666 research outputs found
Ecology and Epidemiology of Integrated Malaria Vector Management in Dar es Salaam, Tanzania
No full textMalaria remains one of the major contributors to the global burden of disease with approximately 70% of the clinical malaria attacks occurring in sub-Saharan Africa. Sub- Saharan Africa has the highest risk as ideal climatic conditions for transmission coincide with occurrence of some of the most efficient malaria vectors, namely Anopheles gambiae s.s., Anopheles arabiensis and Anopheles funestus.. Even though it is estimated that by the year 2030 more than 50% of the African population will live in towns and cities, relatively little is known about urban malaria epidemiology, larval ecology and adult mosquito behaviour. Although integrated malaria control programs including environmental management and larviciding have proven successful before the Global Eradication Campaign started in 1955, they were neglected after the invention of DDT. Lately interest into these control measures has revived but it remains to be determined whether they are feasible and cost-effective in urban Africa. The overall goal of the research presented in this thesis was to enhance current understanding of urban malaria epidemiology and ecology and to take an in-depth look at the effectiveness of larviciding with Bacillus thuringiensis (Bti) in the context of the Urban Malaria Control Program (UMCP) in Dar es Salaam, Tanzania. Our findings are based on data derived from the first 3 years of the UMCP, where data collection started in March 2004. The project area includes 5 wards in each of the 3 municipalities which consist of 67 mitaa covering an area of 55 km2 in which 611,871 people lived during the population census of 2002. Achieving the UMCPs objectives fundamentally relies on three component activities: 1) Mapping and surveillance of potential Anopheles breeding sites, 2) Monitoring of adult mosquito densities, and 3) Household surveys with questionnaires and blood smears testing for malaria parasite infection. In the third year of the UMCP, beginning in March 2006, the routine application of the microbial larvicides Bti in open habitats and Bs in closed habitats was initiated in 3 of the 15 wards in the study area, adding to existing interventions such as bednets, house screening, ceiling boards, repellents, spray and coils. At the same time a detailed survey of mosquito biting behaviour, human behaviour and domestic protection measures was conducted in 12 Ten Cell Units (TCU), the smallest subunit of local government in Tanzania, which presented the highest An. gambiae s.l. densities during the early period of the UMCP surveillance system. Human landing catch (HLC) was conducted in 216 houses on an hourly basis indoors and outdoors from 6 pm till 7 am and residents were interviewed about their sleeping behaviour, where they spend their evenings and what kind of preventive measures against malaria they use. Personal protection of an insecticide treated net (ITN) was evaluated using an extension of a recently developed mathematical model. Overall An. gambiae s.l. exhibited a classical hourly biting pattern. In contrast one of the complex’s component sibling species, namely An. arabiensis, had an early biting peak before 10 pm. Both sibling species, namely An. gambiae s.s. and An. arabiensis, as well as An. funestus and An. coustani were highly exophagic. This behaviour led to a reduced personal protection against exposure to An. gambiae s.s. by ITNs which conferred 59% reduction of exposure in Dar es Salaam compared to 70% in rural Tanzania. An. arabiensis is a vector of only modest importance in Dar es Salaam which is fortunate because ITNs only conferred 38% protection against exposure to this species of mosquito. ITNs conferred slightly less protection against exposure to malaria vectors in good quality houses. This is mainly because people living in good houses tend to spend more time indoors before they go to bed. An. gambiae s.l. is the most important vector in Dar es Salaam , responsible for an EIR (entomological inoculation rate) of 1.00 infectious bites per person per year whereas An. funestus has an EIR of 0.13. Surprisingly, An. coustani also acts as a notable vector in Dar es Salaam with an EIR of 0.20 infectious bites per person per year. Malaria transmission is seasonal with two peaks of malaria prevalence during and after the two rainy seasons. Malaria prevalence was only related to EIR in children under 5 years of age, with a classical ageprevalence distribution similar to most of rural Africa. Malaria prevalence steadily declined from 2004 onwards as the use of window screenings, ceiling boards and more effective drugs like amodiaquine and artemisin-based drugs increased. ITNs (prevalence reduction estimate 20%, 95% CI 0%-36%; P=0.060; year 1) and ceiling boards (prevalence reduction estimate 22%, 95% CI 3%-38%; P=0.026; year 2) conferred modest personal protection and reduced malaria prevalence by approximately one fifth. By comparison, a much greater reduction (prevalence reduction estimate 50%, 95% CI 20%-64%; P=0.002) of malaria prevalence was achieved by larviciding with Bti. This was mainly achieved through major reductions of An. gambiae during July and August when most of the sporozoite infected mosquitoes were caught, combined with all-year-round suppression of the secondary vectors, namely An. funestus and An. coustani. This major achievement was only possible through the novel surveillance and staff management procedures developed by the UMCP to enable effective community based implementation in a decentralized manner. Standards of the surveillance improved greatly after the onset of the program with realized reaction times to vector surveillance at observations being one day, week and month at ward, municipality and city level, respectively. These results of changing biting behaviour of the main malaria vectors in urban settings and the therefore lower but still useful personal protection offered by ITNs call for additional complementary vector control methods such as environmental management or larviciding. The UMCP demonstrated that major reductions in malaria prevalence can be achieved through routine application of microbial larvicides with its new practical management and surveillance system. As these represent the early results of the program, we expect substantial improvement with time and investment. Here we demonstrated for the first time since before the Global Eradication Campaign era, a success story of a malaria control program integrating larviciding, which could be easily adapted by other African cities as a cost-effective option for malaria prevention
Die ‚noethische‘ Funktion von Wissenschaftssprache und -mustern bei Ulrike Draesner
No full textUlrike Draesner, in her multifaceted activity as a scholar, translator, essayist, but above all author of poetry
and prose, develops a discourse on the body, landscapes and memory that is always polyphonic and cross-
linguistic. Memory travels through unexpected connections between areas of knowledge and experience,
capable of linking organic and inorganic nature, ancient world memory, individual and collective historical
memory and post-memory, theory of knowledge and ethics of living together among people, between
humans and things, between human kind and nature.
In my contribution I will be trying, through case-studies, to highlight the poetic, ethical, creative, therefore
po(i)ethical role played by scientific languages and lexika in Ulrike Draesner's writing.
As a “poeta docta”, Draesner is an artist and not as a scientist or philosopher. The aggregations of sense and
memory do not only travel on the logic of images and themes, but also on the surprising intersections
between sense and sound, as well as between different languages
Dose-response tests and semi-field evaluation of lethal and sub-lethal effects of slow release pyriproxyfen granules (Sumilarv®0.5G) for the control of the malaria vectors Anopheles gambiae sensu lato.
No full textBACKGROUND: Recently research has shown that larviciding can be an effective tool for integrated malaria vector control. Nevertheless, the uptake of this intervention has been hampered by the need to re-apply larvicides frequently. There is a need to explore persistent, environmentally friendly larvicides for malaria vector control to reduce intervention efforts and costs by reducing the frequency of application. In this study, the efficacy of a 0.5% pyriproxyfen granule (Surmilarv®0.5G, Sumitomo Chemicals) was assessed for the control of Anopheles gambiae sensu stricto and Anopheles arabiensis, the major malaria vectors in sub-Saharan Africa. METHODS: Dose-response and standardized field tests were implemented following standard procedures of the World Health Organization's Pesticide Evaluation Scheme to determine: (i) the susceptibility of vectors to this formulation; (ii) the residual activity and appropriate retreatment schedule for field application; and, (iii) sub-lethal impacts on the number and viability of eggs laid by adults after exposure to Sumilarv®0.5G during larval development. RESULTS: Anopheles gambiae s.s. and An. arabiensis were highly susceptible to Sumilarv®0.5G. Estimated emergence inhibition (EI) values were very low and similar for both species. The minimum dosage that completely inhibited adult emergence was between 0.01-0.03 parts per million (ppm) active ingredient (ai). Compared to the untreated control, an application of 0.018 ppm ai prevented 85% (95% confidence interval (CI) 82%-88%) of adult emergence over six weeks under standardized field conditions. A fivefold increase in dosage of 0.09 ppm ai prevented 97% (95% CI 94%-98%) emergence. Significant sub-lethal effects were observed in the standardized field tests. Female An. gambiae s.s. that were exposed to 0.018 ppm ai as larvae laid 47% less eggs, and females exposed to 0.09 ppm ai laid 74% less eggs than females that were unexposed to the treatment. Furthermore, 77% of eggs laid by females exposed to 0.018 ppm ai failed to hatch, whilst 98% of eggs laid by females exposed to 0.09 ppm ai did not hatch. CONCLUSION: Anopheles gambiae s.s. and An. arabiensis are highly susceptible to Sumilarv®0.5G at very low dosages. The persistence of this granule formulation in treated habitats under standardized field conditions and its sub-lethal impact, reducing the number of viable eggs from adults emerging from treated ponds, enhances its potential as malaria vector control tool. These unique properties warrant further field testing to determine its suitability for inclusion in malaria vector control programmes
TRAUM: Transforming Author Museums, 2019
No full textWhat roles have author museums as creators of cultural identity? What kind of representations do they use to communicate knowledge about literature and its authors? How are real and literary spaces, texts and objects interlinked? Author museums are in the public imagination often associated with an old-fashioned cult of the author, they are being transformed into interactive spaces in line with changing understandings of literature, developments in exhibition practices and larger processes of democratization. This interdisciplinary project aimed to provide analyses of museums as cultural texts and performative spaces of memory and production. In the past years, the alleged crisis of the humanities has been a recurring topic of debate. While criticism has been levelled at the humanities for lack of relevance, informal polls made in various countries across Europe asking for the most important personality in national history have consistently placed artists on the top, often writers, and in the case of Norway, Henrik Ibsen. There is a paradoxical relationship between the discourse of the uselessness of humanities and the actual interest in and identification with some of its actors. The project aimed to investigate how and why (certain) writers and literature have been turned into cultural heritage, helped by the display of auratic places such as their homes in combination with the aestheticization of personal "relics" within specific cultural-political contexts. Combining humanities, social sciences and artistic perspectives, it will critically reflect on existing and historical exhibition strategies and consider alternative and innovative ways of displaying literature, focusing on the potentials of author museums and other literary museums and centres as sites of cultural production and literary creativity. On a meta-level the project aimed to contribute to a better understanding of how to communicate the relevance of humanities to the public. The project is part of the NFR project “TRAUM-Transforming Author Museums (251225)”. The focus of the sub-project is on exhibitions in author homes. The analysis includes the role of archival material in exhibitions (published article by Ulrike Spring), communication processes in literary museums and the author's role as ghost in author homes (articles in preparation by Ulrike Spring and Johan Schimanski). For further information about ”TRAUM: Transforming Author Museums, 2019”, please contact the principal investigator
Analysing the role of semiochemicals in the oviposition substrate choices of the malaria vector mosquito Anopheles gambiae sensu lato
No full textThe search for tools that target malaria vector that resist insecticides and bite outdoors has become a research priority. Such tools will be necessary for managing residual malaria transmission and hastening the eradication of this devastating disease. This study investigated chemicals that potentially affect the oviposition substrate choices of Anopheles gambiae sensu lato (s.l.). It is foreseen that increased knowledge of the oviposition behaviour of this major malaria vectors and chemicals cues that mediate oviposition site-selection can be applied in the development of additional sampling methods and alternative interventions that to trap gravid malaria mosquitoes outdoors.
To achieve a reproducible high egg-laying success of An. gambiae sensu stricto (s.s.) and An. arabiensis four factors were evaluated: (1) the time provided for mating; (2) the impact of cage size, mosquito age and female body size on insemination; (3) the peak oviposition time; and, (4) the host source of blood meals. Then four bioassays were optimised for studying oviposition responses of An. gambiae s.s. in the laboratory and semi-field conditions: a WHO-tube bioassay and a wind-tunnel that detected short-range attraction in the laboratory; a two-tier choice egg-count bioassay that compared the relative proportion of eggs laid in substrates in the laboratory; and a modified BG Sentinel mosquito gravid trap that evaluated long-range attraction of gravid females to olfactory cues in the semi-field. Finally, the oviposition responses of gravid An. gambiae s.s. mosquitoes to water vapour, Bermuda grass hay infusion (hay infusion), and putative semiochemicals identified from the hay infusion and a soil infusion previously shown to elicit higher egg deposition compared to filtered Lake Victoria water (lake water) in two choice egg-count bioassays (Herrera-Varela et al. 2014), were evaluated.
High oviposition rates [84%, 95% confidence interval (CI) 77-89%] were achieved when 300 male and 300 blood-fed female An. gambiae s.s. were held together in a cage for four days. The chance of oviposition in the mosquitoes dropped when human host source of blood-meal was substituted with a rabbit (Odds ratio (OR) 0.30, 95% CI 0.14-0.66) but egg-numbers per female were not affected. All four optimised oviposition bioassays effectively showed between 15-20% shifts in oviposition substrate choices of mosquitoes with 80% statistical power and 5% significance. Using the WHO-tube bioassay, gravid An. gambiae s.s. were shown to be 2.4 times (95% CI 1.3-4.7 times) more likely to move towards high humidity in still air compared to non-gravid
Preamble mosquitoes. This was more pronounced in the airflow olfactometer where the gravid mosquitoes were 10.6 times (95% CI 5.4-20.8 times) more likely to fly into a chamber with water than a dry chamber.
Two-choice egg-count bioassays showed that An. gambiae s.s. were less likely to lay eggs in six-day old hay infusion (OR 0.10, 95% CI 0.03-0.33) compared to lake water. Ten putative semiochemicals were identified from the hay infusion using mass spectrometry and published electrophysiology data: 4-hepten-1-ol, 4-ethylphenol, phenylmethanol, 2-phenylethanol, indole, phenol, 3-methylindole, 3-methyl-1-butanol, 4-ethylphenol, and nonanal. Tested in two-choice egg-count bioassays, the first four listed compounds had no effect on egg deposition at the tested concentrations (between 0.01-5 parts per million) but mosquitoes were less likely to lay eggs in at least one concentration of 3-methylindole (OR 0.39, 95% CI 0.21-0.71), indole (OR 0.57, 95% CI 0.37-0.87), 3-methyl-1-butanol (OR 0.32, 95% CI 0.22-0.47), phenol (OR 0.55, 0.32-0.95), 4-methylphenol (OR 0.32, 0.18-0.57) and nonanal (OR 0.66, 95% CI 0.47-0.91) compared to lake water. In contrast to the hay infusion and hay infusion volatiles, An. gambiae s.s. were about two times more likely to lay eggs in cedrol, a sesquiterpene alcohol identified from the soil infusion, compared to lake water (OR 1.84, 95% CI 1.16-2.91). Cedrol attracted twice as many gravid mosquitoes in the semi-field also (OR 1.92, 95% CI 1.63-2.27). In the field, modified BG-Sentinel traps, electrocuting nets and OviART gravid traps with lake water and cedrol were three times more likely to trap malaria mosquitoes compared to traps with water only (OR 3.3, 95% CI 1.4-7.9).
In conclusion, water vapour was shown to be a strong, non-specific pre-oviposition attractant for gravid An. gambiae s.s. in still air and moving air. It is probably the long range cue that gravid An. gambiae s.l. use to detect the presence aquatic habitats beyond the range of chemical cues. Evidence showed that An. gambiae s.s. discriminate between potential oviposition substrates and that this selective process is in-part mediated by volatile organic compounds originating from the site. Water vapour leads gravid mosquitoes to aquatic sites but semiochemicals enable the mosquitoes to discriminate and select between potential habitats. It was demonstrated that synthetic equivalents of semiochemicals found to attract gravid mosquitoes such as cedrol can be used to trap malaria mosquitoes outdoors
Novel insecticides and application strategies for malaria vector control
No full textTargeting malaria vector mosquitoes outdoors has become a research priority to address residual malaria transmission. Mosquito larval source management provides an excellent and well established tool. However, there is a need to reduce the cost and effort of larviciding programmes by testing persistent larvicides that reduce the frequency of application and by exploring novel strategies of application. This thesis aimed to evaluate two larval control agents, with unique mode of actions: the self-spreading silicone-based film Aquatain Mosquito Formulation (AMF) and the pyriproxyfen-based insect growth regulator Sumilarv®.
Dose-response tests and standardized field tests were conducted to assess the susceptibility of Anopheles gambiae sensu stricto and An. arabiensis to the two insecticides and determine their residual activity. Adults that survived exposure to larvicide-treated water at the larval stages were assessed for possible effects on fecundity and fertility. Both species were highly susceptible to both control agents at very low doses. Both control agents provided residual control of up to six weeks. Adults that emerged from larvicide-treated water laid fewer eggs and had low egg hatching rates. Consequently, the impact of three-weekly operational application of pyriproxyfen to habitats in the western Kenya highlands was assessed by comparing adult vector emergences from aquatic habitats in intervention and non-intervention sites. Pyriproxyfen application led to over 80% adult vector emergence inhibition from treated aquatic habitats.
To assess if larvicide-treated water could serve as ‘reproductive sinks’ for gravid mosquitoes, the oviposition response of gravid An. gambiae s.s. to water treated with pyriproxyfen or surface film was tested under semi-field conditions using squares of electrocuting nets. Larvicide-treated water did not affect the pre-oviposition behaviour of gravid females. This study however did not demonstrate that ‘attract and kill’ strategies could be used for control of malaria vectors as the addition of an oviposition attractant to ponds containing larvicide-treated water did not increase the proportion of gravid females orienting towards this pond.
To explore the effect of pyriproxyfen exposure on adults, individual An. gambiae s.s. and Cx. quinquefasciatus females were exposed to pyriproxyfen at seven time points around blood feeding. Fecundity and ability to transfer pyriproxyfen to an oviposition substrate
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were studied in the laboratory. The impact of pyriproxyfen was dependent on the time of exposure. Females were nearly completely sterilized when exposure occurred around the blood meal while pyriproxyfen was only transferred by females that were exposed while gravid and close to egg-laying time.
Consequently, a baiting station for gravid females was developed and semi-field experiments implemented to explore the transfer of pyriproxyfen by gravid An. gambiae s.s. from the baiting station to aquatic habitats. Horizontal transfer was observed but the extent of emergence inhibition was dependent on the distance of the habitat from the baiting station. Only the closest habitats received sufficient pyriproxyfen to control significant numbers of offspring.
In conclusion, this study demonstrated great potential of the two control agents for the control of vector immature stages and adults caused by sterilizing effects of pyriproxyfen. Results suggest that they are suitable for inclusion into integrated vector management programmes for malaria control. Auto-dissemination of pyriproxyfen however, appears not to be a feasible strategy for malaria vector control
Larval habitat discrimination by the African malaria vector Anopheles gambiae sensu lato: Observations from standardized experiments and field studies
No full textCurrent malaria vector control strategies in Africa target indoor resting and biting mosquitoes and rely heavily on a small number of insecticides. These interventions have lead to the selection of insecticide resistance, behavioural adaptations of the vectors and leave naturally exophilic species nearly untouched. Gravid Anopheles gambiae s.l. female searching for an oviposition site would be a novel target for vector control. However, little is known about the oviposition-site selection behaviour (criteria) of this mosquito.
The major aim of the presented research was to investigate if gravid An. gambiae s.l make informed choices when selecting an oviposition site and to identify physical, chemical and biological parameters associated with these choices under standardized experimental and natural field conditions.
Standardized field tests and dual-choice oviposition bioassays were used to evaluate responses to soil and rabbit food pellets infusions and habitat water and also to test if bacteria and the volatile chemicals that bacteria produce are relevant to habitat selection. A case–control approach was used to study natural aquatic habitats on Rusinga Island in Lake Victoria during the long rainy season in 2012 to compare the characteristics of habitats colonized (cases) and not colonized (controls) by early instar Anopheles larvae. Factors evaluated included biological characteristics of the sites, zooplankton, invertebrate fauna, physical parameters, nutrients, bacteria communities and volatile chemicals released from the water. Multivariate analyses were used to investigate associations between oviposition site characteristics and habitat selection by Anopheles.
The experimental work illustrated that wild and caged An. gambiae s.l. females discriminate between potential aquatic habitats for oviposition and gravid An. gambiae s.l. female select suitable habitats using preferred and avoided chemical cues from water bodies. It furthermore emphasizes that natural infusions can be used to manipulate the oviposition behaviour of An. gambiae s.l.. In the field no evidence was found that bacteria from natural habitat water were involved in habitat selection. Although chemical cues were highly diverse analysis suggests that cases and control habitats differ in the headspace volatile profile of the water. High turbidity >200 nephelometric turbidity units (NTU) was the only environmental factor strongly associated with cases. Other risk factors were higher grass coverage (positive association), and the abundance of creeping water bugs of the family Naucoridae and fish (negative associations).
This study demonstrates that gravid An. gambiae females choose suitable habitats for oviposition using a complex system of chemical and visual cues from water bodies. Habitats preferred by An. gambiae exhibited distinct and measurable characteristics that can be potentially exploited to attract and kill gravid females to improve malaria vector monitoring and control
Community-owned resource persons for malaria vector control: enabling factors and challenges in an operational programme in Dar es Salaam, United Republic of Tanzania.
No full textUNLABELLED\ud
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ABSTRACT:\ud
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BACKGROUND\ud
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Community participation in vector control and health services in general is of great interest to public health practitioners in developing countries, but remains complex and poorly understood. The Urban Malaria Control Program (UMCP) in Dar es Salaam, United Republic of Tanzania, implements larval control of malaria vector mosquitoes. The UMCP delegates responsibility for routine mosquito control and surveillance to community-owned resource persons (CORPs), recruited from within local communities via the elected local government.\ud
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METHODS\ud
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A mixed method, cross-sectional survey assessed the ability of CORPs to detect mosquito breeding sites and larvae, and investigated demographic characteristics of the CORPs, their reasons for participating in the UMCP, and their work performance. Detection coverage was estimated as the proportion of wet habitats found by the investigator which had been reported by CORP. Detection sensitivity was estimated as the proportion of wet habitats found by the CORPS which the investigator found to contain Anopheles larvae that were also reported to be occupied by the CORP.\ud
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RESULTS\ud
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The CORPs themselves perceived their role as professional rather than voluntary, with participation being a de facto form of employment. Habitat detection coverage was lower among CORPs that were recruited through the program administrative staff, compared to CORPs recruited by local government officials or health committees (Odds Ratio = 0.660, 95% confidence interval = [0.438, 0.995], P = 0.047). Staff living within their areas of responsibility had > 70% higher detection sensitivity for both Anopheline (P = 0.016) and Culicine (P = 0.012): positive habitats compared to those living outside those same areas.\ud
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DISCUSSION AND CONCLUSIONS\ud
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Improved employment conditions as well as involving the local health committees in recruiting individual program staff, communication and community engagement skills are required to optimize achieving effective community participation, particularly to improve access to fenced compounds. A simpler, more direct, less extensive community-based surveillance system in the hands of a few, less burdened, better paid and maintained program personnel may improve performance and data quality
Larvicidal Effects of a Neem (Azadirachta indica) Oil Formulation on the Malaria Vector Anopheles Gambiae.
No full textLarviciding is a key strategy used in many vector control programmes around the world. Costs could be reduced if larvicides could be manufactured locally. The potential of natural products as larvicides against the main African malaria vector, Anopheles gambiae s.s was evaluated. To assess the larvicidal efficacy of a neem (Azadirachta indica) oil formulation (azadirachtin content of 0.03% w/v) on An. gambiae s.s., larvae were exposed as third and fourth instars to a normal diet supplemented with the neem oil formulations in different concentrations. A control group of larvae was exposed to a corn oil formulation in similar concentrations. Neem oil had an LC50 value of 11 ppm after 8 days, which was nearly five times more toxic than the corn oil formulation. Adult emergence was inhibited by 50% at a concentration of 6 ppm. Significant reductions on growth indices and pupation, besides prolonged larval periods, were observed at neem oil concentrations above 8 ppm. The corn oil formulation, in contrast, produced no growth disruption within the tested range of concentrations. Neem oil has good larvicidal properties for An. gambiae s.s. and suppresses successful adult emergence at very low concentrations. Considering the wide distribution and availability of this tree and its products along the East African coast, this may prove a readily available and cheap alternative to conventional larvicides
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