Distribution of Lutzomyia ayacuchensis, the vector of Andean-type cutaneous leishmaniasis, at different altitudes on the Andean slope of Ecuador

Spatial variations in Leishmaniasis: A biogeographic approach to mapping the distribution of Leishmania species

Cutaneous Leishmaniasis (CL) is the most prevalent form of Leishmaniasis and is widely endemic in the Americas. Several species of Leishmania are responsible for CL, a severely neglected tropical disease and the treatment of CL vary according to the different species of Leishmania. We proposed to map the distribution of the Leishmania species reported in French Guiana (FG) using a biogeographic approach based on environmental predictors. We also measured species endemism i.e., the uniqueness of species to a defined geographic location. Our results show that the distribution patterns varied between Leishmania spp. and were spatially dependent on climatic covariates. The species distribution modelling of the eco-epidemiological spatial patterns of Leishmania spp. is the first to measure endemism based on bioclimatic factors in FG. The study also emphasizes the impact of tree cover loss and climate on the increasing distribution of L. (Viannia) braziliensis in the most anthropized regions. Detection of high-risk regions for the different between Leishmania spp. is essential for monitoring and active surveillance of the vector. As climate plays a major role in the spatial distribution of the vector and reservoir and the survival of the pathogen, climatic covariates should be included in the analysis and mapping of vector-borne diseases. This study underscores the significance of local land management and the urgency of considering the impact of climate change in the development of vector-borne disease management strategies at the global scale.

Comparative Analysis of Bacterial Communities in Lutzomyia ayacuchensis Populations with Different Vector Competence to Leishmania Parasites in Ecuador and Peru

Differences in the gut microbial content of Lutzomyia (Lu.) ayacuchensis, a primary vector of Andean-type cutaneous leishmaniasis in Ecuador and Peru, may influence the susceptibility of these sand flies to infection by Leishmania. As a first step toward addressing this hypothesis, a comparative analysis of bacterial and fungal compositions from Lu. ayacuchensis populations with differential susceptibilities to Leishmania was performed. Bacterial 16S rRNA gene amplification and Illumina MiSeq sequencing approaches were used to characterize the bacterial composition in wild-caught populations from the Andean areas of Ecuador and southern Peru at which the sand fly species transmit Leishmania (Leishmania) mexicana and Leishmania (Viannia) peruviana, respectively, and a population from the northern Peruvian Andes at which the transmission of Leishmania by Lu. ayacuchensis has not been reported. In the present study, 59 genera were identified, 21 of which were widely identified and comprised more than 95% of all bacteria. Of the 21 dominant bacterial genera identified in the sand flies collected, 10 genera had never been detected in field sand flies. The Ecuador and southern Peru populations each comprised individuals of particular genera, while overlap was clearly observed between microbes isolated from different sites, such as the number of soil organisms. Similarly, Corynebacterium and Micrococcus were slightly more dominant bacterial genera in the southern Peru population, while Ochrobactrum was the most frequently isolated from other populations. On the other hand, fungi were only found in the southern Peru population and dominated by the Papiliotrema genus. These results suggest that variation in the insect gut microbiota may be elucidated by the ecological diversity of sand flies in Peru and Ecuador, which may influence susceptibility to Leishmania infection. The present study provides key insights for understanding the role of the microbiota during the course of L. (L.) mexicana and L. (V.) peruviana infections in this important vector.

Anthropophilic phlebotomine sand fly Lutzomyia species and search for the natural Leishmania infections in an area endemic for cutaneous leishmaniasis in Ecuador

By employing protected human bait landing and modified Shannon light trap, a total of 1924 phlebotomine sand fly Lutzomyia spp. were captured in an area from which L. (V.) guyanensis was reported as the causative parasite of cutaneous leishmaniasis (CL). The sand flies captured alive were dissected and identified at species level, based mainly on their spermathecae. At the same time, the sand flies dissected were searched for the Leishmania parasites by microscopic-test, and later on by PCR-test. No positive sand flies were detected by both tests, while considerable numbers of anthropophilic sand fly species of the genus Lutzomyia were observed as probable vectors of the Leishmania parasite in the areas. Those were eight species, Lu. robusta, Lu. trapidoi, Lu. maranonensis, Lu. gomezi, Lu. shannoni, Lu. migonei, Lu. punctigeniculata and Lu. spathotrichia. Among them, the first two species Lu. robusta and Lu. trapidoi were most dominant, suggesting probable vectors of the Leishmania parasite prevailing in the area. Lu. punctigeniculata and Lu. spathotrichia were for the first time recorded for the Manabí province, Ecuador. These findings provide basic information useful for future planning of the control and management of the disease in the areas, though further study to incriminate the vector sand fly remains.

Natural Leishmania (Leishmania) mexicana infection and biting activity of anthropophilic sand fly Lutzomyia ayacuchensis in the Ecuadorian Andes

To elucidate the transmission mode of Andean cutaneous leishmaniasis (Andean-CL), natural Leishmania infection and biting activity of sand flies were tested in a selected sylvatic focus of the endemic area of the Ecuadorian Andes. Monthly sand fly collections and dissections were conducted during 12 months from July 2018 to June 2019. The Leishmania positive specimens/slides with innumerable amounts of actively mobile flagellates made us easy to detect positive sand flies. The promastigotes observed located in the anterior and posterior midgut, without the hindgut localization. The parasite isolated was identified as L. (L.) mexicana by cytochrome b gene analysis. No other Leishmania or flagellate species parasitic in sand flies was observed in the area. Only Lu. ayacuchensis was caught throughout. Monthly microscopic examination of Lu. ayacuchensis revealed 0.75-8.33% of natural L. (L.) mexicana infection rates. Higher Leishmania infection months were present at the end of the wet season of the Andes, while higher sand fly numbers occurred during the dry season. Diurnal biting (blood meal seeking) activity of sand flies started around 17:30 before sunset, increased between 18:00 and 19:30, and thereafter decreased drastically probably because of low temperature (15-18 °C) in the area. The results provide information important for the planning of vector control strategy and management of the disease in the Andean-CL endemic area of Ecuador.

Leishmaniasis caused by Leishmania (Viannia) guyanensis in north-central Pacific region of Ecuador: A clinico-epidemiological feature

The current four year study was undertaken to investigate the clinical and epidemiological features of Leishmania (Viannia) guyanensis infections in Valle Hermoso, Santo Domingo de Los Tsachilas province, north-central Pacific areas of Ecuador. A total of 155 parasitologically confirmed (Leishmania-amastigote-positive) clinical cases diagnosed at a rural health center during January 2014-December 2017 were analyzed thoroughly. Molecular characterization of the causative Leishmania parasites from different endemic sites within the study areas was performed by PCR amplification of cytochrome b (cyt b) sequencing. All the FTA-card and/or smear impregnated materials tested were characterized, and identified as L. (V.) guyanensis, without detecting any other Leishmania species. The following features were described: 1) the majority of patients were suffered from a single ulcer lesion (simple and mild to chronic), followed by multiple lesions, including recidiva cutis-"like" and Chiclero's ulcer-"like" clinical forms; 2) the majority (65.70%) of lesions were less than 10 mm in size, and distributed mainly on the upper body regions (arm, forearm, face, and neck including ear and head); 3) about 30% (29.68%) of the subjects tested were less than 10 years of age, strongly suggesting the intra- and/or peri-domestic transmission of the disease in the areas. The current clinico-epidemiological feature detected emphasizes the need for further such investigations of the L. (V.) guyanensis infections prevalent at different Pacific ecoregions of Ecuador, including Amazon regions.

Seroprevalence and risk factors for infection with Bartonella bacilliformis in Loja province, Ecuador

The seroprevalence and epidemiology of Bartonella bacilliformis infection in the Andean highlands of Ecuador is largely unknown. We conducted a sero-epidemiologic survey of 319 healthy children aged 1-15 years living in six rural, mountain communities in Loja Province, Ecuador. Blood was collected by finger stick onto filter paper and dried, and the eluted sera analyzed for antibodies to B. bacilliformis by rPap31 ELISA. Demographic, entomologic, and household variables were assessed to investigate associated risk factors for antibody seropositivity to B. bacilliformis. Seroprevalence of 28% was found among children in the study communities. Increased risk of seropositivity was associated with the presence of lumber piles near houses. Decreased risk of seropositivity was observed with the presence of animal waste and incremental 100 meter increases in elevation. Although investigation of clinical cases of Carrion's disease was not within the scope of this study, our serology data suggest that infection of children with B. bacilliformis is prevalent in this region of Ecuador and is largely unrecognized and undiagnosed. This study highlights the need to further investigate the prevalence, pathogenesis, epidemiology, and disease impact of this pathogen in Ecuador.

EA, Cáceres AG, Velez LN, Villegas NV, Hashiguchi K, Mimori T, Uezato H, Kato H. Andean cutaneous leishmaniasis (Andean-CL, uta) in Peru and Ecuador: the vector Lutzomyia sand flies and reservoir mammals

The vector Lutzomyia sand flies and reservoir host mammals of the Leishmania parasites, causing the Andean cutaneous leishmaniasis (Andean-CL, uta) in Peru and Ecuador were thoroughly reviewed, performing a survey of literatures including our unpublished data. The Peruvian L. (V.) peruviana, a principal Leishmania species causing Andean-CL in Peru, possessed three Lutzomyia species, Lu. peruensis, Lu. verrucarum and Lu. ayacuchensis as vectors, while the Ecuadorian L. (L.) mexicana parasite possessed only one species Lu. ayacuchensis as the vector. Among these, the Ecuadorian showed a markedly higher rate of natural Leishmania infections. However, the monthly and diurnal biting activities were mostly similar among these vector species was in both countries, and the higher rates of infection (transmission) reported, corresponded to sand fly's higher monthly-activity season (rainy season). The Lu. tejadai sand fly participated as a vector of a hybrid parasite of L. (V.) braziliensis/L. (V.) peruviana in the Peruvian Andes. Dogs were considered to be principal reservoir hosts of the L. (V.) peruviana and L. (L.) mexicana parasites in both countries, followed by other sylvatic mammals such as Phyllotis andium, Didelphis albiventris and Akodon sp. in Peru, and Rattus rattus in Ecuador, but information on the reservoir hosts/mammals was extremely poor in both countries. Thus, the Peruvian disease form demonstrated more complicated transmission dynamics than the Ecuadorian. A brief review was also given to the control of vector and reservoirs in the Andes areas. Such information is crucial for future development of the control strategies of the disease.

Andean cutaneous leishmaniasis (Andean-CL, uta) in Peru and Ecuador: the causative Leishmania parasites and clinico-epidemiological features

This study provides comprehensive information on the past and current status of the Andean cutaneous leishmaniasis (Andean-CL, uta) in Peru and Ecuador, mainly focusing on the causative Leishmania parasites and clinico-epidemiological features. Available information and data including our unpublished works were analyzed thoroughly. Endemic regions of the Andean-CL (uta) in Peru run from the north Piura/Cajamarca to the south Ayacucho at a wide range of the Pacific watersheds of the Andes through several departments, while in Ecuador those exist at limited and spotted areas in the country's mid-southwestern two provinces, Azuay and Chimborazo. The principal species of the genus Leishmania are completely different at subgenus level, L. (Viannia) peruviana in Peru, and L. (Leishmania) mexicana and L. (L.) major-like (infrequent occurrence) in Ecuador. The Peruvian uta is now prevalent in different age and sex groups, being not clearly defined as found in the past. The precise reasons are not known and should be elucidated further, though probable factors, such as emergence of other Leishmania parasites, non-immune peoples' migration into the areas, etc., were discussed briefly in the text. The Andean-CL cases in Ecuador are more rural than before, probably because of a rapid development of the Leishmania-positive communities and towns, and the change of life-styles of the inhabitants, including newly constructed houses and roads in the endemic areas. Such information is helpful for future management of the disease, not only for Leishmania-endemic areas in the Andes but also for other endemic areas.

Molecular Identification of Leishmania spp. in Sand Flies (Diptera: Psychodidae, Phlebotominae) From Ecuador

The detection and identification of natural infections in sand flies by Leishmania protozoan species in endemic areas is a key factor in assessing the risk of leishmaniasis and in designing prevention and control measures for this infectious disease. In this study, we analyzed the Leishmania DNA using nuclear ribosomal internal transcript spacer (ITS) sequences. Parasite DNA was extracted from naturally infected, blood-fed sand flies collected in nine localities considered leishmaniasis-endemic foci in Ecuador.

The species of parasites identified in sand flies were Leishmania major-like, Leishmania naiffi, Leishmania mexicana, Leishmania lainsoni, and “Leishmania sp. siamensis”. Sand fly specimens of Brumptomyia leopoldoi, Mycropigomyia cayennensis, Nyssomyia yuilli yuilli, Nyssomyia trapidoi, Pressatia triacantha, Pressatia dysponeta, Psychodopygus carrerai carrerai, Psychodopygus panamensis, and Trichophoromyia ubiquitalis were found positive for Leishmania parasite. These findings contribute to a better understanding of the epidemiology and transmission dynamics of the disease in high-risk areas of Ecuador.

Eco-epidemiological aspects, natural detection and molecular identification of Leishmania spp. in Lutzomyia reburra, Lutzomyia barrettoi majuscula and Lutzomyia trapidoi

Introducción. La provincia de Pichincha, Ecuador, es un área endémica de leishmaniasis cutánea, en donde se han determinado como vectores los flebotomíneos antropofílicos con infección natural por Leishmania spp. Sin embargo, no se ha evaluado el papel en la transmisión de las especies zoofílicas.Objetivo. Evaluar la infección natural por Leishmania en dos especies de flebotomíneos zoofílicos, Lutzomyia reburra y Lu. barrettoi majuscula, y en una antropofílica, Lu. trapidoi, así como la endofagia y la sinantropía de estas especies en el noroccidente de Pichincha.Materiales y métodos. Los flebotomíneos se recolectaron en trampas de luz CDC colocadas en diferentes hábitats y altitudes en sitios que son focos de leishmaniasis cutánea. La infección con Leishmania spp. se detectó en el ADN genómico de hembras de las especies de flebotomíneos de interés. Se amplificó el gen espaciador interno de la transcripción del ARN ribosómico, unidad I (ITS1), y los genes de las topoiso-merasas mitocondrial II (mtTOPOII) y nuclear II (TopoII). Se determinaron los porcentajes de positividad para Leishmania a escala espaciotemporal, la proporción de endofagia y el índice de sinantropía.Resultados. Se determinó la presencia de infección natural por Le. amazonensis en Lu. reburra (9,5 %) y Lu. b. majuscula (23,8 %); en Lu. trapidoi se detectaron Le. amazonensis, Le. brazilienis y Le. naiffi-lainsoni. Los flebotomíneos eran asinantrópicos y con baja endofagia.Conclusión. Se registró por primera vez la presencia de infección natural en Lu. reburra y Lu. barrettoi majuscula por Le. amazonensis, y se demostró la importancia de los flebotomíneos zoofílicos en el mantenimiento del ciclo de transmisión de Leishmania spp. en focos endémicos.

Leishmaniases in Ecuador: Comprehensive review and current status

This article reviews current knowledge about leishmaniases in Ecuador, proceeding from 1920, when the first human case was described, to the present, mainly focusing on the recent research events published. Regarding basic situations, it appears that 23 of Ecuador's 24 provinces have leishmaniasis-case reports. The disease is one of the mandatory notification infectious diseases in the country since 2005. All the 21,305 cases notified to the Ministry of Public Health, during the period from 2001 through 2014, were said to involve different clinical features of cutaneous leishmaniasis (CL) but not visceral (VL). Eight Leishmania species, L. (Viannia) guyanensis, L. (V.) panamensis, L. (V.) braziliensis, L. (Leishmania) mexicana, L. (L.) amazonensis, L. (L.) major-like, L. (V.) naiffiand L. (V.) lainsoni were characterized. The last two species were most recently reported from the Ecuadorian Amazon regions. Of the 73 Ecuadorian Lutzomyia species (43 man-biting species) recorded, only four, Lu. trapidoi, Lu. gomezi, Lu. ayacuchensis, and Lu. tortura were incriminated as vectors of the Leishmania parasites. Current knowledge on the reservoir hosts of Leishmania in Ecuador is extremely poor. Recently, in Ecuador different kinds of molecular techniques were developed for diagnosis and mass screening of the disease, employing various materials derived from patients and sand fly vectors. These are PCR-RFLP, colorimetric FTA-LAMP etc. Brief comments and recommendations were also given, for future research and control of leishmaniases in Ecuador.

Ecological Niche Modelling Predicts Southward Expansion of Lutzomyia (Nyssomyia) flaviscutellata (Diptera: Psychodidae: Phlebotominae), Vector of Leishmania (Leishmania) amazonensis in South America, under Climate Change

Vector borne diseases are susceptible to climate change because distributions and densities of many vectors are climate driven. The Amazon region is endemic for cutaneous leishmaniasis and is predicted to be severely impacted by climate change. Recent records suggest that the distributions of Lutzomyia (Nyssomyia) flaviscutellata and the parasite it transmits, Leishmania (Leishmania) amazonensis, are expanding southward, possibly due to climate change, and sometimes associated with new human infection cases. We define the vector's climatic niche and explore future projections under climate change scenarios. Vector occurrence records were compiled from the literature, museum collections and Brazilian Health Departments. Six bioclimatic variables were used as predictors in six ecological niche model algorithms (BIOCLIM, DOMAIN, MaxEnt, GARP, logistic regression and Random Forest). Projections for 2050 used 17 general circulation models in two greenhouse gas representative concentration pathways: "stabilization" and "high increase". Ensemble models and consensus maps were produced by overlapping binary predictions. Final model outputs showed good performance and significance. The use of species absence data substantially improved model performance. Currently, L. flaviscutellata is widely distributed in the Amazon region, with records in the Atlantic Forest and savannah regions of Central Brazil. Future projections indicate expansion of the climatically suitable area for the vector in both scenarios, towards higher latitudes and elevations. L. flaviscutellata is likely to find increasingly suitable conditions for its expansion into areas where human population size and density are much larger than they are in its current locations. If environmental conditions change as predicted, the range of the vector is likely to expand to southeastern and central-southern Brazil, eastern Paraguay and further into the Amazonian areas of Bolivia, Peru, Ecuador, Colombia and Venezuela. These areas will only become endemic for L. amazonensis, however, if they have competent reservoir hosts and transmission dynamics matching those in the Amazon region.

An analysis of reported cases of leishmaniasis in the southern Ecuadorian Amazon region, 1986-2012

An analysis of reported cases of cutaneous leishmaniasis (CL) was performed using the data registered in the southern Ecuadorian Amazon region during 27 years from 1986 to 2012. The cases/subjects with both the suspected CL lesions and the amastigote-positive results were recruited for the analysis. The yearly occurrence of cases showed a markedly higher number during the six years, 1988 and 1993. After 1994 when the insecticide spraying campaign using helicopter in 1993-1994, the number dropped remarkably. Then, the yearly occurrence gradually fluctuated from 101 cases in 1996 to 11 in 2009, maintaining a low number of cases after the campaign. The monthly occurrence of cases showed a markedly high number during March and August, suggesting a correlation to the rainy season (months) in the areas. A statistical significance was found between the monthly average number of the CL case and the average precipitation (p=0.01474). It was suggested that the time of transmission of CL would depend on the rainy seasons at each endemic area of Ecuador, which has a diverse climatic feature depending on the geographic regions. Such information at given leishmaniasis-endemic areas of Ecuador would be important for the future planning of the disease control. Molecular analysis and characterization of clinical samples revealed the presence of Leishmania (Viannia) braziliensis.

DNA barcoding for identification of sand fly species (Diptera: Psychodidae) from leishmaniasis-endemic areas of Peru

Phlebotomine sand flies are the only proven vectors of leishmaniases, a group of human and animal diseases. Accurate knowledge of sand fly species identification is essential in understanding the epidemiology of leishmaniasis and vector control in endemic areas. Classical identification of sand fly species based on morphological characteristics often remains difficult and requires taxonomic expertise. Here, we generated DNA barcodes of the cytochrome c oxidase subunit 1 (COI) gene using 159 adult specimens morphologically identified to be 19 species of sand flies, belonging to 6 subgenera/species groups circulating in Peru, including the vector species. Neighbor-joining (NJ) analysis based on Kimura 2-Parameter genetic distances formed non-overlapping clusters for all species. The levels of intraspecific genetic divergence ranged from 0 to 5.96%, whereas interspecific genetic divergence among different species ranged from 8.39 to 19.08%. The generated COI barcodes could discriminate between all the sand fly taxa. Besides its success in separating known species, we found that DNA barcoding is useful in revealing population differentiation and cryptic diversity, and thus promises to be a valuable tool for epidemiological studies of leishmaniasis.

Genetic divergence in populations of Lutzomyia ayacuchensis, a vector of Andean-type cutaneous leishmaniasis, in Ecuador and Peru

Haplotype and gene network analyses were performed on mitochondrial cytochrome oxidase I and cytochrome b gene sequences of Lutzomyia (Lu.) ayacuchensis populations from Andean areas of Ecuador and southern Peru where the sand fly species transmit Leishmania (Leishmania) mexicana and Leishmania (Viannia) peruviana, respectively, and populations from the northern Peruvian Andes, for which transmission of Leishmania by Lu. ayacuchensis has not been reported. The haplotype analyses showed higher intrapopulation genetic divergence in northern Peruvian Andes populations and less divergence in the southern Peru and Ecuador populations, suggesting that a population bottleneck occurred in the latter populations, but not in former ones. Importantly, both haplotype and phylogenetic analyses showed that populations from Ecuador consisted of clearly distinct clusters from southern Peru, and the two populations were separated from those of northern Peru.

Man-biting sand fly species and natural infection with the Leishmania promastigote in leishmaniasis-endemic areas of Ecuador

A countrywide surveillance of sand flies was performed to obtain information on their geographical distribution and natural infection by Leishmania protozoa in Ecuador. A total of 18,119 sand flies were collected by human landing collections during 32 years from 1982 to 2014, and 29 species were recognized. The most prevalent 10 species were Lutzomyia gomezi, Lu. robusta, Lu. hartmanni, Lu. shannoni, Lu. trapidoi, Lu. panamensis, Lu. maranonensis, Lu. ayacuchensis, Lu. tortura and Lu. yuilli yuilli, and their topographical and vertical distributions were identified. Among all the sand flies, only 197 (1.09%) flies of four Lutzomyia species, Lu. gomezi, Lu. trapidoi, Lu. tortura and Lu. ayacuchensis, were positive for Leishmania. Endotrypanum, a flagellate parasite not pathogenic to humans, were detected in five Lutzomyia species, Lu. robusta, Lu. hartmanni, Lu. trapidoi, Lu. panamensis and Lu. yuilli yuilli, suggesting wide vector-ranges of Endotrypanum species. These data on the genus Lutzomyia and their natural infections with Leishmania and Endotrypanum will be useful for transmission studies and surveillance of leishmaniasis.

Sand fly fauna (Diptera, pcychodidae, phlebotominae) in different leishmaniasis-endemic areas of ecuador, surveyed using a newly named mini-shannon trap

To study the sand fly fauna, surveys were performed at four different leishmaniasis-endemic sites in Ecuador from February 2013 to April 2014. A modified and simplified version of the conventional Shannon trap was named “mini-Shannon trap” and put to multiple uses at the different study sites in limited, forested and narrow spaces. The mini-Shannon, CDC light trap and protected human landing method were employed for sand fly collection. The species identification of sand flies was performed mainly based on the morphology of spermathecae and cibarium, after dissection of fresh samples. In this study, therefore, only female samples were used for analysis. A total of 1,480 female sand flies belonging to 25 Lutzomyia species were collected. The number of female sand flies collected was 417 (28.2%) using the mini-Shannon trap, 259 (17.5%) using the CDC light trap and 804 (54.3%) by human landing. The total number of sand flies per trap collected by the different methods was markedly affected by the study site, probably because of the various composition of species at each locality. Furthermore, as an additional study, the attraction of sand flies to mini-Shannon traps powered with LED white-light and LED black-light was investigated preliminarily, together with the CDC light trap and human landing. As a result, a total of 426 sand flies of nine Lutzomyia species, including seven man-biting and two non-biting species, were collected during three capture trials in May and June 2014 in an area endemic for leishmaniasis (La Ventura). The black-light proved relatively superior to the white-light with regard to capture numbers, but no significant statistical difference was observed between the two traps.