84 research outputs found

    The cost of tsetse control using 'Tiny Targets' in the sleeping sickness endemic forest area of Bonon in Côte d'Ivoire: Implications for comparing costs across different settings.

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    BACKGROUND Work to control the gambiense form of human African trypanosomiasis (gHAT), or sleeping sickness, is now directed towards ending transmission of the parasite by 2030. In order to supplement gHAT case-finding and treatment, since 2011 tsetse control has been implemented using Tiny Targets in a number of gHAT foci. As this intervention is extended to new foci, it is vital to understand the costs involved. Costs have already been analysed for the foci of Arua in Uganda and Mandoul in Chad. This paper examines the costs of controlling Glossina palpalis palpalis in the focus of Bonon in Côte d'Ivoire from 2016 to 2017. METHODOLOGY/PRINCIPAL FINDINGS Some 2000 targets were placed throughout the main gHAT transmission area of 130 km2 at a density of 14.9 per km2. The average annual cost was USD 0.5 per person protected, USD 31.6 per target deployed of which 12% was the cost of the target itself, or USD 471.2 per km2 protected. Broken down by activity, 54% was for deployment and maintenance of targets, 34% for tsetse surveys/monitoring and 12% for sensitising populations. CONCLUSIONS/SIGNIFICANCE The cost of tsetse control per km2 of the gHAT focus protected in Bonon was more expensive than in Chad or Uganda, while the cost per km2 treated, that is the area where the targets were actually deployed, was cheaper. Per person protected, the Bonon cost fell between the two, with Uganda cheaper and Chad more expensive. In Bonon, targets were deployed throughout the protected area, because G. p. palpalis was present everywhere, whereas in Chad and Uganda G. fuscipes fuscipes was found only the riverine fringing vegetation. Thus, differences between gHAT foci, in terms of tsetse ecology and human geography, impact on the cost-effectiveness of tsetse control. It also demonstrates the need to take into account both the area treated and protected alongside other impact indicators, such as the cost per person protected

    Delivering ‘tiny targets’ in a remote region of southern Chad: a cost analysis of tsetse control in the Mandoul sleeping sickness focus

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    Background: Since 2012, the World Health Organisation and the countries affected by the Gambian form of human African trypanosomiasis (HAT) have been committed to eliminating the disease, primarily through active case-finding and treatment. To interrupt transmission of T. b. gambiense and move more rapidly towards elimination, it was decided to add vector control using ‘tiny targets’. Chad’s Mandoul HAT focus extends over 840 km2, with a human population of 39 000 as well as 14 000 cattle and 2 000 pigs. Some 2 700 tiny targets were deployed annually from 2014 onwards. Methods: A protocol was developed for the routine collection of tsetse control costs during all field missions. This was implemented throughout 2015 and 2016, and combined with the recorded costs of the preliminary survey and sensitisation activities. The objective was to calculate the full costs at local prices in Chad. Costs were adjusted to remove research components and to ensure that items outside the project budget lines were included, such as administrative overheads and a share of staff salaries. Results: Targets were deployed at about 60 per linear km of riverine tsetse habitat. The average annual cost of the operation was USD 56 113, working out at USD 66.8 per km2 protected and USD 1.4 per person protected. Of this, 12.8% was an annual share of the initial tsetse survey, 40.6% for regular tsetse monitoring undertaken three times a year, 36.8% for target deployment and checking and 9.8% for sensitisation of local populations. Targets accounted for 8.3% of the cost, and the cost of delivering a target was USD 19.0 per target deployed. Conclusions: This study has confirmed that tiny targets provide a consistently low cost option for controlling tsetse in gambiense HAT foci. Although the study area is remote with a tsetse habitat characterised by wide river marshes, the costs were similar to those of tiny target work in Uganda, with some differences, in particular a higher cost per target delivered. As was the case in Uganda, the cost was between a quarter and a third that of historical target operations using full size targets or traps

    Molecular gas in high redshift QSOs

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    We review cm and mm observations of thermal molecular line emission from high redshift QSOs. These observations reveal the massive gas reservoirs (10^{10} to 10^{11} M_sun) required to fuel star formation at high rates. We discuss evidence for active star formation in QSO host galaxies, and we show that these high redshift, FIR-luminous QSOs follow the non-linear trend of increasing L_{FIR}/L'(CO) with increasing L_{FIR}. We conclude with a brief discussion of the recent CO detection of the most distant QSO at z=6.42, and its implications for cosmic reionization.Comment: To appear in: Multiwavelength AGN Surveys, eds. Maiolino and Mujica (World Scientific), 8 page

    Dynamiques de peuplements, modifications environnementales et variation du risque trypanosomien dans le sud-ouest du Burkina Faso de 2005 à 2014

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    L’augmentation générale des densités de population, dans un contexte de forte variabilité climatique, a provoqué des changements environnementaux majeurs en Afrique de l’Ouest. Si la population a tendance à s’urbaniser, elle reste toujours majoritairement rurale. C’est particulièrement vrai au Burkina-Faso où les modes de vie, les activités de subsistance et les conditions d’accès à l’eau exposent souvent les populations rurales et urbaines aux piqûres d’insectes susceptibles de transmettre des pathogènes responsables de maladies graves et/ou mortelles (paludisme, trypanosomiase, dengue, onchocercose etc.). Nos travaux s’intéressent aux fortes dynamiques de peuplements et de paysages survenues sur les rives du fleuve Comoé (terroirs de Folonzo et de Logogniégué) dans le Sud-ouest du Burkina-Faso entre 2005 et 2014, et au risque encouru par les populations humaines et animales à l’origine de ces dynamiques, de contracter les trypanosomoses transmises par les glossines (ou mouche tsé-tsé). Nos résultats mettent en évidence une multiplication par deux des densités de population humaine, la mise en place d’un élevage sédentaire et une augmentation de l’emprise rurale entre 2005 et 2014, ainsi qu’un rapprochement significatif des populations aux berges de la Comoé infestées de glossines. Ils montrent aussi l’intensification de pratiques spatiales humaines associables au risque trypanosomien, et confirment l’existence de la Trypanosomose Animale Africaine dans le cheptel bovin sédentaire récemment installé dans la zone. Cette étude illustre l’impact que des modifications environnementales engendrées par une dynamique de peuplement peuvent avoir sur les conditions de transmission des trypanosomoses humaines et animales.The general increase of population densities in Subsaharian Africa, in an effective climate change context, caused major population movement and environmental changes. While urbanization is expanding, the population is still mostly rural. Ways of life, subsistence farming and limited access to water sources expose these rural and urban populations to insect bites that could pass on the pathogen responsible for serious or deadly pathological conditions (malaria, trypanosomiasis, dengue fever, onchocerciasis, etc.). In the research conducted in South-West of Burkina Faso, our interest focused on current patterns of settlements and landscapes along river Comoe’s banks and on the exposure risks taken to human and animal trypanosomosis, both transmitted by tsetse flies which live in forest gallery of rivers. To achieve this, human and animal (bovine) populations were counted and mapped, and the rural encroachment on the Comoe’s banks mapped, to make a diachronic comparison between 2005 and 2014. The aim was also to understand the behaviors of people and animals associated with trypanosomosis risks. Simultaneously, tsetse flies were captured to ascertain their density in the studied area. Previously inventoried, bovine blood samples were analyzed in order to determine trypanosomosis infection level. From 2005 to 2014, our results have shown a high rise of the human population located in the area studied (multiplied by two), but also a change in its gender and ethnic structure. Furthermore we noticed a rise of the farmland surface, detrimental to the wooded savannah and gallery forest, and a decrease of tsetse flies densities due to this landscape degradation. Moreover, we observed the beginning of a bovine breeding and a reconciliation of people to the banks of Comoe, still infested by tsetse flies. Our results shown that 10% of the bovines sampled were infected by trypanosomes. This study shows settlements dynamics, mainly due to population growth, and their environmental impact on a savannah ecosystem in Burkina Faso. It aims to describe the consequences of such phenomenon on population health, with the specific example of human and animal trypanosomoses, both transmitted by tsetse flies

    Towards an optimal design of target for tsetse control: comparisons of novel targets for the control of palpalis group tsetse in West Africa

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    Background: Tsetse flies of the Palpalis group are the main vectors of sleeping sickness in Africa. Insecticide impregnated targets are one of the most effective tools for control. However, the cost of these devices still represents a constraint to their wider use. The objective was therefore to improve the cost effectiveness of currently used devices. Methodology/Principal Findings: Experiments were performed on three tsetse species, namely Glossina palpalis gambiensis and G. tachinoides in Burkina Faso and G. p. palpalis in Côte d'Ivoire. The 1×1 m2 black blue black target commonly used in W. Africa was used as the standard, and effects of changes in target size, shape, and the use of netting instead of black cloth were measured. Regarding overall target shape, we observed that horizontal targets (i.e. wider than they were high) killed 1.6-5x more G. p. gambiensis and G. tachinoides than vertical ones (i.e. higher than they were wide) (P<0.001). For the three tsetse species including G. p. palpalis, catches were highly correlated with the size of the target. However, beyond the size of 0.75 m, there was no increase in catches. Replacing the black cloth of the target by netting was the most cost efficient for all three species. Conclusion/Significance: Reducing the size of the current 1*1 m black-blue-black target to horizontal designs of around 50 cm and replacing black cloth by netting will improve cost effectiveness six-fold for both G. p. gambiensis and G. tachinoides. Studying the visual responses of tsetse to different designs of target has allowed us to design more cost-effective devices for the effective control of sleeping sickness and animal trypanosomiasis in Africa

    How do tsetse recognise their hosts? The role of shape in the responses of tsetse (Glossina fuscipes and G. palpalis) to artificial hosts

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    Palpalis-group tsetse, particularly the subspecies of Glossina palpalis and G. fuscipes, are the most important transmitters of human African trypanomiasis (HAT), transmitting .95% of cases. Traps and insecticide-treated targets are used to control tsetse but more cost-effective baits might be developed through a better understanding of the fly’s host-seeking behaviour.Electrocuting grids were used to assess the numbers of G. palpalis palpalis and G. fuscipes quanzensis attracted to and landing on square or oblong targets of black cloth varying in size from 0.01 m2 to 1.0 m2. For both species, increasing the size of a square target from 0.01 m2 (dimensions = 0.1 x 0.1 m) to 1.0 m2 (1.0 x 1.0 m) increased the catch ,4x however the numbers of tsetse killed per unit area of target declined with target size suggesting that the most cost efficient targets are not the largest. For G. f. quanzensis, horizontal oblongs, (1 m wide x 0.5 m high) caught, 1.8x more tsetse than vertical ones (0.5 m wide x 1.0 m high) but the opposite applied for G. p. palpalis. Shape preference was consistent over the range of target sizes. For G. p. palpalis square targets caught as many tsetse as the oblong; while the evidence is less strong the same appears to apply to G. f. quanzensis. The results suggest that targets used to control G. p. palpalis and G. f. quanzensis should be square, and that the most cost-effective designs, as judged by the numbers of tsetse caught per area of target, are likely to be in the region of 0.25 x 0.25 m2. The preference of G. p. palpalis for vertical oblongs is unique amongst tsetse species, and it is suggested that this response might be related to its anthropophagic behaviour and hence importance as a vector of HAT

    Improving the cost-effectiveness of visual devices for the control of Riverine tsetse flies, the major vectors of Human African Trypanosomiasis

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    Control of the Riverine (Palpalis) group of tsetse flies is normally achieved with stationary artificial devices such as traps or insecticide-treated targets. The efficiency of biconical traps (the standard control device), 161 m black targets and small 25625 cm targets with flanking nets was compared using electrocuting sampling methods. The work was done on Glossina tachinoides and G. palpalis gambiensis (Burkina Faso), G. fuscipes quanzensis (Democratic Republic of Congo), G. f. martinii (Tanzania) and G. f. fuscipes (Kenya). The killing effectiveness (measured as the catch per m2 of cloth) for small targets plus flanking nets is 5.5–15X greater than for 1 m2 targets and 8.6–37.5X greater than for biconical traps. This has important implications for the costs of control of the Riverine group of tsetse vectors of sleeping sickness
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