Chagas disease in the context of the 2030 agenda: global warming and vectors

The 2030 Agenda for Sustainable Development is a plan of action for people, planet and prosperity. Thousands of years and centuries of colonisation have passed the precarious housing conditions, food insecurity, lack of sanitation, the limitation of surveillance, health care programs and climate change. Chagas disease continues to be a public health problem. The control programs have been successful in many countries in reducing transmission by T. cruzi; but the results have been variable. WHO makes recommendations for prevention and control with the aim of eliminating Chagas disease as a public health problem. Climate change, deforestation, migration, urbanisation, sylvatic vectors and oral transmission require integrating the economic, social, and environmental dimensions of sustainable development, as well as the links within and between objectives and sectors. While the environment scenarios change around the world, native vector species pose a significant public health threat. The man-made atmosphere change is related to the increase of triatomines' dispersal range, or an increase of the mobility of the vectors from their sylvatic environment to man-made constructions, or humans getting into sylvatic scenarios, leading to an increase of Chagas disease infection. Innovations with the communities and collaborations among municipalities, International cooperation agencies, local governmental agencies, academic partners, developmental agencies, or environmental institutions may present promising solutions, but sustained partnerships, long-term commitment, and strong regional leadership are required. A new world has just opened up for the renewal of surveillance practices, but the lessons learned in the past should be the basis for solutions in the future.

Different profiles and epidemiological scenarios: past, present and future

The multiplicity of epidemiological scenarios shown by Chagas Disease, derived from multiple transmission routes of the aetiological agent, occurring on multiple geo-ecobiosocial settings determines the complexity of the disease and reveal the difficulties for its control. From the first description of the link between the parasite, the vector and its domestic habitat and the disease that Carlos Chagas made in 1909, the epidemiological scenarios of the American Trypanosomiasis has shown a dynamic increasing complexity. These scenarios changed with time and geography because of new understandings of the disease from multiple studies, because of policies change at the national and international levels and because human movements brought the parasite and vectors to new geographies. Paradigms that seemed solid at a time were broken down, and we learnt about the global dispersion of Trypanosoma cruzi infection, the multiplicity of transmission routes, that the infection can be cured, and that triatomines are not only a health threat in Latin America. We consider the multiple epidemiological scenarios through the different T. cruzi transmission routes, with or without the participation of a Triatominae vector. We then consider the scenario of regions with vectors without the parasite, to finish with the consideration of future prospects.

Cambio climático y enfermedades transmitidas por vectores en Argentina / Climate change and vector-borne diseases in Argentina

Resumen Las enfermedades transmitidas por vectores (ETVs) continúan siendo un desafío para los esfuerzos de agencias de salud pública, ya que mantienen o están aumentando su impacto sobre la salud de las comunidades afectadas. La característica común de las ETVs es que la única manera de prevenir exito samente nuevas infecciones es evitar el contacto entre vectores y humanos. No existen vacunas y no existirán en un futuro previsible para las principales ETVs que afectan la salud pública en Argentina. Aunque las epide mias de dengue desde 2009 atrajeron la atención mediática, otras ETVs, tales como Chagas o leishmaniasis, afectan la salud pública en Argentina desde hace décadas. Sobre ellas, y otras que potencialmente podrían instalarse en el territorio nacional (West Nile, Lyme, etc) hay repetidas referencias mediáticas que explican su recrudecimiento por el cambio climático. El argumento se basa en que la "tropicalización" del clima en regiones templadas promueve la instalación de ETVs en áreas previamente no favorables para ellas. Aunque existen muchas evidencias de que el clima está cambiando, son pocas las evidencias de que sea el clima el principal factor que promueve el recrudecimiento de las ETVs en Argentina. En este artículo, se discute la situación de los vectores de enfermedades en Argentina (con énfasis en triatominos), su vinculación con el llamado cambio climático y las actividades de control de vectores implementados por agencias gubernamentales de salud pública.

Abstract Vector-borne diseases (VBDs) continue to pose a challenge to the efforts of public health agencies by increasing their impact on the health of the affected communities. The common feature of VBDs is that the only way of preventing them is by avoid ing the contact between vectors and humans. There are no vaccines, and they will not be available shortly as tools for prevention and control in Argentina. Although dengue outbreaks attracted the attention of mass media from 2009, other VBDs have been affecting public health in Argentina for many decades, as Chagas disease and leishmaniasis. Over these, and others that could potentially settle in the national territory (West Nile, Lyme, etc.), there are repeated mass media claims and political declarations justifying their increase because of climate changes. The argument asserts that the "tropicalization" of the climate in temperate regions promotes the instal lation of VBDs in areas previously unfavorable for them. Although much evidence exists showing that the climate is changing, there is very little evidence that the climate is the main factor promoting the increase of VBDs. In this article, the influence of the so-called climate change on the situation of disease vectors in Argentina (with emphasis on triatomines) and vector control activities implemented by governmental public health agencies are discussed.

Response of Triatoma infestans to pour-on cypermethrin applied to chickens under laboratory conditions

This article reports the effects of a pour-on formulation of cypermethrin (6 percent active ingredient) applied to chickens exposed to Triatoma infestans, the main vector of Chagas disease in rural houses of the Gran Chaco Region of South America. This study was designed as a completely random experiment with three experimental groups and five replicates. Third instar nymphs were fed on chickens treated with 0, 1 and 2 cc of the formulation. Nymphs were allowed to feed on the chickens at different time intervals after the insecticide application. Third-instar nymphs fed on treated chickens showed a higher mortality, took less blood during feeding and had a lower moulting rate. The mortality rate was highest seven days after the insecticide solution application and blood intake was affected until 30 days after the application of the solution.

The biology of Aedes (Ochlerotatus) albifasciatus Macquart, 1838 (Diptera: Culicidae) in Central Argentina

Aedes albifasciatus is a flood water mosquito ocurring in the southern countries of South America. It is a competent vector of the Western Equine Encephalitis (WEE) and causes important losses on milk and beef production in central Argentina. Field work was carried out from December 1990 to March 1993, on a monthly basis during the dry season and biweekly during the rainy season. Larvae were collected using the 'dipping' technique and females with CDC traps baited with CO2. Field collected larvae were used to build laboratory cohorts, from which basic population parameters were estimated. Eggs survived up to six months on dry soil, although there was a linear decrease of viability with time. At 23§C, larval development time was around nine days, and all adults emerged within one week. The estimation of larval development in the laboratory seems to be very near the development on the field, as larvae have been collected on average eight days after a rainfall. Egg to adult survival was 83 por cento, with the highest mortality on fourth larval instar (6 por cento). In the laboratory studies, sex proportion among the adults was 1:1, females lived longer than males (median 13 and five days, respectively), and adult survival pattern showed a constant number of individuals dying per unit time. Field collected females layed an average of 84 eggs per batch, and completing up to five gonotrophic cycles, suggesting an estimated survival of up to 35-50 days.

Systematics of Triatoma sordida, T. guasayana and T. patagonica (Hemiptera, Reduviidae)

Because of the relative epidemiological significance of Triatoma sordida, T. guasayana and T. patagonica, and the need to resolve doubts about their taxonomic validity, we report here a detailed taxonomic comparison of the three species using multivariate analysis of morphometric measures combined with comparisons of their genitalia and antennal structures. From the 17 metric variables studied, the length of the second segment of the rostrum and the anteocular length provided a discrimination function able to separate without error T. sordida from T. guasayana and T. patagonica. The multivariate discriminant functions classified T. guasayana and T. patagonica with an error of 2.44 per cent . Comparison of the male genitalia of T. guasayana and T. sordida showed that there are minor differences in the articulatory apparatus, the median process of the pygophore, the phallosome support and the vesica, with bigger differences in the endosomal process and the phallosome. However, the already described male genitalia of T. patagonica is very similar to that of T. sordida. Analysis of antennal structure by scanning electron microscope showed that sensilla distribution around the pedicel is slightly different in the three species and sensilla density is highest in T. sordida and lowest in T. patagonica. The study showed that the three species form a closely related group. The results confirm the earlier classification of sordida and guasayana as separate species, but they raise some doubts about the taxonomic status of T. patagonica