Low level of the immune response against rabies virus in dogs and cats, a cross-sectional study in sheltered animals, Santander, Colombia / Baixo nível de resposta imune contra o vírus da raiva em cães e gatos, um estudo transversal em animais abrigados, Santander, Colombia

Rabies is an incurable and fatal progressive viral encephalomyelitis that causes approximately 61,000 deaths a year globally mainly by dog bites, which show the importance of anti-rabies vaccination in dogs to achieve elimination of the disease. In Colombia, multiple cases of human rabies transmitted by dogs and cats have been reported since 1999, showing an increased significance of cats in the transmission of rabies, mainly in rabies of wild origin. Therefore, the aim of the present study was to evaluate the development of neutralizing antibodies in dogs and cats during the mass vaccination campaign of the second half of 2015 in the city of Bucaramanga. For this purpose, a descriptive cross-sectional study with convenience sampling was conducted in 382 dogs and cats (295 dogs, 87 cats), and an evaluation of the humoral immune response of the animals was performed by quantitative ELISA. The prevalence of optimal neutralizing antibodies (>0.5 IU/ml) was only 32.76% (95% CI=28.05-37.46%) in the entire population studied and most of the animals did not have an adequate response to the vaccination, or seroconversion was not detected on them (65.45-95% confidence interval, CI=60.68-70.21%). Significant difference was found between the neutralizing antibody titers in cats and dogs, with a higher neutralizing response in cats. In conclusion, although mass vaccination campaigns for dogs and cats are the most important measure to interrupt virus circulation among the animals, achievement of a good neutralizing immune response in the animals is useful to demonstrate that vaccination has been successful, allowing the maintenance of the required minimum levels of population immunity. These results will allow the implementation of corrective measures in Bucaramanga to achieve better seroconversion rates. Other cities are expected to implement similar seroconversion assessments to verify the quality of effective anti-rabies vaccination in animal populations.(AU)

A raiva é uma encefalomielite viral progressiva incurável e fatal que causa aproximadamente 61.000 mortes por ano no mundo, principalmente por mordidas de cães, que mostram a importância da vacinação anti-rábica em cães para conseguir a eliminação da doença. Na Colômbia, vários casos de raiva humana transmitida por cães e gatos foram relatados desde 1999, mostrando um aumento na importância de gatos na transmissão da raiva, principalmente em raiva de origem selvagem. Portanto, o objetivo do presente estudo foi avaliar o desenvolvimento de anticorpos neutralizantes em cães e gatos durante a campanha de vacinação em massa do segundo semestre de 2015 na cidade de Bucaramanga. Para este propósito, um estudo descritivo transversal com amostragem de conveniência foi realizado em 382 cães e gatos (295 cães, 87 gatos), e uma avaliação da resposta imune humoral dos animais foi realizada por ELISA quantitativo. A prevalência de anticorpos neutralizantes ótimos (>0,5 UI/ml) foi de apenas 32,76% (IC 95% = 28,05-37,46%) em toda a população estudada e a maioria dos animais não teve resposta adequada à vacinação, ou a soroconversão foi não detectado neles (65,45-95% intervalo de confiança IC = 60,68-70,21%). Diferença significativa foi encontrada entre os títulos de anticorpos neutralizantes em gatos e cães, com uma maior resposta neutralizante em gatos. Em conclusão, embora as campanhas de vacinação em massa para cães e gatos sejam a medida mais importante para interromper a circulação do vírus entre os animais, a obtenção de uma boa resposta imunológica neutralizante nos animais é útil para demonstrar que a vacinação foi bem sucedida, permitindo a manutenção necessária dos níveis mínimos de imunidade da população. Esses resultados permitirão que a implementação de medidas corretivas em Bucaramanga alcance melhores taxas de soroconversão. Outras cidades devem implementar avaliações similares de soroconversão para verificar a qualidade da vacinação anti-rábica efetiva em populações animais.(AU)

Differences in the replicative capacities of clinical isolates of dengue virus in C6/36 cells and in urban populations of Aedes aegypti from Colombia, South America

ABSTRACT Dengue, the most prevalent arboviral disease worldwide, is caused by any of the four dengue virus (DENV) serotypes that co-circulate constantly in hyperendemic areas such as Medellin (Colombia), and these serotypes are transmitted by mosquitoes of the genus Aedes. In this study, we evaluated the replicative capacity of strains isolated in Medellin between 2003 and 2007 in C6/36 cells and in colonies of Aedes aegypti collected during 2010-2011 from high or low-incidence areas within the same city. The phylogenetic analysis grouped isolates according to the predominant genotypes found in the Americas, and the in vitro characterization showed differences in the morphological changes induced by the isolates of each of the isolated serotypes compared to the reference serotypes. In vitro replicative capacity studies demonstrated that genomic copy number increased at four days post-infection and that cell viability decreased significantly compared to the control for all serotypes. The largest number of genomic copies in C6/36 was produced by DENV-2, followed by DENV-1 and DENV-4; DENV-3 produced the smallest number of genomic copies and had the smallest negative effect on cell viability. Finally, differences in the in vivo replication of intercolonial serotypes between the Rockefeller colony and the field colonies and among the intracolonial serotypes were found. The replication of DENV-2 at 7 and 14 days in both high- and low-incidence colonies was higher than that of the other serotypes, and replication of DENV-3 in the mosquito colonies was the most stable on the days evaluated. Our results support the notion that replication and, possibly, DENV transmission and severity depend on many factors, including serotype and vector characteristics.

Efecto de la competición larval sobre poblaciones del vector del dengue colectadas en Medellín, Colombia / Effect of larval competition on populations of the dengue vector collected in Medellín, Colombia

Introducción: Aedes aegypti es el vector responsable de transmitir el virus dengue, la densidad de la población en los estadios larvales puede afectar las características de vida del adulto, con implicaciones en la capacidad de transmisión viral. Objetivo: determinar el efecto de la competición larval causada por la alta densidad en colonias de Aedes aegypti procedentes de zonas de alta y baja incidencia de dengue en la ciudad de Medellín, Colombia, así como en una colonia de referencia en el laboratorio. Métodos: en las 3 colonias se evaluó el tiempo de desarrollo y supervivencia larval, así como el tamaño y el tiempo de supervivencia de los adultos. Resultados: se encontró que la competición larval en condiciones de alta densidad redujo de manera significativa el tiempo de desarrollo y la supervivencia de los últimos estadios larvales. Por otro lado, la alta densidad experimentada durante la etapa larval, también generó cambios en los adultos de las 3 colonias, representados en una disminución significativa del tamaño y una disminución en el tiempo de supervivencia (esta última solo en las colonias de campo). Conclusión: a pesar de que no se obtuvieron diferencias frente al efecto competitivo entre las colonias de campo provenientes de zonas con desigualdades en la incidencia de dengue en Medellín, la diferencia en respuesta obtenida en la colonia de laboratorio en comparación con las colonias de campo, hace pensar que es importante la evaluación de parámetros ecológicos sobre poblaciones de Aedes aegypti silvestres, porque estas evaluaciones acercarían más al comportamiento del vector. Estudios en curso en el laboratorio permitirán conocer si las diferencias encontradas entre las colonias afectan la competencia de Aedes aegypti frente a la infección por virus dengue(AU)

Introduction: Aedes aegypti is the vector transmitting the dengue virus. Larval density may affect adult life, with an impact on viral transmission capacity. Objective: determine the effect of larval competition caused by high density in Aedes aegypti colonies from areas of high and low dengue incidence in the city of Medellín, Colombia, and in a reference colony in the laboratory. Methods: the three colonies were evaluated for larval development and survival time, as well as size and survival time in adults. Results: it was found that in high density conditions larval competition significantly shortened development and survival time in the last larval stages. High density during the larval stage also brought about changes in adults from the three colonies, represented by a significantly reduced size and a decrease in survival time (the latter only in the field colonies). Conclusion: no differences in competitive effect were found between the field colonies from areas with unequal dengue incidence in Medellín. However, the difference in the response obtained from the laboratory colony in contrast to the field colony, points to the need to evaluate the ecological parameters of wild Aedes aegypti populations to obtain a more accurate view of the behavior of the vector. Laboratory studies in progress will make it possible to know whether the differences found between the colonies affect the competence of Aedes aegypti for dengue virus infection(AU)

Actualización en diagnóstico del dengue: evolución de las técnicas y su aplicación real en la clínica / Update on dengue diagnosis: techniques evolution and their clinical application

Resumen: El dengue es la enfermedad viral transmitida por vectores de mayor importancia en el mundo. Debido a que hasta el momento no existe una vacuna licenciada para la prevención de la infección ni una terapia específica para controlar la enfermedad, el diagnóstico temprano y específico resulta ser una herramienta de vital importancia para brindar un tratamiento rápido y oportuno al paciente. Aunque hace más de seis décadas se dispone de una variedad de técnicas de laboratorio para el diagnóstico de esta enfermedad, es frecuente encontrar que noexista un consenso en el personal o en las entidades colombianas encargadas del diagnóstico de laboratorio sobre las ventajas y las limitaciones de estas técnicas, lo que dificulta dichodiagnóstico. Adicionalmente, debido a que la mayoría de técnicas que se usan se basan en la respuesta inmune frente al virus, y se pueden presentar reacciones cruzadas con otros virusgenéticamente relacionados, la posibilidad de falsos positivos es alta. Principalmente, por estarazón, en los últimos años ha aumentado el desarrollo y la validación de técnicas moleculares,ya que son más sensibles, específicas y rápidas que las técnicas celulares e inmunológicas.Teniendo en cuenta estos antecedentes, se hace necesario comparar a la luz de la literatura disponible la utilidad real de las técnicas de laboratorio existentes, clasificándolas en celulares,inmunológicas y moleculares.

Abstract: Dengue is the vector-borne viral disease of major importance in the world. Because so far there is no licensed vaccine that can be used to prevent the infection and there is no specific antiviral treatment, the early and specific diagnosis is a powerful tool to provide prompt and timely management of the patient. Despite during more than six decades there has been available a wide variety of laboratory techniques that can be used for the diagnosis of dengue, there is often lack of a consensus among the people or entities responsible of the diagnosis about the advantages and disadvantages of these techniques; for this reason, the diagnosis of dengue is more difficult. Moreover, taking into account that most of the techniques used are based on the immune response against dengue virus, and a cross reactivity with other viruses genetically related could be possible; the possibility of false positives is high. Accordingly, in recent years the development and validation of molecular techniques has increased, as they are more sensitive, specific and rapid than the cellular and immunological techniques. Therefore, it is necessary to compare the usefulness of laboratory techniques to dengue diagnosis, such as cellular, immunological and molecular tests.

Competencia vectorial: consideraciones entomológicas y suinfluencia sobre la epidemiología del dengue / Vector competence: entomological considerations and its implications on the epidemiology of dengue

Las enfermedades transmitidas por vectores constituyen un complejo problema de salud en el ámbito mundial, especialmente en áreas tropicales y subtropicales, que por sus condiciones ambientales favorecen la supervivencia del vector. El dengue es la principal enfermedad transmitida por vectores en el mundo, cuyo agente etiológico es el Virus Dengue, el cual es transmitido por la picadura de mosquitos hematófagos de la especie Aedes aegypti. La interacción virus-vector es esencial para una transmisión efectiva y depende de factores tanto virales como vectoriales. Entre los factores relacionados con el vector, la competencia vectorial es considerada de gran importancia, pues se refiere a la capacidad intrínseca del vector para infectarse con el virus, permitir su replicación y posteriormente su transmisión a un huésped susceptible. A su vez, la habilidad para ser un buen vector depende principalmente de barreras naturales a la infección, barreras inmunológicas y presencia de receptores específicos para el virus. Todas estas características, sumadas a las características propias del virus, favorecerán o no la transmisión del mismo. Un estudio integral dela relación virus-vector permitirá comprender sus implicaciones en la epidemiología de la enfermedad. Estos temas han sido revisados en el presente documento, discutiendo su importancia dentro del contexto entomológico y epidemiológico.

Vector-borne diseases are a serious problem in public health, especially in tropical and subtropical areas where environmental conditions favor the survival and expansion of vectors into new habitats. Dengue fever is one of the most important vector-borne diseases transmitted by arthropods (arbovirosis) worldwide. The etiologic agent of the disease is the dengue virus, which is transmitted by the bite of bloodsucking Aedes aegypti mosquitoes. The virus-vector interaction is essential for the efficient transmission of the disease, and depends on both, viral factors and vector competence or intrinsic vector capacity to be infected with the virus. Vector competence allows virus replication and subsequent transmission to susceptible hosts. Factors that influence vector capacity include: natural barriers to infection, immunological defenses as well as the presence of receptors for the virus. All these factors inaddition to the viral characteristics will determine the degree of transmission. There is a need for a better understanding of the virus-vector relationship and its epidemiological implications. These issues are addressed in this article.

Estudio preliminar in vitro de la infección por enterovirus 71 en células TE-671 / Study preliminary in vitro infectio of TE-671 cell by Enterovirus 71

Objetivo. Realizar el seguimiento de la infección in vitro por enterovirus 71 (EV71) sobre celulas TE-671, evaluando la presencia de los antígenos virales y la pérdida de viabilidad en diferentes tiempos de infección. Materiales y métodos. Se infectaron cultivos de células TE-671 con diferentes diluciones de EV71, aislado de un caso de parálisis flácida aguda (3364-COL-94), y por varios tiempos posinfección (6,12,24,48,72 horas). Los cultivos se procesaron por una técnica de inmunoperoxidasa indirecta para obtener las proporciones de infección en cada condición. Simultáneamente, se realizó una prueba de viabilidad por el método bioquímico del MTT para evaluar la pérdida de la viabilidad celular debida a la infección. Resultados. Aunque por inmunocitoquímica se detectó infección desde las 6 horas después de la inoculación (pi), el efecto citopático y la mortalidad celular fueron drásticos después de 48 horas pi. De esta manera, el mejor tiempo para la detección de los antígenos virales fue a las 12 horas pi, momento en el cual la muerte celular no es tan grave, lo cual permite una adecuada detección del antígeno viral. Conclusiones. Se ratificó la alta receptividad de las células TE-671 a la infección por EV71, la cual se correlaciona con el importante efecto citopático evidenciando por la prueba de MTT, lo cual convierte a esta línea celular e un recurso eficiente para el aislamiento y la identificación de EV71 y, también, para estudios de su biología básica