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Search Results: 1 - 10 of 409821 matches for " Marc J. B. Vreysen "
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Prospects for area-wide integrated control of tsetse flies (Diptera:Glossinidae) and trypanosomosis in sub-Saharan Africa
Vreysen,Marc J.B.;
Revista de la Sociedad Entomol?3gica Argentina , 2006,
Abstract: countries in sub-saharan africa are among the least developed in the world and hunger and poverty remains widespread in most of the rural communities. reducing hunger and chronic under nourishment through the introduction of productive livestock as a source of traction and manure for crop production, transport, milk and meat is deemed to be a fundamental first step towards better rural development. the presence of the tsetse fly in one third of the african continent and the disease trypanosomosis it transmits is considered the major barrier to the development of productive livestock. despite the yearly administration of 35 million doses of trypanocidal drugs (at us$ 1 per dose), african farmers lose 3 million cattle every year to the disease and annual direct economic losses are estimated at us$ 600 to 1200 million. tsetse flies mainly affect the rural poor and are rightfully considered 'a root cause of poverty ' in africa . the most desirable way of containing the disease trypanosomosis is undoubtedly the elimination of entire populations of the vector from delimited geographical areas using an integration of various control tactics, i.e. an areawide integrated pest management (aw-ipm) approach. efficient methods to suppress or even eliminate tsetse populations have been available for the last 50 years and are mostly based on the use of insecticides or entail devices that attract and kill. nevertheless, despite gigantic efforts in the past century, there are only a few examples where the elimination of tsetse flies has proven to be sustainable, e.g. the elimination of glossina pallidipes austen from south africa in the 1950 's using mainly aerial spraying of residual insecticides or the creation of a zone free of glossina austeni newstead on unguja island of zanzibar (1994-1997) through the integration of various control tactics including the release of sterile insects. the decentralisation of the tsetse control offices resulting in a shift from large scale eradica
Prospects for area-wide integrated control of tsetse flies (Diptera:Glossinidae) and trypanosomosis in sub-Saharan Africa Perspectivas para el control integrado abarcativo del área de moscas tse-tsé (Diptera: Glossinidae) y la tripanosomiasis en el áfrica sub-Sahariana
Marc J.B. Vreysen
Revista de la Sociedad Entomol?3gica Argentina , 2006,
Abstract: Countries in sub-Saharan Africa are among the least developed in the world and hunger and poverty remains widespread in most of the rural communities. Reducing hunger and chronic under nourishment through the introduction of productive livestock as a source of traction and manure for crop production, transport, milk and meat is deemed to be a fundamental first step towards better rural development. The presence of the tsetse fly in one third of the African continent and the disease trypanosomosis it transmits is considered the major barrier to the development of productive livestock. Despite the yearly administration of 35 million doses of trypanocidal drugs (at US$ 1 per dose), African farmers lose 3 million cattle every year to the disease and annual direct economic losses are estimated at US$ 600 to 1200 million. Tsetse flies mainly affect the rural poor and are rightfully considered 'a root cause of poverty ' in Africa . The most desirable way of containing the disease trypanosomosis is undoubtedly the elimination of entire populations of the vector from delimited geographical areas using an integration of various control tactics, i.e. an areawide integrated pest management (AW-IPM) approach. Efficient methods to suppress or even eliminate tsetse populations have been available for the last 50 years and are mostly based on the use of insecticides or entail devices that attract and kill. Nevertheless, despite gigantic efforts in the past century, there are only a few examples where the elimination of tsetse flies has proven to be sustainable, e.g. the elimination of Glossina pallidipes Austen from South Africa in the 1950 's using mainly aerial spraying of residual insecticides or the creation of a zone free of Glossina austeni Newstead on Unguja Island of Zanzibar (1994-1997) through the integration of various control tactics including the release of sterile insects. The decentralisation of the tsetse control offices resulting in a shift from large scale eradication approaches to localised tsetse control efforts by the local farmer communities, combined with the growing economic crises and political instability in many African countries has most likely contributed to the decline of most tsetse control efforts in the last decades. It is obvious that the sustained removal of the tsetse fly over large geographical areas would result in enormous benefits for the rural farmer community. Tsetse population genetic studies and data derived from satellite remote sensing are providing more and more convincing evidence that tsetse fly populations are not distri
Factory Tsetse Flies Must Behave Like Wild Flies: A Prerequisite for the Sterile Insect Technique
Marc J. B. Vreysen,Khalfan M. Saleh,Renaud Lancelot,Jérémy Bouyer
PLOS Neglected Tropical Diseases , 2011, DOI: 10.1371/journal.pntd.0000907
Abstract:
Reproductive Strategies of Aedes albopictus (Diptera: Culicidae) and Implications for the Sterile Insect Technique
Clelia F. Oliva, David Damiens, Marc J. B. Vreysen, Guy Lemperière, Jérémie Gilles
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0078884
Abstract: Male insects are expected to optimize their reproductive strategy according to the availability of sperm or other ejaculatory materials, and to the availability and reproductive status of females. Here, we investigated the reproductive strategy and sperm management of male and virgin female Aedes albopictus, a mosquito vector of chikungunya and dengue viruses. The dynamics of semen transfer to the female bursa inseminalis and spermathecae were observed. Double-mating experiments were conducted to study the effect of time lapsed or an oviposition event between two copulations on the likelihood of a female double-insemination and the use of sperm for egg fertilization; untreated fertile males and radio-sterilised males were used for this purpose. Multiple inseminations and therefore the possibility of sperm competition were limited to matings closely spaced in time. When two males consecutively mated the same female within a 40 min interval, in ca. 15% of the cases did both males sire progeny. When the intervals between the copulations were longer, all progeny over several gonotrophic cycles were offspring of the first male. The mating behavior of males was examined during a rapid sequence of copulations. Male Ae. albopictus were parceling sperm allocation over several matings; however they would also attempt to copulate with females irrespective of the available sperm supply or accessory gland secretion material. During each mating, they transferred large quantities of sperm that was not stored for egg fertilization, and they attempted to copulate with mated females with a low probability of transferring their genes to the next generation. The outcomes of this study provided in addition some essential insights with respect to the sterile insect technique (SIT) as a vector control method.
Tsetse Salivary Gland Hypertrophy Virus: Hope or Hindrance for Tsetse Control?
Adly M. M. Abd-Alla ,Andrew G. Parker,Marc J. B. Vreysen,Max Bergoin
PLOS Neglected Tropical Diseases , 2011, DOI: 10.1371/journal.pntd.0001220
Abstract: Many species of tsetse flies (Diptera: Glossinidae) are infected with a virus that causes salivary gland hypertrophy (SGH), and flies with SGH symptoms have a reduced fecundity and fertility. The prevalence of SGH in wild tsetse populations is usually very low (0.2%–5%), but higher prevalence rates (15.2%) have been observed occasionally. The successful eradication of a Glossina austeni population from Unguja Island (Zanzibar) using an area-wide integrated pest management approach with a sterile insect technique (SIT) component (1994–1997) encouraged several African countries, including Ethiopia, to incorporate the SIT in their national tsetse control programs. A large facility to produce tsetse flies for SIT application in Ethiopia was inaugurated in 2007. To support this project, a Glossina pallidipes colony originating from Ethiopia was successfully established in 1996, but later up to 85% of adult flies displayed symptoms of SGH. As a result, the colony declined and became extinct by 2002. The difficulties experienced with the rearing of G. pallidipes, epitomized by the collapse of the G. pallidipes colony originating from Ethiopia, prompted the urgent need to develop management strategies for the salivary gland hypertrophy virus (SGHV) for this species. As a first step to identify suitable management strategies, the virus isolated from G. pallidipes (GpSGHV) was recently sequenced and research was initiated on virus transmission and pathology. Different approaches to prevent virus replication and its horizontal transmission during blood feeding have been proposed. These include the use of antiviral drugs such as acyclovir and valacyclovir added to the blood for feeding or the use of antibodies against SGHV virion proteins. In addition, preliminary attempts to silence the expression of an essential viral protein using RNA interference will be discussed.
A Conceptual Model for Assessing the Minimum Size Area for an Area-Wide Integrated Pest Management Program
Hugh J. Barclay,Robert Matlock,Stuart Gilchrist,David M. Suckling,Jesus Reyes,Walther R. Enkerlin,Marc J. B. Vreysen
International Journal of Agronomy , 2011, DOI: 10.1155/2011/409328
Abstract: A conceptual model was developed based on the two basic spatial elements of area-wide integrated pest management (AW-IPM), a core area and a buffer zone, to determine the minimum size of the protected area for the program to be technically feasible and economically justifiable. The model consisted of a biological part (insect dispersal) and an economic part. The biological part used random walks and diffusion equations to describe insect dispersal and to determine the minimum width of the buffer zone required to protect the core area from immigration of pests from outside. In the economic part, the size of the core area was calculated to determine the point at which the revenues from the core area equal the control costs. This model will need to be calibrated and validated for each species and geographic location. Tsetse flies and the Mediterranean fruit fly are used as case studies to illustrate the model. 1. Introduction Classical integrated pest management (IPM), which aims at managing pests by the integration of biological, cultural, physical, and chemical tools in a way that minimizes economic, health, and environmental risks [1], has remained a dominant paradigm of pest control for the last 50 years. The different control tactics can be integrated on a field-by-field basis or by using an area-wide approach [2]. Area-wide integrated pest management (AW-IPM) is the integrated use of various control tactics against an entire pest population within a delimited geographical area to achieve economic control [3]. The importance of this approach of “total pest population management” has significantly increased for many pests in the past decades, and it is now generally accepted that AW-IPM leads, in many cases, to more sustainable pest control especially for mobile insects [2]. A powerful AW control tactic is the sterile insect technique (SIT), which over the past decades has become accepted as an efficient and cost-effective part of AW-IPM programs against a selected number of insect pests of veterinary, human health, and agricultural importance [4]. A recurrent concern for pest managers is the minimum size of the target area that needs to be considered for an AW-IPM program to be technically viable and economically justifiable. Due to the lack of adequate practical experience and the absence of models, decisions were sometimes based on educated guesses rather than on sound, scientific principles. Therefore, a conceptual mathematical model was developed that can assist with estimating the minimum area that needs to be considered to successfully apply a
Release-Recapture Studies Confirm Dispersal of Glossina palpalis gambiensis between River Basins in Mali
Marc J. B. Vreysen,Thomas Balenghien,Khalfan M. Saleh,Sadou Maiga,Zowinde Koudougou,Giuliano Cecchi,Jérémy Bouyer
PLOS Neglected Tropical Diseases , 2013, DOI: 10.1371/journal.pntd.0002022
Abstract:
The Antiviral Drug Valacyclovir Successfully Suppresses Salivary Gland Hypertrophy Virus (SGHV) in Laboratory Colonies of Glossina pallidipes
Adly M.M. Abd-Alla, Henry Adun, Andrew G. Parker, Marc J.B. Vreysen, Max Bergoin
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0038417
Abstract: Many species of tsetse flies are infected with a virus that causes salivary gland hypertrophy (SGH) symptoms associated with a reduced fecundity and fertility. A high prevalence of SGH has been correlated with the collapse of two laboratory colonies of Glossina pallidipes and colony maintenance problems in a mass rearing facility in Ethiopia. Mass-production of G. pallidipes is crucial for programs of tsetse control including the sterile insect technique (SIT), and therefore requires a management strategy for this virus. Based on the homology of DNA polymerase between salivary gland hypertrophy virus and herpes viruses at the amino acid level, two antiviral drugs, valacyclovir and acyclovir, classically used against herpes viruses were selected and tested for their toxicity on tsetse flies and their impact on virus replication. While long term per os administration of acyclovir resulted in a significant reduction of productivity of the colonies, no negative effect was observed in colonies fed with valacyclovir-treated blood. Furthermore, treatment of a tsetse colony with valacyclovir for 83 weeks resulted in a significant reduction of viral loads and consequently suppression of SGH symptoms. The combination of initial selection of SGHV-negative flies by non-destructive PCR, a clean feeding system, and valacyclovir treatment resulted in a colony that was free of SGH syndromes in 33 weeks. This is the first report of the use of a drug to control a viral infection in an insect and of the demonstration that valacyclovir can be used to suppress SGH in colonies of G. pallidipes.
Contrasting Population Structures of Two Vectors of African Trypanosomoses in Burkina Faso: Consequences for Control
Naférima Koné equal contributor,Jérémy Bouyer equal contributor ,Sophie Ravel,Marc J. B. Vreysen,Kouadjo T. Domagni,Sandrine Causse,Philippe Solano,Thierry de Mee?s
PLOS Neglected Tropical Diseases , 2011, DOI: 10.1371/journal.pntd.0001217
Abstract: Background African animal trypanosomosis is a major obstacle to the development of more efficient and sustainable livestock production systems in West Africa. Riverine tsetse species such as Glossina palpalis gambiensis Vanderplank and Glossina tachinoides Westwood are the major vectors. A wide variety of control tactics is available to manage these vectors, but their removal will in most cases only be sustainable if the control effort is targeting an entire tsetse population within a circumscribed area. Methodology/Principal Findings In the present study, genetic variation at microsatellite DNA loci was used to examine the population structure of G. p. gambiensis and G. tachinoides inhabiting four adjacent river basins in Burkina Faso, i.e. the Mouhoun, the Comoé, the Niger and the Sissili River Basins. Isolation by distance was significant for both species across river basins, and dispersal of G. tachinoides was ~3 times higher than that of G. p. gambiensis. Thus, the data presented indicate that no strong barriers to gene flow exists between riverine tsetse populations in adjacent river basins, especially so for G. tachinoides. Conclusions/Significance Therefore, potential re-invasion of flies from adjacent river basins will have to be prevented by establishing buffer zones between the Mouhoun and the other river basin(s), in the framework of the PATTEC (Pan African Tsetse and Trypanosomosis Eradication Campaign) eradication project that is presently targeting the northern part of the Mouhoun River Basin. We argue that these genetic analyses should always be part of the baseline data collection before any tsetse control project is initiated.
Irradiated Male Tsetse from a 40-Year-Old Colony Are Still Competitive in a Riparian Forest in Burkina Faso
Adama Sow, Issa Sidibé, Zakaria Bengaly, Augustin Z. Bancé, Germain J. Sawadogo, Philippe Solano, Marc J. B. Vreysen, Renaud Lancelot, Jeremy Bouyer
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0037124
Abstract: Background Tsetse flies are the cyclical vectors of African trypanosomosis that constitute a major constraint to development in Africa. Their control is an important component of the integrated management of these diseases, and among the techniques available, the sterile insect technique (SIT) is the sole that is efficient at low densities. The government of Burkina Faso has embarked on a tsetse eradication programme in the framework of the PATTEC, where SIT is an important component. The project plans to use flies from a Glossina palpalis gambiensis colony that has been maintained for about 40 years at the Centre International de Recherche-Développement sur l'Elevage en zone Subhumide (CIRDES). It was thus necessary to test the competitiveness of the sterile males originating from this colony. Methodology/Principal Findings During the period January–February 2010, 16,000 sterile male G. p. gambiensis were released along a tributary of the Mouhoun river. The study revealed that with a mean sterile to wild male ratio of 1.16 (s.d. 0.38), the abortion rate of the wild female flies was significantly higher than before (p = 0.026) and after (p = 0.019) the release period. The estimated competitiveness of the sterile males (Fried index) was 0.07 (s.d. 0.02), indicating that a sterile to wild male ratio of 14.4 would be necessary to obtain nearly complete induced sterility in the female population. The aggregation patterns of sterile and wild male flies were similar. The survival rate of the released sterile male flies was similar to that observed in 1983–1985 for the same colony. Conclusions/Significance We conclude that gamma sterilised male G. p. gambiensis derived from the CIRDES colony have a competitiveness that is comparable to their competitiveness obtained 35 years ago and can still be used for an area-wide integrated pest management campaign with a sterile insect component in Burkina Faso.
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