Occurrence of Phlebotominae (Diptera: Psychodidae) in Urban Leishmaniasis Transmission Foci in North-Eastern Brazil

Seasonal dynamics of sand flies in Lençóis Maranhenses National Park: a tourist destination and endemic area for leishmaniasis

Numerous sand fly species have been reported in Lençóis Maranhenses National Park (LMNP) in Northeast Brazil, including important Leishmania vectors, making the park an endemic area for tegumentary and visceral leishmaniasis. We evaluated sand fly abundance monthly over 7 years, correlating it with environmental variables and monthly tourist numbers in LMNP. Sand fly species were observed throughout the year, with Lutzomyia longipalpis Lutz & Neiva and Nyssomyia whitmani Antunes and Coutinho (Diptera: Psychodidae) being the most abundant species, especially from April to June. In addition to seasonal abundance patterns, Lu. longipalpis showed increasing abundance throughout 2013 until April 2014, whereas Ny. whitmani exhibited a consistent increase throughout the study period. Redundancy analysis indicated that monthly sand fly abundances increased with humidity but decreased with mean temperature and wind speed. Ecotourists mainly visit the park from May to September when interdune lagoons are full, coinciding with high-frequency vector activity during the rainy months (May-June). Tourists also visit in January and February during school holidays, when the rains begin and sand fly abundance increases, and in July, when sand fly abundance decreases. To date, no instances of infected tourists have been recorded, likely because visits to LMNP occur during the day when sand flies are inactive. However, there is a potential risk of vector exposure if tourists engage in nighttime cultural visits to villages around the park, where leishmaniasis cases occur annually.

Spatiotemporal Distribution of Leishmaniasis in an Endemic Area of Northeast Brazil: Implications for Intervention Actions

This study aimed to analyze the spatiotemporal distribution of leishmaniases, and contribute to the knowledge of their epidemiological dynamics from 2007 to 2017 in the municipality of Caxias, Maranhão, Northeast Brazil. Data on American tegumentary leishmaniasis (ATL) and human visceral leishmaniasis (HVL) were obtained in the Epidemiological Surveillance Sector of Caxias, while data on canine visceral leishmaniasis (CVL) were obtained in the Zoonoses Surveillance Unit. For data analysis and spatial representation of leishmaniasis cases, the geoprocessing of the data was performed, and the geometric features of the state of Maranhão, Caxias, and the disease registration sites were obtained from the shapefile database of the Brazilian Institute of Geography and Statistics. Geostatistics was used to create maps based on the Kernel density method, starting from the points, producing a raster file for each case with several data frames, allowing the instantaneous comparison of the phenomena. During the study period, ATL, HVL, and CVL were reported in Caxias, accounting for 114,304 and 8,498 cases, respectively. The geoprocessing analysis showed that leishmaniasis is widely distributed in the urban area of Caxias. However, there are risk areas for the transmission of these diseases to humans and dogs, associated with deforestation and urban expansion, and may vary over time. Preventive measures must focus on risk areas, including conservation efforts and urban planning, in order to reduce the transmission of leishmaniases.

Phlebotomine Sandfly (Diptera: Psychodidae) Fauna and The Association Between Climatic Variables and The Abundance of Lutzomyia longipalpis sensu lato in an Intense Transmission Area for Visceral Leishmaniasis in Central Western Brazil

The presence, abundance, and distribution of sandflies are strongly influenced by climate and environmental changes. This study aimed to describe the sandfly fauna in an intense transmission area for visceral leishmaniasis and to evaluate the association between the abundance of Lutzomyia longipalpis sensu lato (Lutz & Neiva 1912) (Diptera: Psychodidae) and climatic variables. Captures were carried out 2 yr (July 2017 to June 2019) with automatic light traps in 16 sites of the urban area of Campo Grande, Mato Grosso do Sul state. The temperature (°C), relative humidity (%), precipitation (mm3), and wind speed (km/h) were obtained by a public domain database. The Wilcoxon test compared the absolute frequencies of the species by sex. The association between climatic variables and the absolute frequency of Lu. longipalpis s.l. was assessed using the Spearman's correlation coefficient. A total of 1,572 sandflies into four species were captured. Lutzomyia longipalpis s.l. was the most abundant species and presented a significant correlation with the average temperature, humidity, and wind speed in different periods. Lutzomyia longipalpis s.l. was captured in all months, showing its plasticity in diverse weather conditions. We emphasize the importance of regular monitoring of vectors and human and canine cases, providing data for surveillance and control actions to continue to be carried out in the municipality.

Predominance of Leishmania (Leishmania) amazonensis DNA in Lutzomyia longipalpis sand flies (Diptera: Psychodidae) from an endemic area for leishmaniasis in Northeastern Brazil

Leishmaniasis is a serious public health concern in the Northeastern region of Brazil, where the sand fly fauna is well studied, although few species have been identified as competent vectors. The detection of Leishmania spp. parasites in wild-caught sand flies could help sanitary authorities draw strategies to avoid the transmission of the parasites and, therefore, the incidence of leishmaniases. We detected Leishmania DNA in wild-caught sand flies and correlated that data with aspects of sand fly ecology in the Caxias municipality, Maranhao State, Brazil. The sand flies were sampled in the peridomicile (open areas in the vicinity of human residences) and intradomicile (inside the residences) from July/2019 to March/2020. Leishmania DNA was detected in females, targeting a fragment of the Internal Transcribed Spacer (ITS1) from ribosomal DNA. Among the fourteen species of sand flies identified, five (Lutzomyia longipalpis, Nyssomyia whitmani, Evandromyia evandroi, Micropygomyia trinidadensis, and Micropygomyia quinquefer) harbored DNA of Leishmania (Leishmania) amazonensis. The most abundant species in rural (Ny. whitmani: 35.2% and Ev. evandroi: 32.4%) and urban areas (Lu. longipalpis: 89.8%) are the permissive vectors of L. (L.) amazonensis, especially Ny. whitmani, a known vector of causative agents of cutaneous leishmaniasis. Although Lu. longipalpis is the vector of L. (L.) infantum, which was not detected in this study, its permissiveness for the transmission of L. (L.) amazonensis has been reported. We suspect that visceral leishmaniasis and cutaneous leishmaniasis are caused by L. (L.) amazonensis, and the transmission may be occurring through Lu. longipalpis, at least in the urban area.

Experimental transmission of Leishmania (Leishmania) amazonensis to immunosuppressed mice through the bite of Lutzomyia longipalpis (Diptera: Psychodidae) results in cutaneous leishmaniasis

Lutzomyia longipalpis is the natural vector of Leishmania (Leishmania) infantum, but it is also permissive for several Leishmania species that are related to cutaneous leishmaniasis (CL). Maranhao State (Northeast of Brazil) is endemic for CL and has the highest number of cases of diffuse cutaneous leishmaniasis (DCL) in the country. It is a rare disease associated with a defective immune response mainly caused by L. (L.) amazonensis. Additionally, the number of immunosuppressed patients infected with the etiologic agents of CL has increased, including regions in which the main vectors of CL are rare. Therefore, we investigated whether Lu. longipalpis is able to transmit L. (L.) amazonensis to uninfected and immunosuppressed mice, resulting in CL. For that, 291 sand flies took an initial blood meal in mice infected with L. (L.) amazonensis. Of these, 17 underwent a second feeding on uninfected and immunosuppressed mice (of which 58.8% were also positive for Leishmania according to data on the dissection of the intestine). After 27 days of infection, these mice exhibited leishmaniotic lesions. The occurrence of parasites on the animal’s skin was confirmed by limiting dilution and immunohistopathological analyses. Parasite DNA was also detected in paw lesions and inguinal lymph nodes. DNA sequencing confirmed the Leishmania species in insects and mice. The results confirmed the ability of Lu. longipalpis to become infected and experimentally transmit L. (L.) amazonensis to immunosuppressed rodents, resulting in leishmaniotic lesions. Our data open perspectives for the potential role of Lu. longipalpis in the epidemiology of urban cutaneous leishmaniasis, especially in immunosuppressed patients.

Spatial and Temporal Variability of Visceral Leishmaniasis in Colombia, 2007 to 2018

Visceral leishmaniasis (VL) is a neglected tropical disease associated with poverty and is endemic in 56 countries worldwide. Brazil, Venezuela, and Colombia are the most affected countries in South America. In Colombia, the National Public Health Surveillance System (SIVIGILA) consolidates epidemiological information and monitors all VL cases nationwide. However, to date, no studies have investigated the occurrence of VL in Colombia using metadata analysis. We studied the demographic data, the spatial and temporal distribution of VL cases, and the association with vector distribution of Leishmania species in Colombia from 2007 to 2018. We found 306 VL cases reported to SIVIGILA for this period, with a coverage of 25.5 cases/year, and a mortality of 2.28% (seven deaths). The highest number of confirmed cases (N = 52) occurred in 2007; the lowest (N = 9) occurred in 2012. The cases were reported mainly in children (< 7 years) affiliated with the subsidized health regimen. Regarding the geographic distribution, the cases were reported by 42 municipalities distributed in 10 departments. The occurrence of VL cases toward the northeast of Colombia, and the distribution of vectors, such as Lutzomyia longipalpis and Lu. evansi, may be changing the panorama of VL in the country. We conclude that VL, mainly in recent years, shows a temporal and spatial variability associated with the occurrence of cases in new settings. Our findings increase our understanding and knowledge of this disease, and suggest the need to monitor and prioritize areas with changes in geographic expansion to improve prevention and control actions in the country.

Maintenance and Productivity of a Lutzomyia longipalpis (Diptera: Psychodidae) Colony from an Area Endemic for Visceral and Cutaneous Leishmaniasis in Northeastern Brazil

Studies on experimental sand fly infection require the availability of colonies and laboratory conditions. In Brazil, Lutzomyia longipalpis (Diptera: Psychodidae) (Lutz and Neiva 1912) is responsible for the highest infection rates by Leishmania spp. and this species is one of the most suitable species for laboratory colonization. In this study, we describe a method for growing Lu. longipalpis in laboratory conditions (10 generations) from natural populations sampled from a region of high endemicity for visceral leishmaniasis in the state of Maranhão, Northeastern Brazil. Using two methods (individualized or grouped females), the colony's highest productivity occurred in the first four generations, where all stages presented with high frequency. Nonviable eggs represented more than 50% of the total eggs produced by engorged females, while pupae were more resistant to fungal contamination, with a mortality rate of only 2%. In both methods, there was a predominance of female emergence; however, the ratio between males and females did not show significant differences, IF (P = 0.8023) and GF (P = 0.1831). Using the method of individualized females, the F4 generation took the longest to appear (234 d; 64 ± 57 d); by grouped females, F3 took the longest to appear (102 d; 47 ± 20 d). This method provides sufficient numbers of insects to perform vector competence tests for Leishmania spp. that cause the cutaneous form of leishmaniasis, usually found in Lu. longipalpis sampled from the study location.

Lutzomyia longipalpis, Gone with the Wind and Other Variables

Lutzomyia longipalpis (Lutz & Neiva) is the main vector of Leishmania infantum (Nicolle) in America, associated in turn with the current spread and urbanization of American visceral leishmaniasis (AVL). The vector distribution in AVL foci shows a spatial-temporal clustering despite the different epidemiological contexts. The factors associated with the macroscale distribution of Lu. longipalpis as a landscape stratification are discussed in the framework of the process of their adaptation to anthropized environments. On the other hand, the fact that Lu. longipalpis is clustered in only a few hot spots or critical sites suggests that microscale approaches that describe the trap surrounding environment and the availability of refuges and food sources are better at explaining the uneven distribution of this vector, and should contribute, together with macroscale variables, to design operational control strategies. With regard to temporal distribution and climatic or vegetation data obtained by remote sensing as variables to explain and forecast the abundance of Lu. longipalpis, it is necessary to take into account the time lags in relation to the life cycle of the vector, the difference between the level of daily activity and actual abundance, and the differences in critical variables and thresholds according to the region or season. In conclusion, this review shows that it is feasible to characterize the distribution of Lu. longipalpis at focus level and within it to identify the main critical sites, proposing a sequential cost-effectivity strategy for urban AVL surveillance and control.

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.

Spatial dynamics and socioeconomic factors correlated with American cutaneous leishmaniasis in Pernambuco, Brazil from 2008 to 2017

INTRODUCTION:

American cutaneous leishmaniasis (ACL) is a public health problem and has been associated with country’s territory. We aimed to analyze the spatial dynamics and socioeconomic factors correlated to the incidence of ACL in Pernambuco, Brazil from 2008 to 2017.

METHODS:

A cross-sectional, ecological study was conducted in the Brazilian municipalities. Patient data were obtained from the Health Hazard Notification System (SINAN); indicators and incidence for the total period and for quinquennium were obtained. Socioeconomic factors were analyzed to evaluate the association between the incidence of ACL and presence of bathroom and running water, garbage collection availability, inadequate water supply, sanitation, rural population, per capita income, and vulnerability to poverty. Spatial analysis considered the gross incidence; the Bayesian local empirical method and Moran spatial autocorrelation index were applied using Terra View and QGIS.

RESULTS:

The incidence of ACL reduced (0.29/100,000 inhabitants per year). Individuals with ACL were young adults (30.3%), men (60.2%), brown skinned (62.9%), rural residents (70.6%), and less educated (46.7%); had autochthonous transmission (78.8%); developed the cutaneous form (97.2%); had evolution to cure (82.7%); and were diagnosed using the clinical epidemiological criterion (70.5%). ACL occurred in the large part of the state and showed heterogeneous distribution, with persistence of two high priority intervention clusters covering Health Regions I, II, III, IV, and XII.

CONCLUSIONS:

Spatial analysis and epidemiological indicators complement each other. The combination of these methods can improve the understanding on ACL occurrence, which will help subsidize planning and enhance the quality and effectiveness of healthcare interventions.