamiento antirretroviral, ya que la restauración de los linfocitos CD4+ permite la recuperación clínica o la erradicación de la infección.

The high opportunistic and severe life-threatening potential of Cryptosporidium in immuno-compromised individuals have increased the importance of cryptosporidiosis as a global public health problem. The prevalence of the parasite in patients infected with the Human Immunodeficiency Virus (HIV) and diarrhea is high, with a median of 32%. These patients are more susceptible to the infection and species that are not usually infectious to humans. People with the Acquired Immunodeficiency Syndrome are susceptible to a devastating form of cryptosporidiosis, manifested by chronic, voluminous, watery diarrhea, and can develop atypical extra-intestinal disease presentations. However, there is actually a marked variability in the clinical presentation, including asymptomatic infection. In general, the risk of infection, severity of illness, and development of unusual complications of cryptosporidiosis is proportional to the decrease of CD4+ cell numbers or function; severe life-threatening diarrhea is limited to patients with cell counts below 150 cells/ml. Symptoms may also be influenced by the genetic differences of the parasite. There is no reliable curative chemotherapy and no vaccines or immuno-therapeutics have been approved for the prevention or treatment of cryptosporidiosis in HIV infected patients. The best approach to prevention and therapy of the infection in these individuals is the maintenance of the immune system function by using the antiretroviral therapy that allows clinical recovery or parasite eradication.

O alto potencial oportunista de Cryptosporidium e a cronicidade e gravidade eventual da infecção em indivíduos imuno-comprometidos tem acentuado sua importância como um problema de saúde pública global. A taxa de infecção do parasito em indivíduos com o Vírus da Imunodeficiência Humana (HIV) e diarréia é alta, com média de 32%. Estes pacientes são mais propensos a infecção e a espécies que geralmente não são infecciosas para os humanos. Os pacientes com a Síndrome de Imunodeficiência Adquirida são susceptíveis a uma forma devastadora da criptosporidiose, manifestada por diarréia aquosa, voluminosa e crônica, e podem experimentar infecções atípicas que afetam tecidos extra-intestinais. No entanto, existe uma marcada variedade na apresentação clínica, incluindo a assintomática. Em geral, o risco à infecção, a enfermidade severa e ao desenvolvimento de complicações é proporcional a diminuição no número e a função dos linfócitos CD4+; a forma crônica mais severa está limitada a pacientes com contas de estas células menores de 150/ml. A variedade genética do parasito também pode afetar a apresentação clínica da infecção. Não existe uma quimioterapia curativa nem imunoterapêuticos ou vacinas aprovadas para o tratamento ou prevenção da infecção em pacientes infectados com o HIV. O melhor para a terapia e prevenção da criptosporidiose nestes pacientes é o tratamento anti-retroviral, já que a restauração dos linfócitos CD4+ permite a recuperação clínica ou a erradicação da infecção.

Environmental risk factors for Cryptosporidium infection in an island from Western Venezuela

Few investigations have been conducted on risk factors for Cryptosporidium infection in communities from developing countries. A study was conducted to determine the prevalence and risk factors for cryptosporidiosis in San Carlos island, Venezuela. A sample of 515 subjects (mean age ± SD: 21.4 ± 17.8 years) was surveyed. Single fecal specimens were collected and modified Ziehl-Neelsen carbolfuchsin staining of formalin-ether concentrate stools were examined for identification of the parasite. Infections with Cryptosporidium (67 of 515, 13 percent) were common. Prevalence of the parasite varied among sectors of the community; 34 of 67(50.7 percent) cases of cryptosporidiosis clustered in two sectors with extreme poverty. Variables strongly associated with a higher risk for the infection (p < 0.01) were residing in these sectors versus the remainder, living in a hut or small residence versus a brick or larger house, using an area of backyard rather than a toilet or latrine for defecation, and having contact with soil contaminated with human feces. Crowding was also a risk (p < 0.05). Contact with human feces contaminated-soil may be an important mode of transmission and poverty a predisposing factor for the infection.

Low prevalence of hepatitis C virus infection in Amerindians from Western Venezuela

Previous studies have not found hepatitis C virus (HCV) infection in Amerindians from Western Venezuela. A survey of 254 Bari and Yukpa natives aged 10-60 years (mean ± SD age = 35 ± 5.4 years) from four communities, two Bari and two Yukpa, in this area were studied to assess the prevalence of antibodies to HCV (anti-HCV) and HCV RNA among these indigenous populations. Serum samples were examined initially for anti-HCV by a four generation enzyme-linked immunosorbent assay (ELISA). Reactive samples were then tested using a third generation recombinant immunoblot assay (RIBA-3). Viral RNA was investigated in all immunoblot-reactive samples by a nested polymerase chain reaction (PCR) method. Six (2.3 percent) of 254 natives were positive by ELISA, one (2.2 percent) of these reactive samples were positive by RIBA, and four (1.5 percent) were indeterminate. Only two (0.8 percent) were positive by PCR, corresponding to 1 (2.1 percent) of 47 inhabitants of a Yukpa community and to 1 (2.2 percent) of 45 subjects of a Bari community. Iatrogenic is thought to play a role in acquisition of the infection. The findings indicate a HCV focus of low endemicity and are compatible with a low degree of exposures of the natives to the virus. Studies are necessary to assess the risk factors for infection in these Amerindians.

Prevalence of human toxoplasmosis in San Carlos Island Venezuela

Se realizó una encuesta serológica de 335 individuos de 1 a 65 años de edad (promedio ± DS de 20,8 ±15.7) en 6 comunidades de la isla de San Carlos en el occidente de Venezuela para estudiar la prevalencia de anticuerpos anti-toxoplasma gondii. La técnica de hemaglutinación indirecta mostró una tasa de infección de 49,8 por ciento (167 de 335) que fluctuó de 23 a 64,8 por ciento de acuerdo a la localidad. No se detectó asociación entre la prevalencia de anticuerpos y la edad a los factores de riesgo. Se observaron tasas de anticuerpos más altas en una comunidad de la costa de barlovento y tazas menores en el sector rural en comparación a otras tres localidades. Las comunidades con las prevalencias de anticuerpos más altas mostraron los mayores títulos geométricos promedios. La toxoplasmosis es prevalente y ampliamente distribuida en la isla. La infección por ooquistes provenientes de heces de gatos parece ser el modo predominante de transmisión y el agua contaminada parece jugar un papel en la transmisión