Crimean-Congo haemorrhagic fever (CCHF), a potentially severe zoonotic viral disease causing fever and haemorrhagic manifestations in humans. As the Crimean-Congo haemorrhagic fever virus (CCHFV) has been detected in ticks in Spain and antibodies against the virus in ruminant sera in Corsica, it was necessary to know more about the situation in France. In 2022-2023, CCHFV was detected in 155 ticks collected from horses and cattle in southern France.

Ehrlichia ruminantium is a tick-borne intracellular pathogen of ruminants that causes heartwater, a disease present in Sub-saharan Africa, islands in the Indian Ocean and the Caribbean, inducing significant economic losses. At present, three avirulent strains of E. ruminantium (Gardel, Welgevonden and Senegal isolates) have been produced by a process of serial passaging in mammalian cells in vitro, but unfortunately their use as vaccines do not offer a large range of protection against other strains, possibly due to the genetic diversity present within the species. So far no genetic basis for virulence attenuation has been identified in any E. ruminantium strain that could offer targets to facilitate vaccine production. Virulence attenuated Senegal strains have been produced twice independently, and require many fewer passages to attenuate than the other strains. We compared the genomes of a virulent and attenuated Senegal strain and identified a likely attenuator gene, ntrX, a global transcription regulator and member of a two-component system that is linked to environmental sensing. This gene has an inverted partial duplicate close to the parental gene that shows evidence of gene conversion in different E. ruminantium strains. The pseudogenisation of the gene in the avirulent Senegal strain occurred by gene conversion from the duplicate to the parent, transferring a 4 bp deletion which is unique to the Senegal strain partial duplicate amongst the wild isolates. We confirmed that the ntrX gene is not expressed in the avirulent Senegal strain by RT-PCR. The inverted duplicate structure combined with the 4 bp deletion in the Senegal strain can explain both the attenuation and the faster speed of attenuation in the Senegal strain relative to other strains of E. ruminantium. Our results identify nrtX as a promising target for the generation of attenuated strains of E. ruminantium by random or directed mutagenesis that could be used for vaccine production.

Ehrlichia ruminantium is an obligate intracellular bacterium, transmitted by ticks of the genus Amblyomma and responsible for heartwater, a disease of domestic and wild ruminants. High genetic diversity of E. ruminantium strains hampers the development of an effective vaccine against all strains present in the field. In order to develop strategies for the control of heartwater through both vaccine and alternative therapeutic approaches, it is important to first gain a better understanding of the early interaction of E. ruminantium and its host cell. Particularly, the mechanisms associated with bacterial adhesion remain to be elucidated. Herein, we studied the role of E. ruminantium membrane protein ERGA_CDS_01230 (UniProt Q5FFA9), a probable iron transporter, in the adhesion process to host bovine aortic endothelial cells (BAEC). The recombinant version of the protein ERGA_CDS_01230, successfully produced in the Leishmania tarentolae system, is O-glycosylated. Following in vitro culture of E. ruminantium in BAEC, the expression of CDS ERGA_CDS_01230 peaks at the extracellular infectious elementary body stages. This result suggest the likely involvement of ERGA_CDS_01230, named hereafter Ape for Adhesion protein of Ehrlichia, in the early interaction of E. ruminantium with its host cells. We showed using flow cytometry and scanning electron microscopy that beads coated with recombinant ERGA_CDS_01230 (rApe) adheres to BAEC. In addition, we also observed that rApe interacts with proteins of the cell lysate, membrane and organelle fractions. Additionally, enzymatic treatment degrading dermatan and chondroitin sulfates on the surface of BAEC is associated with a 50% reduction in the number of bacteria in the host cell after a developmental cycle, indicating that glycosaminoglycans seem to play a role in the adhesion of E. ruminantium to the host cell. Finally, Ape induces a humoral response in vaccinated animals. Globally, our work identifying the role of Ape in E. ruminantium adhesion to host cells makes it a gold vaccine candidate and represents a first step toward the understanding of the mechanisms of cell invasion by E. ruminantium.

This chapter provides state-of-the-art information to the reader with an overview on the trends, advances, and perspectives in vaccines and vaccinology against fastidious microorganisms such as eukaryotic protozoans and aims to obligate intracellular Rickettsiales. Bovine anaplasmosis is caused by the obligate intracellular bacterium A. marginale and transmitted by hematophagous arthropods including ticks and hematophagous dipteral. The chapter describes the main classes of veterinary protozoal and rickettsial vaccine designs and outlines the composition and performance of several vaccines. Two main strategies have been used to develop vaccines against babesiosis: live attenuated and subunit vaccines. The chapter also provides a brief description of what is known about the immune responses triggered by different vaccine candidates for each pathogen. Host immune responses to anti-Babesia vaccines involve several factors. It is important to integrate different approaches to improve the bulk of information available to vaccine developers.

The Rickettsiales Ehrlichia ruminantium, the causal agent of the fatal tick-borne disease Heartwater, induces severe damage to the vascular endothelium in ruminants. Nevertheless, E. ruminantium-induced pathobiology remains largely unknown. Our work paves the way for understanding this phenomenon by using quantitative proteomic analyses (2D-DIGE-MS/MS, 1DE-nanoLC-MS/MS and biotin-nanoUPLC-MS/MS) of host bovine aorta endothelial cells (BAE) during the in vitro bacterium intracellular replication cycle. We detect 265 bacterial proteins (including virulence factors), at all time-points of the E. ruminantium replication cycle, highlighting a dynamic bacterium–host interaction. We show that E. ruminantium infection modulates the expression of 433 host proteins: 98 being over-expressed, 161 under-expressed, 140 detected only in infected BAE cells and 34 exclusively detected in non-infected cells. Cystoscape integrated data analysis shows that these proteins lead to major changes in host cell immune responses, host cell metabolism and vesicle trafficking, with a clear involvement of inflammation-related proteins in this process. Our findings led to the first model of E. ruminantium infection in host cells in vitro, and we highlight potential biomarkers of E. ruminantium infection in endothelial cells (such as ROCK1, TMEM16K, Albumin and PTPN1), which may be important to further combat Heartwater, namely by developing non-antibiotic-based strategies.

We conducted a serologic survey for Crimean-Congo hemorrhagic fever virus antibodies in livestock (cattle, sheep, and goats; N = 3,890) on Corsica (island of France) during 2014–2016. Overall, 9.1% of animals were seropositive, suggesting this virus circulates on Corsica. However, virus identification is needed to confirm these results.

Unraveling which proteins and post-translational modifications (PTMs) affect bacterial pathogenesis and physiology in diverse environments is a tough challenge. Herein, we used mass spectrometry-based assays to study protein phosphorylation and glycosylation in Ehrlichia ruminantium Gardel virulent (ERGvir) and attenuated (ERGatt) variants and, how they can modulate Ehrlichia biological processes. The characterization of the S/T/Y phosphoproteome revealed that both strains share the same set of phosphoproteins (n = 58), 36% being overexpressed in ERGvir. The percentage of tyrosine phosphorylation is high (23%) and 66% of the identified peptides are multi-phosphorylated. Glycoproteomics revealed a high percentage of glycoproteins (67% in ERGvir) with a subset of glycoproteins being specific to ERGvir (n = 64/371) and ERGatt (n = 36/343). These glycoproteins are involved in key biological processes such as protein, amino-acid and purine biosynthesis, translation, virulence, DNA repair, and replication. Label-free quantitative analysis revealed over-expression in 31 proteins in ERGvir and 8 in ERGatt. While further PNGase digestion confidently localized 2 and 5 N-glycoproteins in ERGvir and ERGatt, respectively, western blotting suggests that many glycoproteins are O-GlcNAcylated. Twenty-three proteins were detected in both the phospho- and glycoproteome, for the two variants. This work represents the first comprehensive assessment of PTMs on Ehrlichia biology, rising interesting questions regarding ER–host interactions. Phosphoproteome characterization demonstrates an increased versatility of ER phosphoproteins to participate in different mechanisms. The high number of glycoproteins and the lack of glycosyltransferases-coding genes highlight ER dependence on the host and/or vector cellular machinery for its own protein glycosylation. Moreover, these glycoproteins could be crucial to interact and respond to changes in ER environment. PTMs crosstalk between of O-GlcNAcylation and phosphorylation could be used as a major cellular signaling mechanism in ER. As little is known about the Ehrlichia proteins/proteome and its signaling biology, the results presented herein provide a useful resource for further hypothesis-driven exploration of Ehrlichia protein regulation by phosphorylation and glycosylation events. The mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium with the data set identifier PXD012589.

Effective population sizes have rarely been estimated in ticks despite the importance of this parameter for evaluating the evolutionary and adaptive potential of tick populations. The present study was aimed at evaluating the effective population sizes of Amblyomma variegatum, the tropical bont tick, in three villages in Burkina Faso. For this purpose, microsatellites markers were developed. Eight out of 19 assessed markers provided good amplification results with 4 to 24 alleles recorded per marker on 216 genotyped ticks. The within-samples polymorphism was congruent with Hardy-Weinberg expectations at four markers while sex linkage and/or null alleles were observed at the others. As sampling involved two tick generations, effective population sizes were independently estimated by two methods insensitive to heterozygosity: the first one is based on linkage disequilibrium analysis within a single cohort while the second uses the changes in allele frequencies across generations. Both methods estimated the number of reproducing ticks ranging from two to a few tens reproductive adults per village and cohort. Such small estimates are congruent with the rarity of records of acaricide resistance in A. variegatum.

Heartwater (or cowdriosis) is a tick-borne disease caused by Ehrlichia ruminantium, an obligatory intracellular bacterium of the order Rickettsiales, transmitted by several ticks of the genus Amblyomma. The organism is genetically highly variable which prevented until now the development of efficient vaccines. The disease is enzootic in sub-Sahelian Africa and in some Caribbean islands. It affects domestic and wild ruminants, the susceptibility to cowdriosis varying greatly between breeds and species: African wildlife shows mainly asymptomatic infections; local cattle breeds are generally protected due to enzootic stability; and introduced cattle breeds and small ruminants, even in enzootic regions, are usually susceptible to heartwater and can suffer high mortality rates. Cowdriosis is characterized by a sudden and acute fever followed by nervous, respiratory, and gastrointestinal symptoms and by hydrothorax and hydropericardium during postmortem examination. In West Africa, the only vector is Amblyomma variegatum, present in areas where pluviometry is higher than 500 mm. Therefore, animals of a high proportion of the Sahelian region are usually not infested by the tick and not infected by the bacterium. They are thus susceptible when introduced in southern parts of the Sahel or in the subhumid neighboring areas of the West African countries, for example during transhumance. Tetracyclines are effective drugs to treat heartwater when administered before occurrence of the nervous symptoms. Various vaccines have been tested, and are still developed, but, up to now, none of them showed enough effectiveness against all the field strains of E. ruminantium to allow its marketing. Prevention is therefore mainly achieved by drastic vector control or, on the contrary, acquisition of enzootic stability following tick infestation combined with tetracycline treatment as soon as hyperthermia occurs.

Ehrlichia 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.

The obligate intracellular pathogenic bacterium, Ehrlichia ruminantium, is the causal agent of heartwater, a fatal disease in ruminants transmitted by Amblyomma ticks. So far, three strains have been attenuated by successive passages in mammalian cells. The attenuated strains have improved capacity for growth in vitro, whereas they induced limited clinical signs in vivo and conferred strong protection against homologous challenge. However, the mechanisms of pathogenesis and attenuation remain unknown. In order to improve knowledge of E. ruminantium pathogenesis, we performed a comparative transcriptomic analysis of two distant strains of E. ruminantium, Gardel and Senegal, and their corresponding attenuated strains. Overall, our results showed an upregulation of gene expression encoding for the metabolism pathway in the attenuated strains compared to the virulent strains, which can probably be associated with higher in vitro replicative activity and a better fitness to the host cells. We also observed a significant differential expression of membrane protein-encoding genes between the virulent and attenuated strains. A major downregulation of map1-related genes was observed for the two attenuated strains, whereas upregulation of genes encoding for hypothetical membrane proteins was observed for the four strains. Moreover, CDS_05140, which encodes for a putative porin, displays the highest gene expression in both attenuated strains. For the attenuated strains, the significant downregulation of map1-related gene expression and upregulation of genes encoding other membrane proteins could be important in the implementation of efficient immune responses after vaccination with attenuated vaccines. Moreover, this study revealed an upregulation of gene expression for 8 genes encoding components of Type IV secretion system and 3 potential effectors, mainly in the virulent Gardel strain. Our transcriptomic study, supported by previous proteomic studies, provides and also confirms new information regarding the characterization of genes involved in E. ruminantium virulence and attenuation mechanisms.

The tropical bont tick, Amblyomma variegatum, is a tick species of veterinary importance and is considered as one of major pest of ruminants in Africa and in the Caribbean. It causes direct skin lesions, transmits heartwater, and reactivates bovine dermatophilosis. Tick saliva is reported to affect overall host responses through immunomodulatory and anti-inflammatory molecules, among other bioactive molecules. The general objective of this study was to better understand the role of saliva in interaction between the Amblyomma tick and the host using cellular biology approaches and proteomics, and to discuss its impact on disease transmission and/or activation. We first focused on the immuno-modulating effects of semi-fed A. variegatum female saliva on bovine peripheral blood mononuclear cells (PBMC) and monocyte-derived macrophages in vitro. We analyzed its immuno-suppressive properties by measuring the effect of saliva on PBMC proliferation, and observed a significant decrease in ConA-stimulated PBMC lymphoproliferation. We then studied the effect of saliva on bovine macrophages using flow cytometry to analyze the expression of MHC-II and co-stimulation molecules (CD40, CD80, and CD86) and by measuring the production of nitric oxide (NO) and pro- or anti-inflammatory cytokines. We observed a significant decrease in the expression of MHC-II, CD40, and CD80 molecules, associated with decreased levels of IL-12-p40 and TNF-α and increased level of IL-10, which could explain the saliva-induced modulation of NO. To elucidate these immunomodulatory effects, crude saliva proteins were analyzed using proteomics with an Orbitrap Elite mass spectrometer. Among the 336 proteins identified in A. variegatum saliva, we evidenced bioactive molecules exhibiting anti-inflammatory, immuno-modulatory, and anti-oxidant properties (e.g., serpins, phospholipases A2, heme lipoprotein). We also characterized an intriguing ubiquitination complex that could be involved in saliva-induced immune modulation of the host. We propose a model for the interaction between A. variegatum saliva and host immune cells that could have an effect during tick feeding by favoring pathogen dissemination or activation by reducing the efficiency of host immune response to the corresponding tick-borne diseases.

Effective population sizes have rarely been estimated in ticks despite the importance of this parameter for evaluating the evolutionary and adaptive potential of tick popula-tions. This work was aimed at evaluating the effective population sizes of Amblyomma variegatum. In addition to the direct losses it imposes on livestock, this tick is the main vector of Ehrlichia ruminantium, the agent of heartwater (cowdriosis) that induces up to 80% mortality in susceptible sheep and goats. The usage of acaricide footbaths seems as the most accurate way to protect livestock from all the deleterious effects of A. varie-gatum. The durability of such a protection would depend on the potential of A. variega-tum to evolve acaricide resistances. We developed microsatellite markers to estimate the effective population sizes of A. variegatum in three neighbor villages from Burkina Faso. As sampling involved two tick generations, effective population sizes were in-dependently estimated by two methods insensitive to heterozygosity: the first one is based on linkage disequilibrium analysis within sampling while the second uses the changes in allele frequencies across generations. Both methods estimated the number of reproducing ticks as ranging from two to a few tens reproductive adults per village and cohort. Such small estimates plead for low probabilities of both apparition and se-lection for acaricide resistance mutants, a result congruent with the rarity of records of acaricide resistance in A. variegatum. This situation will be compared with that of the southern cattle tick Rhipicephalus microplus that show much larger effective pop-ulation sizes and numerous reports of acaricide resistances. Meanwhile, we will also examine how the biology of A. variegatum can explain such low estimates in effective population sizes.

In order to determine the prevalence of E. ruminantium in A. hebraeum and variegatum and the E. ruminantium isolate structure in Mozambique, cattle and wildlife were sampled across the south and center of Mozambique as well as in the adjacent Kruger National Park (KNP), South Africa. The prevalence of E. rumimantium in relation to the tick species and locality was analyzed. Mozambican Ehrlichia isolates were typed using MLST and the distribution of groups clustering genotypes were analysed. In total, 722 and 388 of A. hebraeum and A. variegatum ticks were collected from 31 localities and screened for E. ruminantium, using pCS20 nested PCR and Sol1TqM qPCR. E. ruminantium tick prevalence in cattle varied from 0% to 26.7%, with no infected ticks determined in 7 localities. In wildlife, the prevalence was 8.2 % in the KNP and 6.2% in hunting concessions of the Sofala province. However, no significant difference in prevalence was found between sampling sites and tick species. Most MLST genotypes from Mozambique clustered into subgroup 2C and 2E, which were present in similar proportions in 5 of the 19 localities. Interestingly, MLST genotypes from group G1 and G2D were exclusively found in areas of A. variegatum distribution, while subgroup G2C was only detected in A. hebraeum areas. Moreover, genotypes from subgroup G2E were found in both A. hebraeum and A. variegatum areas. These results contribute to a better understanding of spatial distribution of E. ruminantium and will aid in improvement of heartwater monitoring and control strategies in Mozambique. (Texte integral)

Background: Ehrlichia ruminantium is the causal agent of heartwater, a fatal tropical disease affecting ruminants with important economic impacts. This bacterium is transmitted by Amblyomma ticks and is present in sub-Saharan Africa, islands in the Indian Ocean and the Caribbean, where it represents a threat to the American mainland. Methods: An automated DNA extraction method was adapted for Amblyomma ticks and a new qPCR targeting the pCS20 region was developed to improve E. ruminantium screening capacity and diagnosis. The first step in the preparation of tick samples, before extraction, was not automated but was considerably improved by using a Tissue Lyser. The new pCS20 Sol1 qPCR and a previously published pCS20 Cow qPCR were evaluated with the OIE standard pCS20 nested PCR. Results: pCS20 Sol1 qPCR was found to be more specific than the nested PCR, with a 5-fold increase in sensitivity (3 copies/reaction vs 15 copies/reaction), was less prone to contamination and less time-consuming. As pCS20 Sol1 qPCR did not detect Rickettsia, Anasplasma and Babesia species or closely related species such as Panola Mountain Ehrlichia, E. chaffeensis and E. canis, its specificity was also better than Cow qPCR. In parallel, a tick 16S qPCR was developed for the quality control of DNA extraction that confirmed the good reproducibility of the automated extraction. The whole method, including the automated DNA extraction and pCS20 Sol1 qPCR, was shown to be sensitive, specific and highly reproducible with the same limit of detection as the combined manual DNA extraction and nested PCR, i.e. 6 copies/reaction. Finally, 96 samples can be tested in one day compared to the four days required for manual DNA extraction and nested PCR. Conclusions: The adaptation of an automated DNA extraction using a DNA/RNA viral extraction kit for tick samples and the development of a new qPCR increased the accuracy of E. ruminantium epidemiological studies, as well as the diagnostic capabilities and turn-over time for surveillance of heartwater. This new method paves the way for large-scale screening of other bacteria and viruses in ticks as well as genetic characterization of ticks and tick-pathogen coevolution studies.

1. UMR 17 CIRAD-INRA ASTRE « Animal, Santé, Territoires, Risques, Ecosystèmes », AnimalS, health, Territories, Risks, Ecosystems », Campus International de Baillarguet, TA A-15/G, 34398 Montpellier, France 2. Functional Proteomics Platform FPP, CNRS UMR 5203/UMS 3426, Institut de Génomique Fonctionnelle, 141 rue de la Cardonille, 34094 Montpellier, France 3. UMR 17 CIRAD-INRA CMAEE, Domaine de Duclos Prise d'eau, 97170 Petit Bourg, Guadeloupe, French West Indies

West Nile virus (WNV) emerged in the New World in New York, 1999. In the USA, the virus provokes significant morbidity and mortality in birds, horses and humans. The disease further spread southward into the Caribbean, Central and South America. WNV caused no or very limited health impact on animal and human populations in the Caribbean. In order to detect the potential introduction of WNV in Guadeloupe, a surveillance system was implemented in 2002. Equine serological surveys evidenced viral circulation when abundant seroconversions were detected during the rainy season in 2002. Since then, annual serosurveys were implemented in seronegative equines. Important equine seroconversion rates were detected in two additional periods, the first comprised between September 2007 and August 2008, and the second between January 2011 and March 2013. Short after, sentinel chicken based surveillance was coupled to equine surveillance in areas with previous horse seroconversions. Equine and chicken seroconversions were detected between April 2013 and December 2014. Then, an entomological surveillance network was deployed early 2015 in two areas with recent horse and chicken seroconversions. At each area, the dynamics of mosquito populations was studied around sentinel chickens and nearby natural landscapes to determine the presence of potential bridge and enzootic vectors. Seasonality of mosquitoes evidenced that potential vectors of WNV are abundant during the rainy season at all landscapes. The high density of potential vectors during the rainy season does overlap with equine and poultry seroconversion periods suggesting an increased risk for transmission. (Texte integral)

Amblyomma variegatum ticks are considered as main pest of ruminants in Africa and in the Caribbean, transmitting heartwater and reactivating bovine dermatophilosis. The objective of our study was to understand the role of Amblyomma saliva in tick-host interactions using proteomics and cellular biology approaches. Among the 336 proteins identified in A. variegatum saliva, a bioinformatics analysis highlighted bioactive molecules with anti-inflammatory and immuno-modulatory properties. We also characterised an ubiquitination complex that could participate in saliva-induced immune suppression of the host. We focused on the immuno-modulating effects of A. variegatum saliva on bovine peripheral blood mononuclear cells (PBMCs) and on macrophages in vitro. We first evidenced a significant decrease of lymphoproliferation for ConA stimulated PBMCs indicative of saliva immuno-suppressive properties. Then, we studied the effect of saliva on bovine macrophages, by measuring nitric oxide production and pro- or anti-inflammatory cytokines such as interleukins IL-10, IL-12p40, and TNF-α. We also analyzed activation and co-stimulatory molecules such as MHC-II, CD40, CD80 or CD86. Finally, we suggest an integrated model of interaction between tick saliva and host immune cells, with a potential effect during tick feeding to favour pathogens dissemination by decreasing host immune response efficacy. Our results bring new insights for a better understanding of tick-ruminant interactions at the molecular level, and pave the way towards integrative strategies to interfere with both the immunosuppressive and infectious processes in corresponding tick-borne diseases. (Texte integral)

Heartwater, caused by the Rickettsiales Ehrlichia ruminantium, is one of the most important tick-borne diseases of livestock in Africa, but also in the Caribbean from where it threatens the American mainland. All domestic and wild ruminants can be infected by E. ruminantium, a small pleomorphic gram-negative obligate intracellular bacterium invading the cytoplasm of vascular endothelial cells. Clinical diagnosis of heartwater is based on the presence of Amblyomma sp. ticks, nervous signs, and presence of transudates in the pericardium and thorax on post-mortem examination, and efficient molecular diagnostics allow reliable heartwater confirmation but not early detection. The objective of the present study was to evaluate modifications in serum composition in animals infected by E. ruminantium and define new diagnostic biomarkers. For this, sera from goats experimentally infected by intravenous injection of E. ruminantium cultured in bovine aortic endothelial cells in vitro were sampled. Sera at Day 0 and Day 14 post-infection (occurrence of clinical signs) were pre-fractionated by SDS-PAGE and analysed by shotgun next-generation proteomics by means of high-throughput analysis of peptides with a Q-Exactive HF mass spectrometer incorporating an ultra-high-field Orbitrap analyzer. Preliminary data obtained against the Capra hircus and Ehrlichia ruminantium theoretical molecular databases evidenced 6 and 2 proteins of interest for which abundances were increased or decreased, respectively, at Day 14. These proteins could represent a molecular signature of E. ruminantium infection. Here, we demonstrated the relevance of such proteomic approach to propose candidate diagnostic biomarkers of heartwater. Further investigations will be performed for monitoring more precisely the whole kinetics of E. ruminantium infection for delineating biomarkers for early diagnosis. (Texte integral)