Intrusive versus domiciliated triatomines and the challenge of adapting vector control practices against Chagas disease

Chagas disease prevention remains mostly based on triatomine vector control to reduce or eliminate house infestation with these bugs. The level of adaptation of triatomines to human housing is a key part of vector competence and needs to be precisely evaluated to allow for the design of effective vector control strategies. In this review, we examine how the domiciliation/intrusion level of different triatomine species/populations has been defined and measured and discuss how these concepts may be improved for a better understanding of their ecology and evolution, as well as for the design of more effective control strategies against a large variety of triatomine species. We suggest that a major limitation of current criteria for classifying triatomines into sylvatic, intrusive, domiciliary and domestic species is that these are essentially qualitative and do not rely on quantitative variables measuring population sustainability and fitness in their different habitats. However, such assessments may be derived from further analysis and modelling of field data. Such approaches can shed new light on the domiciliation process of triatomines and may represent a key tool for decision-making and the design of vector control interventions.     

Surveillance,health promotion and control of Chagas disease in the Amazon Region - Medical attention in the Brazilian Amazon Region: a proposal

We refer to Oswaldo Cruz''s reports dating from 1913 about the necessities of ahealthcare system for the Brazilian Amazon Region and about the journey of CarlosChagas to 27 locations in this region and the measures that would need to be adopted.We discuss the risks of endemicity of Chagas disease in the Amazon Region. Werecommend that epidemiological surveillance of Chagas disease in the Brazilian AmazonRegion and Pan-Amazon region should be implemented through continuous monitoring ofthe human population that lives in the area, their housing, the environment and thepresence of triatomines. The monitoring should be performed with periodicseroepidemiological surveys, semi-annual visits to homes by health agents and thetraining of malaria microscopists and healthcare technicians to identifyTrypanosoma cruzi from patients'' samples and T.cruzi infection rates among the triatomines caught. We recommend healthpromotion and control of Chagas disease through public health policies, especiallythrough sanitary education regarding the risk factors for Chagas disease. Finally, wepropose a healthcare system through base hospitals, intermediate-level units in theareas of the Brazilian Amazon Region and air transportation, considering thedistances to be covered for medical care.     

城市化与生态系统服务的空间交互关系研究——以长株潭城市群为例

探索生态系统服务与城市化的空间交互关系为城市发展和保护提供新的视角。以长株潭城市群为例,以其2015年的土地利用、经济社会等数据为基础,利用格网分析和空间自相关模型解析城市化与生态系统服务的空间交互规律。结果表明:(1)长株潭城市群城市化水平空间分布区域差异性显著,城市化水平由高到低依次为城市化地区、正在城市化地区和生态绿心保护区,表现出从城市化地区向周边地区依次递减的态势。(2)受城市化水平和土地利用变化等影响,生态系统服务空间分布具有明显的差异性,并呈现出"中心-外围"逐步升高的趋势。(3)长株潭城市群城市化与各项生态系统服务之间呈显著负相关,由于驱动机制的不同,城市化地区、正在城市化地区和生态绿心保护区的城市化对生态系统服务的影响存在显著差异。(4)长株潭城市群的各项生态系统服务与城市化之间存在四种空间相关类型。高高集聚区和低低集聚区零散分布在整个研究区域,面积较小;高低集聚区分布在湘潭县西南部、株洲县东南部,面积较大;低高集聚区分布集中在城市化地区,呈现块状分布,面积较大。     

Sandfly (Diptera: Psychodidae: Phlebotominae) species diversity in an urban area of the municipality of Tapachula,Chiapas, Mexico

Monitoring phlebotomine sandflies in urban areas is key for epidemiological studies in susceptible populations. This paper describes sandfly fauna that were present in an urban area of the municipality of Tapachula, Chiapas, Mexico, and were captured with Shannon and CDC light traps. During February and March of 2014, 1,442 sandflies were captured, specifically Lutzomyia cruciata (Coquillet) (98.8%), Lutzomyia cayennensis cayennensis (Floch and Abonnenc) (0.8%), Lutzomyia chiapanensis (Dampf) (0.3%) and Lutzomyia atulapai (De León) (0.1%). Lu. cruciata was the most abundant and the most frequently trapped species. This is the first record of its remarkable ability to adapt to urban green areas. The three other species trapped represent new records of geographic distribution for the study region. These results indicate the need to establish measures for reducing both human contact with this vector and the risk of possible sites of infection.     

Leishmania infection and host-blood feeding preferences of phlebotomine sandflies and canine leishmaniasis in an endemic European area,the Algarve Region in Portugal

The Algarve Region (AR) in southern Portugal, which is an international tourist destination, has been considered an endemic region of zoonotic leishmaniasis caused by Leishmania infantum since the 1980s. In the present study, phlebotomine and canine surveys were conducted to identify sandfly blood meal sources and to update the occurrence of Leishmania infection in vectors and dogs. Four sandfly species were captured: Phlebotomus perniciosus, Phlebotomus ariasi, Phlebotomus sergenti and Sergentomyia minuta. In one P. perniciosus female, L. infantum DNA was detected. Blood meal tests showed that this species had no host preferences and was an opportunistic feeder. An overall canine leishmaniasis (CanL) seroprevalence of 16.06% was found; the seroprevalence was 3.88% in dogs housed in kennels and 40.63% in dogs that attended veterinary clinics. The simultaneous occurrence of dogs and P. perniciosus infected with L. infantum in the AR indicates that the region continues to be an endemic area for CanL. Our results reinforce the need for the systematic spatial distribution of phlebotomine populations and their Leishmania infection rates and the need to simultaneously perform pathogen monitoring in both invertebrate and vertebrate hosts to investigate the transmission, distribution and spreading of Leishmania infection.     

Asymptomatic infection in individuals from the municipality of Barcelos (Brazilian Amazon) is not associated with the anti-Plasmodium falciparum glycosylphosphatidylinositol antibody response

Anti-glycosylphosphatidylinositol (GPI) antibodies (Abs) may reflect and mediate, at least partially, anti-disease immunity in malaria by neutralising the toxic effect of parasitic GPI. Thus, we assessed the anti-GPI Ab response in asymptomatic individuals living in an area of the Brazilian Amazon that has a high level of malaria transmission. For comparative purposes, we also investigated the Ab response to a crude extract prepared from Plasmodium falciparum, the merozoite surface protein (MSP)3 antigen of P. falciparum and the MSP 1 antigen of Plasmodium vivax (PvMSP1-₁₉) in these individuals and in Angolan patients with acute malaria. Our data suggest that the Ab response against P. falciparum GPI is not associated with P. falciparum asymptomatic infection in individuals who have been chronically exposed to malaria in the Brazilian Amazon. However, this Ab response could be related to ongoing parasitaemia (as was previously shown) in the Angolan patients. In addition, our data show that PvMSP1-₁₉may be a good marker antigen to reflect previous exposure to Plasmodium in areas that have a high transmission rate of P. vivax.     

城市住宅区碳源汇的空间分异规律、影响机制及管理对策——以关中地区为例

城市住宅区作为城市生态系统重要的组成单元,其碳源汇对城市生态系统碳循环和碳平衡产生重要影响.本文采取案例分析、文献查阅、问卷调查等多种方法,获取关中地区城市住宅区CO₂排放(碳源)与吸收(碳汇)数据,并分析其来源及空间分布情况.结果表明: 关中地区住宅区建材生产和改造更新过程CO₂排放量最大;且建材类的CO₂排放量远大于日常生活资料,仅有40%～52%碳排放发生在住宅区,其余发生在外围,呈现出碳源距离的空间波动性、成分的空间差异性以及圈层与分区分布.仅有9%～17%的碳排放可在住宅区内被吸收,外部空间被动承担大量碳汇功能,并显现为分层递变和空间分异.最后提出了碳源、碳汇空间管理技术和干预对策.
     

Spatial distribution of ants (Hymenoptera: Formicidae), vine mealybugs and mealybug parasitoids in vineyards

The mutualistic association between some ant species and honeydew‐producing Hemiptera has been shown to influence the distribution patterns and abundance of these hemipterans and their natural enemies. We studied the spatial distribution patterns of three ant species, mealybugs and mealybug parasitoids for two consecutive growing seasons on three wine grape farms in the Western Cape, South Africa. During the study period, no ant or mealybug controls were applied. Ant and mealybug monitoring was conducted on a total of 21 ha using a presence/absence sampling system, while parasitoids were collected from infested mealybug females. Spatial analysis by distance indices was used to analyse spatial distribution of insects and ArcView? was used to map the gap, patch and local association indices where significant association and disassociation occurred. Significant associations were found between some ants and parasitoids, while significant disassociations between the ants Crematogaster peringueyi and Linepithema humile; and also between Crematogaster peringueyi and Anoplolepis steingroeveri were found. Interspecific competition between ant species could play a role in the distribution of parasitoids and mealybugs. Our results stress the importance of monitoring for ants and mealybugs and further highlight the importance of restricted chemical applications against ants during the growing season.     

Dissolved carbon in an urban area of a river in the Brazilian Amazon

The main objective of this study was to evaluate dissolved organic and inorganic carbon dynamics along upstream and downstream reaches of the Acre River draining the city of Rio Branco, in the state of Acre, Brazil. Dissolved organic carbon (DOC) concentrations in the Acre River were significantly higher during the wet season, ranging from 385 ± 160 to 430 ± 131 ??M among the stations, with no difference in upstream and downstream concentrations. Dissolved inorganic carbon (DIC) showed an inverse pattern, with higher concentrations in the dry season, ranging from 816 ± 215 to 998 ± 754 ??M among the stations, as well as no difference in upstream and downstream DIC concentrations. Bicarbonate was the dominant DIC fraction and was mainly observed during the dry season. Due to lower pH values during the wet season, CO₂ partial pressure (pCO₂) in the Acre River was higher in the wet season, with values ranging from 4,567 ± 1,813 to 4,893 ± 837 ppm among the stations. Our results indicate that, although the Acre River drains a large city with significant sewage disposal into the river, seasonal hydrological processes are the main driver of dissolved carbon dynamics, even in the downstream study reach directly influenced by urbanization.     

Influence of the landscape on dispersal of sylvatic triatomines to anthropic habitats in the Atlantic Forest

Aim The aim of this study was to test the hypothesis that the dispersal of sylvatic triatomines to anthropic habitats is stimulated by degradation of their natural habitat. Location State of Espírito Santo, south‐eastern Brazil. Methods We georeferenced records of domiciliary captures of sylvatic triatomines (1996–2005) obtained from the database of the entomological surveillance programme of the Brazilian National Health Foundation. We partitioned the study area into 543 equal hexagons and attributed information on the presence/absence of triatomines and climatic, topographic and biological variables to each. Using generalized additive models (GAMs), we defined the determinant variables for triatomine presence/absence and demarcated the potential areas in which they might occur. We then subjected the hexagons with a high probability of triatomine presence to a second analysis, adding information on the number of domiciliary captures of triatomines and landscape indices that measured quantitative and spatial patterns of forest fragments. We used GAMs to determine the indices that influenced the number of domiciliary captures of triatomines. Results The presence of triatomines was characterized by a strong positive correlation with variability of terrain slope. This variable was used to demarcate the areas where triatomines were likely to occur. Landscape indices associated with the number of domiciliary captures of triatomines were the number of patches, the fractal dimension index, the total core area and the clumpiness index. Main conclusions Our results do not support the hypothesis that domiciliary invasion by sylvatic triatomines is stimulated by environmental degradation. Instead, the results suggest that less degraded areas maintain larger populations of triatomines and consequently present higher indices of dispersal and domiciliary invasion. Particular landscape patterns and dispositions of human dwellings, however, may enhance the probability of triatomines being attracted to the artificial light of dwellings. Initiation of flight and consequent dispersal is a naturally occurring process that allows triatomines to find and colonize areas that favour the survival of their offspring.     

Domestic,peridomestic and wild hosts in the transmission of Trypanosoma cruzi in the Caatinga area colonised by Triatoma brasiliensis

The role played by different mammal species in the maintenance of Trypanosoma cruzi is not constant and varies in time and place. This study aimed to characterise the importance of domestic, wild and peridomestic hosts in the transmission of T. cruzi in Tauá, state of Ceará, Caatinga area, Brazil, with an emphasis on those environments colonised by Triatoma brasiliensis. Direct parasitological examinations were performed on insects and mammals, serologic tests were performed on household and outdoor mammals and multiplex polymerase chain reaction was used on wild mammals. Cytochrome b was used as a food source for wild insects. The serum prevalence in dogs was 38% (20/53), while in pigs it was 6% (2/34). The percentages of the most abundantly infected wild animals were as follows: Thrichomys laurentius 74% (83/112) and Kerodon rupestris 10% (11/112). Of the 749 triatomines collected in the household research, 49.3% (369/749) were positive for T. brasiliensis, while 6.8% were infected with T. cruzi (25/369). In captured animals, T. brasiliensis shares a natural environment with T. laurentius, K. rupestris, Didelphis albiventris, Monodelphis domestica, Galea spixii, Wiedomys pyrrhorhinos, Conepatus semistriatus and Mus musculus. In animals identified via their food source, T. brasiliensis shares a natural environment with G. spixii, K. rupestris, Capra hircus, Gallus gallus, Tropidurus oreadicus and Tupinambis merianae. The high prevalence of T. cruzi in household and peridomiciliar animals reinforces the narrow relationship between the enzootic cycle and humans in environments with T. brasiliensis and characterises it as ubiquitous.     

Spatial distribution of soil contamination by Toxoplasma gondii in relation to cat defecation behaviour in an urban area

In urban areas, there may be a high local risk of zoonosis due to high densities of stray cat populations. In this study, soil contamination by oocysts of Toxoplasma gondii was searched for, and its spatial distribution was analysed in relation to defecation behaviour of cats living in a high-density population present in one area of Lyon (France). Sixteen defecation sites were first identified. Cats were then repeatedly fed with marked food and the marked faeces were searched for in the defecation sites. Of 260 markers, 72 were recovered from 24 different cats. Defecation sites were frequented by up to 15 individuals. Soil samples were also examined in order to detect the presence of T. gondii using real-time PCR. The entire study area was then sampled according to cat density and vegetation cover type. Only three of 55 samples were positive and all came from defecation sites. In a second series of observations, 16 defecation sites were sampled. Eight of 62 samples tested positive, originating in five defecation sites. Laboratory experiments using experimental seeding of soil showed that the inoculated dose that can be detected in 50% of assays equals 100-1000oocysts/g, depending on the strain. This study shows that high concentrations of oocysts can be detected in soil samples using molecular methods and suggests that spatial distribution of contamination areas is highly heterogeneous. Positive samples were only found in some of the defecation sites, signifying that at-risk points for human and animal infection may be very localised.     

Spatial distribution of an undergrowth palm in fragments of the Brazilian Atlantic Forest

The occurrence of disturbed sectors may be as important as microscaleedge effects in tropical forests fragments. We considered the spatialdistribution dynamics of life stages (youngs, immatures, and adults) of theacaulescent, endemic palm Attalea humilis Mart. ex.Spreng.in fire-prone fragments of the Brazilian Atlantic forest to investigatepopulation responses to fragment size and fire occurrence. From 1996 to 1999,werecorded the number of individuals in different life stages in adjacent10×10-m plots in two perpendicular transects across each of threefragments of different sizes (1.6, 6.4, and 9.9 ha) in the ReservaNacional de Poço das Antas, Southeastern Brazil. A fire burnt thefragments studied in 1997. Application of Morisita's Index showed clumping atmost scales, with a marked reduction in clumping degree from youngs to adults,apattern not influenced by fragment size. After fire, clumping degree increasedtemporarily among the youngs. No association between life stages was detectedusing presence/absence data. Palm density concentrated in the most disturbedtransect arms, a pattern very little affected by fragment size or fire. Noconsistent relationship between palm density and distance from fragment edgewasdetected for any stage, fragment, or year. We hypothesize that short-distanceseed dispersal by scatterhoarding rodents results in discrete, low-densityclumps of youngs dissociated from reproductive plants. The spatial pattern oflater stages is probably conditioned by the distribution of canopy gaps in thelargest, more closed fragment. In the other fragments, the presence of largedisturbed sectors promotes the formation of large, continuous stands of palms.This pattern would be reinforced by fire, which is known to be recurrent onalready disturbed sites. For the species studied, large-scale variations in theforest structure (degraded vs. preserved fragment sectors) seems to be moreimportant than microscale edge effects.     

Good agreements between self and clinician-collected specimens for the detection of human papillomavirus in Brazilian patients

Women infected with human papillomavirus (HPV) are at a higher risk of developing cervical lesions. In the current study, self and clinician-collected vaginal and cervical samples from women were processed to detect HPV DNA using polymerase chain reaction (PCR) with PGMY09/11 primers. HPV genotypes were determined using type-specific PCR. HPV DNA detection showed good concordance between self and clinician-collected samples (84.6%; kappa = 0.72). HPV infection was found in 30% women and genotyping was more concordant among high-risk HPV (HR-HPV) than low-risk HPV (HR-HPV). HPV16 was the most frequently detected among the HR-HPV types. LR-HPV was detected at a higher frequency in self-collected; however, HR-HPV types were more frequently identified in clinician-collected samples than in self-collected samples. HPV infections of multiple types were detected in 20.5% of clinician-collected samples and 15.5% of self-collected samples. In this study, we demonstrated that the HPV DNA detection rate in self-collected samples has good agreement with that of clinician-collected samples. Self-collected sampling, as a primary prevention strategy in countries with few resources, could be effective for identifying cases of HR-HPV, being more acceptable. The use of this method would enhance the coverage of screening programs for cervical cancer.     

Spatial and temporal changes in Lutzomyia longipalpis abundance,a Leishmania infantum vector in an urban area in northeastern Argentina

This study aimed to analyse changes in the spatial distribution of Lutzomyia longipalpis in Posadas, an urban area located in northeastern Argentina. Data were obtained during the summer of 2007 and 2009 through two entomological surveys of peridomiciles distributed around the city. The abundance distribution pattern for 2009 was computed and compared with the previous pattern obtained in 2007, when the first human visceral leishmaniasis cases were reported in the city. Vector abundance was also examined in relation to micro and macrohabitat characteristics. In 2007 and 2009, Lu. longipalpis was distributed among 41.5% and 31% of the households in the study area, respectively. In both years, the abundance rates at most of the trapping sites were below 30 Lu. longipalpis per trap per night; however, for areas exhibiting 30-60 Lu. longipalpis and more than 60 Lu. longipalpis, the areas increased in both size and number from 2007-2009. Lu. longipalpis was more abundant in areas with a higher tree and bush cover (a macrohabitat characteristic) and in peridomiciles with accumulated unused material (a microhabitat characteristic). These results will help to prioritise and focus control efforts by defining which peridomiciles display a potentially high abundance of Lu. longipalpis.     

Factors affecting the distribution of small mammals in an urban area

We investigated the distribution of a range of small mammal species in five urban habitats in north‐west Bristol: residential gardens, woodlands, allotment gardens, scrub and a cemetery. Wood mouse Apodemus sylvaticus abundance in residential gardens was negatively related to the abundance of cats and the distance to the nearest patch of natural or seminatural vegetation. These results suggest that urban small mammal populations may be limited by predation and habitat fragmentation, although the effects of the latter may be offset by the availability of good quality gardens.     

Evaluation of a CO2‐free commercial mosquito attractant to capture triatomines in the laboratory

Efforts have been made to develop vertebrate odor‐based attractants to lure hematophagous triatomines into traps. However, more work is needed to reach a practical, cheap, and efficient odor lure. We carried out attraction and capture tests in a dual‐choice olfactometer and a pitfall trap. Here we report that a three‐component, CO₂‐free, synthetic blend of vertebrate odor (consisting of ammonia, L(+) lactic acid and hexanoic acid, and known as Sweetscent®) significantly induces 3^rd‐instar Rhodnius prolixus and Triatoma infestans nymphs to fall into the test capture‐tube of the olfactometer. Blend constituents presented singly or in two‐component blends did not evoke a response and, therefore, we propose that the insects respond specifically to the three‐component blend in a synergistic way. When tested in a pitfall trap in an experimental arena, this blend induced capture in 37.5% of the lured traps, whereas 9% of the nymphs tested were captured in a single night. No insects were captured in control traps. Our work represents a proof‐of‐concept regarding capture of triatomines using host odor‐based, CO₂‐free synthetic mixtures as lures for pitfall traps. CO₂‐free lures are more practical for field work than natural or CO₂‐containing synthetic blends.     

豚草条纹萤叶甲各虫态的空间分布型

豚草条纹萤叶甲Ophraella communa LeSage是恶性入侵豚草(Ambrosia artemisiifolia L.)的天敌,用频次分布拟合和多种聚集指数测度等方法对该叶甲的成虫、幼虫和蛹、卵的空间分布型进行研究。结果表明,豚草条纹萤叶甲卵、幼虫+蛹、成虫的空间分布符合负二项分布,种群个体的空间分布为聚集分布。用几种衡量聚集度的指标,对上述各虫态分布的聚集程度进行测定;然后计算出各虫态田间最适理论抽样数。     

Spatial patterns in species–area relationships and species distribution in a West African forest–savanna mosaic

Aim To investigate the relationship between the slope z of the species–area relationship (SAR) and the intensity of spatial patterns in species number and dissimilarity for woody plants with different modes of seed dispersal. According to island theory we expect, for any given archipelago, steeper slopes and more pronounced spatial patterns for groups of less dispersive species. Location Ivory Coast, West Africa. Methods In a West African forest–savanna mosaic we collected presence–absence data for woody plant species in 49 forest islands. The parameters of the SARs were fitted by nonlinear regressions and then compared for plant species aggregated according to their mode of seed dispersal. We used the Mantel test to calculate the intensity of spatial patterns in species number, i.e. residual deviation from SAR, and species dissimilarity. Results The z‐value for bird‐dispersed species was lower (0.11) than that for wind‐dispersed species (0.27), with mammal‐dispersed species taking an intermediate value (0.16). This result suggests that, as a group, bird‐dispersed species are better colonizers. The spatial pattern in species number as well as species similarity was more pronounced for bird‐ compared with wind‐dispersed species. Main conclusions The standard interpretation of the theory of island biogeography claims that shallow slopes in the SAR imply low isolation of islands, i.e. good dispersal abilities of species. The results of our study appear to contradict this statement. The contradiction can eventually be resolved by a more detailed account of the colonization process, i.e. by distinguishing between dispersal and consecutive establishment of populations.