Seasonal variation in abundance and blood meal sources of primary and secondary malaria vectors within Kilombero Valley, Southern Tanzania

Background: Existing control tools have significantly reduced malaria over the past two decades. However, progress has been stalled due to increased resistance in primary vectors and the increasing role of secondary vectors. This study aimed to investigate the impact of seasonal change on primary and secondary vector abundance and host preference. Understanding the impact of seasonal dynamics of primary and secondary vectors on disease transmission will inform effective strategies for vector management and control.Methods: Vector abundance was measured through longitudinal collection of mosquitoes, conducted monthly during the wet and dry seasons, in Sagamaganga, a village in the Kilombero Valley, Tanzania. Mosquitoes were collected indoors using CDC light traps and backpack aspirators, and outdoors using resting buckets baited with cattle urine. In addition, a direct measure of host preference was taken monthly using human-and cattle-baited mosquito electrocuting traps. A host census was conducted to provide an indirect measure of host preference together with monthly blood meal source analysis. All collected mosquitoes were assayed for Plasmodium sporozoites.Results: A total of 2828 anophelines were collected, of which 78.5% and 21.4%, were primary and secondary vectors, respectively. The abundance of the primary vectors, Anopheles arabiensis and Anopheles funestus, and of the secondary vectors varied seasonally. Indirect measures of host preference indicated that all vectors varied blood meal choice seasonally, with the direct measure confirming this for An. arabiensis. All anopheline mosquitoes tested negative for sporozoites.Conclusions: At the study location, the abundance of both primary and secondary vectors changed seasonally. Indirect and direct measures of host preference demonstrated that An. arabiensis varied from being zoophilic to being more opportunistic during the wet and dry seasons. A similar trend was observed for the other vectors

Ultrasensitive detection of toxocara canis excretory-secretory antigens by a nanobody electrochemical magnetosensor assay.

peer reviewedHuman Toxocariasis (HT) is a zoonotic disease caused by the migration of the larval stage of the roundworm Toxocara canis in the human host. Despite of being the most cosmopolitan helminthiasis worldwide, its diagnosis is elusive. Currently, the detection of specific immunoglobulins IgG against the Toxocara Excretory-Secretory Antigens (TES), combined with clinical and epidemiological criteria is the only strategy to diagnose HT. Cross-reactivity with other parasites and the inability to distinguish between past and active infections are the main limitations of this approach. Here, we present a sensitive and specific novel strategy to detect and quantify TES, aiming to identify active cases of HT. High specificity is achieved by making use of nanobodies (Nbs), recombinant single variable domain antibodies obtained from camelids, that due to their small molecular size (15kDa) can recognize hidden epitopes not accessible to conventional antibodies. High sensitivity is attained by the design of an electrochemical magnetosensor with an amperometric readout with all components of the assay mixed in one single step. Through this strategy, 10-fold higher sensitivity than a conventional sandwich ELISA was achieved. The assay reached a limit of detection of 2 and15 pg/ml in PBST20 0.05% or serum, spiked with TES, respectively. These limits of detection are sufficient to detect clinically relevant toxocaral infections. Furthermore, our nanobodies showed no cross-reactivity with antigens from Ascaris lumbricoides or Ascaris suum. This is to our knowledge, the most sensitive method to detect and quantify TES so far, and has great potential to significantly improve diagnosis of HT. Moreover, the characteristics of our electrochemical assay are promising for the development of point of care diagnostic systems using nanobodies as a versatile and innovative alternative to antibodies. The next step will be the validation of the assay in clinical and epidemiological contexts

HOW TO MAKE NATURA 2000 WORK PROPERLY? : SOCIO-ECONOMIC, LEGAL AND ECOLOGICAL MANAGEMENT : "SELNAT"

This report includes results obtained from the SELNAT research project, conducted between February 2006 and January 2008, under the auspices of the Belgian Science Policy. The principal subject of this project is the implementation of Natura 2000. The Natura 2000 network of protected areas, made up of sites designated under the Community Birds (BD) and Habitats Directives (HD), is a key pillar of action for the conservation of biodiversity (European Commission, 2008). It is central to achieve the commitment to reverse the decline of biodiversity in the European Union by the year 2010 made at the European Council meeting in Gothenburg in June 2001. It aims at sustainable conservation of habitats and species of community importance, taking into account (i) economic, social and cultural requirements and (ii) regional and local circumstances. Central to the Directives is the creation of a Europe-wide ecological network of protected sites – the Natura 2000 Network – which is destined to conserve over a thousand rare, threatened and endemic species and some 220 Natural habitats listed in their annexes. Around 24,000 sites have been included in the Network so far. (European Commission, 2008) Now that the network set-up is nearing completion, there is a need to increase the focus on the active management of the sites so as to ensure long-term conservation and the achievement of the economic and social objectives of the network (CEE, 2004.) This in turn also raises the question of finding the appropriate management strategy, instruments and sufficient financing (at all levels). The principal question for Member States is how to manage Natura 2000 sites to reach the (juridical fixed) ecological targets in the most cost-efficient way, taking into account economic and social objectives and constraints. Ecologists and nature organisations often start from an techno-ecocentric paradigm: ‘How to conserve and manage species and habitats?’, in order to tackle the question mentioned above. The paradigm starts from the opinion that ‘diversity of species and habitats’ is important as such (while this is believed to be important for several reasons). This approach has been criticised lately for being based on a too narrow set of values. It has not provided enough opportunities for combining nature conservation with other forms of land use such as agriculture, forestry or tourism. In several countries this led to difficulties as regards the co-operation of local stakeholders (Jongman & Kristiansen, 1998). On the other hand, the current biodiversity crisis is a direct result of the way in which society has chosen to interact with its Natural environment. If the causes of the problem are social, it stands to reason that the policies striving to solve the problem will need to be based on a solid understanding of social structures and processes, if they are to have any effect. In this research project we tried to study the management of Natura 2000 sites from a ‘sustainability’ paradigm, instead of from the ecocentric paradigm. The central research question is therefore formulated as ‘How to manage Natura 2000 properly, to contribute to a (local) sustainable society?’ With this research we hope to give decision-makers new insights on the economic, social, and environmental consequences of Natura 2000 management and to guide them in the development of more adequate and sustainable policies for the management of Natura 2000-sites. In the first chapter the general objectives and approach of this project are described. The second chapter gives an overview of some of the current bottlenecks for nature conservation and Natura 2000. The results of the research on the elaboration of strategies for Natura 2000 sites are summarizes in chapter tree. Conclusions and recommendations are presented in the last chapter. More information on the research is documented in the different appendixes. During the research, we benefited from contacts with many persons, and more especially in the scope of a Users’ Committee. Besides the representatives of the Belgian Science Policy, we would like to thank all members of the Users’ Committee, among which those who supported us and/or participated in one or several of the meetings,SELNA

Fast one-step ultrasensitive detection of toxocara canis antigens by a nanobody-based electrochemical magnetosensor

Human toxocariasis (HT) is a cosmopolitan zoonotic disease caused by the migration of the larval stage of the roundworm Toxocara canis. Current HT diagnostic methods do not discriminate between active and past infections. Here, we present a method to quantify Toxocara excretory/secretory antigen, aiming to identify active cases of HT. High specificity is achieved by employing nanobodies (Nbs), single domain antigen binding fragments from camelid heavy chain-only antibodies. High sensitivity is obtained by the design of an electrochemical magnetosensor with an amperometric read-out. Reliable detection of TES antigen at 10 and 30 pg/mL level was demonstrated in phosphate buffered saline and serum, respectively. Moreover, the assay showed no cross-reactivity with other nematode antigens. To our knowledge, this is the most sensitive method to quantify the TES antigen so far. It also has great potential to develop point of care diagnostic systems in other conditions where high sensitivity and specificity are required

Wild populations of malaria vectors can mate both inside and outside human dwellings

Background Wild populations of Anopheles mosquitoes are generally thought to mate outdoors in swarms, although once colonized, they also mate readily inside laboratory cages. This study investigated whether the malaria vectors Anopheles funestus and Anopheles arabiensis can also naturally mate inside human dwellings. Method Mosquitoes were sampled from three volunteer-occupied experimental huts in a rural Tanzanian village at 6:00 p.m. each evening, after which the huts were completely sealed and sampling was repeated at 11:00 p.m and 6 a.m. the next morning to compare the proportions of inseminated females. Similarly timed collections were done inside local unsealed village houses. Lastly, wild-caught larvae and pupae were introduced inside or outside experimental huts constructed inside two semi-field screened chambers. The huts were then sealed and fitted with exit traps, allowing mosquito egress but not entry. Mating was assessed in subsequent days by sampling and dissecting emergent adults caught indoors, outdoors and in exit traps. Results Proportions of inseminated females inside the experimental huts in the village increased from approximately 60% at 6 p.m. to approximately 90% the following morning despite no new mosquitoes entering the huts after 6 p.m. Insemination in the local homes increased from approximately 78% to approximately 93% over the same time points. In the semi-field observations of wild-caught captive mosquitoes, the proportions of inseminated An. funestus were 20.9% (95% confidence interval [CI]: +/- 2.8) outdoors, 25.2% (95% CI: +/- 3.4) indoors and 16.8% (+/- 8.3) in exit traps, while the proportions of inseminated An. arabiensis were 42.3% (95% CI: +/- 5.5) outdoors, 47.4% (95% CI: +/- 4.7) indoors and 37.1% (CI: +/- 6.8) in exit traps. Conclusion Wild populations of An. funestus and An. arabiensis in these study villages can mate both inside and outside human dwellings. Most of the mating clearly happens before the mosquitoes enter houses, but additional mating happens indoors. The ecological significance of such indoor mating remains to be determined. The observed insemination inside the experimental huts fitted with exit traps and in the unsealed village houses suggests that the indoor mating happens voluntarily even under unrestricted egress. These findings may inspire improved vector control, such as by targeting males indoors, and potentially inform alternative methods for colonizing strongly eurygamic Anopheles species (e.g. An. funestus) inside laboratories or semi-field chambers

Non-typhoidal Salmonella intestinal carriage in a Schistosoma mansoni endemic community in a rural area of the Democratic Republic of Congo

BACKGROUND: Clinical observations and animal studies have suggested that Salmonella intestinal carriage is promoted by concurrent Schistosoma infection. The present study assessed association of Salmonella intestinal carriage and Schistosoma mansoni infection among individuals in a Schistosoma endemic area in sub-Saharan Africa. METHODS: From November 2015 to March 2016, a cross-sectional community-wide study was conducted in Kifua II, a rural village in Kongo Central Province, Democratic Republic of Congo. Stool samples were collected and analyzed for Salmonella intestinal carriage (culture) and Schistosoma mansoni infection (Kato Katz microscopy with determination of egg load). Salmonella Typhimurium and Enteritidis isolates were assessed for genetic similarity with blood culture isolates obtained during the same period in a neighboring hospital using multi-locus variable-numbers tandem repeat analysis (MLVA). RESULTS: A total of 1,108 participants were included (median age 15 years (IQR: 7-36), male-to-female ratio of 1:1.1). The overall prevalence of Schistosoma mansoni infection and non-typhoidal Salmonella carriage was 51.2% (95% CI: 48.2-54.1) and 3.4% (95% CI: 2.5-4.7) respectively, with 2.2% (95% CI: 1.5-3.2) of participants coinfected. The proportion of Salmonella carriage tended to be higher among Schistosoma mansoni infected participants compared to non-infected participants but this difference did not reach statistical significance (4.2% versus 2.6%, p = 0.132). However, the proportion of Salmonella carriage among participants with a heavy Schistosoma mansoni infection was significantly higher compared to those with a light and moderate infection (8.7% versus 3.2%, p = 0.012) and compared to Schistosoma mansoni negatives (8.7% versus 2.6%, p = 0.002). The 38 Salmonella isolates comprised five and four Enteritidis and Typhimurium serotypes respectively, the majority of them had MLVA types identical or similar to those observed among blood culture isolates. CONCLUSION: Salmonella intestinal carriage was associated with a heavy intensity of Schistosoma mansoni infection. Further studies are needed to address causation

Non-typhoidal Salmonella intestinal carriage in a Schistosoma mansoni endemic community in a rural area of the Democratic Republic of Congo

BACKGROUND: Clinical observations and animal studies have suggested that Salmonella intestinal carriage is promoted by concurrent Schistosoma infection. The present study assessed association of Salmonella intestinal carriage and Schistosoma mansoni infection among individuals in a Schistosoma endemic area in sub-Saharan Africa. METHODS: From November 2015 to March 2016, a cross-sectional community-wide study was conducted in Kifua II, a rural village in Kongo Central Province, Democratic Republic of Congo. Stool samples were collected and analyzed for Salmonella intestinal carriage (culture) and Schistosoma mansoni infection (Kato Katz microscopy with determination of egg load). Salmonella Typhimurium and Enteritidis isolates were assessed for genetic similarity with blood culture isolates obtained during the same period in a neighboring hospital using multi-locus variable-numbers tandem repeat analysis (MLVA). RESULTS: A total of 1,108 participants were included (median age 15 years (IQR: 7-36), male-to-female ratio of 1:1.1). The overall prevalence of Schistosoma mansoni infection and non-typhoidal Salmonella carriage was 51.2% (95% CI: 48.2-54.1) and 3.4% (95% CI: 2.5-4.7) respectively, with 2.2% (95% CI: 1.5-3.2) of participants coinfected. The proportion of Salmonella carriage tended to be higher among Schistosoma mansoni infected participants compared to non-infected participants but this difference did not reach statistical significance (4.2% versus 2.6%, p = 0.132). However, the proportion of Salmonella carriage among participants with a heavy Schistosoma mansoni infection was significantly higher compared to those with a light and moderate infection (8.7% versus 3.2%, p = 0.012) and compared to Schistosoma mansoni negatives (8.7% versus 2.6%, p = 0.002). The 38 Salmonella isolates comprised five and four Enteritidis and Typhimurium serotypes respectively, the majority of them had MLVA types identical or similar to those observed among blood culture isolates. CONCLUSION: Salmonella intestinal carriage was associated with a heavy intensity of Schistosoma mansoni infection. Further studies are needed to address causation.status: publishe

Effects of competition, shade and soil conditions on the recolonization of three forest herbs in tree-planted riparian zones

Questions: In mesic forests, ecological filters due to past agricultural land-use reduce forest herbs recolonization. Is the recruitment of such species also limited in tree-planted riparian zones, by local filters such as competition, shade level and soil conditions? Location: Two agricultural watersheds, southeastern Québec, Canada. Methods: Three herbs characteristic of natural riparian forests were selected for this study: one graminoid, Glyceria striata, and two ferns, Matteuccia struthiopteris and Onoclea sensibilis. Effects of shade level (75% versus 50%) and soil type (forest versus agricultural soil) on seedling emergence were evaluated in a seed-sowing greenhouse experiment. In a two-year transplant field experiment, seedling and sporophyte establishment was monitored in five natural riparian forests and five tree-planted post-agricultural riparian zones on microsites with understory vegetation kept intact or cleared and on forest or agricultural soils. Using a priori contrasts, we assessed the influence of habitat type (natural riparian forests or tree-planted riparian zones), competition and post-agricultural soil type on transplant survival and growth. Results: Seedling emergence tended to be higher on forest soils for G. striata while sporophyte emergence increased under 75% shade for M. struthiopteris. Transplanted seedlings and sporophytes of the three species survived and grew as well in tree-planted riparian zones as in natural riparian forests. In tree-planted riparian zones however, competing understory vegetation reduced the survival and growth of G. striata and agricultural soil reduced the growth of M. struthiopteris. For O. sensibilis, only sporophyte survival was reduced by competition in tree-planted riparian zones. Conclusions: Planting trees in post-agricultural riparian zones fosters an establishment of forest herbs similar than those observed in natural riparian forests. Additional environmental filters specific to tree-planted riparian zones however offset the positive influence of trees and limit the recolonization of the three studied species. Considering the partial restoration success of establishment niches by tree planting, controlling spontaneous vegetation after tree planting is advised when conceivable and cost-effective to promote the recolonization of environmentally-limited forest herbs. Long-term transplant experiments should be more largely conducted to identify the ecological filters that reduce plant recolonization, and thereby design the most effective restoration strategies

Ecological species groups in forest communities in South Belgium

Cluster analysis, correspondence analysis and the method of ecological profiles were used to determine and characterize ecological species groups in woodlands in South Belgium. Two data sets were used, one composed of 260 relevés, the other of 130 relevés with soil analyses (A1). Correspondence analysis points out the most important factors influencing the floristic composition of the stations. © 1989 Kluwer Academic Publishers.SCOPUS: ar.jFLWINinfo:eu-repo/semantics/publishe