Enterococcus faecalis constitutes an unusual bacterial model in lysozyme resistance

Lysozyme is an important and widespread compound of the host constitutive defense system, and it is assumed that Enterococcus faecalis is one of the few bacteria that are almost completely lysozyme resistant. On the basis of the sequence analysis of the whole genome of E. faecalis V583 strain, we identified two genes that are potentially involved in lysozyme resistance, EF_0783 and EF_1843. Protein products of these two genes share significant homology with Staphylococcus aureus peptidoglycan O-acetyltransferase (OatA) and Streptococcus pneumoniae N-acetylglucosamine deacetylase (PgdA), respectively. In order to determine whether EF_0783 and EF_1843 are involved in lysozyme resistance, we constructed their corresponding mutants and a double mutant. The DeltaEF_0783 mutant and DeltaEF_0783 DeltaEF_1843 double mutant were shown to be more sensitive to lysozyme than the parental E. faecalis JH2-2 strain and DeltaEF_1843 mutant were. However, compared to other bacteria, such as Listeria monocytogenes or S. pneumoniae, the tolerance of DeltaEF_0783 and DeltaEF_0783 DeltaEF_1843 mutants towards lysozyme remains very high. Peptidoglycan structure analysis showed that EF_0783 modifies the peptidoglycan by O acetylation of N-acetyl muramic acid, while the EF_1843 deletion has no obvious effect on peptidoglycan structure under the same conditions. Moreover, the EF_0783 and EF_1843 deletions seem to significantly affect the ability of E. faecalis to survive within murine macrophages. In all, while EF_0783 is currently involved in the lysozyme resistance of E. faecalis, peptidoglycan O acetylation and de-N-acetylation are not the main mechanisms conferring high levels of lysozyme resistance to E. faecalis.

Equine trypanosomosis: enigmas and diagnostic challenges

Equine trypanosomosis is a complex of infectious diseases called dourine, nagana and surra. It is caused by several species of the genus Trypanosoma that are transmitted cyclically by tsetse flies, mechanically by other haematophagous flies, or sexually. Trypanosoma congolense (subgenus Nannomonas) and T. vivax (subgenus Dutonella) are genetically and morphologically distinct from T. brucei, T. equiperdum and T. evansi (subgenus Trypanozoon). It remains controversial whether the three latter taxa should be considered distinct species. Recent outbreaks of surra and dourine in Europe illustrate the risk and consequences of importation of equine trypanosomosis with infected animals into non-endemic countries. Knowledge on the epidemiological situation is fragmentary since many endemic countries do not report the diseases to the World Organisation for Animal Health, OIE. Other major obstacles to the control of equine trypanosomosis are the lack of vaccines, the inability of drugs to cure the neurological stage of the disease, the inconsistent case definition and the limitations of current diagnostics. Especially in view of the ever-increasing movement of horses around the globe, there is not only the obvious need for reliable curative and prophylactic drugs but also for accurate diagnostic tests and algorithms. Unfortunately, clinical signs are not pathognomonic, parasitological tests are not sufficiently sensitive, serological tests miss sensitivity or specificity, and molecular tests cannot distinguish the taxa within the Trypanozoon subgenus. To address the limitations of the current diagnostics for equine trypanosomosis, we recommend studies into improved molecular and serological tests with the highest possible sensitivity and specificity. We realise that this is an ambitious goal, but it is dictated by needs at the point of care. However, depending on available treatment options, it may not always be necessary to identify which trypanosome taxon is responsible for a given infection.

Commitment to cell death is signaled by the appearance of a terminin protein of 30 kDa

Programmed cell death appears to be regulated by a specific molecular program, often dependent upon the activation of unique genes. We have identified terminin in the 60-kDa form as the unique subspecies present only in senescent human diploid fibroblasts. In this report, the biochemical properties of terminin during the process of induced cell death in Swiss 3T3 cells is investigated by total removal of serum, which subsequently activates apoptosis as determined by DNA degradation. Evidence presented here indicates that a specific proteolytic cleavage of terminin proteins occurs during apoptosis, leading to the appearance of a protein species with a molecular mass of 30 kDa (Tp-30) in serum-deprived mouse 3T3 cells. The appearance of Tp-30 can be modulated up to 24 h after serum deprivation by pretreatment with cycloheximide or returning to serum-containing conditions. These studies thus define the association of apoptosis-specific proteolysis of terminin and the appearance of Tp-30 with cell death in mouse 3T3 fibroblasts and can serve as a marker for cells on their way to apoptosis.

Identification of secreted and surface proteins from Enterococcus faecalis

Secreted and surface proteins of bacteria are key molecules that interface the cell with the environment. Some of them, corresponding to virulence factors, have already been described for Enterococcus faecalis , the predominant species involved in enterococcal nosocomial infections. In a global proteomic approach, the identification of the most abundant secreted and surface-associated proteins of E. faecalis JH2-2 strain was carried out. These proteins were separated by gel electrophoresis or directly subjected to in vivo trypsinolysis and then analyzed by liquid chromatography – electrospray ion trap tandem mass spectrometry. Putative functions were assigned by homology to the translated genomic database of E. faecalis. A total of 44 proteins were identified, eight secreted proteins from the supernatant culture and 38 cell surface proteins from two-dimensional gel electrophoresis and in vivo trypsinolysis among which two are common to the two groups. Their sequences analysis revealed that 35 of the 44 proteins harbour characteristic features (signal peptide or transmembrane domains) consistent with an extracellular localization. This study may be considered as an important step to encourage proteomic-based investigations of E. faecalis cell surface associated proteins that could lead to the discovery of virulence factors and to the development of new therapeutic tools.

Diagnosis of animal trypanosomoses: proper use of current tools and future prospects

Reliable diagnostic tools are needed to choose the appropriate treatment and proper control measures for animal trypanosomoses, some of which are pathogenic. Trypanosoma cruzi, for example, is responsible for Chagas disease in Latin America. Similarly, pathogenic animal trypanosomoses of African origin (ATAO), including a variety of Trypanosoma species and subspecies, are currently found in Africa, Latin America and Asia. ATAO limit global livestock productivity and impact food security and the welfare of domestic animals. This review focusses on implementing previously reviewed diagnostic methods, in a complex epizootiological scenario, by critically assessing diagnostic results at the individual or herd level. In most cases, a single diagnostic method applied at a given time does not unequivocally identify the various parasitological and disease statuses of a host. These include "non-infected", "asymptomatic carrier", "sick infected", "cured/not cured" and/or "multi-infected". The diversity of hosts affected by these animal trypanosomoses and their vectors (or other routes of transmission) is such that integrative, diachronic approaches are needed that combine: (i) parasite detection, (ii) DNA, RNA or antigen detection and (iii) antibody detection, along with epizootiological information. The specificity of antibody detection tests is restricted to the genus or subgenus due to cross-reactivity with other Trypanosoma spp. and Trypanosomatidae, but sensitivity is high. The DNA-based methods implemented over the last three decades have yielded higher specificity and sensitivity for active infection detection in hosts and vectors. However, no single diagnostic method can detect all active infections and/or trypanosome species or subspecies. The proposed integrative approach will improve the prevention, surveillance and monitoring of animal trypanosomoses with the available diagnostic tools. However, further developments are required to address specific gaps in diagnostic methods and the sustainable control or elimination of these diseases.

Genomic characterization of the Taylorella genus

The Taylorella genus comprises two species: Taylorella equigenitalis, which causes contagious equine metritis, and Taylorella asinigenitalis, a closely-related species mainly found in donkeys. We herein report on the first genome sequence of T. asinigenitalis, analyzing and comparing it with the recently-sequenced T. equigenitalis genome. The T. asinigenitalis genome contains a single circular chromosome of 1,638,559 bp with a 38.3% GC content and 1,534 coding sequences (CDS). While 212 CDSs were T. asinigenitalis-specific, 1,322 had orthologs in T. equigenitalis. Two hundred and thirty-four T. equigenitalis CDSs had no orthologs in T. asinigenitalis. Analysis of the basic nutrition metabolism of both Taylorella species showed that malate, glutamate and alpha-ketoglutarate may be their main carbon and energy sources. For both species, we identified four different secretion systems and several proteins potentially involved in binding and colonization of host cells, suggesting a strong potential for interaction with their host. T. equigenitalis seems better-equipped than T. asinigenitalis in terms of virulence since we identified numerous proteins potentially involved in pathogenicity, including hemagluttinin-related proteins, a type IV secretion system, TonB-dependent lactoferrin and transferrin receptors, and YadA and Hep_Hag domains containing proteins. This is the first molecular characterization of Taylorella genus members, and the first molecular identification of factors potentially involved in T. asinigenitalis and T. equigenitalis pathogenicity and host colonization. This study facilitates a genetic understanding of growth phenotypes, animal host preference and pathogenic capacity, paving the way for future functional investigations into this largely unknown genus.

Amyloid-enhancing factor: production and response in amyloidosis-susceptible and -resistant mouse strains

Genetic variations in the development of casein-induced amyloidosis exist among inbred strains of mice: CBA/J and C57BL/6J mice are susceptible, while A/J strain mice are resistant to this disease. Amyloidosis is usually induced by daily injections of an inflammatory stimulus for 2-3 wk. The deposition of amyloid in experimental animals can be accelerated by injection of a material called amyloid-enhancing factor (AEF); when injected concomitantly with an inflammatory stimulus, AEF provokes appearance of amyloidosis as early as 2 days after injection. AEF is extracted from amyloid laden or from normal organs (although in small amount). Our studies were designed to determine if the resistance to amyloidosis seen in A/J mice was either due to a lack of AEF production or to an inability of these mice to respond to AEF. A standard source of CBA/J-derived AEF facilitated the development of amyloidosis in the organs of both the susceptible (CBA/J, C57BL/6J) and the resistant A/J mice. On the contrary, amyloidosis was only induced in susceptible CBA/J hosts when material derived from susceptible (CBA/J, C57BL/6J) animals was injected. CBA/J mice injected with A/J-derived AEF preparation did not develop amyloidosis. These results thus suggest that the determination of resistance or susceptibility to secondary amyloidosis could operate at the level of AEF production.

apo-SAA1/apo-SAA2 isotype ratios during casein- and amyloid-enhancing-factor-induced secondary amyloidosis in A/J and C57BL/6J mice mice

A/J mice are resistant while C57BL/6J are susceptible to casein-induced secondary amyloidosis. One mechanism responsible for this phenotypic expression of resistance/susceptibility was shown to operate at the level of production of the 'amyloid-enhancing factor' (AEF). AEF and processing of the apo-SAA protein appear almost concomitantly during amyloidogenesis. In order to determine if AEF played a role in the processing of the apo-SAA protein, three major parameters (apo-SAA1/apo-SAA2 ratios, level of AEF, and fibril formation) were determined during casein-induced secondary amyloidosis. Kinetics of AEF production and serum levels of the two major apo-SAA isotypes were compared in A/J and C57BL/6J animals. Both strains showed equal relative amounts of the two isotypes after seven, 15 and 21 casein injections, irrespective of the fact that the A/J strain had no detectable level of AEF and no amyloid deposition; while C57BL/6J mice had a high AEF level and were amyloidotic after 15 and 21 injections. An increased apo-SAA1/apo-SAA2 ratio due to a decrease in apo-SAA2 was noted after 38 days of casein injections when both strains had extensive deposits of amyloid fibrils. Involvement of AEF as an effector molecule was determined by following the ratio of the two major serum apo-SAA isotypes and fibril formation during an accelerated protocol of amyloid induction in C57BL/6J animals. AEF had no direct effect on apo-SAA isotype ratios in the serum.

Rhodococcus equi's extreme resistance to hydrogen peroxide is mainly conferred by one of its four catalase genes

Rhodococcus equi is one of the most widespread causes of disease in foals aged from 1 to 6 months. R. equi possesses antioxidant defense mechanisms to protect it from reactive oxygen metabolites such as hydrogen peroxide (H(2)O(2)) generated during the respiratory burst of phagocytic cells. These defense mechanisms include enzymes such as catalase, which detoxify hydrogen peroxide. Recently, an analysis of the R. equi 103 genome sequence revealed the presence of four potential catalase genes. We first constructed ΔkatA-, ΔkatB-, ΔkatC-and ΔkatD-deficient mutants to study the ability of R. equi to survive exposure to H(2)O(2)in vitro and within mouse peritoneal macrophages. Results showed that ΔkatA and, to a lesser extent ΔkatC, were affected by 80 mM H(2)O(2). Moreover, katA deletion seems to significantly affect the ability of R. equi to survive within murine macrophages. We finally investigated the expression of the four catalases in response to H(2)O(2) assays with a real time PCR technique. Results showed that katA is overexpressed 367.9 times (± 122.6) in response to exposure to 50 mM of H(2)O(2) added in the stationary phase, and 3.11 times (± 0.59) when treatment was administered in the exponential phase. In untreated bacteria, katB, katC and katD were overexpressed from 4.3 to 17.5 times in the stationary compared to the exponential phase. Taken together, our results show that KatA is the major catalase involved in the extreme H(2)O(2) resistance capability of R. equi.

First Draft Genome Sequence of the Dourine Causative Agent: Trypanosoma Equiperdum Strain OVI

Trypanosoma equiperdum is the causative agent of dourine, a sexually-transmitted infection of horses. This parasite belongs to the subgenus Trypanozoon that also includes the agent of sleeping sickness (Trypanosoma brucei) and surra (Trypanosoma evansi). We herein report the genome sequence of a T. equiperdum strain OVI, isolated from a horse in South-Africa in 1976. This is the first genome sequence of the T. equiperdum species, and its availability will provide important insights for future studies on genetic classification of the subgenus Trypanozoon.

Melarsomine hydrochloride (Cymelarsan®) fails to cure horses with Trypanosoma equiperdum OVI parasites in their cerebrospinal fluid

The aim of this study was to evaluate the ability of melarsomine hydrochloride (Cymelarsan^®) to cure horses suffering from a nervous form of dourine, a sexually-transmitted disease caused by Trypanosoma equiperdum. The recently described experimental model for assessing drug efficacy against horse trypanosomosis allowed us to obtain eight horses (Welsh pony mares) infected by T. equiperdum with parasites in their cerebrospinal fluid. The Cymelarsan^® treatment evaluated consisted of the daily administration of 0.5 mg/kg of Cymelarsan^® over 7 days. Two control horses remained untreated, three horses received the treatment 36 days p.i. and three horses received the treatment 16 days p.i. Following treatment, we observed parasite clearance in blood, stabilization of rectal temperature and a relative improvement in the mean packed cell volume levels for all treated horses. However, live parasites were later observed again in the CSF of all treated horses. Our results indicate the inability of Cymelarsan^® to reach Trypanozoon located in the central nervous system of infected horses and thus discourage the use of Cymelarsan^® to treat animals suffering from a nervous form of dourine.

Development of a multilocus sequence typing scheme for Rhodococcus equi

Rhodococcus equi causes pulmonary and extrapulmonary infections in animals and humans, with endemic situations and significant young foal mortality in stud farms worldwide. Despite its economic impact in the horse-breeding industry, the broad geographic and host distribution, global diversity and population structure of R. equi remain poorly characterised. In this context, we developed a multilocus sequence typing (MLST) scheme using 89 clinical and environmental R. equi of various origins and eight Rhodococcus sp. Data can be accessed at http://pubmlst.org/rhodococcus/. A clonal R. equi population was observed with 16 out of 37 sequence types (STs) grouped into six clonal complexes (CC) based on single-locus variants. One of the six CCs (CC3) is not host-specific, suggesting potential exchanges between different R. equi reservoirs. Most of the virulent equine R. equi CCs/unlinked STs were plasmid-type-specific. Despite this, marked genetic variability with the circulation of multiple R. equi genotypes was generally observed even within the same animal. Focusing on outbreaks, data indicated (i) the potential contagious transmission of R. equi during the 2012-Mayotte equine outbreak because of the poor genotype diversity of clinical strains; (ii) a potential porcine outbreak among the 30 Belgian farms investigated in 2013. This first Rhodococcus equi MLST is a powerful tool for further epidemiological investigations and population biology studies of R. equi isolates.

Monomorphic Trypanozoon: towards reconciling phylogeny and pathologies

Trypanosoma brucei evansi and T. brucei equiperdum are animal infective trypanosomes conventionally classified by their clinical disease presentation, mode of transmission, host range, kinetoplast DNA (kDNA) composition and geographical distribution. Unlike other members of the subgenus Trypanozoon, they are non-tsetse transmitted and predominantly morphologically uniform (monomorphic) in their mammalian host. Their classification as independent species or subspecies has been long debated and genomic studies have found that isolates within T. brucei evansi and T. brucei equiperdum have polyphyletic origins. Since current taxonomy does not fully acknowledge these polyphyletic relationships, we re-analysed publicly available genomic data to carefully define each clade of monomorphic trypanosome. This allowed us to identify, and account for, lineage-specific variation. We included a recently published isolate, IVM-t1, which was originally isolated from the genital mucosa of a horse with dourine and typed as T. equiperdum. Our analyses corroborate previous studies in identifying at least four distinct monomorphic T. brucei clades. We also found clear lineage-specific variation in the selection efficacy and heterozygosity of the monomorphic lineages, supporting their distinct evolutionary histories. The inferred evolutionary position of IVM-t1 suggests its reassignment to the T. brucei evansi type B clade, challenging the relationship between the Trypanozoon species, the infected host, mode of transmission and the associated pathological phenotype. The analysis of IVM-t1 also provides, to our knowledge, the first evidence of the expansion of T. brucei evansi type B, or a fifth monomorphic lineage represented by IVM-t1, outside of Africa, with important possible implications for disease diagnosis.

Splenic macrophage activation and functions in amyloid enhancing factor-induced secondary amyloidosis. Study of phagocytosis, killing, respiratory burst, and MHC class II surface expression

Secondary amyloidosis is a systemic disease characterized by the extracellular tissue deposition of insoluble fibrillar amyloid A protein. Aberrant metabolism of serum amyloid A protein by reticuloendothelial cells is thought to result in the accumulation of fibrils within the tissue. Treatment of mice with amyloid-enhancing factor (AEF) in conjunction with an inflammatory stimulus (i.e., AgNO3) induced amyloid deposition within 48-72 h. The activation state of a macrophage largely defines its enzymatic capabilities. In the studies reported here, we examined the effect of AEF on spleen macrophage activation using both functional and phenotypic assays. We found that while AEF in the presence or absence of AgNO3 has no apparent effect on the ability of spleen and liver macrophages to phagocytose or kill Listeria monocytogenes, it appears to block enhanced respiratory burst function (as measured by O2- production) observed with AgNO3 alone. AEF therefore seems capable of inhibiting certain macrophage activation-associated functions while not affecting others. Our activation phenotype studies, using surface Ia expression, reveal that AEF blocks the increase in number of splenic macrophages expressing Ia seen with AgNO3 alone. Treatment with interferon-gamma was found to restore decreased Ia expression in animals given AEF+AgNO3 but did not prevent amyloid A fibril deposition.

Involvement of occupational therapy departments in research: a provincial survey

It is increasingly recognized that research is necessary to advance the practice of occupational therapy. The objective of this study was to determine whether occupational therapy departments in Quebec were commonly involved in research, and whether participation varied with the size of department and type of work setting. Secondly, enablers and barriers to participation in research were identified. A random sample of occupational therapy departments, stratified by size, were surveyed by mail. Participation rate was 74.8% (107/143). Participation in research was noted in half of the departments surveyed (51/107), most frequently as collaborator. Involvement in research was associated (p < .001) with a greater number of therapists in the department. Furthermore, occupational therapy departments in rehabilitation centres and in university hospitals were more likely to participate in research (79% and 90% respectively), whereas participation was lower for long-term care facilities (29%) and community health clinics (38%). When asked to rank factors that may facilitate participation in research, the highest rankings were given to: time allotted to research, research as a priority for administration, adequate financial support, and presence of an occupational therapy researcher and a research centre on site. This survey demonstrates that a number of factors can promote or prevent the realization of research activities within the clinical setting. Strategies are proposed to enhance the integration of research into clinical practice.

Molecular detection of 7SL-derived small RNA is a promising alternative for trypanosomosis diagnosis

Equine trypanosomosis comprises different parasitic diseases caused by protozoa of the subgenus Trypanozoon: Trypanosoma equiperdum (causative agent of dourine), Trypanosoma brucei (nagana) and Trypanosoma evansi (surra). Due to the absence of a vaccine and the lack of efficacy of the few available drugs, these diseases represent a major health and economic problem for international equine trade. Development of affordable, sensitive and specific diagnostic tests is therefore crucial to ensure the control of these diseases. Recently, it has been shown that a small RNA derived from the 7SL gene (7SL-sRNA) is produced in high concentrations in sera of cattle infected with Trypanosoma congolense, Trypanosoma vivax and Trypanosoma brucei. Our objective was to determine whether 7SL-sRNA could serve as a marker of active infection in equids experimentally infected with Trypanosoma equiperdum by analysing the sensitivity, specificity and stability of the 7SL-sRNA. Using a two-step RT-qPCR, we were able to detect the presence of 7SL-sRNA between 2 and 7 days post-infection, whereas seroconversion was detected by complement fixation test between 5 and 14 days post-infection. There was a rapid loss of 7SL-sRNA signal from the blood of infected animals one day post-trypanocide treatment. The 7SL-sRNA RT-qPCR allowed an early detection of a treatment failure revealed by glucocorticoid-induced immunosuppression. In addition, the 7SL-sRNA remains detectable in positive sera after 7 days of storage at either 4°C, room temperature or 30°C, suggesting that there is no need to refrigerate serum samples before analysis. Our findings demonstrate continual detection of 7SL-sRNA over an extended period of experimental infection, with signals detected more than six weeks after inoculation. The detection of a strong and consistent 7SL-sRNA signal even during subpatent parasitemia and the early detection of treatment failure highlight the very promising nature of this new diagnostic method.

Study of lysozyme resistance in Rhodococcus equi

Lysozyme is an important and widespread component of the innate immune response that constitutes the first line of defense against bacterial pathogens. The bactericidal effect of this enzyme relies on its capacity to hydrolyze the bacterial cell wall and also on a nonenzymatic mechanism involving its cationic antimicrobial peptide (CAMP) properties, which leads to membrane permeabilization. In this paper, we report our findings on the lysozyme resistance ability of Rhodococcus equi, a pulmonary pathogen of young foals and, more recently, of immunocompromised patients, whose pathogenic capacity is conferred by a large virulence plasmid. Our results show that (i) R. equi can be considered to be moderately resistant to lysozyme, (ii) the activity of lysozyme largely depends on its muramidase action rather than on its CAMP activity, and (iii) the virulence plasmid confers part of its lysozyme resistance capacity to R. equi. This study is the first one to demonstrate the influence of the virulence plasmid on the stress resistance capacity of R. equi and improves our understanding of the mechanisms enabling R. equi to resist the host defenses.

Serological evidence of equine infectious anaemia, West Nile fever, surra and equine piroplasmosis in a herd of horses in northern Argentina

Northern Argentina hosts equine populations living under preserved natural areas and extensive breeding conditions, with limited access to veterinary care. Horses can be in contact with i) wildlife considered to be a potential reservoir of horse pathogens (e.g. capybara, coatis and pampas deer) and/or ii) potential disease vectors such as ticks, horse flies, Culicidae and vampire bats. In this context, the aim of this study was to assess the exposure of horses from a herd in northern Argentina to different vector-borne pathogens. Serum samples were collected from 20 horses on a farm in Chaco province. Most of these horses were in good health, but a few showed clinical signs such as fever, neurological signs or emaciation. Potential vectors (ticks, horse flies and Culicidae) were present and a fresh bite of a vampire bat (Desmodus rotundus) was observed on one horse. This serological survey revealed that 100% (20/20) were positive for equine infectious anaemia (EIA), 100% (18/18) for West Nile fever (WNF), 53% (10/19) for surra and 45% (9/20) for equine piroplasmosis (Babesia equi). Among these horses, four were found seropositive for all four infections. On the other hand, all the tested horses were seronegative for equine viral arteritis (EVA), Eastern equine encephalomyelitis (EEE), Venezuelan equine encephalitis (VEE), Western equine encephalomyelitis (WEE) and glanders. The data from this survey conducted on a small number of animals illustrate the need for an effective application of surveillance programmes and control measures for equine diseases in northern Argentina and constitute, to our knowledge, the first report of horses simultaneously seropositive for EIA, WNF, surra and equine piroplasmosis.

Development of a microsphere-based immunoassay for the serological diagnosis of equine trypanosomosis

Trypanozoon infections in equids are caused by three parasite species in the Trypanozoon subgenus: Trypanosoma equiperdum, T. brucei and T. evansi. They are respectively responsible for infectious diseases dourine, nagana and surra. Due to the threat that Trypanozoon infection represents for international horse trading, accurate diagnostic tests are crucial. Current tests suffer from poor sensitivity and specificity, due in the first case to the transient presence of parasites in the blood and in the second, to antigenic cross-reactivity among Trypanozoon subspecies. This study was designed to develop a microsphere‐based immunoassay for diagnosing equine trypanosomosis. We tested beads coated with eight Trypanosoma spp. recombinant antigens: enolase, GM6, PFR1, PFR2, ISG65, VSGat, RoTat1.2 and JN2118HU. Of these, GM6 was identified as the best candidate for the serological diagnosis of Trypanozoon infections in equids. Using a receiver operating characteristic (ROC) analysis on 349 equine sera, anti-GM6 antibodies were detected with an AUC value of 0.994 offering a sensitivity of 97.9% and a specificity of 96.0%. Our findings show that the GM6 antigen is a good target for diagnosing equine trypanosomosis using a microsphere‐based immunoassay. This promising assay could be a useful alternative to the official diagnostic tool for equine trypanosomosis.