Impacto del COVID-19 en la esperanza de vida en los municipios de los estados del noreste de México / COVID-19 impact on life expectancy among municipalities of Northeastern states of Mexico

RESUMEN La mortalidad causada por COVID-19 en México se ha situado entre las más altas del mundo, por lo que es de interés epidemiológico estudiar su impacto respecto a la esperanza de vida (EV). El objetivo del presente trabajo fue analizar el impacto de la pandemia por COVID-19 en la esperanza de vida, comparando datos de 2019 y 2020, y evaluando su efecto por densidad poblacional de los municipios de los estados del noreste de México. La información sobre mortalidad para 2019 y 2020 se obtuvo de la Secretaría de Salud, y la demográfica del Consejo Nacional de Población. Se construyeron tablas de vida mediante el método actuarial estándar; se calcularon percentiles ≤ 25 y ≥ 75 de la diferencia en la EV; se evaluó la relación entre el tamaño de la población de los municipios y la magnitud de la diferencia en la pérdida de años en la EV. La pandemia por COVID-19 impactó en la EV en los estados del noreste de México, con gran heterogeneidad al interior en cada uno de ellos. La pérdida en años en promedio fue, para Coahuila de 5.4, Nuevo León 4.1 y Tamaulipas 4.9. Los municipios del percentil ≥ 75 mostraron una pérdida promedio de 9.2 años y los del percentil ≤ 25 de -0.35 años. La diferencia en la pérdida en años de EV, entre 2019 y 2020, se vio influenciada por el tamaño de la población, tendiendo a ser mayor en aquellos con mayor densidad demográfica, sin ser el único factor determinante.

ABSTRACT COVID-19 mortality in Mexico is among the highest in the world. Therefore, it is of epidemiologic interest to study its impact on life expectancy. The aim of the present paper was to analyze the impact of the COVID-19 pandemic on life expectancy through a comparison of data from 2019 and 2020. Specifically, the effect of population density in municipalities of Northeastern Mexican states. Information regarding 2019 and 2020 mortality rates for was obtained from the Ministry of Health, and demographics from the National Population Council. Life tables were constructed using the standard actuarial method. Percentiles ≤ 25 and ≥ 75 of the difference in life expectancy in the period were calculated. The relationship between the size of the population of the municipalities and the magnitude of the difference in life expectancy loss of years was evaluated. COVID-19 pandemic impacted on life expectancy with great heterogeneity in each of the northeastern states of Mexico. The loss in years in average life expectancy was 5.4 for Coahuila, 4.1 for Nuevo Leon and 4.9 for Tamaulipas. Municipalities above the ≥ 75th percentile showed an average loss of 9.2 years. Those in the lower than ≤ 25th percentile showed a decrease, of -0.35 years. The difference in the loss of life expectancy during 2019 and 2020 was influenced by population size, tending to be greater in those municipalities with higher population density, but was not the only determining factor.

Cross-sectional study to measure household water insecurity and its health outcomes in urban Mexico.

OBJECTIVE: To assess the links between structural and household determinants of household water insecurity and test three water insecurity measures against self-reported diarrhoea, dengue fever and perceived stress in the middle-income and low-income urban areas of Torreón, Mexico. DESIGN: Cross-sectional household survey conducted in two waves (rainy and dry seasons). PARTICIPANTS: 500 households selected via multistage cluster sample in selected communities. Socioeconomic status determined the selection of participant neighbourhoods; five were identified in low socioeconomic status neighbourhoods and five in low-medium socioeconomic status neighbourhoods. We examine how the context of urban water provision is related to a new cross-culturally valid Household Water Insecurity Experiences (HWISE) Scale. PRIMARY OUTCOME MEASURES: The HWISE Scale, self-reported diarrhoea, dengue fever and the Perceived Stress Scale. RESULTS: Water system intermittency (adjusted OR (AOR) 3.96, 95% CI 2.40 to 6.54, p<0.001), unpredictability (AOR 2.24, 95% CI 1.34 to 3.74, p=0.002) and the dry season (AOR 3.47, 95% CI 2.18 to 5.52, p<0.001) were structural correlates of the HWISE Scale. This study also found that the HWISE Scale was associated with two health outcomes, self-reported diarrhoea (AOR 1.09, 95% CI 1.03 to 1.15, p=0.002) and perceived stress (ß=0.28, SE=0.07, t=4.30, p<0.001), but not self-reported dengue fever (AOR 1.02, 95% CI 0.98 to 1.06). A 3-item hygiene subscore and a 3-item water worry subscore were also both positively associated with self-reported diarrhoea and perceived stress. CONCLUSION: Short-form screeners of water insecurity may be useful for assessing certain health risks by lay survey workers in settings with limited healthcare resources, particularly in lieu of more expensive microbiological tests that require specialised training and facilities.

Syphilis infection markers among HIV positive individuals in the Mexico City HIV/AIDS Program / Marcadores de infección por sífilis de individuos VIH positivos en el Programa de VIH/SIDA de la Ciudad de México

Abstract: Objective: The aim of this study is to evaluate the prevalence of T. pallidum infection markers in HIV-positive individuals receiving highly active antiretroviral therapy (ART) in the Mexico City HIV/AIDS Program, as well as predictive characteristics. Materials and methods: The reverse serologic algorithm method was used for the T. pallidum diagnosis, and applied to 2 383 HIV-positive individuals. Sociodemographic characteristics, sexual practices, previous syphilis diagnosis, and length of antiretroviral treatment, were evaluated. Variables significantly associated with syphilis markers were analyzed using a logistic regression model. Results: Prevalence of "active or resolved" and "probable active" infection markers were 44.2 and 28.8%, respectively. Predictive factors were: Clínica Especializada Condesa Iztapalapa (CECI), previous syphilis diagnosis, men in who have sex with men (MSM), and receptive sex practices. Conclusions: The prevalence of T. pallidum infection markers was the highest ever reported in Mexico, and was related to specific sexual practices as well as previous syphilis diagnosis, elements which require preventive measures in the Mexico City HIV/AIDS Program.

Resumen: Objetivo: Evaluar las prevalencias de marcadores de infección por T. pallidum en personas que viven con VIH y reciben tratamiento antirretroviral en el Programa de VIH/SIDA de la Ciudad de México, así como sus características asociadas. Material y métodos: Se siguió el método del algoritmo reverso para el diagnóstico de T. pallidum aplicado a 2 383 individuos VIH positivos, quienes contestaron un cuestionario sobre características sociodemográficas, prácticas sexuales, diagnóstico previo de sífilis y tiempo de tratamiento antirretroviral. Las variables significativamente asociadas con los marcadores de sífilis se analizaron mediante un modelo de regresión logística. Resultados: Las prevalencias de marcadores de infección "activa o resuelta" y "probablemente activa" fueron 44.2 y 28.8%, respectivamente. Las características asociadas con los marcadores fueron Clínica Especializada Condesa Iztapalapa (CECI), diagnóstico previo de infección por sífilis, hombres que tienen sexo con hombres (HSH) y prácticas sexuales receptivas. Conclusiones: Las prevalencias de marcadores de infección por T. pallidum fueron altas y estuvieron relacionadas con prácticas sexuales específicas y con el diagnóstico previo de sífilis, características que requieren medidas preventivas dentro del programa.

Syphilis Infection Markers Among HIV Positive Individuals In The Mexico City HIV/AIDS Program.

OBJECTIVE: The aim of this study is to evaluate the prevalence of T. pallidum infection markers in HIV-positive individuals receiving highly active antiretroviral therapy (ART) in the Mexico City HIV/AIDS Program, as well as predictive characteristics. METHODS: The reverse serologic algorithm method was used for the T. pallidum diagnosis, and applied to 2,383 HIV-positive individuals. Socio-demographic characteristics, sexual practices, previous syphilis diagnosis, and length of antiretroviral treatment, were evaluated. Variables significantly associated with syphilis markers were analyzed using a logistic regression model. RESULTS: Prevalence of "active or resolved" and "probable active" infection markers were 44.2% and 28.8%, respectively. Predictive factors were: Clinic Specialized Condesa Iztapalapa (CECI), previous syphilis diagnosis, MSM, and receptive sex practices. CONCLUSIONS: The prevalence of T. pallidum infection markers was the highest ever reported in Mexico, and was related to specific sexual practices as well as previous syphilis diagnosis, elements which require preventive measures in the Mexico City HIV/AIDS Program.

Association between life-style behaviors and health outcomes in Adventist and non-Adventist adolescents in Mexico: a pilot study.

BACKGROUND: Identifying lifestyle-related health predictors affecting adolescent behaviors is a matter of interest and study for diverse audiences, including the religious sphere. The Adventist religion recommends their followers to adopt a healthy diet, adequate rest, physical activity, sufficient water intake, and non-use of addictive substances such as alcohol, tobacco, and drugs, as well as fostering faith and hope to give meaning to life. METHODS: A cross-sectional and observational study was conducted among adolescent students aged 13 to 19 years old in Montemorelos City, Nuevo León, Northern Mexico, between September 14, 2017 and February 13, 2018. This study included 363 Mexican adolescents, consisting of 202 Adventists and 161 non-Adventists. The binomial logistic regression analysis was performed to examine the relationships between religious affiliation and life-style behaviors and evaluate the effect of life-style behaviors on health outcomes by religious affiliation. Age, gender, type of residence, and place of birth were controlled. RESULTS: We found that Adventist adolescents were more likely to be watching TV for 2 h or less per day (p < 0.001), have enough sleeping time for 7 h or more (p < 0.001), go to bed early at 11 o'clock or before (p < 0.001), and have breakfast (p = 0.006) than non-Adventist adolescents significantly. It indicates that Adventist students are more likely to have healthier life-style behaviors than non-Adventist students. The multiple binomial regression models showed that in the group of Adventist adolescents sporting activity and hours watching TV were significantly associated with obesity risk (p = 0.001) and risky eating patterns (p = 0.044), respectively, controlling for age, gender, type of residence, and place of birth. No relationship was found between life-style behaviors and health outcomes in non-Adventist adolescents. CONCLUSIONS: Religious affiliation could serve as a predictor of healthy behaviors among adolescents. This study concluded that Adventist adolescents are more likely to have a healthier lifestyle behavior than non-Adventist adolescents and various health-related behaviors were specifically identified among Adventist participants.

Evaluation of HIV, STI and CD4 results among voluntary attendees at the HIV/AIDS program of Mexico City.

OBJECTIVE:: To describe results of HIV, sexually transmitted diseases (STI) and CD4 counts at the HIV-specialized Condesa Clinic (CC) in Mexico City. MATERIALS AND METHODS:: Individuals who requested voluntary counseling and testing at CC were studied. We identified antibodies against HIV, syphilis, hepatitis C, and hepatitis B HBsAg. CD4 cell counts and viral load of HIV positive individuals were also obtained. Late HIV infection diagnosis was established if CD4 counts were lower than 200 cells/µL. RESULTS:: Global seroprevalence of HIV, syphilis, HBsAg, and anti HCV markers was of 20.1, 6, 1 and 1, respectively. Men displayed higher seroprevalence of infection markers than women. Among men, HIV infection was related to age and with all STI markers. Late HIV diagnosis was 31.8%. The risk of late HIV diagnosis was higher among women and it increased as age increased. CONCLUSIONS:: Differences between genders regarding HIV and STIs prevalence as well as risk factors for HIV infection and late HIV diagnosis were observed.

Evaluation of HIV, STI and CD4 results among voluntary attendees at the HIV/AIDS program of Mexico City / Evaluación de resultados de VIH, ETS y CD4 en asistentes al programa de VIH/SIDA de la Ciudad de México

Abstract: Objective: To describe results of HIV, sexually transmitted diseases (STI) and CD4 counts at the HIV-specialized Condesa Clinic (CC) in Mexico City. Materials and methods: Individuals who requested voluntary counseling and testing at CC were studied. We identified antibodies against HIV, syphilis, hepatitis C, and hepatitis B HBsAg. CD4 cell counts and viral load of HIV positive individuals were also obtained. Late HIV infection diagnosis was established if CD4 counts were lower than 200 cells/μL. Results: Global seroprevalence of HIV, syphilis, HBsAg, and anti HCV markers was of 20.1, 6, 1 and 1, respectively. Men displayed higher seroprevalence of infection markers than women. Among men, HIV infection was related to age and with all STI markers. Late HIV diagnosis was 31.8%. The risk of late HIV diagnosis was higher among women and it increased as age increased. Conclusions: Differences between genders regarding HIV and STIs prevalence as well as risk factors for HIV infection and late HIV diagnosis were observed.

Resumen: Objetivo: Describir resultados del programa VIH/SIDA de la Clínica Especializada Condesa (CC). Material y métodos: Se identificaron anticuerpos contra VIH, sífilis y hepatitis C, así como HBsAg del virus de la hepatitis B. Se hizo un conteo de CD4 y carga viral en los positivos a VIH asistentes a la CC. El conteo CD4 menor a 200 células/μL definió el diagnóstico tardío de la infección por VIH. Resultados: La prevalencia de VIH, sífilis, HBsAg y virus de la hepatitis (HCV) fue de 20.1, 6, 1 y 1, respectivamente. Los hombres mostraron prevalencias mayores de infección que las mujeres y en ellos la infección por VIH estuvo relacionada con la edad y con los marcadores de ITS. El diagnóstico tardío de VIH fue de 31.8% y su riesgo fue mayor en las mujeres y se incrementó conforme la edad. Conclusión: Se encontraron diferencias de género en las prevalencias de VIH e ITS, en los riesgos de infección por VIH y en el diagnóstico tardío de esta infección.

HPV infection, risk factors and viral load among Mexican male college students

Objectives: To determine the prevalence of HPV and the risky sexual behaviors associated to it in a sample of male college students, taking into account genotype and viral load. Methods: From 2002 to 2003, male students from the Autonomous University of Morelos State completed a questionnaire and provided self-collected genital samples to detect and quantify HPV. We performed a bivariate and a multivariate logistic regression analysis to identify correlates associated with the infection and to assess the viral load as a function of the viral infecting type. The fragments of β-globin gene and L1 of HPV, were amplified, purified and cloned, to evaluate viral load. Results: Among 253 subjects, HPV prevalence was 19.4%, and HPV16 was the most common subtype. History of STIs (OR = 4.8; 95% CI 1.2–18.9), contraceptive pill use by female partner (OR = 2.6; 95% CI 1.1–6.3) and exchanging sex for money (OR = 4.9; 95% CI 1.2–20) were associated to the HPV infection. HPV16 viral load was 7.8 copies (HPV/beta-globin) compared to 0.9 copies for other HPV types. Discussion: HPV16 displayed the highest viral load, and it was the most prevalent. It was found that using contraceptive pills by female partners was associated with HPV infection. .

HPV infection, risk factors and viral load among Mexican male college students.

OBJECTIVES: To determine the prevalence of HPV and the risky sexual behaviors associated to it in a sample of male college students, taking into account genotype and viral load. METHODS: From 2002 to 2003, male students from the Autonomous University of Morelos State completed a questionnaire and provided self-collected genital samples to detect and quantify HPV. We performed a bivariate and a multivariate logistic regression analysis to identify correlates associated with the infection and to assess the viral load as a function of the viral infecting type. The fragments of ß-globin gene and L1 of HPV, were amplified, purified and cloned, to evaluate viral load. RESULTS: Among 253 subjects, HPV prevalence was 19.4%, and HPV16 was the most common subtype. History of STIs (OR=4.8; 95% CI 1.2-18.9), contraceptive pill use by female partner (OR=2.6; 95% CI 1.1-6.3) and exchanging sex for money (OR=4.9; 95% CI 1.2-20) were associated to the HPV infection. HPV16 viral load was 7.8 copies (HPV/beta-globin) compared to 0.9 copies for other HPV types. DISCUSSION: HPV16 displayed the highest viral load, and it was the most prevalent. It was found that using contraceptive pills by female partners was associated with HPV infection.

Seroprevalence and national distribution of human toxoplasmosis in Mexico: analysis of the 2000 and 2006 National Health Surveys.

Global warming has had serious implications on dispersion of infectious diseases like toxoplasmosis. Since the frequency of Toxoplasma gondii largely depends on climatic conditions, we studied its prevalence by means of 3599 samples of the National Health Survey 2000 (NHS-2000) and 2916 of the National Health and Nutrition Survey 2006 (NHNS-2006) serum banks, obtained from 1-98 year old subjects of both genders and all states of Mexico. Anti-T.gondii IgG antibodies were determined by ELISA and confirmed by western blot. Crude, epidemiologically weighted and diagnosis-performance-adjusted prevalence values were calculated. Seroprevalence changes were compared between both surveys and among regions (north, center and coast). Also, correlations between changes in temperature or humidity and those in prevalence were measured. National crude prevalence was 60.1% and 62.6% for NHS-2000 and NHNS-2006, respectively. Weighted and adjusted values were 62.5% and 40.0% for NHS-2000, and 63.7 and 43.1% for NHNS-2006. Coastal states and children presented the largest increases between surveys, while the center of the country showed a decrease. An apparently higher prevalence of T. gondii infection was observed in both surveys compared to that performed in 1987, while a geographical re-distribution was found from 2000 to 2006, with a positive correlation between temperature and frequency deltas in 21 states where prevalence increased.

Heterogeneous distribution of hepatitis B serological markers in rural areas of Mexico.

OBJECTIVE: To study the distribution of the hepatitis B antibody (anti-HBc) based on a national serosurvey from 10 Mexican states showing a mean HBV prevalence higher than the national one. MATERIALS AND METHODS: This was a cross-sectional study. During 2003, anti-HBc was analyzed at INSP in 19 907 sera, and the related sociodemographic factors were determined. RESULTS: Anti-HBc prevalence was greater among men, but it was also associated to age, residence in a rural area, low socio-economic status, and illiteracy. Clusters of very high anti-HBc prevalence were found in several rural communities where the prevalence of anti-HBc in adults is 3 to 20 times the national average. CONCLUSIONS: Besides a low endemicity of HBV in Mexico, distribution is heterogeneous as was shown in several of the states studied, where there are rural towns with very high prevalence of HBV markers. National serosurveys are useful tools for identifying communities with hepatitis B hyperendemicity, where focused research and control measures are needed.

[Serological markers of hepatitis B and C, and HIV in La Calera and Cuambio, Guerrero, México]. / Marcadores serológicos de hepatitis B y C, y VIH en La Calera y Cuambio, Guerrero, México.

OBJECTIVE: To perform a hepatitis B, C, and HIV survey in an enhanced sample from two rural communities with the highest anti-HBc prevalence found in ENSA 2000. MATERIALS AND METHODS: This was a cross-sectional study.We studied the communities of La Calera and Cuambio, two adjacent rural towns of the district of Zirándaro, Guerrero, targeted because of the high prevalence of anti-HBc shown in ENSA 2000.We assessed the prevalence of hepatitis B and C, and HIV serological markers and associated factors among inhabitants older than 10 years. RESULTS: A very high prevalence of hepatitis B markers associated with socioeconomic factors was confirmed, while hepatitis C prevalence was low and HIV absent in the two communities addressed. CONCLUSIONS: National serosurveys are an accurate tool for identifying communities with hepatitis B high endemicity where focused research and control measures are needed.

Heterogeneous distribution of hepatitis B serological markers in rural areas of Mexico

OBJECTIVE: To study the distribution of the hepatitis B antibody (anti-HBc) based on a national serosurvey from 10 Mexican states showing a mean HBV prevalence higher than the national one. MATERIALS AND METHODS: This was a cross-sectional study. During 2003, anti-HBc was analyzed at INSP in 19 907 sera, and the related sociodemographic factors were determined. RESULTS: Anti-HBc prevalence was greater among men, but it was also associated to age, residence in a rural area, low socio-economic status, and illiteracy. Clusters of very high anti-HBc prevalence were found in several rural communities where the prevalence of anti-HBc in adults is 3 to 20 times the national average. CONCLUSIONS: Besides a low endemicity of HBV in Mexico, distribution is heterogeneous as was shown in several of the states studied, where there are rural towns with very high prevalence of HBV markers. National serosurveys are useful tools for identifying communities with hepatitis B hyperendemicity, where focused research and control measures are needed.

OBJETIVO: Estudiar la distribución de anti-HBc en 10 estados con prevalencia mayor a la media nacional en la ENSA 2000. MATERIAL Y MÉTODOS: Durante 2003 se analizó en el INSP anti-HBc en 19 907 muestras de suero, se determinaron factores sociodemográficos relacionados. RESULTADOS: La prevalencia de anti-HBc fue mayor en hombres. Se asoció con la edad, residencia en áreas rurales, bajo nivel socioeconómico y analfabetismo. Se encontraron agrupamientos de alta prevalencia de anti-HBc en comunidades rurales en las cuales la prevalencia de anti-HBc en adultos está entre 3 y 20 veces por arriba de la media nacional. CONCLUSIONES: Contrastando con la baja endemicidad del VHB en México, su distribución es heterogénea. En varios estados se hallaron localidades rurales con muy alta prevalencia de anti-HBc. Las encuestas de salud permiten identificar comunidades donde la hepatitis B es hiperendémica y en las cuales se requiere enfocar la investigación y tomar medidas de control.

Marcadores serológicos de hepatitis B y C, y VIH en La Calera y Cuambio, Guerrero, México

OBJETIVO: Determinar la prevalencia de hepatitis B, C, y VIH en una muestra ampliada de dos de las comunidades rurales en las que se registró la mayor prevalencia de anticuerpos anti-core del virus de la hepatitis (anti-HBc) en la Encuesta Nacional de Salud 2000 (ENSA 2000). MATERIAL Y MÉTODOS: Se realizó un estudio transversal en las comunidades de La Calera y Cuambio, dos poblaciones rurales adyacentes del municipio de Zirándaro, Guerrero, seleccionadas por mostrar muy alta prevalencia de anti-HBc en la ENSA 2000. Se determinó la prevalencia de marcadores séricos de hepatitis B y C, y VIH, así como factores sociodemográficos asociados entre los habitantes mayores de 10 años. RESULTADOS: Se confirmó una muy alta prevalencia de marcadores de hepatitis B, asociada con la edad, baja escolaridad y relaciones con trabajadoras sexuales en Estados Unidos, mientras que la prevalencia de hepatitis C fue baja y no se detectó ningún caso de VIH. CONCLUSIONES: Existen en México comunidades rurales con alta endemicidad de hepatitis B, en las cuales es conveniente profundizar la investigación de determinantes de la transmisión de este virus. Estas comunidades son identificadas con certeza por las encuestas nacionales de salud.

OBJECTIVE: To perform a hepatitis B, C, and HIV survey in an enhanced sample from two rural communities with the highest anti-HBc prevalence found in ENSA 2000. MATERIALS AND METHODS: This was a cross-sectional study.We studied the communities of La Calera and Cuambio, two adjacent rural towns of the district of Zirándaro, Guerrero, targeted because of the high prevalence of anti-HBc shown in ENSA 2000.We assessed the prevalence of hepatitis B and C, and HIV serological markers and associated factors among inhabitants older than 10 years. RESULTS: A very high prevalence of hepatitis B markers associated with socioeconomic factors was confirmed, while hepatitis C prevalence was low and HIV absent in the two communities addressed. CONCLUSIONS: National serosurveys are an accurate tool for identifying communities with hepatitis B high endemicity where focused research and control measures are needed.

HSV-2 seroincidence among Mexican college students: the delay of sexual debut is not enough to avoid risky sexual behaviours and virus transmission.

OBJECTIVES: Early sexual debut is a behaviour that has been associated with acquiring sexually transmitted infections. Higher schooling may delay sexual debut, thus the university population is categorised with low-risk sexual behaviours. The rate ratio of herpes simplex virus type 2 (HSV-2) seroincidence according to demographic characteristics and sexual behaviour was estimated for a cohort of university students. METHODS: A dynamic cohort of university students was followed at the Autonomous University of Morelos, in central Mexico, during the years 2001-5. After obtaining informed consent, information was gathered annually regarding demographic characteristics and sexual behaviour and blood samples were obtained to determine HSV-2 antibodies. Seroincidence was estimated and the incidence rate ratio was evaluated using the Poisson regression model. RESULTS: A total of 404 students participated, with 669.2 person-years of follow-up. An incidence of 4.2 cases per 100 person-years was estimated. The variables delayed sexual debut (≥18 years) and multiple sexual partners (two or more sexual partners during the past year) had a rate ratio of 4.1 (95% CI 1.2 to 14.3) and 2.5 (95% CI 1.1 to 5.6), respectively. Incidence for students with delayed sexual debut and multiple partners is estimated to be 10.3 cases per 100 person-years. CONCLUSIONS: Delayed sexual debut was a risk factor for acquiring HSV-2, due to a subgroup with sexual debut at 18 years of age or older that had multiple sexual partners; therefore, in the university population that tends to delay sexual debut, it is necessary to implement prevention programmes to promote the decrease of other risky sexual behaviours, as well as the promotion of the consistent use of condoms.

Microbiological indicators of water quality in the Xochimilco canals, Mexico City.

OBJECTIVE: To quantify microbiology indicators of fecal contamination in the effluents of two waste water treatment plants and in samples collected in several canals in Xochimilco. MATERIAL AND METHODS: A cross sectional study was performed. Ten sites, 5 from plant effluents and 5 from canals, were selected for sampling during November and December 2001. Fecal coliforms and enterococci were quantified by membrane filtration, male specific (F+) and somatic coliphages by double agar layer technique, and Cryptosporidium oocysts and Giardia cysts by concentration with Envirocheck filter followed by immunofluorescence microscopy quantification. The average of organisms counts from effluents and canal water were compared with t Student test. RESULTS: Treated water discharge in canals showed a low count of Fecal Coliforms (average 40.4/100 ml), enterococci (average 58.8/100 ml) and Cryptosporidium oocysts (average 13.2/100 l), while coliphages and Giardia cyst rendered higher counts (average 1467.5/100 ml and 1199.8/100 l, respectively) suggesting the water treatment methods could fail to remove these agents. A significant lower count of Giardia cysts (average 45/100 l) and no Cryptosporidium oocysts were found in irrigation canals, which suggests a natural clearance of these pathogens. Strains of Escherichia coli isolated in one of the canals contaminated with sewage had antimicrobial multi-resistance that was transferred by conjugation suggesting that resistance is encoded in a plasmid potentially transferable to other pathogenic bacteria. CONCLUSIONS: Cost effective and culturally acceptable waste treatment methods will require careful planning and consultation if they are to be adopted and mantained by local populations.

Microbiological indicators of water quality in the Xochimilco canals, Mexico City

OBJETIVO: Cuantificar diversos indicadores de contaminación fecal en los efluentes de dos plantas de tratamiento de aguas residuales y en muestras recogidas en varios canales de Xochimilco. MATERIAL Y MÉTODOS: Estudio transversal efectuado en Xochimilco, México. Durante noviembre y diciembre de 2001 se muestrearon 10 sitios, cinco efluentes y cinco canales, para la cuantificación de coliformes fecales y enterococos (filtración en membrana de nitrocelulosa), colifagos somáticos (técnica de doble capa de agar), ooquistes de Cryptosporidium sp. y quistes de Giardia sp. (concentración en filtros Envirocheck y microscopía de inmunofluorescencia). Se efectuó comparación de los promedios de las cuentas de organismos hallados, en efluentes y canales, mediante t de Student. RESULTADOS: El agua tratada que descarga en los canales mostró cantidades bajas de coliformes fecales (media de 40.4/100 ml), enterococos (media de 58.8/100 ml) y quistes de Cryptosporidium (media de 13.2/100 l), mientras que los colifagos y quistes de Giardia estuvieron presentes en gran cantidad (media de 1467.5/100 ml y 1199.8/100 l, respectivamente), sugiriendo que el tratamiento del agua puede ser ineficaz para remover estos agentes. En los canales de irrigación de vegetales se encontró una cantidad significativamente menor de quistes de Giardia (media de 45/100 l) y no se encontraron ooquistes de Cryptosporidium, lo que sugiere la remoción natural de estos agentes. Algunos aislamientos de E coli obtenidos de un canal contaminado con descargas cloacales mostraron una multirresistencia a antibióticos que fue transferida por conjugación a otras bacterias mediante plásmidos. Esto sugiere la posible diseminación de la resistencia a bacterias del medio (posibles patógenas). Existen numerosos asentamientos humanos cercanos a las chinampas que descargan desechos directamente a los canales. CONCLUSIONES: La implantación de métodos de tratamiento de excretas que resulten costeables y culturalmente aceptables debe realizarse mediante una cuidadosa planeación y consulta, si estos métodos han de ser adoptados y sostenidos por la población local