Dispersal patterns of Trypanosoma cruzi in Arequipa, Peru.

Anthropogenic environmental alterations such as urbanization can threaten native populations as well as create novel environments that allow human pests and pathogens to thrive. As the number and size of urban environments increase globally, it is more important than ever to understand the dispersal dynamics of hosts, vectors and pathogens of zoonotic disease systems. For example, a protozoan parasite and the causative agent of Chagas disease in humans, Trypanosoma cruzi, recently colonized and spread through the city of Arequipa, Peru. We used population genomic and phylogenomic tools to analyze whole genomes of 123 T. cruzi isolates derived from vectors and non-human mammals throughout Arequipa to determine patterns of T. cruzi dispersal. The data show significant population genetic structure within city blocks-parasites in the same block tend to be very closely related-but no population structure among blocks within districts-parasites in neighboring blocks are no more closely related to one another than to parasites in distant districts. These data suggest that T. cruzi dispersal within a block occurs regularly and that occasional long-range dispersal events allow the establishment of new T. cruzi populations in distant blocks. Movement of domestic animals may be the primary mechanism of inter-block and inter-district T. cruzi dispersal.

Elaboración y validación de una regla de predicción clinica para identificar compromiso sistemico en casos de loxoscelismo / Preparation And Validation Of A Systemic Loxoscelism Prediction Protocol

Introducción: El loxoscelismo sistémico es la complicación más severa del loxoscelismo. El manejo del cuadro por parte del personal de salud presenta una alta variabilidad por factores que se desconocen actualmente. No se cuenta con un estándar de referencia ni con un modelo de predicción clínica que pueda guiar nuestras decisiones al momento del abordaje de un paciente con mordedura de araña. Objetivo: Elaborar y validar una regla de predicción clínica para loxoscelismo sistémico. Métodos: Se llevó a cabo un estudio observacional de derivación y validación de un modelo de predicción clínica con validación de prueba diagnóstica basada en una cohorte histórica de un solo brazo en pacientes atendidos en el Hospital Vitarte entre los años 2007 al 2016 y reportes clínicos internacionales publicados. Resultados: El loxoscelismo sistémico se presentó solo en el 32,9 % (n=24) de casos. Para el análisis bivariado, las variables que demostraron presentar una asociación estadísticamente significativa (P<0,05) fueron el sexo, mordedura en abdomen independiente en relación a otras partes del cuerpo, mordedura en otras partes del cuerpo que no sea el abdomen, vómito, fiebre y hemoglobinuria. El análisis de regresión incluyó en el análisis a las variables: sexo, vómito, fiebre y hemoglobinuria. El bootstrapping determinó la validez interna del modelo. El área bajo la curva fue de 0,91 (P<0,05) y la sensibilidad, espeficidad, LR+ y LR- fueron de 79,1%, 93,8%, 12,9 y 0,22 respectivamente. Conclusiones: El protocolo de predicción del loxoscelismo sistémico derivado es válido, por el momento.

Introduction: Systemic loxoscelism is the most severe complication of loxoscelism. The management of the cadre by health personnel presents a high variability due to factors that are currently unknown. There is no standard of reference or a clinical prediction model that can guide our decisions when approaching a spider bite patient. Objective: Develop and validate a clinical prediction rule for systemic loxoscelism. Methods: An observational study of derivation and validation of a clinical prediction model was carried out with diagnostic test validation based on a historical single-arm cohort in patients treated at Vitarte Hospital between 2007 and 2016 and international clinical reports published. Results: Systemic loxoscelism occurred only in 32.9% (n = 24) of cases. For the bivariate analysis, the variables that showed a statistically significant association (P <0.05) were sex, bite in an independent abdomen in relation to other parts of the body, bite in other parts of the body than the abdomen, vomiting , fever and hemoglobinuria. The regression analysis included in the analysis the variables: sex, vomit, fever and hemoglobinuria. Bootstrapping determined the internal validity of the model. The area under the curve was 0.91 (P <0.05) and the sensitivity, specificity, LR + and LR- were 79.1%, 93.8%, 12.9 and 0.22 respectively. Conclusions: The protocol of prediction of systemic derived loxoscelism is valid, for the moment.

Immigration and establishment of Trypanosoma cruzi in Arequipa, Peru.

Changing environmental conditions, including those caused by human activities, reshape biological communities through both loss of native species and establishment of non-native species in the altered habitats. Dynamic interactions with the abiotic environment impact both immigration and initial establishment of non-native species into these altered habitats. The repeated emergence of disease systems in urban areas worldwide highlights the importance of understanding how dynamic migratory processes affect the current and future distribution and abundance of pathogens in urban environments. In this study, we examine the pattern of invasion of Trypanosoma cruzi-the causative agent of human Chagas disease-in the city of Arequipa, Peru. Phylogenetic analyses of 136 T. cruzi isolates from Arequipa and other South American locations suggest that only one T. cruzi lineage established a population in Arequipa as all T. cruzi isolated from vectors in Arequipa form a recent monophyletic group within the broader South American phylogeny. We discuss several hypotheses that may explain the limited number of established T. cruzi lineages despite multiple introductions of the parasite.

Socio-spatial heterogeneity in participation in mass dog rabies vaccination campaigns, Arequipa, Peru.

To control and prevent rabies in Latin America, mass dog vaccination campaigns (MDVC) are implemented mainly through fixed-location vaccination points: owners have to bring their dogs to the vaccination points where they receive the vaccination free of charge. Dog rabies is still endemic in some Latin-American countries and high overall dog vaccination coverage and even distribution of vaccinated dogs are desired attributes of MDVC to halt rabies virus transmission. In Arequipa, Peru, we conducted a door-to-door post-campaign survey on >6,000 houses to assess the placement of vaccination points on these two attributes. We found that the odds of participating in the campaign decreased by 16% for every 100 m from the owner's house to the nearest vaccination point (p = 0.041) after controlling for potential covariates. We found social determinants associated with participating in the MDVC: for each child under 5 in the household, the odds of participating in the MDVC decreased by 13% (p = 0.032), and for each decade less lived in the area, the odds of participating in the MDVC decreased by 8% (p<0.001), after controlling for distance and other covariates. We also found significant spatial clustering of unvaccinated dogs over 500 m from the vaccination points, which created pockets of unvaccinated dogs that may sustain rabies virus transmission. Understanding the barriers to dog owners' participation in community-based dog-vaccination programs will be crucial to implementing effective zoonotic disease preventive activities. Spatial and social elements of urbanization play an important role in coverage of MDVC and should be considered during their planning and evaluation.

Sexual reproduction in a natural Trypanosoma cruzi population.

BACKGROUND: Sexual reproduction provides an evolutionary advantageous mechanism that combines favorable mutations that have arisen in separate lineages into the same individual. This advantage is especially pronounced in microparasites as allelic reassortment among individuals caused by sexual reproduction promotes allelic diversity at immune evasion genes within individuals which is often essential to evade host immune systems. Despite these advantages, many eukaryotic microparasites exhibit highly-clonal population structures suggesting that genetic exchange through sexual reproduction is rare. Evidence supporting clonality is particularly convincing in the causative agent of Chagas disease, Trypanosoma cruzi, despite equally convincing evidence of the capacity to engage in sexual reproduction. METHODOLOGY/ PRINCIPLE FINDINGS: In the present study, we investigated two hypotheses that can reconcile the apparent contradiction between the observed clonal population structure and the capacity to engage in sexual reproduction by analyzing the genome sequences of 123 T. cruzi isolates from a natural population in Arequipa, Peru. The distribution of polymorphic markers within and among isolates provides clear evidence of the occurrence of sexual reproduction. Large genetic segments are rearranged among chromosomes due to crossing over during meiosis leading to a decay in the genetic linkage among polymorphic markers compared to the expectations from a purely asexually-reproducing population. Nevertheless, the population structure appears clonal due to a high level of inbreeding during sexual reproduction which increases homozygosity, and thus reduces diversity, within each inbreeding lineage. CONCLUSIONS/ SIGNIFICANCE: These results effectively reconcile the apparent contradiction by demonstrating that the clonal population structure is derived not from infrequent sex in natural populations but from high levels of inbreeding. We discuss epidemiological consequences of this reproductive strategy on genome evolution, population structure, and phenotypic diversity of this medically important parasite.

Integrating evidence, models and maps to enhance Chagas disease vector surveillance.

BACKGROUND: Until recently, the Chagas disease vector, Triatoma infestans, was widespread in Arequipa, Perú, but as a result of a decades-long campaign in which over 70,000 houses were treated with insecticides, infestation prevalence is now greatly reduced. To monitor for T. infestans resurgence, the city is currently in a surveillance phase in which a sample of houses is selected for inspection each year. Despite extensive data from the control campaign that could be used to inform surveillance, the selection of houses to inspect is often carried out haphazardly or by convenience. Therefore, we asked, how can we enhance efforts toward preventing T. infestans resurgence by creating the opportunity for vector surveillance to be informed by data? METHODOLOGY/PRINCIPAL FINDINGS: To this end, we developed a mobile app that provides vector infestation risk maps generated with data from the control campaign run in a predictive model. The app is intended to enhance vector surveillance activities by giving inspectors the opportunity to incorporate the infestation risk information into their surveillance activities, but it does not dictate which houses to surveil. Therefore, a critical question becomes, will inspectors use the risk information? To answer this question, we ran a pilot study in which we compared surveillance using the app to the current practice (paper maps). We hypothesized that inspectors would use the risk information provided by the app, as measured by the frequency of higher risk houses visited, and qualitative analyses of inspector movement patterns in the field. We also compared the efficiency of both mediums to identify factors that might discourage risk information use. Over the course of ten days (five with each medium), 1,081 houses were visited using the paper maps, of which 366 (34%) were inspected, while 1,038 houses were visited using the app, with 401 (39%) inspected. Five out of eight inspectors (62.5%) visited more higher risk houses when using the app (Fisher's exact test, p < 0.001). Among all inspectors, there was an upward shift in proportional visits to higher risk houses when using the app (Mantel-Haenszel test, common odds ratio (OR) = 2.42, 95% CI 2.00-2.92), and in a second analysis using generalized linear mixed models, app use increased the odds of visiting a higher risk house 2.73-fold (95% CI 2.24-3.32), suggesting that the risk information provided by the app was used by most inspectors. Qualitative analyses of inspector movement revealed indications of risk information use in seven out of eight (87.5%) inspectors. There was no difference between the app and paper maps in the number of houses visited (paired t-test, p = 0.67) or inspected (p = 0.17), suggesting that app use did not reduce surveillance efficiency. CONCLUSIONS/SIGNIFICANCE: Without staying vigilant to remaining and re-emerging vector foci following a vector control campaign, disease transmission eventually returns and progress achieved is reversed. Our results suggest that, when provided the opportunity, most inspectors will use risk information to direct their surveillance activities, at least over the short term. The study is an initial, but key, step toward evidence-based vector surveillance.

Heterogeneous infectiousness in guinea pigs experimentally infected with Trypanosoma cruzi.

Guinea pigs are important reservoirs of Trypanosoma cruzi, the causative parasite of Chagas disease, and in the Southern Cone of South America, transmission is mediated mainly by the vector Triatoma infestans. Interestingly, colonies of Triatoma infestans captured from guinea pig corrals sporadically have infection prevalence rates above 80%. Such high values are not consistent with the relatively short 7-8 week parasitemic period that has been reported for guinea pigs in the literature. We experimentally measured the infectious periods of a group of T. cruzi-infected guinea pigs by performing xenodiagnosis and direct microscopy each week for one year. Another group of infected guinea pigs received only direct microscopy to control for the effect that inoculation by triatomine saliva may have on parasitemia in the host. We observed infectious periods longer than those previously reported in a number of guinea pigs from both the xenodiagnosis and control groups. While some guinea pigs were infectious for a short time, other "super-shedders" were parasitemic up to 22 weeks after infection, and/or positive by xenodiagnosis for a year after infection. This heterogeneity in infectiousness has strong implications for T. cruzi transmission dynamics and control, as super-shedder guinea pigs may play a disproportionate role in pathogen spread.

Bottlenecks in domestic animal populations can facilitate the emergence of Trypanosoma cruzi, the aetiological agent of Chagas disease.

Faeces-mediated transmission of Trypanosoma cruzi (the aetiological agent of Chagas disease) by triatomine insects is extremely inefficient. Still, the parasite emerges frequently, and has infected millions of people and domestic animals. We synthesize here the results of field and laboratory studies of T. cruzi transmission conducted in and around Arequipa, Peru. We document the repeated occurrence of large colonies of triatomine bugs (more than 1000) with very high infection prevalence (more than 85%). By inoculating guinea pigs, an important reservoir of T. cruzi in Peru, and feeding triatomine bugs on them weekly, we demonstrate that, while most animals quickly control parasitaemia, a subset of animals remains highly infectious to vectors for many months. However, we argue that the presence of these persistently infectious hosts is insufficient to explain the observed prevalence of T. cruzi in vector colonies. We posit that seasonal rains, leading to a fluctuation in the price of guinea pig food (alfalfa), leading to annual guinea pig roasts, leading to a concentration of vectors on a small subpopulation of animals maintained for reproduction, can propel T. cruzi through vector colonies and create a considerable force of infection for a pathogen whose transmission might otherwise fizzle out.

Urbanization, land tenure security and vector-borne Chagas disease.

Modern cities represent one of the fastest growing ecosystems on the planet. Urbanization occurs in stages; each stage characterized by a distinct habitat that may be more or less susceptible to the establishment of disease vector populations and the transmission of vector-borne pathogens. We performed longitudinal entomological and epidemiological surveys in households along a 1900 × 125 m transect of Arequipa, Peru, a major city of nearly one million inhabitants, in which the transmission of Trypanosoma cruzi, the aetiological agent of Chagas disease, by the insect vector Triatoma infestans, is an ongoing problem. The transect spans a cline of urban development from established communities to land invasions. We find that the vector is tracking the development of the city, and the parasite, in turn, is tracking the dispersal of the vector. New urbanizations are free of vector infestation for decades. T. cruzi transmission is very recent and concentrated in more established communities. The increase in land tenure security during the course of urbanization, if not accompanied by reasonable and enforceable zoning codes, initiates an influx of construction materials, people and animals that creates fertile conditions for epidemics of some vector-borne diseases.

Manual de procedimientos para el diagnóstico serológico de las zoonosis parasitarias / Manual of procedures for the serological diagnosis of parasitic zoonoses

El presente manual uniformiza los procedimientos de diagnóstico serológico de las principales zoonosis parasitarias estandarizados en el Laboratorio de Zoonosis Parasitarias del Centro Nacional de Salud Pública del Instituto Nacional de Salud. En esta segunda edición se ha considerado, además de las técnicas ya existentes, la prueba de ELISA y la técnica de aglutinación de látex para el diagnóstico de la hidatidosis humana

Manual de procedimientos para el diagnóstico serológico de las zoonosis parasitarias / Manual of procedures for the serological diagnosis of parasitic zoonoses

El presente manual uniformiza los procedimientos de diagnóstico serológico de las principales zoonosis parasitarias estandarizados en el Laboratorio de Zoonosis Parasitarias del Centro Nacional de Salud Pública del Instituto Nacional de Salud. En esta segunda edición se ha considerado, además de las técnicas ya existentes, la prueba de ELISA y la técnica de aglutinación de látex para el diagnóstico de la hidatidosis humana(AU)

Manual de procedimientos de laboratorio para el diagnóstico de la Trypanosomiosis Americana (Enfermedad de Chagas) / Manual of laboratory procedures for the diagnosis of American Trypanosomiasis (Chagas Disease)

El manual hace una descripción de los métodos más frecuentes e incluye el fundamento, el procedimiento y la lectura de los resultados. En el flujograma se señalan las pruebas que pueden desarrollarse en los laboratorios locales, intermedios y regionales de la Red Nacional de Laboratorios en Salud Pública, así como los canales de envío de muestras e información. Se han añadido los capítulos de bioseguridad, control de calidad y anexos, el cual se refiere a los reactivos y la preparación requerida para los métodos de diagnóstico. El manual está especialmente dirigido para ser usado en todos los laboratorios de la red por el personal encargado del diagnóstico parasitológico y serológico de la trypanosomiosis americana o enfermedad de Chagas. Cabe puntualizar que el avance en la búsqueda de métodos más específicos y sensibles, permitirá disponer de técnicas más eficientes y que en su oportunidad serán incorporados a los que usa la red.

Toxocariosis humana: seroprevalencia en población de Lima mediante técnica de ELISA / Human toxocariosis: seroprevalence in Lima inhabitants by ELISA technique

OBJETIVO: Estimar la seroprevalencia de toxocariosis humana en población de la ciudad de Lima. Diseño: estudio transversal, la selección fue no aleatoria. MATERIAL Y MÉTODOS: En pobladores de la ciudad de Lima que pertenecían a comunidades urbano marginales, se realizó entrevista y examen clínico, y se obtuvo una muestra de suero para procesar la técnica de ELISA para detectar anticuerpos contra Toxocara. También, se solicitó muestras de heces para buscar parásitos intestinales que pudieran originar reacciones cruzadas en la serología. RESULTADOS: Se examinó 553 personas, siendo 23,3 por ciento de ellos reactivos. No hubo diferencias en cuanto a sexo ni entre el resultado de ELISA y la presencia de anemia, leucocitosis, eosinofilia y parásitos intestinales. Los mayores de 15 años tuvieron doble probabilidad de resultar reactivos que los menores de 15 años. Disminución de la agudeza visual fue el síntoma más frecuente en los sujetos reactivos. Los parásitos intestinales más frecuentes fueron Blastocystis hominis, Entamoeba coli, Giardia lamblia. CONCLUSIONES: La toxocariosis humana es frecuente en la población de Lima. No se observa asociación estadística entre el hallazgo de anemia y alteraciones de la fórmula leucocitaria con el resultado de ELISA. Es necesario desarrollar programas de difusión para detectar precozmente la infección y así prevenirla.

Blastocystosis humana: Estudio prospectivo, sintomatología y factores epidemiológicos asociados / Human blastocystosis: prospective study symptomatology and associated epidemiological factors

Se intenta contribuir en el conocimiento de los síntomas y factores asociados a la infección por Blastocystis hominis en concurrentes a la consulta externa del Departamento de Enfermedades Transmisibles y Dermatológicas (DETD) del HNCH. Este es un estudio caso-control realizado en personas entre los 5 y 80 años de edad en el período de enero a Marzo de 1999. Los casos tuvieron exámenes parasitológicos positivos a B. hominis en ausencia de otros enteropatógenos. Los controles tuvieron exámenes parasitológicos negativos a B. hominis, en ausnecia de otros enteropatógenos. Seutilizó una ficha clínica donde se registró datos de sintomatología y factores asociados a la infección por B. hominis. Se estudiaron 74 casops y 70 controles, pareados ppor edad y sexo. Se obtuvo una correlación estadística (p<0.05) entre sujetos sintomáticos y presencia de B. hominis (91.9 por ciento). La sintomatología asociada a la infección de B. hominis por orden de significancia estadística (p<0.05) fue: dolor abdominal (OR=3) (1.47

Estandarización de la técnica de ELISA para el diagnóstico de Toxocariasis humana / ELISA technique standardisation for human toxocariasis diagnosis

OBJETIVO: Estandarizar la técnica ELISA para el diagnóstico de infección humana por Toxocara canis con antígeno excretado-secretado preparado en nuestro medio. MATERIAL Y MÉTODOS: Se colectó huevos de T. canis y se les incubó con formol (2 por ciento) a 28oC hasta obtener larvas de tercer estadio, las que luego de ser liberadas fueron incubadas en RPMI a 37ºC por 7 días; se reemplazó el medio por otro similar y almacenó a -20ºC. Se concentró el antígeno y se dosó proteínas. Para la técnica de ELISA se utilizó sueros de pacientes con toxocariasis y de niños recién nacidos, como controles positivos y negativos, respectivamente, diluidos desde » hasta 1/1024. Se sensibilizó placas de poliestireno con varias concentraciones de antígeno, utilizándose conjugado de peroxidasa e IgG de carnero anti IgG humana y sustrato OPD. Se realizó lectura de absorbancia a 492 nm con espectrofotómetro (Multiskan plus labsystems), siendo el punto de corte el promedio aritmético de la absorbancia de los sueros negativos más 3 desviaciones estándar. RESULTADOS: La concentración óptima del antígeno fue 50 ug/mL, la dilución del suero 1/128, la dilución del conjugado 1/1000 con densidad óptica mayor a 0,241. CONCLUSIONES: La técnica de ELISA para diagnóstico serológico de infección humana por Toxocara canis podría ser utilizada en estudios epidemiológicos en nuestro país. Queda pendiente la evaluación de su eficacia en futuros estudios.

Aislamiento de Acanthamoeba en pacientes del Servicio de Oftalmología del Hospital Nacional Cayetano Heredia / Isolation of Acanthamoeba in Cayetano Heredia National Hospital Ophtalmology Service Patients

OBJETIVO: Determinar la presencia de parásitos del género Acanthamoeba en sujetos asintomáticos. LUGAR: Servicio de Oftalmología del Hospital Nacional Cayetano Heredia. MATERIAL Y MÉTODOS: Se examinó mediante hisopado corneal a 100 individuos sin evidencia de lesión en la cornea durante los meses de abril y mayo de 1999. Las muestras fueron sembradas en agar napolitano y en agar no nutritivo al 2 por ciento, incubadas y observadas a los 7 días. RESULTADOS: De las 100 muestras revisadas, en 16 se observó quistes de Acanthamoeba; 44 individuos fueron varones, no hubo diferencias significativas del diagnóstico entre los sexos; 63 por ciento de los individuos era menor de 20 años, con predominio de la infección en sujetos más jóvenes; 89 por ciento refirió haber visitado zonas donde hay reportes de la presencia del parásito (Piura, Ica), 58 sujetos manifestaron haber nadado en piscinas o ríos. De 76 sujetos que informaron sobre la fuente de provisión de agua para uso doméstico, 63 por ciento la obtuvo de camiones cisterna y 25 por ciento de pozos, pero la infección fue más frecuente en estos últimos (31,6 por ciento vs. 12,5 por ciento). El hallazgo de Acanthamoeba coincidió con ametropía (44 por ciento), conjuntivitis (16.4 por ciento) y blefaritis (12,3 por ciento). CONCLUSIÓN: Se evidencia la presencia del parásito en individuos jóvenes sin lesión corneal quienes están en riesgo de sufrir queratitis.