Performance of light-emitting diode traps for collecting sand flies in entomological surveys in Argentina

The perfect storm: Cutaneous leishmaniasis in troops deployed in the Atlantic forest of Argentina

American cutaneous leishmaniasis (ACL) is the most prevalent form of leishmaniasis, associated with an ulcerative and stigmatizing mucocutaneous pathology. This study assessed the incidence of Leishmania (Viannia) braziliensis in members of the Argentine Army who were exposed to sandfly bites in Iguazú National Park (INP), northeastern Argentina, during an outbreak of ACL in 2019, and the presence of Leishmania in rodents, opossums and phlebotomine sandflies collected in the area of exposure. Samples from military personnel, wild animals and phlebotomine sandflies were analysed. A total of 20 (40%) patients among the Army personnel and two Akodon montensis rodents (11%) were positive for the presence of Leishmania sp. genes by PCR, while Nyssomyia whitmani and Migonemyia migonei, competent vectors of Leishmania, were also found at the same site. Sequences of hsp70 DNA fragments obtained from human samples confirmed the identity of L. (V.) braziliensis. The risk to which military personnel carrying out activities in the forest are exposed is highlighted, and this risk extends to any worker and visitor who circulates without protection in the INP, coming into contact with transmission "hot spots" due to the concentration of vectors, reservoirs and/or parasites.

Cryptic Diversity in Sympatric Migonemyia migonei (Diptera: Psychodidae), Eventual Meaning for Leishmaniasis Transmission

Migonemyia migonei (Franҫa, 1920) (Diptera: Psychodidae) belongs to the subfamily Phlebotominae, of epidemiological importance due to its role as a vector in leishmaniasis transmission cycles and its broad geographic distribution in South America. Few morphometric and genetic studies have demonstrated the existence of variability among geographically distant populations in Brazil. The aim of the study was to estimate the genetic distance within the morphospecies Mg. migonei through the analysis of cytochrome C oxidase subunit I (COI) sequences of specimens captured in Argentina and those available in online databases. The COI sequences from specimens collected in different localities of Argentina and sequences available in online databases were utilized. Genetic distances were analyzed and a median-joining haplotype network was constructed. Finally, phylogenetic reconstruction was performed according to Bayesian inference. The analyses led to the identification of at least two haplogroups: haplogroup I with sequences of specimens from Colombia, Brazil and Argentina, and haplogroup II with sequences of specimens from Argentina. Interestingly, specimens from Argentina whose haplotypes corresponded to both haplogroups, were collected in sympatry. The results suggest that Mg. migonei could be a species complex with at least two distinct members. This hypothesis could explain the known characteristics of adaptability and vector permissiveness of the species, as the putative cryptic species of the complex could differ in traits of epidemiological importance.

Field evaluation of a new suction light trap for the capture of phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae), vectors of leishmaniasis

Phlebotomine sand flies are crepuscular and nocturnal small dipteran insects in the family Psychodidae. Several disease agents, including Leishmania parasites, are transmitted to humans and other vertebrate hosts by the bite of an infected female sand fly. As part of leishmaniasis surveillance programs, light traps have been routinely used in sand fly collections. In this context, new trapping devices are always being required to improve vector monitoring. Here, the efficiency of a new suction light trap, named Silva suction trap or SS trap, was field evaluated in collecting sand flies. Two SS traps, one with green (520 nm, 15,000 mcd) and the other with white (wide spectrum, 18,000 mcd) LEDs, and one CDC-type trap were deployed in a rural forested environment. A total of 4686 phlebotomine sand flies were captured. The most frequent species were females of the Ps. Chagasi series (77.8%) followed by males of Ps. wellcomei (11.6%), Nyssomyia whitmani (3.3%), and Bichromomyia flaviscutellata (2.4%). The CDC-type light trap collected 101.9 ± 20.89 sand flies and 14 species, followed by the white-baited SS trap (87.78 ± 16.36, 14), and the green-baited SS trap (70.61 ± 14.75, 15), but there were no statistically significant differences among traps. A discussion on the considerable advantages of the use of SS traps over CDC traps is included. In this study, the Silva suction trap proved to be efficient and can be an alternative to CDC traps for monitoring adult phlebotomine sand fly populations.

Population dynamics of Nyssomyia whitmani (Diptera: Psychodidae) in domestic and peridomestic environments in Northeast Argentina, a tegumentary leishmaniasis outbreak area

In the present study, the temporal dynamics of the main vector of Leishmania braziliensis, Nyssomyia whitmani, was measured by monthly captures of phlebotominae sandflies during 5 consecutive years (from 2011 to 2016) in the Paranaense region of South America. The captures were performed in environments where the human-vector contact risk is high: domiciliary and peridomiciliary environments in a rural area endemic of tegumentary leishmaniasis. Nyssomyia whitmani was recorded as the dominant species of the phlebotominae ensemble in all domiciliary and peridomiciliary environments (House, Chicken Shed, Pigsty, and Forest Edge). Using generalized additive models, intra- and interannual fluctuations were observed, modulated by meteorological variables such as the minimum temperature and the accumulated precipitation 1 wk prior to capture. The installation of a pigsty by the farmer during the study period allowed us to observe and describe the so-called "pigsty effect" where the Ny. whitmani population was spatially redistributed, turning the pigsty as the environment that obtained the highest phlebotominae record counts, thus maintaining the farm overall abundance, supporting the idea that the environmental management of the peridomicile could have an impact on the reduction of epidemiological risk by altering the spatial distribution of the phlebotominae ensemble in the environments.

Genetic variability highlights the invasion route of the Lutzomyia longipalpis complex, the main vector of Visceral Leishmaniasis in Uruguay

In the Americas, the sandfly Lutzomyia longipalpis is the main vector of the parasitic protozoa Leishmania infantum, the etiological agent of visceral leishmaniasis (VL). The Lu. longipalpis species complex is currently discontinuously distributed across the Neotropical region, from Mexico to the north of Argentina and Uruguay. During its continental spreading, it must have adapted to several biomes and temperature amplitudes, when founder events should have contributed to the high genetic divergence and geographical structure currently observed, reinforcing the speciation process. The first report of Lu. longipalpis in Uruguay was in 2010, calling the attention of Public Health authorities. Five years later, the parasite Le. infantum was recorded and in 2015 the first case of VL in canids was reported. Hitherto seven human cases by VL have been reported in Uruguay. Here, we publish the first DNA sequences from the mitochondrial genes ND4 and CYTB of Lu. longipalpis collected in Uruguay, and we used these molecular markers to investigate their genetic variability and population structure. We described four new ND4 haplotypes in a total of 98 (4/98) and one CYTB in a total of 77 (1/77). As expected, we were able to establish that the Lu. longipalpis collected in two localities (i.e. Salto and Bella Unión) from the north of Uruguay are closely related to the populations from neighbouring countries. We also propose that the possible route for the vector arrival to the region may have been through vegetation and forest corridors of the Uruguay River system, as well as it may have benefited from landscape modifications generated by commercial forestation. The ecological-scale processes shaping Lu. longipalpis populations, the identification of genetically homogeneous groups and the gene flow among them must be carefully investigated by using highly sensible molecular markers (i.e. genome wide SNPs) since it will help to the understanding of VL transmission and contribute to the planification of public policies on its control.

Nyssomyia whitmani (Diptera: Psychodidae) Activity From Sunset to Sunrise: A Two-Year Study in a Rural Area in Northeast Argentina

We model the nocturnal patterns of the main vector of Leishmania braziliensis (Vianna) in the Paranaense region of South America, Nyssomyia whitmani (Antunes & Coutinho). Occurrence and abundance variation were analyzed by hourly periods, and in relation to sunrise and sunset to avoid differences in luminosity at fixed times throughout the year. The possible role of climatic and environmental variables on nocturnal activity curves was explored. A rotating light trap was operated biweekly in the peridomestic henhouse of a farm in Puerto Iguazú, from May 2016 to May 2018. Ny. whitmani, is the predominant Phlebotominae species (6,720 specimens captured), and is present throughout the night and seasons. Generalized additive models of nocturnal abundance of Ny. whitmani show a bell shape with an acrophase in the early evening. Models of abundance distribution as a function of total abundance showed significant nonlinear variations, only for the tertile of highest vector abundance, in the curves by hourly periods, and related to dawn, while female abundance relative to total abundance showed an asymptotic increasing curve, suggesting density-dependent events with abundance thresholds. Finally, temperature was the variable that best explained the pattern of abundance distribution of Ny. whitmani during the night, although triggers for scotophase activity due to internal clocks or luminosity could not be ruled out. The relationship of activity and abundance with climatic variables would also explain the nights of extraordinary abundance, and therefore of greater probability of vector-human and vector-reservoir contacts.

Color preference of Sergentomyia minuta (Diptera: Phlebotominae) determined using Flebocollect Do It Yourself light traps based on LED technology

Whether phlebotomine sand flies show a preference for different light colors remains controversial. As light-capture methods are widely used to study sand flies, knowing the visual stimuli they respond to could help the design of novel control tools to prevent their attraction to hosts. We have detected a significant preference of male Sergentomyia minuta for green and red light sources. Accordingly, male S. minuta were 2.16 and 2.01 times more likely to be lured by Flebocollect model traps with green and red diode-lights, respectively, than the commercial CDC traps. Flebocollect traps are homemade light traps developed through citizen science. Dipterans are widely considered unable to distinguish the color red so this finding was unexpected. To our knowledge, this is the first description of a color preference in a species of the genus Sergentomyia. Our research also confirms the great potential of Flebocollect light traps for use in medical entomology studies.

Abundance of Lutzomyia longipalpis and Nyssomyia whitmani, the Leishmania spp. vectors in northeastern of Argentina: Are spatial and temporal changing patterns consistence?

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The spatial distribution of the species was the same in both periods.

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The seasonal pattern of abundance changes between periods.

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-The study defines the "where" and "when" to implement mitigation actions.

Lutzomyia longipalpis and Nyssomyia whitmani were incriminated as vectors of Leishmania sp. Spatial heterogeneity together with seasonal changes in abundance constitute important elements for the understanding of the dynamics of vector populations, and there are fundamental for the development of adequate prevention and control strategies. The aim of this work was to compare the spatial and seasonal abundance of Lu. longipalpis and Ny. whitmani at a city spatial scale between two periods separated by three years. To study the spatial distribution, we compared the abundance distribution of these species at two warm times, 2011 with 2014. Respect to inter-annual seasonal abundance changes, we compared the four seasons of the year between two periods (2011–2012 vs 2014–2016). The spatial distribution for both species were found to be distributed mainly in the same areas of the city in both periods. We change for: Respect to the seasonal pattern of abundance, we observed that seasonal patterns showed changes between periods. Our study defines the ‘where’ and ‘when’ implement the actions to mitigate leishmaniasis cases.

Update of the Phlebotominae Fauna with New Records for Argentina and Observations on Leishmaniasis Transmission Scenarios at a Regional Scale

Phlebotominae are small insects distributed in the Americas from Canada to Argentina and Uruguay, counting with more than 500 neotropical species. Some of them have a vectorial role in the transmission of Leishmania Ross, the causative agent of leishmaniases, a group of worldwide distributed diseases with different clinical manifestations and transmission cycles. Our aim was to update the Phlebotominae fauna of Argentina and to make observations on the American Cutaneous (ACL) and Visceral Leishmaniasis (AVL) transmission scenarios, according to the distribution of proven or suspected Leishmania vector species and recent changes in land use. Primary data (entomological captures) and secondary data (review of 65 scientific publications with Phlebotominae records) were used. With 9 new records, 46 Phlebotominae species are now recorded through the area comprising 14 political jurisdictions and 6 phytogeographic provinces. Distribution maps were constructed for the 5 proven or incriminated Leishmania vector species, and the evidence supporting the vectorial incrimination of these species is discussed. Three main ACL transmission scenarios are described in the phytogeographic provinces of the Yungas, Chaco, and Paranaense, associated with deforestation processes, while the transmission scenarios of AVL are urban outbreaks and scattered cases in rural areas. We update the available knowledge on the Phlebotominae fauna present in Argentina, emphasizing its epidemiological relevance in the current context of the increasing frequency of ACL outbreaks and geographic spread of AVL.

Peridomestic natural breeding sites of Nyssomyia whitmani (Antunes and Coutinho) in an endemic area of tegumentary leishmaniasis in northeastern Argentina

The scarce information about breeding sites of phlebotomines limits our understanding of the epidemiology of tegumentary leishmaniasis. Identifying the breeding sites and seasons of immature stages of these vectors is essential to propose prevention and control strategies different from those targeting the adult stage. Here we identified the rural breeding environments of immature stages of Ny. whitmani, vector species of Leishmania braziliensis in the north of Misiones province, Argentina; then we determined and compared the environmental and structural characteristics of those sites. We also identified the season of greatest emergence and its relationship with adult abundance. During a first collection period, between 28 and 48 emergence traps were set continuously for 16 months in six environments of the farm peridomicile and domicile: below house, chicken shed, experimental chicken shed, forest edge, pigsty and under fruit tree. Traps were checked and rotated every 40 nights. A total of 146 newly emerged individuals were collected (93.8% of them were Ny. whitmani), totaling an effort of 23,040 emergence trap-nights. The most productive environments were chicken shed and below house, and the greatest emergence was recorded in spring and summer. During a second collection period, emergence traps and light traps for adult capture were placed in the chicken shed and below house environments of eight farms. Emergence traps were active continuously during spring, summer, and early autumn. Environmental and structural characteristics of each environment were recorded. A total of 84 newly emerged phlebotomines (92.9% Ny. whitmani; 72,144 emergence trap-nights) and 13,993 adult phlebotomines (147 light trap-nights) were recorded in the chicken shed and below house environments. A positive correlation was also observed between trap success of newly emerged phlebotomines and of adults after 120 days. A high spatial variability was observed in the emergence of Ny. whitmani, with the number of newly emerged individuals being highest in soils of chicken sheds with the highest number of chickens and closest to forest edge. Moreover, below house was found to be as important as chicken sheds as breeding sites of Ny. whitmani. Management of the number of chickens in sheds, soil moisture and pH, and the decision of where to localize the chicken sheds in relation to the houses and the forest edge, might contribute to reduce the risk of human vector exposure and transmission of Leishmania.

Preferential attraction of different colours of light emitting diodes for Culicoides species in West Bengal, India

The preferential attraction of adult Culicoides (Diptera: Ceratopogonidae) to specific wavelengths was studied in West Bengal, India. A total of 280 collections were made with suction light traps fitted with various colours of light emitting diodes (LEDs) placed at cattle sheds during June, August and November in 2017. In addition, the numbers that have been collected in the evening and morning were compared. Locally manufactured suction light traps fitted with ultra violet (UV), blue, green, yellow, pink, red and white LEDs were compared. UV light attracted the highest number of midges followed by blue and then green LED. Culicoides peregrinus Kieffer and Culicoides oxystoma Kieffer were the most abundant followed by Culicoides fulvus Sen and Das Gupta, Culicoides innoxius Sen and Das Gupta, Culicoides anophelis Edwards and Culicoides huffi Causey. The species composition remained similar across the wavelengths. Although significant variations in midge population have been observed across the months, no significant difference in dusk and dawn abundance was noticed. The females showed a mixed population with less parous individuals.

Variation of the Phlebotominae (Diptera: Psychodidae: Phlebotominae) Assemblage in Response to Land Use Changes in an Endemic Area of Leishmania Transmission in Northeast Argentina

Leishmaniases are a global health problem and in Argentina are considered emerging diseases. The new transmission scenarios of tegumentary leishmaniasis are especially important given that large areas of forest are being transformed into rural and urban systems. The aim of this study was to analyze the impact of the construction of a large public building and a neighborhood on the assemblage of Phlebotominae in a rural area with forest remnants and to correlate the changes observed in the species assemblage with characteristics of the environment. Entomological surveys with light traps were conducted on the construction campus in the northeastern region of Argentina at six sites representing different environmental situations. Structural environmental characteristics and meteorological conditions were recorded and analyzed. At least 16 species of Phlebotominae sand flies were collected, the most prevalent being Nyssomyia whitmani (Antunes & Coutinho), followed by the genus Brumptomyia (França & Parrot) and Migonemyia migonei (França). Our study provides evidence of how the structure of the assemblages and prevalent species respond to anthropogenic disturbances. As the construction progressed, both Ny. whitmani and the genus Brumptomyia were favored. The genus Brumptomyia was favored at sites surrounded by high proportions of forest, within patches of remnant vegetation, and relatively far from anthropogenic disturbances, while Ny. whitmani, the main vector of tegumentary leishmaniasis in the region, increases their abundant at short and intermediate distances from vegetation margins and areas close to anthropogenic disturbances, therefore increasing the risk of human exposure to vectors.

Multiscale environmental determinants of Leishmania vectors in the urban-rural context

Background

In South America, cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL) are emerging diseases, expanding in the border area of Argentina, Brazil and Paraguay. Outbreaks of CL were reported since the 1990s, with Nyssomyia whitmani as the main vector in this region. Regarding VL, urban reports started in 2010 with Lutzomyia longipalpis as the main vector. The aim of this study was to evaluate environmental determinants related to the main vectors of leishmaniasis, to contribute to the prevention and control response to the emergence of VL and CL in the Argentina-Brazil-Paraguay border region.

Methods

The cross-sectional survey includes two cities and two close rural areas in the Argentinean Northeast Region, between November 2014 and January 2015, with a total of 95 sampling sites. REDILA-BL traps were set for three consecutive nights, and a total of 68 meso- and microscale environmental and landscape characteristics were surveyed. The association between vector abundance with different variables was evaluated using a generalized linear model with zero-inflated negative binomial distribution. We analyzed females for detection of Leishmania DNA.

Results

The analysis for Lu. longipalpis indicates an excess of absences when the mean NDWI around the sites were higher. The abundance of Lu. longipalpis at mesoscale level was higher when more urban services were present, and when blood sources such as chickens or dogs at the microscale level were present. For Ny. whitmani, no variable was found to be associated with the absences, while its abundance increased in association with the following variables: percentage of tree cover, presence of garbage collection service, hosted people and, at microscale, the presence of poultry. Leshmania infantum DNA was detected in 2/49 (4%) Lu. longipalpis.

Conclusions

The abundance of both species is influenced by variables at different scales, their influence probably has a hierarchy and they are acting on different aspects of the biology of these vectors. The urban spatial segregation of Lu. longipalpis and the peri-urban and rural segregation of N. whitmani increase the risk of VL and CL. The selection of the better variables for each scale will allow the design of appropriate control strategies depending on species.

Phlebotomines (Diptera: Psychodidae) and Mosquitoes (Diptera: Culicidae) Surrounding an Environmental Protection Zone in the Metropolitan Region of Natal: Use of Light-Emitting Diode (LED) Bulbs in Entomological Surveillance

Entomological surveillance is very important for parasite and arbovirus vector control programs. Light traps with incandescent bulbs are used to attract insects and analyze the factors that contribute to the occurrence of species surrounding an environmental protection zone. Phlebotomine and mosquito abundance and their diversity were analyzed. Captures occurred monthly using six CDC light traps with two incandescent bulbs, two blue and two red LED lights. A total of 2211 phlebotomines of seven species and 4486 mosquitoes belonging to 20 taxa were captured. Different phlebotomine and mosquito species were found in the forest and peridomestic environments, with a predominance of the sand fly Evandromyia walkeri (Newstead) and the mosquito Coquillettidia venezuelensis (Theobald). There was a significant difference in the abundance of sand flies captured with the three bulbs tested, the blue bulb being the most efficient. The Shannon-Wiener diversity index showed that the trap equipped with a red LED light obtained a higher value than that of the blue LED and incandescent bulb. Analyses showed that the potential vectors and non-vectors of the two groups circulate between the forest and the peridomestic environment, suggesting an adaptation process of species to the altered environment. An incandescent light bulb can be substituted by an LED bulb, without compromising the sensitivity of the method. A blue LED is indicated for the abundant capture of mosquitoes and sand flies, while a red LED obtains a better result in terms of species diversity per capture.

Lutzomyia longipalpis (Diptera: Psychodidae) Argentina-Bolivia border: new report and genetic diversity

American visceral leishmaniasis (AVL) has two main scenarios of transmission as follows: scattered cases in rural areas and urban outbreaks. Urban AVL is in active dispersion from the northeastern border of Argentina-Paraguay-Brazil to the South. The presence of Lutzomyia longipalpis was initially reported in urban environments in the northwestern border of the country. The presence of Lu. longipalpis, environmental variables associated with its distribution, and its genetic diversity were assessed in Salvador Mazza, Argentina, on the border with Bolivia. The genetic analysis showed high haplotype diversity, low nucleotide diversity, and low nucleotide polymorphism index. We discuss the hypothesis of an expanding urban population with introgressive hybridisation of older haplogroups found in their path in natural forest or rural environments, acquiring a new adaptability to urban environments, and the possibility of changes in vector capacity.

Phlebotominae in peri-domestic and forest environments inhabited by Alouatta caraya in northeastern Argentina

Multiple species of Phlebotominae are vectors of Leishmania (Protozoa: Trypanosomatidae), which causes visceral leishmaniasis (VL) and cutaneous leishmaniasis (CL). To describe the Phlebotominae (Diptera: Psychodidae) related to the environments of black and gold howler monkeys Alouatta caraya (Humbodlt, 1812) (Primates: Atelidae), potential vectors were sampled in different landscapes and vertical strata of sleeping trees. Phlebotomine captured between December 2011 and March 2012 (2365 individuals) belonged to eight species, of which Nyssomyia neivai (Pinto, 1926) (61.4%) and Migonemyia migonei (França, 1920) (18.73%) were the most abundant, and Ny. withmani was recorded for the first time in the Chaco province. In the 'peri-domestic' landscape, the phlebotomine were mainly captured in henhouses (78.7%), whereas the tree canopy in 'rural' and 'wild' landscapes yielded 31.2% and 29.1% of the phlebotomine, respectively. A significant association between the type of landscape and the species of phlebotomine was observed by multivariate analysis. Lutzomyia longipalpis (Lutz & Neiva, 1912) and Mg. migonei were associated with 'peri-domestic' landscape, and Ny. neivai was associated with the 'wild' landscape. The results of this prospective study suggest that the interaction between phlebotomine and A. caraya could be a key factor with respect to understanding the epidemiology of leishmaniasis.

High effectiveness of an adulticide-larvicide formulation for field control of sandflies (Diptera: Psychodidae) in the city of Clorinda, Argentina

In Argentina, Leishmania infantum (syn. L. chagasi) is the etiologic agent of human visceral leishmaniosis (HVL), and Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae) is the main vector. The objective of this study was to evaluate the effectiveness and residual effect of two commercial insecticide formulations, one with permethrin and pyriproxyfen as active ingredients (Dragon Max®) and the other with only permethrin (Flop®) for the control of sandflies. Both formulations were applied in chicken coops and other surroundings structures of the peridomicile of urban houses in Clorinda, Formosa (Argentina). Entomological monitoring was carried out weekly for 44 weeks after the intervention. The results showed great effectiveness and residual effect up to 21 weeks post-intervention for Dragon Max®. This result could be explained by the excellent larvicidal activity of the Insect Growth Regulator (IGR) pyriproxyfen against the immature forms of phlebotomines and by the delay on the restoration of the natural threshold of the vector population in treated sites.

Spatiotemporal dynamics of Lutzomyia longipalpis and macro-habitat characterization using satellite images in a leishmaniasis-endemic city in Argentina

The spatiotemporal population dynamics of Lutzomyia longipalpis (Lutz & Neiva, 1912) (Diptera: Psychodidae) were evaluated in a city in Argentina in which visceral leishmaniasis is endemic. Over 14 sampling sessions, 5244 specimens of five species of Phlebotominae (Diptera: Psychodidae) were captured, of which 2458 (46.87%) specimens were L. longipalpis. Generalized linear models were constructed to evaluate the associations between L. longipalpis abundance and explanatory variables derived from satellite images. The spatial variable 'stratum' and the temporal variable 'season' were also included in the models. Three variables were found to have significant associations: the normalized difference vegetation index; land surface temperature, and low urban coverage. The last two of these were associated with L. longipalpis abundance only during summer and winter, respectively. This variation between seasons supports the development of models that include temporal variables because models of distributions of the abundance of a species may show different critical variables according to the climatic period of the year. Abundance decreased gradually towards the downtown area, which suggests that L. longipalpis responds to a meta-population structure, in which rural-periurban source populations that persist over time may colonize adjacent areas. This information allows for a spatiotemporal stratification of risk, which provides public health authorities with a valuable tool to help optimize prevention measures against visceral leishmaniasis.

Genetic diversity, phylogeography and molecular clock of the Lutzomyia longipalpis complex (Diptera: Psychodidae)

BACKGROUND

The Lutzomyia longipalpis complex has a wide but discontinuous distribution in Latin America, extending throughout the Neotropical realm between Mexico and northern Argentina and Uruguay. In the Americas, this sandfly is the main vector of Leishmania infantum, the parasite responsible for Visceral Leishmaniasis (VL). The Lu. longipalpis complex consists of at least four sibling species, however, there is no current consensus on the number of haplogroups, or on their divergence. Particularly in Argentina, there have been few genetic analyses of Lu. longipalpis, despite its southern expansion and recent colonization of urban environments. The aim of this study was to analyze the genetic diversity and structure of Lu. longipalpis from Argentina, and to integrate these data to re-evaluate the phylogeography of the Lu. longipalpis complex using mitochondrial markers at a Latin American scale.

METHODOLOGY/PRINCIPAL FINDINGS

Genetic diversity was estimated from six sites in Argentina, using a fragment of the ND4 and the 3´ extreme of the cyt b genes. Greatest genetic diversity was found in Tartagal, Santo Tomé and San Ignacio. There was high genetic differentiation of Lu. longipalpis in Argentina using both markers: ND4 (FST = 0.452, p < 0.0001), cyt b (FST = 0.201, p < 0.0001). Genetic and spatial Geneland analyses reveal the existence of two primary genetic clusters in Argentina, cluster 1: Tartagal, Santo Tomé, and San Ignacio; cluster 2: Puerto Iguazú, Clorinda, and Corrientes city. Phylogeographic analyses using ND4 and cyt b gene sequences available in GenBank from diverse geographic sites suggest greater divergence than previously reported. At least eight haplogroups (three of these identified in Argentina), each separated by multiple mutational steps using the ND4, are differentiated across the Neotropical realm. The divergence of the Lu. longipalpis complex from its most recent common ancestor (MRCA) was estimated to have occurred 0.70 MYA (95% HPD interval = 0.48-0.99 MYA).

CONCLUSIONS/SIGNIFICANCE

This study provides new evidence supporting two Lu. longipalpis genetic clusters and three of the total eight haplogroups circulating in Argentina. There was a high level of phylogeographic divergence among the eight haplogroups of the Lu. longipalpis complex across the Neotropical realm. These findings suggest the need to analyze vector competence, among other parameters intrinsic to a zoonosis, according to vector haplogroup, and to consider these in the design and surveillance of vector and transmission control strategies.

Co-occurrence and seasonal and environmental distributions of the sandflies Lutzomyia longipalpis and Nyssomyia whitmani in the city of Puerto Iguazú, northeastern Argentina

The aim of this work was to study the distribution of Phlebotominae (Diptera: Psycodidade) abundance in time and space in an area in northeastern Argentina with vector transmission of visceral and tegumentary leishmaniasis. For this, 51 households were selected using a 'worst scenario' criterion where one light trap was set during two consecutive nights in peridomiciles in the transitions between the four seasons, and the environment was surveyed simultaneously. The relationships of phlebotomine assemblage structure and the most abundant species with seasonality and environmental variables were evaluated using a canonical correspondence analysis and generalized linear mixed models, respectively. A total of 5110 individuals were captured. Lutzomyia longipalpis (Lutz & Neiva, 1912) and Nyssomyia whitmani (Antunes & Coutinho, 1939) were the most abundant species captured in all samplings (98.3% of the total capture). The period of highest abundance of Lu. longipalpis was early autumn, and it was distributed in the most urbanized areas. Nyssomyia whitmani occupied mainly the less urbanized areas, showing peaks of abundance in early spring and summer. Other species were captured in low numbers and showed seasonal-spatial variations similar to those of Ny. whitmani. We confirmed Leishmania spp. vector persistence throughout the year in spatial patches of high abundance even during the less favorable season.

Environmental suitability for Lutzomyia longipalpis in a subtropical city with a recently established visceral leishmaniasis transmission cycle, Argentina

BACKGROUND

Visceral leishmaniasis (VL) is an endemic disease in northeastern Argentina including the Corrientes province, where the presence of the vector and canine cases of VL were recently confirmed in December 2008.

OBJECTIVES

The objective of this study was to assess the modelling of micro- and macro-habitat variables to evaluate the urban environmental suitability for the spatial distribution of Lutzomyia longipalpis presence and abundance in an urban scenario.

METHODS

Sampling of 45 sites distributed throughout Corrientes city (Argentina) was carried out using REDILA-BL minilight traps in December 2013. The sampled specimens were identified according to methods described by Galati (2003). The analysis of variables derived from the processing of satellite images (macro-habitat variables) and from the entomological sampling and surveys (micro-habitat variables) was performed using the statistical software R. Three generalised linear models were constructed composed of micro- and macro-habitat variables to explain the spatial distribution of the abundance of Lu. longipalpis and one composed of micro-habitat variables to explain the occurrence of the vector.

FINDINGS

A total of 609 phlebotominae belonging to five species were collected, of which 56% were Lu. longipalpis. In addition, the presence of Nyssomyia neivai and Migonemya migonei, which are vectors of tegumentary leishmaniasis, were also documented and represented 34.81% and 6.74% of the collections, respectively. The explanatory variable normalised difference vegetation index (NDVI) described the abundance distribution, whereas the presence of farmyard animals was important for explaining both the abundance and the occurrence of the vector.

MAIN CONCLUSIONS

The results contribute to the identification of variables that can be used to establish priority areas for entomological surveillance and provide an efficient transfer tool for the control and prevention of vector-borne diseases.

Leishmania infantum DNA detected in phlebotomine species from Puerto Iguazú City, Misiones province, Argentina

In Puerto Iguazú City, Argentina, human and canine Visceral Leishmaniasis cases have been recorded since the year 2010, with Leishmania infantum as the etiological agent and Lutzomyia longipalpis as its main vector. In the present study, polymerase chain reaction and sequencing were used to detect L. infantum DNA in 3.9% of the female sandflies captured in Puerto Iguazú City. This is the first report of L. infantum DNA detection in Micropygomyia quinquefer, and the second one in Lu. longipalpis and Nyssomyia whitmani for Argentina. Although the detection of Leishmania DNA itself is not enough to determine a Phlebotomine species as a vector, these results are significant in setting the direction of further investigations of vectorial competence and capacity, necessary to define the roles of different sandflies species as specific or permissive vectors in the transmission VL cycle.

Description of Pintomyia salomoni sp. n., a new phlebotomine species from northwest Argentina

A new species of phlebotomine sandfly is described and illustrated using male and female specimens collected in the provinces of Jujuy and Tucumán, Argentina. Both male and female morphological characters allow the inclusion of the new species within the Pintomyia genus, Pifanomyia subgenus, serrana series (Diptera: Psychodidae). The species was denominated as Pintomyia salomoni n. sp., and is closely related to Pintomyia (Pifanomyia) torresi and Pintomyia (Piffanomyia) boliviana.

Evaluation of efficacy of impregnated curtains in experimental hen houses as a phlebotomine control tool in northeast Argentina

The aim of this study was to evaluate the effectiveness of insecticide-impregnated curtains against the entry of phlebotomine (Diptera: Psychodidae) flies into experimental slatted hen houses in an area endemic for American cutaneous leishmaniasis (ACL). Three treatments in experimental dwellings containing three chickens each were applied using, respectively, an impregnated curtain (IC), a non-impregnated curtain (NIC) and no curtain (NC). A control site without chickens (WC) was included. The study used permethrin at 0.05 g/m² . During each month for 1 year, each experimental hen house randomly received all treatments. Phlebotomine sandflies were captured using REDILA BL traps placed inside the hen house. Significant differences in abundances of phlebotomine flies/trap/night were observed between treatments (χ²  = 17853.58, d.f. = 3, P < 0.0001): 59.7% of phlebotomines were captured in the NC treatment, 26.3% in the NIC treatment, 8.0% in the IC treatment and 6.1% in the WC condition. Nyssomyia whitmani (Antunes & Coutinho) was the most abundant species in all collections (89.9%). These results showed a lower abundance of phlebotomines in the experimental hen house in the IC condition than in the hen house in the NC condition (P < 0.05) and that the presence of NIC represents an effective physical barrier against phlebotomines (P < 0.05). Therefore, the use of curtains may be an alternative eco-friendly method for the prevention of indoor ACL transmission in slatted dwellings, which represent a common house type in northeast Argentina.

An Evaluation of Light-Emitting Diode (LED) Traps at Capturing Phlebotomine Sand Flies (Diptera: Psychodidae) in a Livestock Area in Brazil

A study to evaluate the use of light-emitting diodes (LEDs) as an attractant for phlebotomine sand flies at two animal pens in a livestock area in Brazil was performed. Light-suction traps were operated overnight with the following light sources: green, blue, and incandescent (control) lights. In total, 22 individual collections were made at each site and 44 with each trap type. In total, 2,542 specimens belonging to 14 phlebotomine species were collected. The most abundant species in the light traps were Nyssomyia whitmani, Evandromyia evandroi, Micropygomyia goiana, Lutzomyia longipalpis, and Bichromomyia flaviscutellata Taking the two sites together, the green-LED light was the most attractive, followed by the blue and incandescent lights, and the difference between the green-LED and the control was statistically significant. Most species were green-biased at both sites, but some species-specific differences were observed. However, even with these differences, the standard incandescent light was outcompeted by LEDs. The green-LED-biased response observed in the present study, together with numerous advantages in favor of LEDs, suggests that the green-LED light source can be used as an effective substitute for the currently used incandescent bulb in monitoring traps for phlebotomine sand flies in Brazil.