Las vacunas contra el dengue ¿una realidad para la Argentina? / Dengue vaccines. A reality for Argentina?

Los brotes de dengue se suceden anualmente en Argentina desde el año 1998. Existen vacunas contra esta enfermedad en distintos grados de desarrollo que han sido probadas en países endémicos. La más avanzada hasta el momento fue autorizada para su comercialización en tres países de América Latina, para niños mayores de 9 años. En este artículo se discuten los beneficios e inconvenientes de las vacunas, así como los desafíos para la implementación de una estrategia de vacunación. Asimismo, se plantea la necesidad de una estratificación de riesgo con nuevos criterios y visión multidisciplinaria como un camino posible para evaluar la pertinencia de un programa de vacunación en las áreas con mayor riesgo de transmisión, y/o en individuos con mayor riesgo de dengue grave. Se sugiere también que la definición del estatus de endemicidad debe tomar en cuenta a las realidades locales. Por último, este artículo propone una discusión amplia de las evidencias, impacto esperado y aspectos instrumentales que estarían involucrados en la incorporación de una vacuna contra el dengue, ya en mercado o en desarrollo, en el programa nacional de inmunizaciones, y especialmente a qué subpoblaciones debería ser dirigida para que la estrategia de inmunización sea costo-efectiva.

Dengue outbreaks have occurred yearly in Argentina since 1998. A number of candidate vaccines have been tested in endemic countries. The most advanced one was licensed in three countries of Latin America for children over 9 years of age. In the present article the benefits and drawbacks of these vaccines as well as the challenges for the implementation of a vaccination strategy in Argentina are discussed. Furthermore, a risk stratification strategy with new criteria and a multidisciplinary vision is suggested as a possible path for the assessment of the pertinence of a vaccination program in areas showing the highest risk of dengue transmission and/or for people at the greatest risk of developing severe dengue. It is also suggested that the definition regarding the status of endemicity should take into account the local realities. Finally, this paper proposes a broad discussion on the evidences, the expected impact and instrumental aspects that would be involved in the incorporation of a dengue vaccine, marketed or in development, into the national immunization program, and especially which subpopulation should be targeted for the immunization strategy to be cost-effective.

Transmision de la leishmaniasis tegumentaria en la Argentina / Transmission of tegumentary leishmaniasis in Argentina

La leishmaniasis tegumentaria ha experimentado en Argentina, desde 1985, un incremento de casos totales, de la frecuencia, intensidad y distribución de brotes epidémicos, y de la incidencia relativa en mujeres y en niños. Es necesario caracterizar los nuevas circunstancias de transmisión generadas en las últimas décadas para el diseño de estrategias apropiadas de control. Con dicho objeto, basados en indicadores epidemiológicos, entomológicos y en el análisis cualitativo de imágenes satelitales, se describen cuatro brotes epidémicos tomados como casos de estudio: Urugua-í (2004), Esperanza (1998), Alberdi (2003) y Monteros-Simoca (2004). A partir de dichas descripciones se caracterizaron cuatro ciclos: a) silvestre con transmisión en vegetación primaria o residual; b) silvestre con transmisión eventual peridoméstica por alteración deparches de vegetación residual; c) silvestre con transmisión peridoméstica por contigüidad con vegetación residual; d) peridoméstico en ambientes rurales, periurbano ruralizado o interfase urbano-rural. Todos los brotes epidémicos ocurridos desde 1985 se correspondieron con uno de estos ciclos, demostrando ser hasta el momento una tipificación abarcativa de la transmisión de leishmaniasis tegumentaria en la Argentina. De esta manera se categorizaron cuatro patrones epidémicos en el país, destacando a su vez la utilidad del análisis cualitativo, de datos de terreno e imágenes satelitales, como herramientas para comprender la epidemiología de la enfermedad y poder desarrollar medidas adecuadas de prevención y control.

The total cases of tegumentary leishmaniasis in Argentina increased since 1985, as the frequency, intensity and geographic distribution of the epidemic outbreaks, and the relative incidence in women and children. The characterization of the new scenarios of transmission generated in the last decades is needed for the design of appropriate control measures. With this aim, four outbreaks were described as case studies, based on epidemiological and entomological data together with the qualitative analysis of satellite imaginery: Urugua-í (2004), Esperanza (1998), Alberdi (2003) and Monteros-Simoca (2004). These descriptions allowed to define four scenarios of transmission according to a cycle: a) sylvatic with transmission in primary or residual vegetation; b) sylvatic with eventual peridomestic transmission due to changes within patches of residual vegetation; c) sylvatic with peridomestic transmission in domiciles contiguous with the residual vegetation; and d) peridomestic in rural, ruralized periurban or urban-rural interfase environment. All the epidemic outbreaks since 1985 were consistent with the scenarios characterized here, indicating that the tipification is comprehensive of the transmission of tegumentary leishmaniasis in Argentina up to now. In conclusion, four scenarios of epidemic outbreaks were defined for Argentina, while it is highlighted the qualitative analysis of field and remote sensing data as a tool to understand the epidemiology of the disease, and so to develop adequate measures for prevention and control.

Lutzomyia longipalpis in Clorinda, Formosa province, an area of potential visceral leishmaniasis transmission in Argentina

Phlebotomine captures were performed during 2004 in Clorinda, Argentina. Clorinda is located across the branches of the Paraguay river in front of Asunción city, Paraguay. Reports of canine and human visceral leishmaniasis in Asunción have been increasing since 1997, however neither leishmaniasis cases nor sand flies were ever recorded from Clorinda. Light traps were located in migration paths (bridges, port), and peridomestic environments of Clorinda and surrounding localities. Lutzomyia longipalpis was found in Clorinda and Puerto Pilcomayo, first report in a potential visceral leishmaniasis transmission area for Argentina. Active surveillance is required immediately in the localities involved and the surrounding area.

Effects of flooding and temperature on Aedes albifasciatus development time and larval density in two rain pools at Buenos Aires University City

Aedes albifasciatus is a floodwater mosquito that breeds in temporary waters. This semi-domestic species, widely distributed in Argentina, is a competent vector of the western equine encephalitis. The present study was carried out in two rain pools of the city of Buenos Aires, from April 1998 through March 1999. Samples were taken twice a week during the cold season and daily during the warmer months, starting from October. Immature mosquitoes were collected with a dipper, being the number of dippers proportional to the flooded area. The estimated rainfall thresholds to initiate cohorts of Ae. albifasciatus were: 16-17 mm in the fall-winter period, 25 mm in the spring, and 30 mm in the summer. The development time of the different cohorts and the mean air temperature of their respective periods were estimated in all seasons, ranging from six days (at 24o.C) to 32 days (at 13o.C). The equation that best expresses the relationship between development time and mean air temperature is dt =166,27.e-0,1435.T (R2=0,92). Significantly shorter development times were recorded for larvae of the first three stages as compared to the fourth larval stage and pupae