Challenges for the Introduction and Evaluation of the Impact of Innovative Aedes aegypti Control Strategies

Innovative control tools for the dengue, chikungunya and Zika vector Aedes aegypti, such as genetically modified mosquitoes and biological control and manipulation with the bacteria Wolbachia, are now becoming available and their incorporation into institutional vector control programs is imminent. The objective of this chapter is to examine the technical and organizational mechanisms together with the necessary processes for their introduction and implementation, as well as the indispensable indicators to measure their entomological effect on vector populations and their epidemiological impact in the short, medium and long term as part of an integrated vector management approach

Dengue immunopathogenesis : a cross talk between host and viral factors leading to disease : part I - Dengue virus tropism, host innate immune responses, and subversion of antiviral responses

Two part articleThis detailed paper addresses the general features of the dengue virus (DENV) infections complex, including the virus structure and genome, epidemiology, and clinical outcomes. This is followed by an updated review of the literature describing the host innate immune strategies as well as the viral mechanisms acting against and in favor of the DENV replication cycle and infection.Canadian Institutes of Health ResearchFondo Mixto CONACYT-Gobierno del Estado de Yucatá

Clinical Manifestations in Pregnant Women and Congenital Abnormalities in Fetus and Newborns during a Zika Transmission Period in South Mexico

Dengue, Chikungunya and Zika are arboviruses transmitted by Ae. aegypti with significant public health impact. In the first trimester of 2015, autochthonous Zika transmission was reported in Mexico. The state of Yucatan is an endemic region where pregnant women with acute infection and related congenital abnormalities in fetus and newborns were observed. We describe results from a cohort of pregnant women and their babies followed up in Yucatan during the first Zika transmission outbreak (2016–2018). Clinical manifestations of acute ZIKV infection, persistence of viral RNA in pregnant women, as well as congenital abnormalities were observed. In addition, we describe the phenotype of newborns from confirmed or suspected ZIKV prenatal infection

Domestic Animal Hosts Strongly Influence Human-Feeding Rates of the Chagas Disease Vector Triatoma infestans in Argentina

Background: The host species composition in a household and their relative availability affect the host-feeding choices of blood-sucking insects and parasite transmission risks. We investigated four hypotheses regarding factors that affect blood-feeding rates, proportion of human-fed bugs (human blood index), and daily human-feeding rates of Triatoma infestans, the main vector of Chagas disease. Methods: A cross-sectional survey collected triatomines in human sleeping quarters (domiciles) of 49 of 270 rural houses in northwestern Argentina. We developed an improved way of estimating the human-feeding rate of domestic T. infestans populations. We fitted generalized linear mixed-effects models to a global model with six explanatory variables (chicken blood index, dog blood index, bug stage, numbers of human residents, bug abundance, and maximum temperature during the night preceding bug catch) and three response variables (daily blood-feeding rate, human blood index, and daily human-feeding rate). Coefficients were estimated via multimodel inference with model averaging. Findings: Median blood-feeding intervals per late-stage bug were 4.1 days, with large variations among households. The main bloodmeal sources were humans (68%), chickens (22%), and dogs (9%). Blood-feeding rates decreased with increases in the chicken blood index. Both the human blood index and daily human-feeding rate decreased substantially with increasing proportions of chicken- or dog-fed bugs, or the presence of chickens indoors. Improved calculations estimated the mean daily human-feeding rate per late-stage bug at 0.231 (95% confidence interval, 0.157–0.305). Conclusions and Significance: Based on the changing availability of chickens in domiciles during spring-summer and the much larger infectivity of dogs compared with humans, we infer that the net effects of chickens in the presence of transmission-competent hosts may be more adequately described by zoopotentiation than by zooprophylaxis. Domestic animals in domiciles profoundly affect the host-feeding choices, human-vector contact rates and parasite transmission predicted by a model based on these estimates

Dengue Immunopathogenesis: A Crosstalk between Host and Viral Factors Leading to Disease: Part I - Dengue Virus Tropism, Host Innate Immune Responses, and Subversion of Antiviral Responses

Dengue is the most prevalent emerging mosquito-borne viral disease, affecting more than 40% of the human population worldwide. Many symptomatic dengue virus (DENV) infections result in a relatively benign disease course known as dengue fever (DF). However, a small proportion of patients develop severe clinical manifestations, englobed in two main categories known as dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Secondary infection with any of the four dengue virus serotypes (DENV1, -2, -3, and -4) is a risk factor to develop severe forms of dengue disease. DSS is primarily characterized by sudden and abrupt endothelial dysfunction, resulting in vascular leak and organ impairment, which may progress to hypovolemic shock and death. Severe DENV disease (DHF/DSS) is thought to follow a complex relationship between distinct immunopathogenic processes involving host and viral factors, such as the serotype cross-reactive antibody-dependent enhancement (ADE), the activation of T cells and complement pathways, the phenomenon of the cytokine storm, and the newly described viral toxin activity of the nonstructural protein 1 (NS1), which together play critical roles in inducing vascular leak and virus pathogenesis. In this chapter that is divided in two parts, we will outline the recent advances in our understanding of DENV pathogenesis, highlighting key viral-host interactions and discussing how these interactions may contribute to DENV immunopathology and the development of vascular leak, a hallmark of severe dengue. Part I will address the general features of the DENV complex, including the virus structure and genome, epidemiology, and clinical outcomes, followed by an updated review of the literature describing the host innate immune strategies as well as the viral mechanisms acting against and in favor of the DENV replication cycle and infection

Dengue Immunopathogenesis: A Crosstalk between Host and Viral Factors Leading to Disease: PART II - DENV Infection, Adaptive Immune Responses, and NS1 Pathogenesis

Severe disease is associated with serial infection with DENV of different serotypes. Thus, primary DENV infections normally cause asymptomatic infections, and secondary heterotypic infections with a new DENV serotype potentially increase the risks of developing severe disease. Despite many proposed hypotheses trying to explain it, the exact immunological mechanism leading to severe dengue disease is unknown. In turn, severe manifestations are believed to be a consequence of the combinations of many immunopathogenic mechanisms involving viral and host factors leading to increased pathogenesis and disease. Of these mechanisms, the adaptive immune response has been proposed to play a critical role in the development of severe dengue manifestations. This includes the effect of non-neutralizing but enhancing antibodies produced during primary infections, which results in enhanced-DENV infection of Fc-γ-receptor-expressing cells (e.g. monocytes and macrophages) during DENV heterotypic exposure in a phenomenon called antibody-dependent enhancement (ADE); the increased activation of memory T cells during secondary infections, which has low affinity for the current infecting serotype and high affinity for a past infection with a different serotype known as the original antigenic sin; the unbalanced production of pro-inflammatory cytokines that have a direct effect on vascular endothelial cells resulting in plasma leak in a phenomenon known as cytokine storm; and the excessive activation of the complement system that causes exacerbated inflammatory responses, increasing disease severity. In addition to the adaptive immune responses, a secreted viral factor known as the nonstructural protein 1 (NS1) has been recently proposed as the missing corner piece of the DENV pathogenesis influencing disease. This Part II of the chapter will discuss the interplay between the distinct host adaptive immune responses and viral factors that together contribute to the development of DENV pathogenesis and severe disease

An Integrated Intervention Model for the Prevention of Zika and Other Aedes-Borne Diseases in Women and their Families in Mexico

We describe and discuss the rationale, design and current implementation of a model for an integrated intervention for the primary and secondary prevention of Zika and other Aedes-borne diseases and sexually transmitted infections that impact reproductive health, pregnancy and perinatal life stages in women and their families in Merida, Mexico. The intervention includes enhanced surveillance of pregnant women, implementation of communication strategies to promote good practices to prevent disease transmission, determination of the frequency of structural anomalies detected prenatally in the foetus, umbilical cord and placenta of pregnancies diagnosed with ZIK infection, detection of ZIKV and other arboviruses/viruses in products of abortion, in-utero and early newborn, provision of Aedes aegypti-proof houses? (protecting homes with door/window screens with insecticide to prevent the access of mosquitoes), mosquito repellents, larvicides and education/promotion of best practices for the prevention of infection with dengue (DENV), chikungunya (CHIKV) and Zika (ZIKV) and an anthropological studies on sociocultural factors of pregnant women associated with ZIKV. This intervention is being developed in a population of 10,000 people of the city of Merida and with the participation of a multidisciplinary group of public health professionals in collaboration with the Ministry of Health and the Government of Yucatan

Seroprevalencia de Trypanosoma cruzi en niños de Veracruz, México: línea de base epidemiológica para un modelo de control fundamentado en la transmisión activa de la enfermedad de Chagas

Introduction. In 2021 the Ministry of Health of Mexico and the Pan American Health Organization launched an initiative to interrupt intra-domiciliary vector transmission of Chagas Disease (CD), based on knowledge of the prevalence of this disease in children. The Mexican State of Veracruz was the leading of this initiative.Objective. To estimate the seroprevalence of Trypanosoma cruzi infection among children under 15 years of age from rural areas of Veracruz, Mexico.Materials and methods. Eight priority localities from the Municipality of Tempoal, Veracruz, were identified for baseline serology. Blood samples were collected on filter paperfrom 817 individuals (June-August 2017) for screening using a third-generation enzyme immunoassay. Reactive cases were confirmed by indirect hemagglutination (HAI), Enzyme linked immunosorbent assay (ELISA), and indirect immunofluorescence (IIF) tests with peripheral blood serum samples. Seroprevalence and its 95% confidence interval (95% C.I.) were calculated.. Results. In the localities Citlaltepetl, Cornizuelo, Cruz de Palma y Rancho Nuevo, CD cases were confirmed in children under 15 years of age with a seroprevalence of 1,9% (95% C.I.: 1,12-3,16%). Conclusions. These results indicate that these communities present recent transmission of CD and allow establishing an epidemiological baseline for the design and implementation of a model based on activities focused on geographic areas with active transmission to advance towards the elimination of intra-domiciliary vector transmission of CD in Mexico.Introducción. En 2021 la Secretaría de Salud de México y la Organización Panamericana de la Salud lanzaron una iniciativa para la interrupción de la transmisión vectorial intradomiciliaria de la enfermedad de Chagas (EC), fundamentada en el conocimiento de la prevalencia de esta enfermedad en población infantil. El estado mexicano de Veracruz fue punta de lanza de esta iniciativa.Objetivo. Estimar la seroprevalencia de infección por Trypanosoma cruzi en menores de 15 años de localidades rurales de Veracruz, México.Materiales y métodos. Se identificaron 8 localidades prioritarias para la serología basal en el municipio de Tempoal, Veracruz. Se colectaron muestra de sangre en papel filtro de 817 individuos (junio-agosto de 2017) para su tamizaje usando un inmunoensayo enzimático de tercera generación. Los casos reactivos del tamizaje se confirmaron mediante pruebas de hemaglutinación indirecta (HAI), ensayo por inmunoabsorción ligado a enzimas (ELISA) e inmunofluorescencia indirecta (IFI) en muestras de suero colectadas en tubo. Se calculó la seroprevalencia y su intervalo de confianza del 95% (I.C. 95%).Resultados. En las localidades Citlaltépetl, Cornizuelo, Cruz de Palma y Rancho Nuevo se confirmaron casos de la EC en menores de 15 años con una seroprevalencia de 1,9% (I.C. 95%: 1,12-3,16%).Conclusiones. Los resultados indican que estas comunidades presentan transmisión reciente de la EC y permiten establecer una línea de base epidemiológica para el diseño e implementación de un modelo fundamentado en acciones dirigidas a áreas geográficas con transmisión activa para avanzar hacia la eliminación de transmisión vectorial intradomiciliar de la EC en México

Effects of vector control actions on Triatoma infestans infestation al multiple spatial and temporal scales in rural communities of Santiago del Estero

Triatoma infestans es el principal vector de Trypanosoma cruzi, agente causal de la Enfermedad de Chagas, en el Cono Sur de América. Con la meta de avanzar en el conocimiento de los factores y mecanismos asociados con la persistente infestación por T. infestans en las comunidades rurales de la región del Gran Chaco se implementó un análisis a múltiples escalas espaciales y temporales cuyos objetivos fueron: a) evaluar el costo económico y el efecto de la estrategia de control de T. infestans basada en la participación comunitaria sobre la prevalencia de infestación por T. infestans y el número de casos agudos notificados en el Depto. Moreno (Santiago del Estero) durante 1993-2004; b) realizar un análisis comparativo de costo-efectividad de diferentes estrategias de control vectorial de T. infestan (e.g., horizontal, vertical y mixta) en el Depto. Moreno; c) describir y cuantificar el patrón de agregación espacial de la prevalencia de infestación por T. infestans por comunidad en todo el Depto. Moreno y de la abundancia de T. infestans por sitio y por casa en un grupo de 12 comunidades rurales contiguas pertenecientes a dicho Departamento, e identificar los factores y mecanismos asociados con la agregación espacial de T. infestans en cada escala; y d) identificar los factores asociados con la reinfestación por T. infestans por sitio durante los dos años y medio que siguieron a un rociado de insecticidas con poder residual en las 12 comunidades rurales de estudio. A partir del análisis detallado de información para todo el Depto. Moreno contenida en las bases de datos del Ministerio de Salud, y de su integración con investigaciones operativas a campo en un área definida del mismo Departamento y con poderosas herramientas analíticas (Sistemas de Información Geográfica, imágenes satelitales de alta resolución y pruebas de análisis espacial explícito) se identificaron los factores y mecanismos asociados con la infestación y distribución espacial de T. infestans al nivel del Departamento Provincial, de la comunidad rural, de la casa y del sitio y se evaluó la importancia de los mismos en el proceso de reinfestación de las comunidades rurales luego del rociado de insecticidas con poder residual.Triatoma infestans es el principal vector de Trypanosoma cruzi, agente causal de la Enfermedad de Chagas, en el Cono Sur de América. Con la meta de avanzar en el conocimiento de los factores y mecanismos asociados con la persistente infestación por T. infestans en las comunidades rurales de la región del Gran Chaco se implementó un análisis a múltiples escalas espaciales y temporales cuyos objetivos fueron: a) evaluar el costo económico y el efecto de la estrategia de control de T. infestans basada en la participación comunitaria sobre la prevalencia de infestación por T. infestans y el número de casos agudos notificados en el Depto. Moreno (Santiago del Estero) durante 1993-2004; b) realizar un análisis comparativo de costo-efectividad de diferentes estrategias de control vectorial de T. infestan (e.g., horizontal, vertical y mixta) en el Depto. Moreno; c) describir y cuantificar el patrón de agregación espacial de la prevalencia de infestación por T. infestans por comunidad en todo el Depto. Moreno y de la abundancia de T. infestans por sitio y por casa en un grupo de 12 comunidades rurales contiguas pertenecientes a dicho Departamento, e identificar los factores y mecanismos asociados con la agregación espacial de T. infestans en cada escala; y d) identificar los factores asociados con la reinfestación por T. infestans por sitio durante los dos años y medio que siguieron a un rociado de insecticidas con poder residual en las 12 comunidades rurales de estudio. A partir del análisis detallado de información para todo el Depto. Moreno contenida en las bases de datos del Ministerio de Salud, y de su integración con investigaciones operativas a campo en un área definida del mismo Departamento y con poderosas herramientas analíticas (Sistemas de Información Geográfica, imágenes satelitales de alta resolución y pruebas de análisis espacial explícito) se identificaron los factores y mecanismos asociados con la infestación y distribución espacial de T. infestans al nivel del Departamento Provincial, de la comunidad rural, de la casa y del sitio y se evaluó la importancia de los mismos en el proceso de reinfestación de las comunidades rurales luego del rociado de insecticidas con poder residual.Fil: Vázquez-Prokopec, Gonzalo Martín. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Dengue immunopathogenesis : a crosstalk between host and viral factors leading to disease : part II—DENV infection, adaptive immune responses, and NS1 pathogenesis

Two part articleThis chapter details the interplay between distinct host adaptive immune responses and viral factors that together contribute to the development of the dengue virus (DENV) pathogenesis and severe disease. As Part II, it addresses: the multifactorial immunopathogenic process of DENV infection from the perspective of the pre-existing serotype cross-reactive antibodies; the hyperactivation of DENV infected immune cells (monocytes, mast cells) leading to increased cytokine production; the role of T cell responses; the activation of complement pathways; and the new pathogenic roles of the secreted NS1 of DENV that may act together to occasionally cause severe dengue manifestations.Canadian Institutes of Health ResearchFondo Mixto CONACYT-Gobierno del Estado de Yucata