The Recent Evolution of a Maternally-Inherited Endosymbiont of Ticks Led to the Emergence of the Q Fever Pathogen, Coxiella burnetii

International audienceQ fever is a highly infectious disease with a worldwide distribution. Its causative agent, the intracellular bacterium Coxiella burnetii, infects a variety of vertebrate species, including humans. Its evolutionary origin remains almost entirely unknown and uncertainty persists regarding the identity and lifestyle of its ancestors. A few tick species were recently found to harbor maternally-inherited Coxiella-like organisms engaged in symbiotic interactions, but their relationships to the Q fever pathogen remain unclear. Here, we extensively sampled ticks, identifying new and atypical Coxiella strains from 40 of 58 examined species, and used this data to infer the evolutionary processes leading to the emergence of C. burnetii. Phylogenetic analyses of multi-locus typing and whole-genome sequencing data revealed that Coxiella-like organisms represent an ancient and monophyletic group allied to ticks. Remarkably, all known C. burnetii strains originate within this group and are the descendants of a Coxiella-like progenitor hosted by ticks. Using both colony-reared and field-collected gravid females, we further establish the presence of highly efficient maternal transmission of these Coxiella-like organisms in four examined tick species, a pattern coherent with an endosymbiotic lifestyle. Our laboratory culture assays also showed that these Coxiella-like organisms were not amenable to culture in the vertebrate cell environment, suggesting different metabolic requirements compared to C. burnetii. Altogether, this corpus of data demonstrates that C. burnetii recently evolved from an inherited symbiont of ticks which succeeded in infecting vertebrate cells, likely by the acquisition of novel virulence factors

Moulting and survival of Amblyomma variegatum (Acari: Ixodidae) nymphs in quasi-natural conditions in Burkina Faso; tick predators as an important limiting factor

The survival rate of Amblyomma variegatum engorged nymphs was studied in 9 cohorts released during the first part of the dry season (i.e. the nymph infestation period in the region) and placed on a natural savannah, either in plastic containers or in cages driven into the soil and open at the bottom. All nymphs put in the containers placed in the sun died rapidly, while a high moulting rate (94%) was observed in containers placed in the shade. This rate reached 63% for the ticks released in the cages. The moulting period lasted from less than 4 to more than 6 weeks, depending on the release period: unfed adults are therefore present in the pasture 4-5 months before the onset of the adult infestation period. The survival rate of the unfed adults did not vary according to the release period of the nymphs: at the beginning of the rainy season, 20-25% of the adult ticks were still alive in the cages. Very important variations in survival and disappearance rates were observed according to the place where the cages had been installed: within a few metres, the survival rate could vary from 0 to 90%, presumably because of the activity of predators which removed also dead tick from the plastic containers. Predators may then have a great but highly variable and unpredictable impact on the natural population of A. variegatum adults. Engorged nymphs released on pasture were able to find suitable micro-habitats allowing survival, covered up to 2.8 metres to reach them, and grouped together at the neck or root network of bushes and grass clumps, sometimes burrowing to a depth of 10 cm. (Résumé d'auteur

Effet de l’utilisation des gousses de Faidherbia albida sur les performances de croissance des taurillons à l’Ouest du Burkina Faso

Français La présente étude a pour objectif la valorisation des gousses de Faidherbia albida dans l’alimentation des bovins pour pallier le déficit alimentaire pendant la saison sèche à l’Ouest du Burkina Faso. Elle a consis- té à déterminer la composition chimique et la consommation des aliments utilisés, puis à évaluer l’effet des gousses de F. albida sur les performances de croissance de taurillons en stabulation. La composition chimique des aliments a été évaluée à travers l’analyse de la Matière Sèche, la Matière Minérale, la Matière Organique, la Matière Azotée Totale, la Cellulose Brute et les fibres. La consommation des ali- ments a été évaluée sur 12 taurillons repartis en deux lots qui recevaient deux rations différentes. Les per- formances pondérales ont été déterminées à travers des pesées bihebdomadaires des taurillons. Les teneurs des aliments sont faibles en MAT (entre 4,37 % à 6,63 %) mais riches en parois cellulaires (entre 16,50 % à 37,23 %). La consommation alimentaire est de 3 824,52 g/animal/j pour la ration 1 et de 4 410,87 g/ani- mal/j pour la ration 2. Les GMq obtenus sont de 486,11 g/j pour la ration 1 et 623,02 g/j pour la ration 2. En définitive, l’utilisation des gousses de F. albida dans la complémentation alimentaire des bovins appa- rait comme une alternative pour améliorer les productions animales. Anglais The objective of this study was to investigate the use of Faidherbia albida pods by farmers to improve cattle feeding for overcoming the feed deficit during the dry season in Western Burkina Faso. It consisted in determining the chemical composition and the consumption of the feed used and to evaluate the effect of F. albida pods on the growth performance of young cattle in experimental settings. The chemical com- position of the feeds concerned analysis of dry matter, the mineral matter, organic matter, the nitrogenous matter Total, crude fiber and the fibers. The consumption of the feed was evaluated on 12 young cattle dis- tributed in two lots which received two different rations. The growth performance of these young cattle was evaluated through weight monitoring every two weeks. Chemical analyzes of feeds are low of NMT between 4.37 % and 6.63 %) but rich in cell walls (between16.50 % and 37.23 %). The consumption of feed is 3 824.52 g/animal/day for the diet 1 and 4 410.87 g/animal/day for the diet 2. The average daily weight gain (ADG) obtained from the feeding trial were 486.11 g/d for the diet 1 and 623.02 g/d, for the diet 2. Finally, the use of F. albida pods in cattle food supplementation appears as an alternative to improve animal production during the dry season

Community structure, seasonal variations and interactions between native and invasive cattle tick species in Benin and Burkina Faso

International audienceBackground: The variation of tick abundance on ruminants had received little attention in West Africa before Rhipicephalus (Boophilus) microplus started to invade this region in the early 2000s. Ten years later, R. microplus was suspected to have replaced the native ticks. In addition to testing this hypothesis, this study investigated the interactions between native and invasive ticks and the relative role of climatic and geographical variables in the variations of tick community composition (beta diversity) on cattle herds.Methods: A one-year-long survey was performed in Benin and Burkina Faso during which adult ticks were collected from 144 steers from 12 localities in four different areas once a month. Morphological features were used to assign the collected ticks to different species (A. variegatum, R. annulatus, R. decoloratus, R. microplus and R. geigyi). Beta diversity analyses and generalized linear models allowed characterizing the geographical variations in species assemblage and the effect of co-infestation patterns on the seasonal variations in the abundance and incidence rates of each taxon.Results: About 68 % (22,491/32,148) of all the adult ticks collected in one year were R. microplus. The most heterogeneously distributed taxa were Hyalomma spp and R. microplus and the lowest specific diversity was found in Central Burkina Faso. Although climatic variables did not provide any additional information on the variation in species assemblages compared with the sampling geography, adult tick abundance tended to peak during the late (Boophilus subgenus) or early (other taxa) rainy season. In most taxon-per-locality analyses, the abundance and incidence rate of a given tick taxon significantly increased when the host was co-infested by other taxa. The comparison with previous estimates (when possible) did not support the hypothesis that R. microplus invasion led to a decrease in native tick species abundance.Conclusion: The co-infestation patterns among native and invasive tick species are key factors for the determination of the community structure and the infestation dynamics of each tick taxon in West African cattle

Influence des activités agricoles sur la végétation le long d’un gradient pluviométrique nord-sud du Burkina Faso

Evaluation of the ecological state of Burkina Faso landscapes is necessary to understand human action on environment. This study aimed at characterizing the study sites to understand interactions between climate, humans and ecosystems along a rainfall gradient. The study was carried out along anthropic gradients overlapping protected areas, cropping areas and grazing areas in four agro-sylvo-pastoral areas of Burkina Faso. Floristic inventories were conducted at ecological surveys sites, according to an itinerant inventory method. The floristic richness is decreasing along the rainfall gradient and anthropic gradients. Correspondence analysis of floristic surveys allowed us separating the sahelian to savannah area and representing three types of landscapes (protected, cropping and grazing areas) in each zone based on land use, thus proving human impacts on ecosystem. Human action and climate aridity seems to have the same effect on vegetation. Grazing areas appear as intermediate ecology zones between cropping areas and protected areas.Les écosystèmes subissent à la foi la pression humaine et climatique depuis des décennies, ainsi l’évaluation de l’état écologique des paysages agraires du Burkina Faso est nécessaire pour mettre en évidence l’action humaine sur l’environnement. Dans le cadre de cette étude, l’objectif est de caractériser quatre zones agro-sylvo-pastorales pour comprendre l’interaction entre le climat, l’action humaine et l’écosystème le long d’un gradient pluviométrique. L’étude a été réalisée sur des gradients anthropiques recoupant les aires protégées, les zones de cultures et les zones pâturées dans quatre zones agro-sylvo-pastorales du Burkina Faso. Des relevés floristiques ont été effectués au niveau des sites de suivis écologiques mis en place, selon la méthode d’inventaire itinérante. La richesse spécifique de la flore a été décroissante le long du gradient pluviométrique et du gradient anthropique. L’analyse factorielle des correspondances des relevés floristiques a permis de séparer le domaine sahélien de la savane. Elle a permis également de représenter 3 types de paysages (aires protégées, zones de cultures et zones pâturées) dans chaque zone agro-sylvo-pastorale. La répartition paysagère s’est faite en fonction de l’occupation du sol, mettant ainsi en évidence l’action humaine. Les zones pâturées se présentent comme des zones à écologie intermédiaire entre les zones de cultures et les aires protégées

Distribution des tiques du bétail dans cinq régions du Burkina Faso et évaluation de la connaissance de ces ectoparasites par les éleveurs : Nécessité de campagnes de sensibilisation

Français Les menaces des tiques sur la santé du bétail se sont accrues en Afrique de l’ouest, suite à la double introduction accidentelle de Rhipicephalus (Boophilus) microplus. La présente étude avait pour but d’appréhender la distribution des tiques et d’évaluer la perception des éleveurs sur les tiques dans cinq régions du Burkina Faso. 250 éleveurs dont 50 par région ont été enquêtés et des collectes de tiques ont été réalisées. Les analyses révèlent que les espèces de tiques natives sont plus répandues que la tique invasive dans nos sites d’études. La connaissance des tiques par les éleveurs varie significativement au sein et entre régions.De façon générale, la connaissance des taxa de tiques est liée à leur présence effective, au fait qu’elles soient considérées comme étant les plus abondantes ou pas, à l’âge des éleveurs et/ou à son année d’expérience dans l’élevage. Par ailleurs, il existe une faible concordance entre la connaissance des tiques et la description qu’en donnent les éleveurs. Afin de constituer une veille active en ce qui concerne l’invasion de R. (B.) microplus au Burkina Faso, il s’avère nécessaire que des campagnes de sensibilisation soient réalisées à l’endroit des éleveurs sur la description de cette tique invasive notamment. Anglais The ticks’ threats on cattle health have increased in West Africa since the casual double introduction of Rhipicephalus (Boophilus) microplus. The current study aims to investigate the cattle ticks distribution and to assess the herders perceptions on ticks in five regions of Burkina Faso. 250 herders, of which 50 herders per study area, were surveyed and ticks collection were carried out. Analyses revealed that natives cattle tick species are more widespread than the invasive tick in our study areas. Besides, the knowledge of the ticks by the herders varies significantly (Pvalue<0.05) within and across areas. Furthermore, the knowledge of ticks taxa is related to their effective presence, the fact that they are considered as the most abundant or not, the age of herders and/or its year of livestock practice. In addition, there is a weak agreement between the knowledge of the tick taxa and description given by herders. Therefore, in order to constitute an active alert regarding the invasion of R. (B.) microplus in Burkina Faso, sensitization campaigns need to be carried out for herders on tick description knowledge and that of the invasive tick in particular

Ehrlichia ruminantium infects Rhipicephalus microplus in West Africa

International audienceBackground: The invasion of West Africa by Rhipicephalus microplus during the past decade has changed the ecological situation of the agent of heartwater Ehrlichia ruminantium in this area. Before, its local vector, Amblyomma variegatum, was the most abundant tick species found on livestock. Today, the abundance of the R. microplus is one magnitude higher than that of A. variegatum in many west-African localities. We investigated the potential of this new ecological situation to impact the circulation of E. ruminantium in West Africa