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Using knowledge about plant–insect interactions in a crop protection perspective is a pre-requisite to promote the development of novel pest management strategies. Enhancing plant natural defenses has been described as a promising way to improve the management of pests. In cotton, plant topping (cutting off the top of the plant) for inducing such defenses has been proposed as a promising tool for integrated pest management. The main objective of this study was to explore the effect of cotton topping on the performance of the cotton aphid, Aphis gosypii, under greenhouse conditions. The effect of plant topping was evaluated on topped and on neighbor non-topped plants. Results showed that cotton topping disturbed A. gossypii aphids not only on the topped plant but also on neighbor non-topped plants. The population of aphids grew slower in the topped compared to the control treatment and lower abundances of aphids were found in the topped treatment up to a distance of 100 cm to the topped plant. When an individual nymph was confined in a clip-cage, the production of winged adults after 15 days of confinement was higher in the topped compared to the control treatment. This difference decreased as the distance to the topped plant increased. In conclusion, our study proves that cotton topping mediates plant-pest interactions on the focal and neighbor plants. We discuss how cotton topping is a promising technique that could be used as part of an integrated pest management program, particularly for smallholders in West Africa, for controlling aphid infestations.

The South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), has invaded most Afro-Eurasian countries and is threatening worldwide tomato production. Various strategies have been developed and implemented to manage this pest. Here, we present a timely review on the up-to-date development and practical implementation of integrated pest management (IPM) programs for tomato crops across different world regions infested by T. absoluta. While insecticide resistance is a growing concern, biological control via releasing or conserving arthropod natural enemies and sex pheromone-based biotechnical control are the most successful management practices. Agronomic control-related research is an emerging area where the soil fertilization and/or irrigation, as well as breeding of resistant cultivars, has the potential to enhance IPM effectiveness. Grower survey responses in the native areas (i.e., South America), early-invaded areas (i.e., first report between 2006 and 2012) and newly invaded areas (i.e., first report after 2012) showed that the control programs evolved along with the areas and time since invasion. Growers in the early-invaded areas shifted more rapidly from chemical control to biological control compared to those from the native area. In all concerned regions, the pest control failure risk following chemical insecticide applications and the high cost associated with either biological or biotechnical control methods have been the greatest concerns for growers. The information gathered from the native and/or early-invaded areas may help achieve a more effective management in newly invaded areas. Lastly, researchers are expected to break the bottlenecks of some key issues that would enable lowering application cost of novel biorational alternative management options.

Competent arbovirus vectors are found in the culicid mosquito fauna of south-west Indian Ocean (SWIO) islands. In La Reunion, Aedes albopictus and Aedes aegypti mosquitoes are known vectors of dengue and chikungunya viruses. Culex quinquefasciatus is a potential vector of Rift Valley fever and West Nile viruses. To prepare a vector-control field trial against Ae. aegypti, this study aimed at identifying the best trapping strategy to catch adult Ae. aegypti, using BG-Sentinel traps (Biogents, Germany). It was implemented in two sites in southern La Reunion. Catches of Ae. albopictus and Cx. quinquefasciatus mosquitoes were also recorded. A Latin square design was used to estimate the detection probability and the apparent daily density—according to the BG-Sentinel trapping strategy: none, carbon dioxide (CO2), a commercial attractant—BG-Lure (Biogents, Germany), or both. The use of CO2 alone was associated with a higher detection probability for Ae. aegypti and Cx. quinquefasciatus mosquitoes, as well as a large increase in their apparent density. Traps with BG-Lure—alone or in combination with CO2, did not improve the detection probability of Ae. aegypti and Cx. quinquefasciatus mosquitoes. The same result was found for male Ae. albopictus. For females, baiting BG-Sentinel traps with CO2 or BG-Lure had no significant effect. The same apparent densities were found for Ae. aegypti and Ae. albopictus mosquitoes in both study sites—where Ae. aegypti mosquitoes were found at very low densities during previous surveys.

Sur la période 2016-2020, les agriculteurs des filières légumes-maraîchage, horticulture, arboriculture et cultures tropicales du réseau DEPHY FERME ont adopté des modèles décisionnels, des pratiques particulièrement remarquables, des trajectoires d'exploitations et ont produit des notes techniques. Cet ensemble de données dresse un panorama des pratiques alternatives mises en oeuvre dans le réseau pour diminuer l'usage des produits phytopharmaceutiques. C'est aussi une source d'information sur les coûts, les inconvénients et les bénéfices de ces pratiques aux yeux des agricultrices et des agriculteurs. Bien que des modifications profondes de systèmes soient rarement évoquées, certaines exploitations combinent de nombreuses pratiques, souvent en lien avec la gestion de l'enherbement et de la fertilité.

En une trentaine d'années, les moustiquaires imprégnées de pyrétrinoïdes se sont imposées en protection personnelle et en santé publique comme un moyen de prévention du paludisme. Un des acteurs de ces découvertes présente un panorama des moustiquaires imprégnées d'insecticide et apporte ici son témoignage, se fondant particulièrement sur les circonstances et les états d'esprit qui ont prévalu dans les années 1980, décennie cruciale pour ces avancées qui ont servi l'humanité. C'est en 1983 qu'a été réalisée la première expérimentation testant l'effet des moustiquaires imprégnées de pyréthrinoïdes et qui a mis en évidence l'impact de cette méthode sur la réduction de la transmission du Plasmodium. Cette découverte a été faite dans une station expérimentale de terrain au Burkina Faso montrant que chacun des nombreux paramètres entomologiques mesurés allait dans le sens d'une nette réduction du contact moustique-humain. Quelques années plus tard, toujours au Burkina Faso, il a été montré que les moustiquaires imprégnées, utilisées massivement dans un village, réduisaient la longévité et la capacité vectrice de la population de moustiques, à tel point que ces moustiquaires agissaient comme un moyen de lutte antivectorielle. Ces recherches ont toutes été effectuées par des chercheurs de l'Office de la recherche scientifique et technique outre-mer, devenu Institut de recherche pour le développement, dans le cadre du centre Muraz de l'Organisation de coordination et de coopération pour la lutte contre les grandes endémies, en bénéficiant de l'appui scientifique et financier de la Division de la biologie et de la lutte contre les vecteurs de l'Organisation mondiale de la santé.

International audience; The Sterile Insect Technique (SIT) is a promising technique to control mosquitoes, vectors of diseases, like dengue, chikungunya or Zika. However, its application in the field is not easy, and its success hinges upon several constraints, one of them being that the treated area must be sufficiently isolated to limit migration or re-invasion by mosquitoes from the outside. In this manuscript we study the impact of males and (fertile) females migration on SIT. We show that a critical release rate for sterile males exists for every migration level, in the context of continuous or periodic releases. In particular, when (fertile) females migration is sufficiently low, then SIT can be conducted successfully using either open-loop control or closed-loop control (or a combination of both methods) when regular measurements of the wild population are completed. Numerical simulations to illustrate our theoretical results are presented and discussed. Finally, we derive a threshold value for the females migration rate, when viruses are circulating, under which it is possible to lower the epidemiological risk in the treated area, according to the size of the human population.

Biological control can be an effective conservation strategy to manage invasive species when other conventional methods cannot be implemented. Estimating the benefits of biological control for the conservation of native biodiversity remains a challenging task. Following the introduction of a defoliating sawfly, Cibdela janthina, for biological control of invasive giant bramble, Rubus alceifolius, on Reunion Island (Mascarene Archipelago), we monitored the consequent change in R. alceifolius cover as well as species richness and cover of non-native species and native species within a set of patches along an altitudinal gradient in the National Park of Reunion Island. There was an increase in native species richness and cover together with a decrease in R. alceifolius cover, showing that biological control positively impacted the native plant communities. The effectiveness of C. janthina was influenced by the altitudinal range, the surface area of the patches and the location of each patch, i.e forest edge or forest matrix. We discuss the extent to which the use of biological control within an integrated approach can optimize benefits for biodiversity conservation in the short to medium term by selecting complementary and standardised protocols.

International audience; The expansion of mosquito species worldwide is creating a powerful network for the spread of arboviruses. In addition to the destruction of breeding sites (prevention) and mass trapping, methods based on the sterile insect technique (SIT), the autodissemination of pyriproxyfen (ADT), and a fusion of elements from both of these known as boosted SIT (BSIT), are being developed to meet the urgent need for effective vector control. However, the comparative potential of these methods has yet to be explored in different environments. This is needed to propose and integrate informed guidelines into sustainable mosquito management plans. We extended a weather-dependent model of Aedes albopictus population dynamics to assess the effectiveness of these different vector control methods, alone or in combination, in a tropical (Reunion island, southwest Indian Ocean) and a temperate (Montpellier area, southern France) climate. Our results confirm the potential efficiency of SIT in temperate climates when performed early in the year (mid-March for northern hemisphere). In such a climate, the timing of the vector control action was the key factor in its success. In tropical climates, the potential of the combination of methods becomes more relevant. BSIT and the combination of ADT with SIT were twice as effective compared to the use of SIT alone.

Suppression or eradication of insect pest populations by the release of sterile insects is often dependent on supplementary methods of pest reduction to levels where the target pest population can be overflooded with sterile insects. Population suppression activities often take place in advance of, or coincide with, the production and release of sterile insects. Supplementary methods to remove breeding opportunities, or management methods that prevent access of pests or vectors to the hosts, may reduce the population or prevent damage or disease transmission. Insecticides have been used widely in direct applications or applied as baits, in traps, or on specific sites where the pest makes contact or reproduces, although they are increasingly being replaced by biopesticides. As sterile insect release does not kill the pest, adult biting pests or fertile mated females of the pests will continue to attack hosts after the release of sterile insects. Thus supplementary pest suppression programmes and quarantine measures are essential to prevent damage or the spread of disease. Eradication or effective pest management requires that the entire population of the pest be treated, or that the programme apply immigration barriers. It also requires taking into account interactions among control methods; they can be additive, synergistic or antagonistic. When supplementary pest control activities directly benefit the human population in areas being treated, such as in mosquito or screwworm control programmes, these area-wide suppression activities are usually acceptable to the public, but when the public receives no direct benefit from supplementary control activities such as in crop pest programmes, social resistance may develop unless public information is managed properly.

National audience; Ralstonia solanacearum species complex (RSSC) is one of the most devastating bacterial plant pathogens causing bacterial wilt in a wide range of hosts including crops and wild plants. These soil-borne Gram-negative bacteria have a worldwide geographic distribution and significantly reduce crop yields especially in tropical regions such as the southwestern Indian Ocean. Due to the lack of efficient curative measures and the high persistence of RSSC, phage therapy represents a sustainable plant disease management strategy to be applied in agricultural settings. However, using phages as a biocontrol tool raises concerns about the potential of phage resistance evolution in plant pathogenic bacterial populations. To explore this question, we first evaluated the in vitro virulence of a local phage collection against the most prevalent strain of RSSC in Reunion Island. Then, we examined the temporal adaptation of the strain to these phages, and its consequences for bacterial fitness. Analysis of the virulence of the 10 phages tested showed that they were all able to effectively reduce bacterial growth. The emergence of bacterial resistance was reported after two or three days. Absence of clear lysis plaques were observed in evolved bacteria not only against the phage encountered but also against the entire phage collection, which included several phage species and genera. These results show high cross-resistance emergence, which resulted in a fitness cost for the bacteria, as measured by a reduction in growth rate and loss of swimming ability for 8 of 10 evolved bacteria exposed to the different phages. These results suggest that phylogenetically distant phages can be rapidly blocked in bacteria. Mechanistically different phages or complementary strategies may be needed to efficiently control phytopathogens. Conversely, fitness costs in bacteria point in the direction of a reduced virulence in planta. Further in vivo and genetic analysis will bring light to these questions.

Le moustique tigre, Aedes albopictus, représente une menace sanitaire par la transmission de maladies virales humaines. Malgré l'existence de moyens de lutte, le contrôle des populations d'Ae. albopictus reste un enjeu contraint par une connaissance fine de leur dynamique dans l'espace et le temps. Dans ce contexte, les modèles mathématiques sont des outils de choix pour tester et optimiser ces stratégies de contrôle. L'objectif de cette thèse était d'explorer les effets des méthodes de contrôle sur les populations d'Ae. albopictus en milieu tropical (La Réunion) et tempéré (Montpellier). L'étude s'est basée sur l'utilisation de modèle déterministe détaillant l'ensemble du cycle de vie du moustique, piloté par le climat et l'abondance de gîtes larvaires. Nous avons intégré au modèle les effets de différentes méthodes de lutte sur la dynamique des populations d'Ae. albopictus. Une attention particulière a été portée aux méthodes basées sur des lâchers de mâles stériles. L'analyse du modèle nous a permis de mieux comprendre et identifier les stratégies de lutte efficaces en terme de réduction et résilience des populations d'Ae. albopictus, afin de les optimiser en conséquence. Les stratégies de lutte intégrée ont pour objectif final de prévenir l'émergence d'épidémie. C'est pourquoi le modèle de dynamique des populations à La Réunion a été couplé avec un modèle épidémiologique. Des études supplémentaires devront être réalisées pour ajuster les prédictions du modèle avant de pouvoir étudier l'impact de stratégies de lutte intégrée sur la transmission de la dengue.

Dès 1917, dans l’article où il décrit ses premières observations et propose le nom de bactériophage, Félix d’Hérelle rapporte une première utilisation de ces virus pour traiter des infections bactériennes, donnant ainsi naissance à la phagothérapie. Le développement de cette application a montré qu’il était possible de mettre en place des traitements ciblant spécifiquement les bactéries, tels que ceux basés sur l’utilisation d’antibiotiques. Ces derniers, de par leur très grande efficacité et simplicité d’utilisation, ont provoqué le quasi-abandon de la phagothérapie. Aujourd’hui, un nombre croissant de bactéries pathogènes pour l’homme présente des phénotypes de résistance à plusieurs familles d’antibiotiques. Les infections causées par ces bactéries imposent l’utilisation de molécules au spectre d’activité toujours plus large et placent certains patients en situation d’impasse thérapeutique. Cet état de fait a relancé les recherches pour permettre le déploiement de la phagothérapie afin de traiter des patients mais aussi des animaux et des plantes. En fait, les domaines d’applications thérapeutiques des bactériophages s’élargissent au fur et à mesure que les agents antibactériens de nature chimique sont remis en cause, voire interdits. Cette revue revient sur les principes fondamentaux des applications thérapeutiques des bactériophages et expose les données récentes dans les domaines pour lesquels une exploitation commerciale est en cours ou sur le point d’émerger., In the 1917 article in which Félix d'Hérelle describes his first observations and proposes the name of bacteriophage, he also reports the first use of these viruses to treat bacterial infections, thus giving birth to phage therapy. Soon after antibiotics supplanted bacteriophages. Today, bacteria resistant to multiple antibiotics become a growing public health issue worldwide. This situation has revived research aiming at developing the antibacterial activity of bacteriophages to treat patients as well as diseases in animals and plants. In fact, the areas of applications of bacteriophages as antibacterial are widening as current solutions of chemical nature are questioned. This review summarizes the basic principles of therapeutic applications of bacteriophages and presents recent data in areas where commercial exploitation is occurring or about to emerge.

Three phages targeting Pseudomonas syringae GAW0113 have been isolated from organic waste samples: Pseudomonas phage Bertil, Misse and Strit. The phages have double-stranded DNA genomes ranging from 41342 to 41374 bp in size comprising 50 to 51 open reading frames. The three phages genomes are highly similar and genomic comparison analyses shows that they all belong to the Autographivirinae subfamily of the family Podoviridae. The phages are however only distantly related to other members of this family, and have limited gene synteny with type-phages of other genera within Autographivirinae, suggesting that the newly isolated phages could represent a new genus.

Au Mali, l’efficacité de la lutte chimique systématique (traitements calendaires) contre les ravageurs du cotonnier est régulièrement remise en cause. Des alternatives à cette lutte, comme la lutte étagée ciblée, l’intervention sur seuil et la culture biologique, visant toutes à réduire les quantités de pesticides utilisées, sont diffusées ; d’autres sont testées chez les producteurs, comme l’écimage du cotonnier. Cette étude analyse la perception de la technique de l’écimage du cotonnier par des producteurs. Elle a été conduite dans quatre villages de la zone cotonnière, à l’aide de focus groups d’hommes et de femmes et d’entretiens avec 40 producteurs ayant pratiqué ou non l’écimage. Les avantages de l’écimage identifiés par la majorité des producteurs interrogés sont : (i) une technique manuelle facile à mettre en œuvre, (ii) la diminution des risques de chute d’organes fructifères, (iii) la réduction de la hauteur des plants, s’étalant davantage (iv) une amélioration du rendement et (v) la réduction de la population des ravageurs et donc de l’utilisation des pesticides, ayant des effets positifs sur la santé humaine et l’environnement, et diminuant les coûts de production. Ses principales contraintes sont le besoin supplémentaire de main-d’œuvre et son coût par rapport à la culture de coton non écimé. Des partenariats avec les sociétés cotonnières et les organisations paysannes et la formation de leurs agents à l’écimage sont indispensables pour une adoption de cette technique à une plus large échelle.

International audience; African swine fever is a devastating disease that can result in death in almost all infected pigs. The continuing spread of African swine fever from Africa to Europe and recently to the high-pig production countries of China and others in Southeast Asia threatens global pork production and food security. The African swine fever virus is an unusual complex DNA virus and is not related to other viruses. This has presented challenges for vaccine development, and currently none is available. The virus is extremely well adapted to replicate in its hosts in the sylvatic cycle in East and South Africa. Its spread to other regions, with different wildlife hosts, climatic conditions, and pig production systems, has revealed unexpected epidemiological scenarios and different challenges for control. Here we review the epidemiology of African swine fever in these different scenarios and methods used for control. We also discuss progress toward vaccine development and research priorities to better understand this complex disease and improve control.

We analyze the alignment mechanisms involved in socio-technical transitions. The multi-level perspective has made the notion of alignment one of the pillars of its analytical framework, but its definition remains rather vague. Using a case study of the development of biological alternatives to agricultural pesticides in Brazil, we show that alignments are based on pairings between entities of the same nature, positioned in the niche and in the regime. The strength of these pairings relies on the coherence of the new sets formed. Several types of entities need to be matched to enable alignments. In this case study, we identify three types of paired entities: technologies, users and their interests, public and private organizations. Understanding these alignment mechanisms is an invitation to deepen the analysis of the relationships between incumbent and alternative technologies in sociotechnical transitions.

The invasive fruit fly Bactrocera dorsalis poses a major threat to the production and trade of mango in sub-Saharan Africa. Farmers devise different innovations to manage the pest in an attempt to minimize yield loss and production costs while maximizing revenues. Using survey data obtained from Embu County, Kenya, we analyzed farmers’ knowledge and perception as regards the invasive fruit fly, their innovations for the management of the pest, and the determinants of their adoption and dis-adoption decisions of recently developed and promoted integrated pest management (IPM) technologies for suppression of the pest. The results show that farmers consider fruit flies as a major threat to mango production (99%) and primarily depend on pesticides (90%) for the management of the pest. Some farmers (35%) however use indigenous methods to manage the pest. Though farmers possess good knowledge of different IPM strategies, uptake is relatively low. The regression estimates show that continued use of IPM is positively associated with the gender and education of the household head, size of a mango orchard, knowledge on mango pests, training, contact with an extension officer, and use of at least one non-pesticide practice for fruit fly management, while IPM dis-adoption was negatively correlated with the size of the mango orchard, practice score and use of indigenous innovations for fruit fly management. We recommend enhancing farmer′s knowledge through increased access to training programs and extension services for enhanced adoption of sustainable management practices for B. dorsalis.

La lutte contre l'onchocercose, ou cécité des rivières, une maladie parasitaire endémique, fut entreprise en Afrique de l'Ouest dans une perspective do développement durable. Tous les moyens technologiques disponibles ont de ce fait été mobilisés pour le contrôle du vecteur, une simulie, puis du parasite responsables de cette maladie, par le Programme de Lutte contre l’Onchocercose en Afrique de l'Ouest (OCP). La lutte antivectorielle consistant en épandages d’insecticides chimiques sur les sites de développement de la simulie dans les rivières, il est apparu indispensable d’assurer la sauvegarde de l’environnement aquatique qui fournit aux communautés riveraines eau et ressources biologiques. Les technologies les plus modernes ont été mises en œuvre dès leur mise au point, pour combattre la maladie, contribuant ainsi à la protection de ce milieu. Le programme de surveillance écologique des rivières traitées par des larvicides anti-simulies a été mis en place dès le lancement d’OCP. et assuré par des spécialistes de I' hydrobiologie des pays africains participants du Programme, sous la supervision d’un groupe international d’experts indépendants, le Groupe Écologique. OCP est incontestablement un succès aussi bien pour ce qui est du contrôle de la maladie que de la protection de l'environnement. Il est l'exemple unique au monde d’un programme de santé publique de longue durée qui depuis son origine a mis en œuvre tout ce qui était possible pour harmoniser les enjeux de l’amélioration de la santé et ceux de la protection de l’environnement. Il s'est achevé avec la satisfaction de laisser aux générations montantes un environnement non dégradé et des vallées libérées de l’onchocercose, qui permettront d’accroître la productivité agricole des pays africains. The control of onchocerciasis, or river blindness, an endemic parasitic disease, was implemented in West Africa in the perspective of sustainable development AH the available technological means to fight this disease, by way of the control of its blackfly vector, then its parasite, were therefore implemented by the Onchocerciasis Control Programme in West Africa (OCP). Vector control being achieved through applications of chemicals on its river breeding sites, it was necessary, at the same time, to fight for the preservation of the aquatic environment, which supplies the communities that live along the rivers with water and biological resources. This was the spirit in which the OCP was set up and implemented, and the most modem technologies were used as they become available to fight the disease, thus facilitating the preservation of the aquatic environment. This Programme has indisputably been a success as regards the control of the disease as also from the point of view of the preservation of the environment The aquatic monitoring programme of the rivers under treatment with anti-simulid larvicides was set up right from the very beginning, and performed by national experts of the Participating Countries of the Programme, under the aegis of a group of international independent experts, the Ecological Croup The Onchocerciasis Control Programme in West Africa is an unique example in the world of a long-term public health programme which has made every effort possible from its inception to adequately combine health and environment issues. It ended with the satisfaction of bequeathing to the coming generations a non degraded environment and valleys freed from onchocerciasis which would increase the agricultural productivity of the countries.

Since its inception in 1974, the Onchocerciasis Control Programme in West Africa (OCP) has implemented a strategy of onchocerciasis (river blindness) control which has been aimed at the long-term interruption of the transmission of the causative agent (the filarial worm Onchocerca volvulus), in all areas where there was a human reservoir of infection of the severe blinding form of the parasite. In operational terms, this has required the weekly application of insecticides (mainly by aircraft)...

Avant les années 1980, la seule méthode de lutte contre l’onchocercose était l’élimination des populations de simulies vectrices. Cette stratégie a été utilisée avec un succès considérable dans le cadre du Programme de Lutte contre l’Onchocercose en Afrique de l’ouest (OCP). La découverte de l’ivermectine, premier médicament efficace contre Onchocerca volvulus et pouvant être distribué à large échelle, suscite depuis 10 ans une nouvelle mobilisation internationale tant au niveau de la recherche fondamentale que de l’élaboration de nouvelles stratégies de lutte applicables en dehors de l’aire d’OCP. Cet article résume l’état des connaissances sur les aspects parasitologiques, cliniques, diagnostiques et épidémiologiques de l’onchocercose. Si le mode de développement des premiers stades parasitaires chez l’homme est encore très mal connu, des progrès importants ont été accomplis dans la connaissance de la dynamique de population d’Onchocerca volvulus. L’étude de la pathogénie des lésions dermatologiques et oculaires a fait l’objet de nombreux travaux. Des études épidémiologiques sont menées en vue d’apprécier l’importance des manifestations systémiques de l’onchocercose. De nouvelles méthodes diagnostiques, plus sensibles que la technique parasitologique classique, ont été mises au point. La répartition de l’onchocercose a été précisée grâce à l’utilisation systématique d’une méthode d’évaluation rapide des niveaux d’endémie. Les techniques de biologie moléculaire, utilisées en routine en Afrique de l’ouest, permettent de différencier les différentes espèces du genre Onchocerca ainsi que plusieurs souches d’Onchocerca volvulus, de pathogénicité différente. Enfin, de nouvelles méthodes de quantification des handicaps ont permis de préciser l’impact socio-économique des complications oculaires et cutanées de l’onchocercose. Before the 1980s, the only available method for control of onchocerciasis was elimination of blackfly vector populations. This strategy was used with considerable success in the Onchocerciasis Control Programme in West Africa (OCP). The discovery of ivermectin, the first effective drug suitable for mass treatment of onchocerciasis, has revived international interest not only in fundamental research but also in development of new strategies to control onchocerciasis in the countries outside the OCP area. This report gives an overview of current parasitological, clinical, epidemiological and diagnostic data about onchocerciasis. Although little is known about the early development of Onchocerca volvulus in the human host, significant insight has been gained into the population dynamics of the parasite. The pathogenesis of cutaneous and ocular manifestations in onchocerciasis is now better understood. Epidemiological studies are under way to evaluate the extent of systemic manifestations. Recently developed diagnostic methods are more sensitive than conventional parasitological techniques. A new method for rapid assessment of endemic level has provided a detailed picture of the distribution of onchocerciasis. Species-and strain-specific DNA probes have been developed for identification of parasites in West Africa. New methods for quantifying disability allow evaluation of the socio-economic impact of the cutaneous and ocular complications of onchocerciasis.