Molecular typing reveals the co-existence of two transmission cycles of American cutaneous leishmaniasis in the Andean Region of Venezuela with Lutzomyia migonei as the vector

BACKGROUND The transmission routes for American cutaneous leishmaniasis (ACL) are in flux, so studies examining its transmission in humans, mammalian hosts, and sand fly vectors are urgently needed. OBJECTIVES The aim of this work was understand the epidemiological cycles of Leishmania spp., which causes ACL in the Andean Region of Venezuela, by identifying the Leishmania and the sand fly species involved in human and dog infections. METHODS Thirty-one biopsies from patients in Mérida and Táchira states with suspected ACL were studied by both parasitological tests (cultures and hamster inoculation) and a molecular test [Internal transcribed spacer 1 (ITS1) nested polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP)]. We also conducted a survey to detect Leishmania infection in dogs (Immunifluorescence antibody test and ITS1 nested PCR-RFLP) and sand flies (ITS1 nested PCR-RFLP) from El Carrizal, a highly endemic focus of ACL in Venezuela. FINDINGS Three different Leishmania species were identified in the clinical samples from humans (Leishmania braziliensis, L. guyanensis, and L. mexicana) and dogs (L. guyanensis and L. mexicana). The predominant sand fly species found were those from the Verrucarum group (infected with L. mexicana) and Lutzomyia migonei (infected with L. guyanensis and L. mexicana). MAIN CONCLUSIONS We show that Lu. migonei may be the putative vector in two ACL epidemiological cycles, involving L. guyanensis and L. mexicana. We also report for the first time the presence of L. guyanensis in domestic animals.

Aspects of the bionomics of three phlebotomine vector species (Diptera: Psychodidae) at El Carrizal, an endemic focus of cutaneous leishmaniasis (CL) in the Venezuelan Andean Region / Bionomía de tres especies de flebótomos vectores (Diptera: Psychodidae) en El Carrizal, un foco endémico de leishmaniasis cutánea en la región Andina Venezolana

We studied some aspects of the bionomics of phlebotomine vectors of cutaneous leishmaniasis (CL) at El Carrizal, Municipality Tovar, Venezuela: Lutzomyia youngi, Lutzomyia spinicrassa and Lutzomyia migonei. Monthly catches were performed throughout 2008 using CDC and Shannon traps. We investigated: (i) species richness, (ii) relationships richness-traps-habitats (domestic, peri-domestic and forest), (iii) monthly fluctuations and relationship with climatic variables, (iv) relationship climatic factors-cutaneous leishmaniasis cases at El Carrizal and Municipality Tovar (2000-2008). Females in the Verrucarum group and males of Lu. youngi prevailed. Catches with CDC revealed the predominance of Lu. migonei outdoors where probably they maintains cutaneous leishmaniasis transmission, while females in the Verrucarum group would contribute to maintain it indoors. The greatest abundance of the three species occurred in November after the heaviest peak of rains. The correlation species-climate for Lu. migonei indicated that temperature seems a limiting factor and precipitation a favouring factor, which agreed with results obtained through Ecological Niche Modelling of this species over 23 records at national level. The correlation cutaneous leishmaniasis incidence-climate showed that the greatest number of cases tends to occur, with a month lag, in the months of most rainfall. These data may support the Ministry of Health, since they provide robust information about "when", "where" and "how" to implement target phlebotomine vectors control methods in the Andean Region of Venezuela.

Se estudiaron algunos aspectos de la bionomía de vectores de leishmaniasis cutánea en la localidad El Carrizal, Municipio Tovar, Venezuela: Lutzomyia youngi, Lutzomyia spinicrassa y Lutzomyia migonei. Las capturas mensuales se realizaron a lo largo del año 2008 usando trampas CDC y Shannon. Se investigó: (i) riqueza de especies, (ii) relaciones riqueza-trampa-hábitat (doméstico, peri-doméstico y selvático), (iii) fluctuaciones mensuales y relación con variables climáticas, (iv) relación factores climáticos-casos de leishmaniasis cutánea en El Carrizal y Tovar (2000-2008). Predominaron las hembras del grupo Verrucarum y los machos de Lu. youngi. Las capturas con CDC revelaron el predominio de Lu. migonei en el habitat peridoméstico donde probablemente mantienen la transmisión, mientras que las hembras del grupo Verrucarum contribuirían a mantenerla dentro de las casas. La mayor abundancia de las tres especies ocurrió en noviembre después del pico más alto de lluvias. La correlación especie-clima para Lu. migonei indicó que la temperatura parece ser un factor limitante y la precipitación un factor favorecedor, lo cual coincidió con los resultados obtenidos a través de la Modelación de Nichos Ecológicóos de esta especie sobre 23 registros a nivel nacional. La correlación de incidencia de leishmaniasis cutánea-clima mostró que el mayor número de casos tiende a ocurrir, con un mes de retraso, en los meses de mayor precipitación. Estos datos pueden ser utiles al Ministerio de Salud ya que proveen información sólida sobre "cuándo", "dónde" y "cómo" implementar métodos de control de vectores en la Región Andina de Venezuela.

Lutzomyia longipalpis urbanisation and control

Since the description of Lutzomyia longipalpis by Lutz and Neiva more than 100 years ago, much has been written in the scientific literature about this phlebotomine species. Soares and Turco (2003) and Lainson and Rangel (2005) have written extensive reviews focused on vector-host-parasite interactions and American visceral leishmaniasis ecology. However, during the last two decades, the success of Lu. longipalpis in colonising urban environments and its simultaneous geographical spreading have led to new theoretical and operational questions. Therefore, this review updates the general information about this species and notes the more challenging topics regarding the new scenario of urbanisation-spreading and its control in America. Here, we summarise the literature on these issues and the remaining unsolved questions, which pose recommendations for operational research.

Effect of Leishmania spp infection on the survival, life expectancy, fecundity and fertility of Lutzomyia longipalpiss.l. and Lutzomyia pseudolongipalpis

We evaluated the effects of Leishmaniaspp infection on several population parameters of Lutzomyia longipalpis sensu lato andLutzomyia pseudolongipalpis, vectors of visceral leishmaniasis in Venezuela, under experimental conditions during the first post-feeding period. Females of both species were allowed to feed and engorge on a suspension of fresh washed human red blood cells in foetal calf serum. These blood cells were either non-infected or infected with one of the fourLeishmaniaspp strains and were offered through a chicken skin membrane. The longevity, life expectancy and the fecundity of uninfected flies were similar in both species, but the fertility was significantly lower in uninfected Lu. longipalpis females. In all cases, the infection of Lu. longipalpis and Lu. pseudolongipalpis by the Leishmaniastrains resulted in significant detrimental effects, which exerted a fitness cost expressed by reduced survival and life expectancy, as well as decreased fertility and fecundity compared with the control groups. Nevertheless, differences in these parameters were observed between these vector species depending on whether they were infected with the autochthonous Venezuelan Leishmania infantum strain (NESA) or the Brazilian reference strain (PP75). The experimental data obtained agree with field data on the natural infection of these vector species and the significance of this scenario is discussed.