Parapatric distribution and sexual competition between two tick species, [i]Amblyomma variegatum[/i] and [i]A. hebraeum[/i] (Acari, Ixodidae), in Mozambique

[b]Background[/b]: [i]Amblyomma variegatum[/i] and [i]A. hebraeum[/i] are two ticks of veterinary and human health importance in south-east Africa. In Zimbabwe they occupy parapatric (marginally overlapping and juxtaposed) distributions. Understanding the mechanisms behind this parapatry is essential for predicting the spatio-temporal dynamics of Amblyomma spp. and the impacts of associated diseases. It has been hypothesized that exclusive competition between these species results from competition at the levels of male signal reception (attraction-aggregation-attachment pheromones) or sexual competition for mates. This hypothesis predicts that the parapatry described in Zimbabwe could also be present in other countries in the region. [br/][b]Methods[/b]: To explore this competitive exclusion hypothesis we conducted field surveys at the two species' range limits in Mozambique to identify areas of sympatry (overlapping areas) and to study potential interactions (communicative and reproductive interference effects) in those areas. At sympatric sites, hetero-specific mating pairs were collected and inter-specific attractiveness/repellent effects acting at long and short distances were assessed by analyzing species co-occurrences on co-infested herds and co-infested hosts.[br/] [b]Results[/b]: Co-occurrences of both species at sampling sites were infrequent and localized in areas where both tick and host densities were low. At sympatric sites, high percentages of individuals of both species shared attachment sites on hosts and inter-specific mating rates were high. Although cross-mating rates were not significantly different for[i] A. variegatum[/i] and [i]A. hebraeum[/i] females, attraction towards hetero-specific males was greater for [i]A. hebraeum[/i] females than for A. variegatum females and we observed small asymmetrical repellent effects between males at attachment sites.[br/][b]Conclusions[/b]: Our observations suggest near-symmetrical reproductive interference between [i]A. variegatum[/i] and [i]A. hebraeum[/i], despite between-species differences in the strength of reproductive isolation barriers acting at the aggregation, fixation and partner contact levels. Theoretical models predict that sexual competition coupled with hybrid inviability, greatly reduces the probability of one species becoming established in an otherwise suitable location when the other species is already established. This mechanism can explain why the parapatric boundary in Mozambique has formed within an area of low tick densities and relatively infrequent host-mediated dispersal events

Purification of native HBHA from Mycobacterium avium subsp. paratuberculosis.

International audienceBACKGROUND: Paratuberculosis remains today a major global problem in animal health, especially for dairy cattle. However, the diagnosis of its etiologic agent, Mycobacterium avium subsp. paratuberculosis (Map), still lacks sensitivity because of the lack of available antigens. Little is known about the virulence factors for this pathogen. In this study we have developed a method to produce and purify the heparin-binding hemagglutinin (HBHA), a major adhesin of Mycobacteria, from a culture of Map. FINDINGS: For this extremely slow-growing Mycobacterium, a culture was established in a 3-liter bioreactor. Using the bioreactor the amount of the Map biomass was increased 5-fold compared to a classical culture in flasks. The map-HBHA was purified from a Map lysate by heparin-Sepharose chromatography on HiTrap columns. Binding of map-HBHA onto heparin-Sepharose can be reduced in the presence of salt. Consequently, all steps of sample preparation and column equilibration were carried out in 20 mM Tris-HCl (pH 7.2). The map-HBHA was eluted by a linear NaCl gradient. High resolution mass spectrometry analyses revealed that the native form of map-HBHA has posttranslational modifications, including the removal of the initiation methionine, acetylation of the alanine residue at the N-terminal extremity and the presence of methylated lysines in the C-terminal domain of the protein. CONCLUSIONS: An optimized culture of Map in a bioreactor was established to purify the native map-HBHA from a Map lysate by heparin-Sepharose chromatography. The availability of this antigen offers the possibility to study the structure of the protein and to examine its role in pathogenicity, in particular to better understand the specific interactions of Map with the intestinal tissue. The map-HBHA obtained in its native immunogenic form may also be useful to improve the diagnostic test, especially for the development of a new T-cell-based interferon gamma release assays

Spadin, a Sortilin-Derived Peptide, Targeting Rodent TREK-1 Channels: A New Concept in the Antidepressant Drug Design

We found that spadin, a natural peptide derived from sortilin, blocks the mouse TREK-1 channel and might be an efficient and fast-acting antidepressant

Entre COVARS et Une Seule Santé : veille et anticipation des risques sanitaires

International audienceLa crise COVID-19, les impacts croissants du changement climatique et de l’effondrement de la biodiversité, ont ébranlé les sociétés plus que jamais. Cette situation a créé un « monde d’après » où la mise en œuvre du concept Une seule santé (One Health) est devenue une évidence mondiale avalisée récemment par l’OMS, l’OMSA, la FAO et le PNUE. Le concept enjoint de raisonner de manière systémique et décloisonnée, pour trouver des solutions qui répondent à la fois aux questions de santé et aux questions écologiques, dans la multiplicité des échelles auxquelles elles se posent. Thierry Lefrançois, vétérinaire, et Patrick Giraudoux, écologue, le premier intégré au conseil scientifique COVID19 alors qu’il était initialement essentiellement médical, et les deux au CoVARS à sa création présenteront en quoi cet itinéraire est nourri du concept Une seule santé, et les enjeux qu’il représente

Epidémiologie de la maladie de West Nile en Tunisie

Nous avons cherché à mieux comprendre la situation épidémiologique du virus West Nile (VWN) en Tunisie. Nous avons tout d'abord produit une carte du risque de transmission du VWN aux équidés montrant un risque élevé dans de nombreuses régions, dépendant de facteurs environnementaux : zones humides et climat favorables aux populations d'oiseaux sauvages et de moustiques. Le taux élevé de séroprévalence observé chez les équidés est compatible avec l'hypothèse d'une circulation endémique du VWN sans exclure la possibilité d'introductions répétées.Une étude complémentaire a démontré l'exposition des oiseaux domestiques, péri-domestiques et sauvages au VWN et a permis d'établir un premier inventaire des espèces d'oiseaux les plus exposées, pouvant servir de base à un système de surveillance de l'avifaune sauvage en Tunisie.Le suivi sérologique mensuel de poules sentinelles a permis de détecter la circulation du virus en fin de saison chaude (septembre, octobre) à proximité de zones humides pendant une période de forte activité des moustiques et d abondance des oiseaux sauvages. L'occurrence simultanée de cas humains de fièvre West Nile (FWN) laisse penser qu'un système de poules sentinelles serait utile pour une alerte précoce de recrudescence de l'activité du VWN.A l'issue de ce travail, nous proposons des pistes pour un système de surveillance multidisciplinaire de la FWN, adapté au contexte tunisien, et devant permettre la détection précoce de toute circulation virale.Our investigations aimed at clarifying some aspects of the West Nile virus (WNV) epidemiological situation in Tunisia, and in particular at identifying areas at high risk of WNV circulation. A major achievement was the establishment of a risk map for the transmission of WNF in horses. This map shows that the risk of transmission strongly depends on environmental factors: increased risk associated to wetlands proximity and climatic factors favourable to wild birds and mosquitoes. The high seroprevalence observed in horses is compatible with an endemic circulation of WNV without excluding the possibility of repeated introductions.Another study in birds showed the exposure of domestic, wild resident and migratory birds to WNV, and helped establishing an initial inventory of bird species most exposed to WNV. These studies can serve as a basis for a monitoring system of wild birds in Tunisia.A system of monthly follow-up of sentinel chickens detected virus circulation at the end of the hot season (September, October), near wetlands and during a period of high mosquito activity, and abundance of wild birds. The simultaneous occurrence of human cases of WNF brought us to suggest that active surveillance in sentinel chickens would be useful for early warning of increased activity of WNV. This work allows us to propose trails for a WNV multidisciplinary monitoring system adapted to the Tunisian situation, enabling early detection of viral circulation.MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Stratégies innovantes de lutte contre les maladies émergentes animales

National audienceSanitary systems are vulnerable vis-a-vis the risks of emergence of animal diseases. Three innovating approaches of control of these diseases in the Caribbean are presented by taking as an exampleheartwater, bacterial tropical fatal disease of the ruminants transmitted by the ticks. An inactivated vaccine was developed and adapted to the industrial conditions. The great diversity ofstrains in the field implies to develop innovative studies of molecular epidemiology. In addition, understanding of virulence mechanisms by high throughput techniques of the genome aims at developing a recombinant vaccine. A surveillance network of nervous diseases of the ruminants was set up in Guadeloupe. A geographical data base to be filed on line by the various actors of the monitoring (veterinarians, laboratory) and consultable by the decision makers and the field actors (veterinary services and association ofbreeders) makes it possible to target the communication and to fight against heartwater. The Caribbean animal health network CaribVET contributes to reinforcing monitoring and control of transboundary animal diseases. The permanent interaction between research and surveillance is shown by the use of mathematical modeling of population dynamics of ticks to target the surveillance or to testvarious strategies of control.Les dispositifs sanitaires sont vulnérables face aux risques d’émergence de maladies animales. Trois approches innovantes de lutte contre ces maladies dans la Caraïbe sont présentées en prenant comme exemple la cowdriose, maladie bactérienne tropicale mortelle des ruminants transmise par les tiques. Un vaccin inactivé a été développé puis adapté aux conditions industrielles. La grande diversité de souches sur le terrain implique de développer des études d’épidémiologie moléculaire innovantes. En complément, la compréhension des mécanismes de virulence par des techniques haut débit d’étude du génome visent à développer un vaccin recombinant. Un réseau de surveillance des pathologies nerveuses chez les ruminants a été mis en place en Guadeloupe. Une base de donnée cartographiée remplissable en ligne par les différents acteurs de la surveillance (vétérinaires, laboratoire) et consultable par les décideurs et les acteurs de terrain (services vétérinaires et groupement de défense sanitaire) permet de cibler la communication et la lutte contre la cowdriose. Le réseau caribéen de santéanimale CaribVET contribue au renforcement de la surveillance et du contrôle des maladies animales transfrontalières. L’interaction permanente entre recherche et surveillance est démontrée par l’utilisation des travaux de modélisation mathématique de la dynamique de population de tiques pour cibler la surveillance ou de tester différentes stratégies de contrôle

Stratégies de lutte contre les pathologies et maladies émergentes animales et végétales

National audienc

Iron Starvation Conditions Upregulate Ehrlichia ruminantium Type IV Secretion System, tr1 Transcription Factor and map1 Genes Family through the Master Regulatory Protein ErxR

International audienceEhrlichia ruminantium is an obligatory intracellular bacterium that causes heartwater, a fatal disease in ruminants. Due to its intracellular nature, E. ruminantium requires a set of specific virulence factors, such as the type IV secretion system (T4SS), and outer membrane proteins (Map proteins) in order to avoid and subvert the host's immune response. Several studies have been conducted to understand the regulation of the T4SS or outer membrane proteins, in Ehrlichia, but no integrated approach has been used to understand the regulation of Ehrlichia pathogenicity determinants in response to environmental cues. Iron is known to be a key nutrient for bacterial growth both in the environment and within hosts. In this study, we experimentally demonstrated the regulation of virB, map1, and tr1 genes by the newly identified master regulator ErxR (for Ehrlichia ruminantium expression regulator). We also analyzed the effect of iron depletion on the expression of erxR gene, tr1 transcription factor, T4SS and map1 genes clusters in E. ruminantium. We show that exposure of E. ruminantium to iron starvation induces erxR and subsequently tr1, virB, and map1 genes. Our results reveal tight co-regulation of T4SS and map1 genes via the ErxR regulatory protein at the transcriptional level, and, for the first time link map genes to the virulence function sensu stricto, thereby advancing our understanding of Ehrlichia's infection process. These results suggest that Ehrlichia is able to sense changes in iron concentrations in the environment and to regulate the expression of virulence factors accordingly