Effects of temperature and photoperiod on daily activity rhythms of Lutzomyia longipalpis (Diptera: Psychodidae)

Temporal and Spatial Patterns of Mating in Rhodnius prolixus

The kissing bug Rhodnius prolixus is a nocturnal species; however, its temporal mating patterns remain unexplored. Copulation lasts about fifty minutes, during which time the couple remains almost motionless. We hypothesized that R. prolixus copulates within shelters to reduce its vulnerability. To test this, we examined the spatial and temporal patterns of its copulation, as well as the potential endogenous regulation of its circadian rhythm, under three conditions: a light:dark cycle (L/D), constant light (L/L), and constant darkness (D/D). Over ten days, the number and the timing of copulation of pairs in arenas containing a shelter were video-recorded. Under the L/D cycle, the pairs mated mainly during daylight hours. This rhythm persisted under the D/D cycle, with a peak extending from the first half of the subjective day to the first half of the subjective night. No rhythm was observed under the L/L cycle. A greater proportion of mating occurred within the shelters during the L/D and L/L cycles, whereas its spatial distribution was random under the D/D cycle. Our results reveal an endogenously controlled circadian rhythm of mating behavior, with mating activity mainly occurring during daylight hours. Additionally, we showed that the pairs copulated inside the shelters. These results provide new insights into the reproductive behavior of R. prolixus.

Nocturnal activity and forestry-urban dispersal of phlebotomine sand flies (Diptera: Psychodidae) from an ecotourism park in Amazonian Brazil

Phlebotomine sand flies are insects of notorious importance in public health, mainly due to their involvement in the transmission of Leishmania protozoa. Their flight activity occurs predominantly in the twilight/night period, being stimulated mainly by the need to search for food and reproduction. Despite being naturally wild, some species are able to invade anthropized environments. Present work aimed to assess the nocturnal activity and forestry-urban dispersal of phlebotomine sand flies from an ecotourism park in Belém, Amazonian Brazil. The study area comprised a horizontal transect, extending from a forest park to the neighboring urban environment, in Belém. Sampling was conducted with night-operating light traps. Nocturnal activity was assessed through time-set captures with a collection bottle rotator in the forest environment. Dispersal was assessed through captures carried out along the transect, starting from the forest edge (0 m), extending to the urban environment (50-200 m), phlebotomine sand flies were identified. Abundance, richness, diversity, and sampling sufficiency were estimated. Fourteen species were recorded in the surveyed environments, with Nyssomyia antunesi, Trichophoromyia brachipyga, and Trichophoromyia ubiquitalis being the most abundant. Nocturnal activity behavior of Ny. antunesi occurred between 8 PM and 4 AM while that of Th. brachipyga and Th. ubiquitalis occurred between 2 AM and 6 AM. In the urban environment, the 150 m site presented the highest abundance. Bichromomyia flaviscutellata was sampled in all sites. Gravid females of Pressatia choti and Bi. flaviscutellata were sampled in the urban environment. Putative differential activity between the species herein assessed and their urban dispersal observed are worthy of note, adding data for supporting vector surveillance at a local scale.

Ecological determinants of leishmaniasis vector, Lutzomyia spp.: A scoping review

Leishmania spp. are zoonotic parasites transmitted by phlebotomine sand flies, including those of the Lutzomyia genus, which can cause leishmaniases in both humans and dogs. Lutzomyia spp. are established in many countries in South and Central America and some areas of the southern United States, with suspected potential of these vectors to undergo further range expansion due to climate change. A scoping review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extensions for Scoping Reviews (PRISMA-ScR) guidelines to describe the current state of knowledge on the key ecological factors associated with Lutzomyia spp. survival, reproduction and establishment. The following electronic databases were searched for eligible studies published from 1 January 1990, to the date of search, 26 April 2023: CAB Direct (CABI), MEDLINE (via Ovid), Biological Sciences Database and Environmental Sciences Database. Primary research articles that were available in English and focused on ecological factors associated with Lutzomyia spp., such as climatic and habitat factors, geographic range, seasonality and temporality, and host abundance, were eligible for inclusion in the study. Following de-duplication, a total of 167 studies were included in Level 1 screening, 64 studies were included in Level 2 screening and 31 studies met the criteria for data extraction. Study locations included Argentina, Brazil, Colombia, Peru, Venezuela, the United States, Mexico and Canada, with some studies including multiple regions. A total of 31 different Lutzomyia spp. were assessed across these studies, with most (51.6%) of the studies focused on Lutzomyia longipalpis. Eligible studies investigated factors such as seasonality (n = 5), temperature (n = 19), precipitation (n = 13), humidity (n = 2), vegetation presence or requirements (n = 13), ecotypes (n = 7), and/or community type (i.e., urban, suburban, rural) (n = 5). Lutzomyia spp. activity was found to be higher during the rainy season, and peak when temperatures were between 20 and 25°C. Lutzomyia spp. were also found to preferentially reside in tropical or subtropical forests, which are characterised by their lack of a distinct dry season and high precipitation. This scoping review summarised the current state of the literature on the ecological factors associated with the survival, activity and reproduction of Lutzomyia spp. While there appears to be some consensus in the literature regarding some ecological requirements (such as seasonality, temperature and habitat features), overall, there is a lack of published research in this topic. This poses a significant challenge for future studies, which aim to predict the future distribution of Lutzomyia spp. in the context of climate and land use changes. Additional ecological research is urgently needed on Lutzomyia spp. given their relevance to both human and animal health.

Interaction and effects of temperature preference under a controlled environment on the diversity and abundance of the microbiome in Lutzomyia longipalpis (Diptera: Psychodidae)

Characterization of the temperature effects on the abundance and richness of the microbiota of Lutzomyia longipalpis, insect vector of Leishmania infantum in America, is an aspect of pivotal importance to understand the interactions between temperature, bacteria, and Leishmania infection. We developed and used a customized device with a temperature gradient (21-34 °C) to assess the temperature preferences of wild females of Lu. longipalpis collected in a rural area (Ricaurte, Cundinamarca, Colombia). Each replicate consisted of 50 females exposed to the gradient for an hour. At the end of the exposure time, insects were collected and separated by the temperature ranges selected varying from 21 °C to 34 °C. They were organized in 17 pools from which total DNA extracts were obtained, and samples were subjected to 16S rRNA amplicon sequencing analyzes. The most abundant phyla across the different temperature ranges were Proteobacteria (17.22-90.73 %), Firmicutes (5.99-77.21 %) and Actinobacteria (1.56-59.85 %). Results also showed an abundance (30 % to 57.36 %) of Pseudomonas (mainly at temperatures of 21-29 °C and 34 °C) that decreased to 6.55 %-13.20 % at temperatures of 31-33 °C, while Bacillus increase its abundance to 67.24 % at 29-33 °C. Serratia also had a greater representation (49.79 %), specifically in sand flies recovered at 25-27 °C. No significant differences were found at α-diversity level when comparing richness using the Shannon-Wiener, Simpson, and Chao1 indices, while β-diversity differences were found using the Bray-Curtis index (F-value of 3.5073, p-value < 0.013, R-squared of 0,4889), especially in the groups of Lu. longipalpis associated at higher temperatures (29-33 °C). It was also possible to detect the presence of endosymbionts such as Spiroplasma and Arsenophonus in the range of 29-33 °C. Rickettsia was only detected in Lu. longipalpis sand flies recovered between 25-27 °C. It was possible to characterize Lu. longipalpis microbiota in response to intraspecific temperature preferences and observe changes in bacterial communities and endosymbionts at different ranges of said environmental variable, which may be important in its vector competence and environmental plasticity to adapt to new climate change scenarios.

Optimizing tick artificial membrane feeding for Ixodes scapularis

Artificial membrane feeding (AMF) is a powerful and versatile technique with a wide range of applications in the study of disease vectors species. Since its first description, AMF has been under constant optimization and standardization for different tick species and life stages. In the USA, Ixodes scapularis is the main vector of tick-borne zoonoses including the pathogens causing Lyme disease in humans and animals. Seeking to improve the overall fitness of I. scapularis adult females fed artificially, here, we have optimized the AMF technique, considerably enhancing attachment rate, engorgement success, egg laying, and egg hatching compared to those described in previous studies. Parameters such as the membrane thickness and the light/dark cycle to which the ticks were exposed were refined to more closely reflect the tick's natural behavior and life cycle. Additionally, ticks were fed on blood only, blood + ATP or blood + ATP + gentamicin. The artificial feeding of ticks on blood only was successful and generated a progeny capable of feeding naturally on a host, i.e., mice. Adding ATP as a feeding stimulant did not improve tick attachment or engorgement. Notably, the administration of gentamicin, an antibiotic commonly used in tick AMF to prevent microbial contamination, negatively impacted Rickettsia buchneri endosymbiont levels in the progeny of artificially fed ticks. In addition, gentamicin-fed ticks showed a reduction in oviposition success compared to ticks artificially fed on blood only, discouraging the use of antibiotics in AMF. Overall, our data suggest that the AMF of adult females on blood only, in association with the natural feeding of their progeny on mice, might be used as an integrated approach in tick rearing, eliminating the use of protected species under the Animal Welfare Act (AWA). Of note, although optimized for I. scapularis adult ticks, I. scapularis nymphs, other tick species, and sand flies could also be fed using the membrane described in this study, indicating that it might be a suitable alternative for the artificial feeding of a variety of hematophagous species.

Response to thermal and infection stresses in an American vector of visceral leishmaniasis

Lutzomyia longipalpis is known as one of the primary insect vectors of visceral leishmaniasis. For such ectothermic organisms, the ambient temperature is a critical life factor. However, the impact of temperature has been ignored in many induced-stress situations of the vector life. Therefore, this study explored the interaction of Lu. longipalpis with temperature by evaluating its behaviour across a thermal gradient, thermographic recordings during blood-feeding on mice, and the gene expression of heat shock proteins (HSP) when insects were exposed to extreme temperature or infected. The results showed that 72 h after blood ingestion, Lu. longipalpis became less active and preferred relatively low temperatures. However, at later stages of blood digestion, females increased their activity and remained at higher temperatures. Real-time imaging showed that the body temperature of females can adjust rapidly to the host and remain constant until the end of blood-feeding. Insects also increased the expression of HSP90(83) during blood-feeding. Our findings suggest that Lu. longipalpis interacts with temperature by using its behaviour to avoid temperature-induced physiological damage during the gonotrophic cycle. However, the expression of certain HSP might be triggered to mitigate thermal stress in situations where a behavioural response is not the best option.

Spatio-temporal relative risks and priority areas for visceral leishmaniasis control in Brazil, between 2001 and 2020

Visceral leishmaniasis (VL) is a pressing public health problem in Brazil. The proper implementation of disease control programs in priority areas is a challenge for healthcare managers. The present study aimed to analyze the spatio-temporal distribution and identify high risk areas of VL occurrence in the Brazilian territory. We analyzed data regarding new cases with confirmed diagnosis of VL in Brazilian municipalities, from 2001 to 2020, extracted from the Brazilian Information System for Notifiable Diseases. The Local Index of Spatial Autocorrelation (LISA) was used to identify contiguous areas with high incidence rates in different periods of the temporal series. Clusters of high spatio-temporal risk were identified using the scan statistics. The accumulated incidence rate in the analyzed period was 33.53 cases per 100,000 inhabitants. The number of municipalities that reported cases showed an upward trend from 2001 onward, although there was a decrease in 2019 and 2020. According to LISA, the number of municipalities considered a priority increased in Brazil and in most states. Priority municipalities were predominantly concentrated in the states of Tocantins, Maranhão, Piauí, and Mato Grosso do Sul, in addition to more specific areas of Pará, Ceará, Piauí, Alagoas, Pernambuco, Bahia, São Paulo, Minas Gerais, and Roraima. The spatio-temporal clusters of high-risk areas varied throughout the time series and were relatively higher in the North and Northeast regions. Recent high-risk areas were found in Roraima and municipalities in northeastern states. VL expanded territorially in Brazil in the 21st century. However, there is still a considerable spatial concentration of cases. The areas identified in the present study should be prioritized for disease control actions.

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.

Factors associated with human visceral leishmaniasis cases during urban epidemics in Brazil: a systematic review

Visceral leishmaniasis (VL) is endemic in 70 countries and has been reported in 12 countries of Latin America, with over 90% of the cases reported in Brazil, where epidemics have occurred since 1980. The objective of this review is to describe the factors associated with the occurrence of VL epidemics in humans in urban areas. A systematic review was conducted according to the PRISMA-P guidelines. The databases PubMed (by Medline), Cochrane Library, Embase, Amed, LILACS and grey literature [Google Scholar and handsearch of the database of the Information System for Notifiable Diseases (SINAN) of Brazil's Unified Health System] were used. The protocol was registered under PROSPERO (CRD42019128998). Climatic, environmental factors and indicators of urban social structure were described as influencing the outbreaks in the North and Northeast regions. Gender and age characteristics were related to a greater chance of developing VL in the Central-West, Northeast and Southeast regions. Vector indicators showed a positive correlation with the incidence of VL in studies in the Northeast region. In the Southeast and Northeast regions, studies revealed the presence of dogs with positive correlation with VL. Knowledge gaps remain regarding the contribution to the increase in the risk factors described in ecological approaches, as no analysis was performed at the individual level, and it is still necessary to discuss the influence of other associated elements in epidemic episodes in the spread of VL.

Epidemiological aspects and spatial patterns of human visceral leishmaniasis in Brazil

Human visceral leishmaniasis (HVL) cases are important public health problems due to their zoonotic aspect, with high rates of morbidity and mortality in Brazil. The aim of this this study was to identify spatial patterns in both rates of HVL cases in Brazilian states during the period from 2006 to 2015. This is an ecological study, using geoprocessing tools to create choropleth maps, based on secondary data from open access platforms, to identify priority areas for control actions of the disease. Data were collected in 2017 and analysed according to the global and local Moran's I, using TerraView 4.2.2 software. Similar clusters were observed in neighbouring municipalities in thematic maps of HVL, suggesting spatial similarity in the distribution of the disease in humans mainly in the North and Northeast Regions, which concentrate the states with the highest rates of HVL. Heterogeneous spatial patterns were observed in the distribution of HVL, which show municipalities that need higher priority in the intensification of disease surveillance and control strategies.

Epidemiology of Visceral Leishmaniasis with Emphasis on the Dynamic Activity of Sand Flies in an Important Endemic Focus of Disease in Northwestern Iran

Background

Leishmaniasis diseases are known to be one of the most important public health problems in World and Iran. Visceral leishmaniasis is considered to be the most serious form and transmitted by sand flies species. The aim of this study was to investigate the dynamic activities of sandflies in northwestern Iran.

Methods

This crass-sectional study was conducted from April to December 2018 in Meshkinshahr County, Ardabil Province. Sticky traps have been used to collect sand flies. They are stored in 70% alcohol and finally identified using valid keys. The aspects of the synoptic information were inquired from the Meshkin Shahr weather department and results analyzed for SPSS24.

Results

Totally 259 sandflies were collected during study period. From collected samples 78.7% were male and 21.3% female. There were 8 different species. Phlebotomus kandelakii was the most prevalent one (30.8%). The average temperature, relative humidity, and average wind speed was 13.5 °C, 84%, and 2 meters per hour on the onset of sandflies' activity, respectively. These values were 18.3 °C, 85% and 1.5 meters per hour at the peak of their activity and 16 °C, 62% and 5 meters per hour at the final stage of their activity. Sand flies had one peak in July which is strongly influenced by temperature and humidity conditions. Two species of Ph. kandelakii and Phlebotomus perfilewi transcaucasicus, had the highest activity in this endemic area.

Conclusion

The results of current study will provide a guideline for control of diseases in the country.

Effects of El Niño-Southern Oscillation on human visceral leishmaniasis in the Brazilian State of Mato Grosso do Sul

BACKGROUND

Leishmaniases are considered a major public health problem in South America, specifically in Brazil. Moreover, the transmission and epidemiology of leishmaniasis are possibly associated with climatic and environmental variations.

OBJECTIVE

This study aimed to assess the association between the extreme climatic phenomenon El Niño-Southern Oscillation (ENSO), the maximum and minimum variations of temperature, precipitation, and soil moisture and the incidence of visceral leishmaniasis (VL) in Mato Grosso do Sul (MS), Brazil, from 2002 to 2015.

METHODS

The Niño 3.4 index was used for the ENSO variation. The other climatic data were obtained from the climatic tool TerraClimate. Records regarding VL were obtained from the Notification of Injury Information System.

FINDINGS

From 2002 to 2015, there were 3,137 cases of VL recorded in MS. The annual incidence of the disease was negatively associated with the ENSO index and soil moisture in MS. The VL incidence increased during the negative phase of ENSO and decreased during the positive phase.

MAIN CONCLUSIONS

The results demonstrated that the interannual cycles of incidence of human VL are significantly associated with the occurrence of the ENSO phenomenon and its phases, El Niño and La Niña.

Leishmaniose visceral e sua relação com fatores climáticos e ambientais no Estado do Tocantins, Brasil, 2007 a 2014

Resumo: A leishmaniose visceral (LV) pode ser influenciada por fatores climáticos e ambientais. Tocantins é o estado com mais incidência no Brasil, contribuindo para o aumento dos casos na macrorregião Norte. Este estudo tem objetivo de identificar a correlação entre a taxa de incidência de LV e fatores climáticos e ambientais, nos municípios do Estado do Tocantins de 2007 a 2014. As correlações entre a taxa de incidência bruta de LV e as variáveis elevação, precipitação, Índice de Vegetação Melhorado (EVI - Enhanced Vegetation Index) e temperatura foram testadas por meio dos índices de Moran Global e Local, identificando também clusters de incidência de LV. A análise de variância para tendência linear foi testada entre as médias das variáveis em cada categoria da taxa. Os resultados apontam aumento nas taxas de incidência, na medida em que aumentam os valores de precipitação anual, umidade, EVI e temperatura noturna; e uma relação inversa para a elevação e temperatura diurna. Os clusters identificados evidenciam que variáveis climáticas e ambientais se relacionam à incidência de LV, devendo haver outros estudos que ajustem os fatores associados aos sujeitos, a fim de dimensionar o quanto o ambiente ou a influência do homem nele impacta na doença.

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.

Risk profile for Leishmania infection in dogs coming from an area of visceral leishmaniasis reemergence

Until the 1980s, visceral leishmaniasis was concentrated in poor rural areas of Brazil. The Vale do Rio Doce, located in the Southeastern Brazilian state of Minas Gerais, was an endemic area with high numbers of human and canine cases. Prophylactic measures adopted since the 1960s reduced the number of cases and the region became a 'controlled endemic' area. In the early 1990s, however, the program was interrupted, and the human disease reemerged in 2008. This cross-sectional study evaluated the prevalence and the risk profile of infection of dogs with Leishmania spp in this reemergence area of visceral leishmaniasis. Among a population of approximately 280,000 people, a total of 3835 dog owners were interviewed about socioeconomic conditions, housing, peridomicile features, and their dogs' characteristics and behavior. Blood samples were collected from 5822 dogs of an estimated canine population of 20,000 and anti-Leishmaniasis antibodies were identified using Dual-Path Platform and ELISA. We observed that 1282 of the 5822 dogs were seropositive for the protozoan indicating a seroprevalence of 22%. The risk factors associated with Leishmania infection in dogs were: non-paved backyard (OR 1.4; 95%CI 1.2-1.7); the presence of dry leaves and decaying fruit in the backyard (OR 1.3; 95%CI 1.1-1.5); medium-sized (OR 1.3; 95% 1.1-1.5) or big-sized dogs (OR 1.8; 95%CI 1.5-2.3); short-haired dogs (OR 1.8; 95%CI 1.5-2.1); dogs that slept in the backyard (OR 2.6; 95%CI 1.8-3.6) or in the balcony (OR 1.6; 95%CI 1.1-2.3); and history of canine visceral leishmaniasis in the household (OR 1.3; 95%CI 1.1-1.5). Our results suggest a strong reemergence of canine visceral leishmaniasis after the discontinuation of the control programs. Also, the observed risk factors reinforce the role of health education and environmental management measures to the effective control of the disease.

Diel periodicity of Drosophila suzukii (Diptera: Drosophilidae) under field conditions

Drosophila suzukii Matsumura (Diptera: Drosophilidae), an economically important pest of blueberry and other thin-skinned fruits, persists and prolifically reproduces under seemingly lethal climatic conditions in the field. However, behavioral and physiological mechanisms employed by D. suzukii to tolerate such extreme climatic conditions in the field are unknown. The primary objective of this project was to investigate diel periodicity of D. suzukii and their reproductive success under field conditions as related by climatic factors such as temperature and relative humidity. Results show that D. suzukii reproductive success was significantly higher during the night (including dawn and dusk periods) than the day in terms of oviposition, pupation, adult eclosion, and the number of progeny per female. Female D. suzukii reproductive success was not significantly different between specific regions of a blueberry bush in relation to the amount of shade provided by the canopy. Our studies indicate that D. suzukii flight activity is crepuscular and is sensitive to fluctuations in temperature and relative humidity. Results also suggest that the majority of fly activity during peak hours is concentrated in areas around the border and within the center of blueberry orchards with little activity in the surrounding wooded areas. These findings suggest that D. suzukii prefers microclimate with mild temperatures and high humidity, and does not function well when exposed to direct sunlight with extreme heat. The authors propose that D. suzukii management strategies should be implemented during the early morning and immediately before darkness to maximize efficacy.

Nycthemeral Rhythm of Phlebotominae (Diptera: Psychodidae) in a Craggy Region, Transitioning Between the Wetland and the Plateau, Brazil

Recording the nycthemeral rhythm of sand flies allows the evaluation of the daily activity in different ecotypes, the period of greatest activity, and their degree of anthropophily. We investigated the fauna and the rhythm of sand fly activity in an ecotourism region in Mato Grosso do Sul (MS) state, Brazil. Sand flies were captured monthly, using a Shannon trap for 24 h periods between July 2012 and June 2014. We collected 1,815 sand flies, in which Lutzomyia whitmani (=Nyssomyia whitmani, sensu Galati) and Lutzomyia longipalpis were the most abundant species during the dry season, with activity from 5 p.m.-7 a.m. and 6 p.m.-5 a.m., respectively. Both species require particular attention as vectors of Leishmania (Viannia) braziliensis and Leishmania (Leishmania) infantum in several regions of Brazil, including MS. However, Lutzomyia dispar was more anthropophilic, and was most active between January and March, from 5 p.m. to 5 a.m. Lutzomyia misionensis (=Pintomyia misionensis, sensu Galati) was present throughout both years, active from 4 p.m. to 5 a.m. Other species were active from 5 p.m. to 6 a.m. Due to intense tourism in the months that coincide with a high number of vectors for leishmaniases in Piraputanga, it is essential to determine vector-monitoring strategies in the area by investigating sand fly rhythm while not neglecting other periods of the year when the insects are present.

Rhodnius prolixus and R. robustus (Hemiptera: Reduviidae) nymphs show different locomotor patterns on an automated recording system

BACKGROUND

Circadian rhythms of triatomines, vectors of the etiological agent Trypanosoma cruzi responsible for Chagas disease, have been extensively studied in adults of the two most epidemiologically relevant vector species, Rhodnius prolixus and Triatoma infestans. However, little attention has been dedicated to the activity patterns in earlier developmental stages, even though triatomine nymphs are equally capable of transmitting T. cruzi to humans. Because circadian rhythms may differ even between closely related species, studies that focus on this behavioral trait can also be used to shed light on the taxonomy of controversial taxa, which becomes especially relevant regarding vector species.

METHODS

We compared the daily locomotor activity patterns of second- and third-instar nymphs of Rhodnius prolixus and Rhodnius robustus in order to unveil possible behavioral differences between these cryptic species. Mitochondrial and nuclear markers were sequenced to confirm species identification.

RESULTS

Nymphs of both species had a bimodal pattern of locomotion and similar daily activity patterns, but R. prolixus is more active under light/dark cycles and depicts a more pronounced activity rhythm under constant darkness conditions.

CONCLUSIONS

We describe the implementation of an often-used automated method for the recording of individual locomotor activity to differentiate sibling species of Rhodnius with distinct epidemiological relevance. The higher levels of activity observed in the nymphs of R. prolixus could potentially contribute to increased vector capacity.

Seasonal Dynamics of Phlebotomine Sand Fly Species Proven Vectors of Mediterranean Leishmaniasis Caused by Leishmania infantum

Background

The recent geographical expansion of phlebotomine vectors of Leishmania infantum in the Mediterranean subregion has been attributed to ongoing climate changes. At these latitudes, the activity of sand flies is typically seasonal; because seasonal phenomena are also sensitive to general variations in climate, current phenological data sets can provide a baseline for continuing investigations on sand fly population dynamics that may impact on future scenarios of leishmaniasis transmission. With this aim, in 2011–2013 a consortium of partners from eight Mediterranean countries carried out entomological investigations in sites where L. infantum transmission was recently reported.

Methods/Principal Findings

A common protocol for sand fly collection included monthly captures by CDC light traps, complemented by sticky traps in most of the sites. Collections were replicated for more than one season in order to reduce the effects of local weather events. In each site, the trapping effort was left unchanged throughout the survey to legitimate inter-seasonal comparisons. Data from 99,000 collected specimens were analyzed, resulting in the description of seasonal dynamics of 56,000 sand flies belonging to L. infantum vector species throughout a wide geographical area, namely P. perniciosus (Portugal, Spain and Italy), P. ariasi (France), P. neglectus (Greece), P. tobbi (Cyprus and Turkey), P. balcanicus and P. kandelakii (Georgia). Time of sand fly appearance/disappearance in collections differed between sites, and seasonal densities showed variations in each site. Significant correlations were found between latitude/mean annual temperature of sites and i) the first month of sand fly appearance, that ranged from early April to the first half of June; ii) the type of density trend, varying from a single peak in July/August to multiple peaks increasing in magnitude from May through September. A 3-modal trend, recorded for P. tobbi in Cyprus, represents a novel finding for a L. infantum vector. Adults ended the activity starting from mid September through November, without significant correlation with latitude/mean annual temperature of sites. The period of potential exposure to L.infantum in the Mediterranean subregion, as inferred by adult densities calculated from 3 years, 37 sites and 6 competent vector species, was associated to a regular bell-shaped density curve having a wide peak center encompassing the July-September period, and falling between early May to late October for more than 99% of values. Apparently no risk for leishmaniasis transmission took place from December through March in the years considered. We found a common pattern of nocturnal females activity, whose density peaked between 11 pm and 2 am.

Conclusions

Despite annual variations, multiple collections performed over consecutive years provided homogeneous patterns of the potential behavior of leishmaniasis vectors in selected sites, which we propose may represent sentinel areas for future monitoring. In the investigated years, higher potential risk for L. infantum transmission in the Mediterranean was identified in the June-October period (97% relative vector density), however such risk was not equally distributed throughout the region, since density waves of adults occurred earlier and were more frequent in southern territories.

Recent projections on global warming indicate a constant rise of temperatures in the Mediterranean subregion in the near-mid future. While this phenomenon already caused geographical expansion of several arthropod-borne diseases, it is likely to affect also temporal parameters of seasonally transmitted diseases such as leishmaniasis, a protozoan infection spread by the bite of phlebotomine sand flies. Phenology of sand flies consists in the periods of emergence of adults and their disappearance from collections following an activity period during warm months, which can be characterized by peaks of abundance. Current phenological observations can be important for continuing investigations on sand fly dynamics that may impact on leishmaniasis transmission in the future. With this aim, partners from eight Mediterranean countries identified sites with documented Leishmania infantum transmission by six different vector species and performed multiannual trappings. From the high number of 56,000 specimens collected throughout an area spanning from Portugal at west to Georgia at east, the current seasonal dynamics of Mediterranean vectors was obtained. Both, period of adults emergence and type of density trend were found to be significantly correlated with latitude or mean annual temperature of trapping sites. At the southernmost latitudes, vector activity started as early as begin of April and ended by late November, showing that the no-risk period of potential exposure to L. infantum lasted only 4 months.

"The Environment is Everything That Isn't Me": Molecular Mechanisms and Evolutionary Dynamics of Insect Clocks in Variable Surroundings

Circadian rhythms are oscillations in behavior, metabolism and physiology that have a period close to 24 h. These rhythms are controlled by an internal pacemaker that evolved under strong selective pressures imposed by environmental cyclical changes, mainly of light and temperature. The molecular nature of the circadian pacemaker was extensively studied in a number of organisms under controlled laboratory conditions. But although these studies were fundamental to our understanding of the circadian clock, most of the environmental conditions used resembled rather crudely the relatively constant situation at lower latitudes. At higher latitudes light-dark and temperature cycles vary considerably across different seasons, with summers having long and hot days and winters short and cold ones. Considering these differences and other external cues, such as moonlight, recent studies in more natural and semi-natural situations revealed unexpected features at both molecular and behavioral levels, highlighting the dramatic influence of multiple environmental variables in the molecular clockwork. This emphasizes the importance of studying the circadian clock in the wild, where seasonal environmental changes fine-tune the underlying circadian mechanism, affecting population dynamics and impacting the geographical variation in clock genes. Indeed, latitudinal clines in clock gene frequencies suggest that natural selection and demography shape the circadian clock over wide geographical ranges. In this review we will discuss the recent advances in understanding the molecular underpinnings of the circadian clock, how it resonates with the surrounding variables (both in the laboratory and in semi-natural conditions) and its impact on population dynamics and evolution. In addition, we will elaborate on how next-generation sequencing technologies will complement classical reductionist approaches by identifying causal variants in natural populations that will link genetic variation to circadian phenotypes, illuminating how the circadian clock functions in the real world.

Clocks do not tick in unison: isolation of Clock and vrille shed new light on the clockwork model of the sand fly Lutzomyia longipalpis

BACKGROUND

Behavior rhythms of insect vectors directly interfere with the dynamics of pathogen transmission to humans. The sand fly Lutzomyia longipalpis is the main vector of visceral leishmaniasis in America and concentrates its activity around dusk. Despite the accumulation of behavioral data, very little is known about the molecular bases of the clock mechanism in this species. This study aims to characterize, within an evolutionary perspective, two important circadian clock genes, Clock and vrille.

FINDINGS

We have cloned and isolated the coding sequence of L. longipalpis' genes Clock and vrille. The former is structured in eight exons and encodes a protein of 696 amino acids, and the latter comprises three exons and translates to a protein of 469 amino acids. When compared to other insects' orthologues, L. longipalpis CLOCK shows a high degree of conservation in the functional domains bHLH and PAS, but a much shorter glutamine-rich (poly-Q) C-terminal region. As for L. longipalpis VRILLE, a high degree of conservation was found in the bZIP domain. To support these observations and provide an elegant view of the evolution of both genes in insects, phylogenetic analyses based on maximum-likelihood and Bayesian inferences were performed, corroborating the previously known insect systematics.

CONCLUSIONS

The isolation and phylogenetic analyses of Clock and vrille orthologues in L. longipalpis bring novel and important data to characterize this species' circadian clock. Interestingly, the poly-Q shortening observed in CLOCK suggests that its transcription activity might be impaired and we speculate if this effect could be compensated by other clock factors such as CYCLE.

Alternative Method for the Mass Rearing of Lutzomyia (Lutzomyia) cruzi (Diptera: Psychodidae) in a Laboratory Setting

The understanding of the transmission dynamics of Leishmania spp. Ross as well as the epidemiology and spread of leishmaniasis is related to parasite-vector-host interactions. These interactions can be studied using specimens of a sand fly population reared in the laboratory, exposing individuals to experimental infection for the investigation of vector competence and parameters of the vectorial capacity of the species. The present study sought to describe an alternative method for the implantation of a Lutzomyia (Lutzomyia) cruzi colony with wild specimens captured in the municipality of Corumbá, Brazil. With Method 1, engorged females were individualized for oviposition. The eggs were transferred to an acrylic petri dish with a layer of plaster on the bottom, on which food was placed after hatching of the first larvae. With Method 2, females were kept in groups for oviposition in containers, in which soil and food were placed on their bottom for the larvae. In addition, the exposure time of the larvae to light was reduced in comparison with Method 1. With Method 2, a significantly greater number of specimens of Lu. cruzi was obtained. The ratio between the number of emerged adults and the females followed for oviposition was 0.42 with Method 1 and 2.75 with Method 2. The optimization of the rearing conditions for Lu. cruzi will enable the establishment of a colony providing a sufficient number of specimens to develop experimental infection by Leishmania as well as vectorial competence and some parameters of the vectorial capacity of this sand fly.