Strengthening preventive care programs: a permanent challenge for healthcare systems; lessons from PREVENIMSS México.

BACKGROUND: In 2001, the Instituto Mexicano del Seguro Social (IMSS) carried out a major reorganization to provide comprehensive preventive care to reinforce primary care services through the PREVENIMSS program. This program divides the population into programmatic age groups that receive specific preventive services: children (0-9 years), adolescents (10-19 years), men (20-59 years), women (20-59 years) and older adults (> = 60 years). The objective of this paper is to describe the improvement of the PREVENIMSS program in terms of the increase of coverage of preventive actions and the identification of unmet needs of unsolved and emergent health problems. METHODS: From 2003 to 2006, four nation-wide cross-sectional probabilistic population based surveys were conducted using a four stage sampling design. Thirty thousand households were visited in each survey. The number of IMSS members interviewed ranged from 79,797 respondents in 2003 to 117,036 respondents in 2006. RESULTS: The four surveys showed a substantial increase in coverage indicators for each age group: children, completed schemes of vaccination (> 90%), iron supplementation (17.8% to 65.5%), newborn screening for metabolic disorders (60.3% to 81.6%). Adolescents, measles - rubella vaccine (52.4% to 71.4%), hepatitis vaccine (9.3% to 46.2%), use of condoms (17.9% to 59.9%). Women, measles-rubella vaccine (28.5% to 59-2%), cervical cancer screening (66.7% to 75%), breast cancer screening (> 2.1%). Men, type 2 diabetes screening (38.6% to 57.8%) hypertension screening (48-4% to 64.0%). Older adults, pneumococcal vaccine (13.2% to 24.9%), influenza vaccine (12.6% to 52.9) Regarding the unmet needs, the prevalence of anemia in children was 30% and a growing prevalence of overweight and obesity, type 2 diabetes, and hypertension was found in men, women and older adults. CONCLUSION: PREVENIMSS showed an important increase in the coverage of preventive services and stressed the magnitude of the old and new challenges that this healthcare system faces. The unsolved problems such as anemia, and the emerging ones such as overweight, obesity, among others, point out the need to strength preventive care through designing and implementing innovative programs aimed to attain effective coverage for those conditions in which prevention obtains substandard results.

Lewis antigen expression by Helicobacter pylori strains colonizing different regions of the stomach of individual patients.

The diversity in the expression of Lewis antigens (Le) of 226 single colonies of Helicobacter pylori isolated from four regions of the stomach of eight adults is shown. Le(y) was expressed more in strains colonizing antrum than in strains colonizing fundus, whereas Le(x) was more common in fundus strains. cagA(+) strains were more associated with Le-negative strains.

A primary Helicobacter pylori infection does not protect against reinfection in children after eradication therapy.

BACKGROUND: Helicobacter pylori infection is one of the most common chronic infections in the world, and is acquired mainly during childhood. It is not clear to which extent a primary infection protects the child from reinfection. Our aim was to determine the possible protection conferred by a primary infection against H. pylori reinfection in children. METHODS: A follow-up study with 120 children distributed in two cohorts; the first included 80 children without previous H. pylori infection (primo-infection cohort); the second included 40 infected children successfully eradicated (reinfection cohort). Cohorts were monitored during 2 years with urea-breath-test (UBT) at 3, 6, 9, 12, 18 and 24 months for the acquisition of H. pylori infection. We compared the rate of reinfection in eradicated children with the rate of infection in children without previous infection. H. pylori infection during the follow-up was analyzed and compared between cohorts using chi2 and survival curves. A questionnaire was performed for the evaluation of possible risk factors for infection in both cohorts. RESULTS: No significant differences in rates of primo-infection or reinfection were found; 17 (21.2%) primo-infections and 10 (25%) reinfections were documented. Most of the primo-infections (14/17) occurred in the first year of follow-up. In contrast, reinfection episodes occurred more frequently during the second year (6/10). In both cohorts, most infections were transient. Risk factors were similar for both, primo and reinfection cohorts. CONCLUSION: A primary infection does not protect from reinfection in the population of children studied.

Giardia duodenalis: analysis of secreted proteases upon trophozoite-epithelial cell interaction in vitro.

Protease secretion by Giardia duodenalis trophozoites upon interaction with epithelial cells and its association with the parasite adhesion was studied in co-cultures of parasites with IEC6 epithelial cell monolayers in the presence or absence of protease inhibitors. Proteolytic activity in supernatants from trophozoites was enhanced when they were co-cultured with IEC6 cells. This activity was strongly inhibited by pre-incubation of live trophozoites with E-64 and TPCK and a concomitant inhibition of parasite adhesion to IEC6 cells was observed. These data suggest that trophozoites secrete cysteine-type proteases that play a role in the adhesion of G. duodenalis to epithelial cells.

Giardia duodenalis: analysis of secreted proteases upon trophozoite-epithelial cell interaction in vitro

Protease secretion by Giardia duodenalis trophozoites upon interaction with epithelial cells and its association with the parasite adhesion was studied in co-cultures of parasites with IEC6 epithelial cell monolayers in the presence or absence of protease inhibitors. Proteolytic activity in supernatants from trophozoites was enhanced when they were co-cultured with IEC6 cells. This activity was strongly inhibited by pre-incubation of live trophozoites with E-64 and TPCK and a concomitant inhibition of parasite adhesion to IEC6 cells was observed. These data suggest that trophozoites secrete cysteine-type proteases that play a role in the adhesion of G. duodenalis to epithelial cells.

High correlation of human immunodeficiency virus type-1 viral load measured in dried-blood spot samples and in plasma under different storage conditions.

BACKGROUND: To measure HIV-1 RNA concentration requires venous extraction of blood, use of RNAase-free materials, and transport in a cold chain, which makes difficult the management of samples in developing countries. We evaluated the utility of the determination of HIV-1 RNA concentration in blood samples dried on filter paper (DBS) and subjected to different conditions, as contrasted with determination in plasma. METHODS: HIV-1 RNA concentration was determined in HIV-infected patients in DBS and in plasma samples. Samples were subjected to the following: DBS were stored at 4, 22, and 37 degrees C for 1, 3, and 7 days; samples from patients from four regions of Mexico were mailed to a reference laboratory; DBS were sent under environmental conditions; and plasma samples were sent frozen. HIV-1 RNA concentrations were determined by NucliSens in DBS and by Amplicor test in plasma. RESULTS: HIV-1 RNA concentration determined in DBS subjected to different temperatures and times had a significant correlation (r=0.99) with those obtained in plasma. When compared with values in plasma, Kappa agreement coefficients of values in DBS stored for 7 days at 4, 22, and 37 degrees C were 0.98, 0.83, and 0.94, respectively. Quantification of HIV-1 RNA in 108 DBS mailed from remote areas with different climates demonstrated significant correlation with those obtained in plasma (r=0.95; p <0.001). CONCLUSIONS: DBS is a simple and reliable method to measure HIV-1 RNA concentration, especially when samples are mailed from remote areas to a reference center. This collection method is an economic and suitable alternative for use in developing countries.

Natural rotavirus infection is not associated to intussusception in Mexican children.

AIMS: To determine whether natural rotavirus infection or infection by another enteropathogen is associated to intussusception (IS); and to describe the seasonality of IS compared with severe diarrhea (SD) and rotavirus SD in Mexican children. METHODS: A prospective, observational, multicenter and case-control study was conducted in Mexico City from December 1999 to February 2001. Cases were children younger than 1 year old hospitalized for IS; diagnosis was made by clinical features, radiologic and/or surgery findings. Controls were children younger than 1 year old hospitalized for another disease than a gastrointestinal illness (NGI). Cases and controls were paired by age and date of admission (+/-3 months; for both), in a 1:2 ratio. A surveillance of IS cases, SD and rotavirus SD episodes was conducted during the study period. Stool samples collected soon after IS resolution or at admission were tested for rotavirus, adenovirus, astrovirus, bacteria and parasites. RESULTS: Thirty cases of IS and 60 controls with NGI were studied. Rotavirus was not detected in any case of IS. Adenovirus (17%) was the only enteropathogen detected in IS. Rotavirus (8%), adenovirus (2%), astrovirus (2%) and bacteria (2%) were detected in NGI. Rotavirus infection was not associated with IS (odds ratio, 0; 95% confidence interval, 0-2.9), whereas adenovirus infection was strongly associated as risk factor for IS (odds ratio undefined; P = 0.003), compared with NGI. Seasonal variation in admissions for IS was small, whereas admissions for SD and rotavirus SD showed a marked seasonal increase during fall-winter. CONCLUSIONS: In Mexican children, rotavirus infection was not associated to IS; whereas a significant association was observed between adenovirus and IS. Also there was no increase in IS cases during the sharply defined fall-winter rotavirus outbreak. Observations from this controlled study suggest that natural rotavirus infection is not a risk factor for IS. This information may have implications for development of a safer and effective rotavirus vaccine.

Prevalence and genetic diversity of human astroviruses in Mexican children with symptomatic and asymptomatic infections.

The prevalence and type diversity of human astroviruses (HAstV) in children with symptomatic and asymptomatic infections were determined in five localities of Mexico. HAstV were detected in 4.6 (24 of 522) and 2.6% (11 of 428) of children with and without diarrhea, respectively. Genotyping of the detected strains showed that at least seven (types 1 to 4 and 6 to 8) of the eight known HAstV types circulated in Mexico between October 1994 and March 1995. HAstV types 1 and 3 were the most prevalent in children with diarrhea, although they were not found in all localities studied. HAstV type 8 was found in Mexico City, Monterrey, and Mérida; in the last it was as prevalent (40%) as type 1 viruses, indicating that this astrovirus type is more common than previously recognized. A correlation between the HAstV infecting type and the presence or absence of diarrheic symptoms was not observed. Enteric adenoviruses were also studied, and they were found to be present in 2.3 (12 of 522) and 1.4% (6 of 428) of symptomatic and asymptomatic children, respectively.

High rates of recurrence and of transient reinfections of Helicobacter pylori in a population with high prevalence of infection.

OBJECTIVES: Little is known concerning the magnitude of reinfection versus recrudescence of Helicobacter pylori (H. pylori) infection after eradication treatment. The aims of this study were to determine the magnitude of H. pylori reinfection versus recrudescence, and to identify possible risk factors for reinfection. METHODS: Children and adults with upper GI symptoms treated at the Centro Médico Nacional Siglo XXI (Instituto Mexicano del Seguro Social, in Mexico City, Mexico) were studied. H. pylori infection was diagnosed with urea breath test (UBT), histology, and culture. Infected patients received triple therapy, and those who became UBT negative 4-6 wk after treatment were considered as eradicated and were included in the study. A cohort of 141 patients in whom the disease was eradicated was monitored for recurrence with UBT at 3, 6, 9, 12, 18, and 24 months. H. pylori was isolated from gastric biopsy samples before treatment and at recurrence and isolates compared by genotyping. RESULTS: During this period, 32 (22.7%) cases of recurrence were documented the majority occurring during yr 1. In nine of the 32 (28.1%) cases, recurrence was eradicated spontaneously, suggesting these were transient reinfections. Recurrence rates were significantly higher in the subjects 41-60 yr of age than in younger or older subjects. H. pylori isolates from 12 recurrence cases were genotyped; nine (75%) were classified as true reinfection and three as recrudescence. CONCLUSIONS: In our population, recurrence rate is high in adults and transient reinfection is common. In several cases, reinfection occurred by multiple strains, which suggests that soon after eradication, patients are exposed to multiple sources of reinfection.

Intensity of inflammation, density of colonization and interleukin-8 response in the gastric mucosa of children infected with Helicobacter pylori.

BACKGROUND: Few reports exist on inflammation and interleukin (IL)-8 response in H. pylori-infected children. The aim of this study was to determine the intensity of inflammation, density of colonization and magnitude of IL-8 response in children with and without H. pylori infection. MATERIALS AND METHODS: We studied 45 children with dyspeptic symptoms, 21 infected with H. pylori and 24 without infection. Antrum and corpus gastric biopsies were obtained and studied for H. pylori infection with an immunofluorescence technique and for IL-8 with an immunohistochemical assay. Biopsy specimens were stained with hematoxilin and eosin and gastritis was graded according to the Sydney system. The magnitudes of the IL-8 response and H. pylori colonization were estimated microscopically with image analyzer software. RESULTS: In H. pylori-infected children, mild mono-nuclear cell infiltration was found in 50%, and no neutrophils in 40% of cases. In the antrum but not in the corpus, the intensity of colonization correlated with neutrophil and mononuclear cell infiltration. The IL-8 response was significantly higher in the antrum (p <.05) and corpus (p <.02) of infected children, and was localized mainly in the surface and crypts of the epithelium. No correlation was found between the magnitude of the IL-8 response and the infiltration of either neutrophil or mononuclear cells. CONCLUSIONS: In H. pylori-infected children, poor mononuclear and neutrophil infiltration was observed. Infection was associated with a higher IL-8 response by gastric epithelial cells. The density of colonization but not the IL-8 response correlated with neutrophil cell infiltration.

Estudio seroepidemiológico de borreliosis de Lyme en la Ciudad de México y el noreste de la República Mexicana / Seroepidemiologic survey of Lyme Borreliosis in Mexico City and the Northeast region of the country

OBJETIVO: Investigar mediante métodos serológicos la infección por B burgdorferi en individuos del Distrito Federal y la zona noreste de México. MATERIAL Y MÉTODOS: Se obtuvo una muestra representativa de sueros del Distrito Federal y la zona noreste de México, obtenidas en la Encuesta Seroepidemiológica Nacional de 1987-1988. Se detectaron anticuerpos IgG vs B burgdorferi por ELISA, confirmados con Western blot. En este trabajo se utilizó estadística descriptiva. RESULTADOS: Fueron estudiados 2 346 sueros; 297 (12.6 por ciento) fueron positivos por inmunoensayo enzimático, y 122/297 fueron confirmados por Western blot. La seroprevalencia fue de 3.43 por ciento en el Distrito Federal y 6.2 por ciento en la zona noreste del país. Tamaulipas fue el estado con la seroprevalencia más alta. CONCLUSIONES: La prevalencia de casos seropositivos sugieren que la infección por B burgdorferi ocurre en el noreste de México y el Distrito Federal. Es necesario identificar casos clínicos y buscar el vector infectado para confirmar la presencia de la enfermedad de Lyme en México

Evaluation of the enzyme-linked immunoelectrotransfer blot assay for diagnosis of neurocysticercosis in children.

Neurocysticercosis is a common problem in developing countries, and it causes neurologic disorders in children. Immunodiagnosis with Taenia solium glycoproteins as an antigen has been validated in adults but not in children. The aim of this work was to evaluate a Taenia solium glycoproteins-based enzyme-linked immunoelectrotransfer blot assay in children with neurocysticercosis. Twenty-five confirmed cases of neurocysticercosis and 50 healthy children from the same community were included. The test had a sensitivity of 72% and a specificity of 96%. Sensitivity was higher (100%) in cases with multiple cysts and in multiple sites. Sensitivity was higher when cysts were in parenchyma (86%) than when they were in the subarachnoid space. The most frequently recognized proteins were 24, 39 to 42, and 50 kDa. Diagnosis was more efficient in serum than in cerebrospinal fluid. Western blot is a reliable method for serologic diagnosis of neurocysticercosis in children. Multiple cysts and infections in multiple sites elicited a stronger immune response.

Evaluation of albendazole prodrugs in experimental trichinellosis

Background. Two albendazole (ABZ) prodrugs, N-methoxycarbonyl-N'-[(2-nitro-4-propylthio) phenyl] thiourea (compound 2), and N-methoxycarbonyl-N'-[2-nitro-5-propylthio) phenyl] thiourea (compound 3) have recently been synthesized. These compounds showed greater solubility than ABZ itself. Methods. In order to evaluate the biotransformation of compounds 2 and 3 to ABZ and/or ABZ-sulphoxide (ABZ-SO), plasma samples taken from mice treated with the prodrugs were analyzed by HPLC. Also, the anthelmintic activity of compounds 2 and 3 against Trichinella spiralis was evaluated in mice experimentally infected with the prarasite. Results. The presence of ABZ and/or ABZ-SO was demostrated in plasma samples taken at different time intervals after prodrug administration, although their levels were low compared to those reached in mice treated with ABZ. Additionally, prodrugs 2 and 3 were also detected in these samples. In regrad to the anthelmintic activity of ABZ prodrugs, it was shown that compound 3 was more active than compound 2. Additionally, it was as effective as ABZ against T. spiralis pre-adult, adult, and female fecundity. However, compound 3 was not as active sa ABZ against the muscle stage of the parasite. Conclusions. Compound 3 had better anthelmintic activity againts T. spiralis than compound 2. The bioconversion of compounds 2 and 3 to ABZ and/or ABZ-SO was demostrated by HPLC, but they did not reach equivalant concentrarion to that of ABZ. Prodrugs 2 and 3 were also present in plasma samples, suggesting that prodrugs were not efficiently reduced in the intestine of mice

Seroepidemiology of hepatitis E virus infection in Mexican subjects 1 to 29 tears of age

Background. Hepatitis E virus (HEV) infection causes an acute, self-limited hepatitis associated with high mortality in pregnant women. Community-based surverys are scarce and information on HEV infection in populations in needed. The aim of this work was to study seroprevalence to HEV in young adults and children in Mexico, using a community-based survey. Methods. Serum samples from 3,459 individuals were studied; the population included subjects from 1 to 29 years old from all regions of the country representing all socioeconomic levels, IgG anti-HEV was determined by ELISA. Results. Anti-HEV antibodies were found in 374 (10.5 percent) individuals. Seroprevalence increased with age from 1.1 percent in children young than 5 years to 14.2 percent in persons 26 to 29 years of age (p = 0.006). Risk factors for infection included living in rural communities and a low educational level. Seroprevalence was not associated with the level of regional development. Conclusions. HEV infection is endemic in Mexico. Age, type of community, and educational level were identified as risk factors for infection

Susceptibility to varicella-zoster infection in individuals 1 to 29 years of age in Mexico

Background. The prevalence of varicella zoster virus (VZV) infection has been poorly studied in Latin America. The aim of this work was to study the seroprevalence of antibody to VZV infection in Mexico. Infection was determined in 3,737 individuals. Methods. Samples were collected during a national serologic survey performed during 1987-1988 and represented individuals 1- to 29-years-old from all socioeconomic levels and from rural and urban communities throughout the country. Antibodies anti-VZV were measured with a commercially available enzyme-linked immunosorbent assay (VARELISA Merck, Germany). Results. In the population studied, 464 individuals (12.4 percent) were seronegative or susceptible to infection, whereas about 17.0 percent of individuals 1- to 19-years-old were susceptible to infection. Between the ages of 20 to 24 years, 8.4 percent were susceptible and between 25 to 29 years, 5.0 percent of persons were still susceptible to infection. Conclusions. Socioeconomic level, density of population, crowding, and gender were not found as risk factors for susceptibility to VZV infection in adolescents and young adults. Low educational level was found as a risk factor for susceptibility. High proportions of adolescents and young adults in Mexico are susceptible to VZV infection and should receive special attention when desingning vaccination programs

Selorogic evidences suggesting the presence of borrelia burgdorferi infection in Mexico

Background. Lyme disease is the most common vector-borne Human disease in Europe and the United States. In Mexico, clinical cases suggestive of lyme borreliosis have been reported; however, infection was not confirmed by serologic or microbiologic tests. Methods. To study the prevalence of IgG antibodies againts Borrelia burgdorferi among Mexican persons, a community-based sero-survery including all states of Mexico was done. A sample of 2,890 sera representing individuals of all ages and all socioeconomic levels was studied. Antibodies ati-B. burgdorferi were determined by enzyme-linked immunosorbent assay (ELISA) using a whole-cell sonicated extract of B. burgdorferi strain B31. Serum specimens positive for ELISA were further studied by Western blot (WB). A serum sample was considered positive by WB if at least three of the following protein bands were recognized: 18, 24, 28, 31, 34, 39, 41, 45, 58, 62, 66, and 93 KDa. Some WB positive specimens were futher confirmed with an inmmunodot-blot (IDB) test using recombinant and purified B. burgdorferi proteins. Results. Of the 2,890 specimens, 34 were positive for ELISA; nine of these 34 were confirmed as positive by WB. Four of the nine WB positive sera were testd by IDB and all four were positive. The prevalence of WB confirmed cases in the sample studied was 0.3 percent. Positive specimens were from residents of the northeastern and central areas of Mexico. Conclusions. the resological evidences of this study suggest that Borrelia burgdorferi infection is present in the Mexican population. This finding should be confirmed by documenting the infection in clinical cases and in tick vectors

Comparación de dos tinciones en la detección de Pneumocystis carinii / Comparison of two staining methods in the detection of pneumocystis carinii

Evaluar dos metodologías para identificar P. carinii en lavado bronquio-alveolar. Material y métodos. Se obtuvo lavado bronquio-alveolar de 20 ratas a las que se indujo una infección de P. carinii por inmunosupresión. Las muestras se tiñieron con tres métodos: azul de toluidina modificada (ATM), Diff Quik (DQ), y tinción de plata como estándar de oro. Dos observadores hicieron la búsqueda de P. carinii en forma independiente. Resultados. La tinción de plata mostró P. carinii en 15 de las 20 muestras. Con DQ hubo una especificidad de 100 por ciento pero 27 por ciento de sensibilidad; con ATM la sensibilidad fue de 93 por ciento pero especificidad de 80 por ciento. La concordancia interobservadores (índice kappa) fue de 0.11 con DQ y de 0.53 con ATM. Conclusión. Nuestros resultados sugieren la conveniencia de usar la tinción de plata para garantizar los resultados en el diagnóstico de neumonía por P carinii

Seroepidemiología del sarampión en individuos de 5 a 14 años de edad de la República Mexicana / Seroepidemiology of measles in child of 5-14 years old in the Mexican Republic

Introducción: El sarampión continúa siendo un problema de salud pública en el mundo, especialmente en países en vías de desarrollo, por lo que es necesario realizar periódicamente estudios epidemiológicos para identificar grupos susceptibles a la infección, así como las poblaciones en las que se requiere intensificar los programas de vacunación. Material y Métodos. El área de estudio comprendió la República Mexicana con sus 32 entidades federativas, estudiándose 9,075 sueros de individuos de 5 a 14 años de edad. El método empleado para evaluar los anticuerpos inhibidores de la hemaglutinación, fue la técnica en microplaca de acuerdo al procedimiento de Borrby, habiéndose considerado un título 1:8 como valor protector. Resultados. Se identificó un 81.2 por ciento de individuos seropositivos (IC 95 por ciento, 80.4-82.0 por ciento). La proporción de susceptibles por entidad federativa varió de 51.0 a 0.7 por ciento, con una myor proporción de susceptibles en los niños de áreas rurales (20.9 por ciento) y en los niños de nivel socioeconómico bajo (21.4 por ciento). No hubo diferencias en la producción de susceptibles cuando se analizó el nivel de escolaridad y el antecedente de vacunación. Conclusiones. Se encontró un porsentaje elevado (19 por ciento) de niños susceptibles al sarampión en el grupo de 5 a 14 años, predominantemente en el área rural y en los estratos socioeconómicos bajos. Una adecuada estrategia de control del padecimiento es la de aplicar una segunda dosis de vacuna a los escolares, preferentemente en las áreas rurales

Historia natural de la infección amibiana durante el primer año de vida: estudio comparativo de cohortes / Natural history of amebic infection in infants: a cohort comparative study

Introducción. El mecanismo de transmisión intrafamiliar es uno de los más importantes en la infección amibiana; sin embargo el papel de la madre portadora no ha sido demostrado con objetividad y existe escasa información sobre la historia natural de la respuesta inmune humoral en los portadores asintomáticos. Fue objetivo de este estudio identificar el papel de la infección materna por Entamoeba hystolytica en la transmisión del parásito a sus hijos y su relación con la respuesta inmune humoral así como con la caracterización del tipo de zimodemo. Material y métodos. Se efectuó un estudio comparativo y prolectivo de cohortes madre-recién nacido caracterizado por la presencia (n= 21) o ausencia (n= 29) de madres portadoras del parásito, a las cuales se visitó cada 2 semanas durante un año, a partir del nacimiento de los hijos. En cada ocasión se obtuvieron muestras de heces del binomio para la identificación de E. histolytica por estudios coproparasitoscópicos y cultivo de Robinson. Cada 4 meses se colectó sangre venosa del binomio para hemaglutinación indirecta y Western-blot. Resultados. El 51 por ciento de las muestras fecales de las madres portadoras mantuvieron esta característica a lo largo del seguimiento, mientras que sólo en el 1.5 por ciento de las muestras de las madres no portadoras se idenificó al parásito P < 0.0001). La incidencia de infección amibiana durante el primer año de vida de los hijos índice fue de 10 por ciento (5/50), cuatro pertenecientes a la cohorte de madres portadoras y uno a la de no portadoras (P = 0.1). En los cinco niños infectados los títulos de anticuerpos antiamibianos fueron más altos que el resto de los hijos (P < 0.02) y el Western blot mostró que hay fracciones antigénicas que inducen anticuerpos séricos de clase IgG, IgA e IgM contra este parásito desde fases muy tempranas. Conclusiones. ninguno de los portadores, incluidos los cinco niños infectados, presento manifestaciones de enfermedad amibiana. El patrón de excreción de quistes de E. histolytica entre las madres fue diferente, a pesar de compartir las mismas características del medio ambiente. La respuesta inmunológica observada en los niños infectados, sugiere mecanismos de inducción de anticuerpos diferentes a los descritos para la amibiasis intestinal invasora