Visceral leishmaniasis in border areas: clustered distribution of phlebotomine sand flies in Clorinda, Argentina

Three years after the first report of Lutzomyia longipalpis in Clorinda, Argentina, a border city near Asunción, Paraguay, the city was surveyed again. Lu. longipalpis was found clustered in the same neighbourhoods in 2007 as in 2004, even though the scattered distribution of canine visceral leishmaniasis was more related to the traffic of dogs through the border.

Phlebotominae (Diptera: Psycodidae) fauna in the Chaco region and Cutaneous Leishmaniasis transmission patterns in Argentina

In Argentina, the incidence of American Cutaneous Leishmaniasis (ACL) has shown a steady increase over the last few decades. In the Chaco biogeographical region, specifically, several outbreaks of ACL were recently reported in addition to the usual time-space scattering of ACL cases. However, little is known about the sandfly composition in the eastern, humid Chaco (HC) region or the western, dry Chaco (DC) region. Therefore, phlebotomine captures were performed throughout this region and an analysis of the distribution of reported ACL cases was conducted in order to assess the vector diversity in ACL endemic and epidemic scenarios in the Chaco region. The results support the hypothesis of two distinct patterns: (1) the DC, where Lutzomyia migonei was the most prevalent species, had isolated ACL cases and a zoonotic cycle; (2) the HC, where Lutzomyia neivai was the most prevalent species, had an increase in ACL incidence and outbreaks and an anthropozoonotic cycle. The epidemic risk in the Chaco region may be associated with the current climate trends, landscape modification, connection with other ACL foci, and Lu. neivai predominance and abundance. Therefore, changes in sandfly population diversity and density in the Chaco region are an indicator of emergent epidemic risk in sentinel capture sites.

Urban distribution of Phlebotominae in a cutaneous leishmaniasis focus, Argentina

Urbanization and vector domestication are currently proposed as factors that contributed to the recent increase of American cutaneous leishmaniasis (ACL). Is likely also urban transmission? Oran is the main city in the Argentinean hyper-endemic area of ACL, and human cases in urban residences are usually reported. In order to assess the spatial distribution of risk, phlebotomine traps were located in different environments of Oran. A total of 7,787 sand flies were captured: Lutzomyia neivai (98.1 percent), Lutzomyia migonei (1.2 percent), Lutzomyia cortelezzii (0.7 percent), and one Lutzomyia shannoni. During the season of transmission (April-May) a single sand fly was obtained in one out of five urban sites, while a trap in a peri-urban pigsty captured up to 2,985 Lu. neivai/night. Captures performed in the other season of vector activity (September-October) revealed that small-scale changes in the pigsty environment resulted in noticeable changes in the abundance of Lu. neivai. In addition, in a new neighbourhood, on the fringe of the city, 1,073 Lu. neivai/site were captured in the forested edge but one in the yard of the houses. Therefore, in this urban ACL focus the human-vector effective contact risk is still associated with peri-urban vegetation and ecotone modifications despite the urban residence of the cases.

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.