Spatial and temporal changes in Lutzomyia longipalpis abundance, a Leishmania infantum vector in an urban area in northeastern Argentina

This study aimed to analyse changes in the spatial distribution of Lutzomyia longipalpis in Posadas, an urban area located in northeastern Argentina. Data were obtained during the summer of 2007 and 2009 through two entomological surveys of peridomiciles distributed around the city. The abundance distribution pattern for 2009 was computed and compared with the previous pattern obtained in 2007, when the first human visceral leishmaniasis cases were reported in the city. Vector abundance was also examined in relation to micro and macrohabitat characteristics. In 2007 and 2009, Lu. longipalpis was distributed among 41.5% and 31% of the households in the study area, respectively. In both years, the abundance rates at most of the trapping sites were below 30 Lu. longipalpis per trap per night; however, for areas exhibiting 30-60 Lu. longipalpis and more than 60 Lu. longipalpis, the areas increased in both size and number from 2007-2009. Lu. longipalpis was more abundant in areas with a higher tree and bush cover (a macrohabitat characteristic) and in peridomiciles with accumulated unused material (a microhabitat characteristic). These results will help to prioritise and focus control efforts by defining which peridomiciles display a potentially high abundance of Lu. longipalpis. .

Spatial distribttion of phlebotominae in puertoiguazu-misiones, Argentina-Brazzil-Paraguay border aeaa / Distribuicao espacial de Phlebotominae em Puerto Iguazu, Misiones, area de fronteira da Argentina-Brasil-Paraguai

SUMMARY The first Argentinian autochthonous human case of visceral leishmaniasis (VL) was confirmed in Posadas (Misiones) in 2006. Since then, the disease has increased its incidence and geographical distribution. In the 2006-2012 period, 107 human cases were detected (11 deaths). The presence of Lutzomyia longipalpis was detected in peridomiciles in Puerto Iguazú urban area in 2010; some of these findings were associated with households where cases of canine VL had already been reported. The objective of this study was to ascertain the abundance and spatial distribution of Lu. longipalpis in Puerto Iguazú City, on the Argentina-Brazil-Paraguay border. Lu. longipalpis proved to be exclusively urban and was found in 31% of the households sampled (n = 53), 67% of which belonged to areas of low abundance, 20% to areas of moderate abundance and 13% to areas of high abundance. Nyssomyia whitmani was the only species found both in urban and peri-urban environments, and Migonemyia migonei was registered only on the outskirts of the city. Due to the fact that Puerto Iguazú is considered to be at moderate risk at the moment, it is necessary to intensify human and canine case controls, as well as take integrated prevention and control measures regarding the environment, vectors and reservoirs on the Argentina-Brazil-Paraguay border area. .

RESUMO O primeiro caso humano autóctone de leishmaniose visceral (LV) na Argentina ocorreu na cidade de Posadas (Misiones) em 2006, desde então, tem ocorrido um aumento na incidência e distribuição geográfica da doença. No período entre 2006 e 2012 foram detectados 107 casos humanos com 11 mortes. Em 2010 se constatou a presença de Lutzomyia longipalpis no município de Puerto Iguazú, localizado na fronteira entre Argentina-Brasil-Paraguai. O presente estudo teve como objetivo investigar a abundância e distribuição de Lu. longipalpis no município de Puerto Iguazú. Lu. longipalpis foi encontrada exclusivamente na área urbana, em 31% das amostras coletadas dos domicílios de referência (n = 53), 67% das quais pertenciam às áreas de baixa abundância, 20% às de moderada e 13% às de alta abundância da espécie. Nyssomyia whitmani foi coletado em ambientes urbanos e periurbanos e Migonemyia migonei, somente nas periferias da cidade. Na atualidade, a cidade de Puerto Iguazú é considerada como de risco moderado; por isso, é necessário intensificar o controle tanto de casos humanos como de caninos e levar em conta as medidas de prevenção e controle do ambiente, dos vetores e dos reservatórios na zona de fronteira Argentina-Brasil-Paraguai. .

Sex pheromone and period gene characterization of Lutzomyia longipalpis sensu lato (Lutz & Neiva) (Diptera: Psychodidae) from Posadas, Argentina

Lutzomyia longipalpis s.l. is the primary vector of Leishmania (L.) infantum in the New World. In this study, male Lutzomyia longipalpis specimens from Posadas, Argentina were characterized for two polymorphic markers: the male sex pheromone and the period (per) gene. The male sex pheromone was identified as (S)-9-methylgermacrene-B, the same compound produced by Lu. longipalpis from Paraguay and many populations from Brazil. The analysis of per gene sequences revealed that the population from Argentina is significantly differentiated from previously studied Brazilian populations. Marker studies could contribute to the understanding of the distribution and spread of urban American visceral leishmaniasis, thus aiding in the design of regional surveillance and control strategies.

Detection of Leishmania infantum in naturally infected Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae) and Canis familiaris in Misiones, Argentina: the first report of a PCR-RFLP and sequencing-based confirmation assay

In this study, a genotypification of Leishmaniawas performed using polimerase chain reaction-restriction fragment length polymorfism (PCR-RFLP) and sequencing techniques to identify species of Leishmaniaparasites in phlebotomine sand flies and dogs naturally infected. Between January-February of 2009, CDC light traps were used to collect insect samples from 13 capture sites in the municipality of Posadas, which is located in the province of Misiones of Argentina. Sand flies identified as Lutzomyia longipalpiswere grouped into 28 separate pools for molecular biological analysis. Canine samples were taken from lymph node aspirates of two symptomatic stray animals that had been positively diagnosed with canine visceral leishmaniasis. One vector pool of 10 sand flies (1 out of the 28 pools tested) and both of the canine samples tested positively for Leishmania infantumby PCR and RFLP analysis. PCR products were confirmed by sequencing and showed a maximum identity with L. infantum. Given that infection was detected in one out of the 28 pools and that at least one infected insect was infected, it was possible to infer an infection rate at least of 0.47 percent for Lu. longipalpisamong the analyzed samples. These results contribute to incriminate Lu. longipalpis as the vector of L. infantumin the municipality of Posadas, where cases of the disease in humans and dogs have been reported since 2005.

Lutzomyia longipalpis behavior and control at an urban visceral leishmaniasis focus in Argentina / Comportamento e controle de Lutzomyia longipalpis em foco de leishmaniose visceral urbana na Argentina

During the earlier stages of visceral leishmaniasis transmission in Posadas City, Misiones, both the night activity and attraction to humans of Lutzomyia longipalpis were assessed, in order to provide preliminary recommendations. The impact of peridomestic deltamethrin spraying performed by local officials was also evaluated. Although Lu. longipalpis were found in traps located over a dog the entire night, 90 percent of the females were captured from 20.30h to 1.30h, and only landed on a human when he was at a distance of 1.5 m from the dog. Peridomestic spraying of deltamethrin (25 mg/m²) reduced the sand fly capture up to seven days post-intervention without dispersion in the border of the sprayed areas. These results support the recommendations about time-space focus of the protection measures: first half of the night, in the backyard, with pets and domestic animals kept at least 5 m from humans. The deltamethrin as it was used did not seem very effective in this scenario; neither did the eventual use of bed nets, at least in adults, due to the place/hour of sand fly higher activity. This study strengthens the need for a multidisciplinary approach to develop prevention strategies based both on biological and anthropological studies.

Durante os estádios precoces de transmissão da leishmaniose visceral na cidade de Posadas, Misiones, foi avaliada a atividade noturna da Lutzomyia longipalpis e a atração pelos seres humanos, para fornecer recomendações preliminares. O impacto do inseticida deltametrina peridoméstico, e a borrifação executada por funcionários locais, também foi avaliada. Embora existam Lu. longipalpis atingindo as armadilhas localizadas perto de um cão durante toda a noite, 90 por cento das fêmeas foram capturadas a partir das 20.30h até 1.30h, e só atinge seres humanos quando estão a 1,5 m do cão. A borrifação peridoméstica com deltametrina (25 mg/m²) reduziu a área de captura da mosca da areia, até sete dias após a intervenção, sem dispersão nas bordas das áreas pulverizadas. Estes resultados apóiam as recomendações sobre o tempo-espaço, das medidas de proteção: na primeira metade da noite, no quintal, com animais de estimação criados pelo menos a cinco metros de distância dos seres humanos. A deltametrina como ela é usada, não parece muito eficaz neste cenário, nem o eventual uso de mosquiteiros pelo menos em adultos, devido ao lugar/hora de mais alta atividade de vôo da Lu. longipalpis. Este estudo acentua a necessidade de abordagem multidisciplinar, para desenvolver estratégias de prevenção baseadas tanto em estudos biológicos como antropológicos.

Distribución de vectores de leishmaniasis visceral en la Provincia de Corrientes, 2008 / Distribution of vectors of visceral leishmaniasis in the Province of Corrientes, 2008

La leishmaniasis visceral es una parasitosis de importancia en salud pública, producida por Leishmania infantum chagasi. A partir de la urbanización y emergencia en el sur de Brasil y Paraguay, se notificó la presencia del insecto vector Lutzomyia longipalpis en la Argentina; en Formosa, 2004, y en Misiones el primer caso humano en 2006. La notificación de casos de reservorios caninos infectados en la provincia de Corrientes, contigua a Misiones, determinó la búsqueda del vector. Mediante trampeos estandarizados en diciembre del 2008 se capturaron 376 Lu. longipalpis en Ituzaingó, Virasoro, Santo Tomé, Garruchos, Riachuelo, Corrientes y Monte Caseros. Se confirma el riesgo de transmisión vectorial autóctona de leishmaniasis visceral en la provincia de Corrientes. La distribución de vectores en áreas urbanas densamente pobladas, con intenso tránsito de reservorios caninos desde zonas de alta transmisión, y la presencia de reservorios infectados, implica a su vez riesgo epidémico.

Visceral leishmaniasis (VL) is a relevant parasitic disease in public health, produced by Leishmania infantum chagasi. Since the urbanization and emergence in Southern Brazil and Paraguay, the vector Lutzomyia longipalpis in Formosa, 2004, and the first human visceral leishmaniasis case in Misiones, 2006, have been reported in Argentina. Due to the reports of canine VL, a search of the vector in the Province of Corrientes, contiguous to Misiones, was performed during December 2008. Standarized trapping detected 376 Lu. longipalpis in Ituzaingó, Virasoro, Santo Tomé, Garruchos, Riachuelo, Corrientes and Monte Caseros localities. The risk of autochtonous vectorial transmission was then confirmed in the Province of Corrientes. The distribution of vectors in populated urban areas, with intense transit of canine reservoirs from localities with high transmission, and the existence of infected reservoirs, also implies epidemic risk.

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.