The 2023 Society for Vascular Surgery, American Venous Forum, and American Vein and Lymphatic Society clinical practice guidelines for the management of varicose veins of the lower extremities. Part II: Endorsed by the Society of Interventional Radiology and the Society for Vascular Medicine.

The Society for Vascular Surgery, the American Venous Forum, and the American Vein and Lymphatic Society recently published Part I of the 2022 clinical practice guidelines on varicose veins. Recommendations were based on the latest scientific evidence researched following an independent systematic review and meta-analysis of five critical issues affecting the management of patients with lower extremity varicose veins, using the patients, interventions, comparators, and outcome system to answer critical questions. Part I discussed the role of duplex ultrasound scanning in the evaluation of varicose veins and treatment of superficial truncal reflux. Part II focuses on evidence supporting the prevention and management of varicose vein patients with compression, on treatment with drugs and nutritional supplements, on evaluation and treatment of varicose tributaries, on superficial venous aneurysms, and on the management of complications of varicose veins and their treatment. All guidelines were based on systematic reviews, and they were graded according to the level of evidence and the strength of recommendations, using the GRADE method. All ungraded Consensus Statements were supported by an extensive literature review and the unanimous agreement of an expert, multidisciplinary panel. Ungraded Good Practice Statements are recommendations that are supported only by indirect evidence. The topic, however, is usually noncontroversial and agreed upon by most stakeholders. The Implementation Remarks contain technical information that supports the implementation of specific recommendations. This comprehensive document includes a list of all recommendations (Parts I-II), ungraded consensus statements, implementation remarks, and best practice statements to aid practitioners with appropriate, up-to-date management of patients with lower extremity varicose veins.

How to Evaluate and Choose the Proper Treatments for Patients with Lower Extremity Venous Disease.

With an increasing number of interventional and noninterventional treatment options available for venous disorders, it is important that patients undergo a thorough and systematic evaluation. Clinical evaluation should include a personal and family history of venous thromboembolism (VTE), varicose veins, and thrombophilia as these factors affect response and recurrence of disease. Patient should undergo diagnostic and quality of life assessment using validated tools to monitor response to treatment. Duplex ultrasound, both deep and superficial veins, documenting both obstruction and reflux is initial imaging with CT and MRI indicated to document pelvic, iliac vein, and IVC patency and pathology. Conservative therapy including compression, healthy lifestyle with diet, and exercise. New and novel interventional therapies are available for patients with venous disease with recent randomized controlled trials and multisocietal guidelines providing evidence-based recommendations for patients with superficial and deep venous disease. Since the use of anticoagulant and antiplatelet therapies post venous intervention is not well studied nor standardized, patients should routinely undergo evaluation for ongoing risk of recurrent thrombosis and stent occlusion. Finally, patients should be counseled that superficial and deep venous disease is a chronic and often progressive disease, and follow-up at least annually is recommended.

Prediction of patient's neurological recovery from cervical spinal cord injury through XGBoost learning approach.

Due to the diversity of patient characteristics, therapeutic approaches, and radiological findings, it can be challenging to predict outcomes based on neurological consequences accurately within cervical spinal cord injury (SCI) entities and based on machine learning (ML) technique. Accurate neurological outcomes prediction in the patients suffering with cervical spinal cord injury is challenging due to heterogeneity existing in patient characteristics and treatment strategies. Machine learning algorithms are proven technology for achieving greater prediction outcomes. Thus, the research employed machine learning model through extreme gradient boosting (XGBoost) for attaining superior accuracy and reliability followed with other MI algorithms for predicting the neurological outcomes. Besides, it generated a model of a data-driven approach with extreme gradient boosting to enhance fault detection techniques (XGBoost) efficiency rate. To forecast improvements within functionalities of neurological systems, the status has been monitored through motor position (ASIA [American Spinal Injury Association] Impairment Scale [AIS] D and E) followed by the method of prediction employing XGBoost, combined with decision tree for regression logistics. Thus, with the proposed XGBoost approach, the enhanced accuracy in reaching the outcome is 81.1%, and from other models such as decision tree (80%) and logistic regression (82%), in predicting outcomes of neurological improvements within cervical SCI patients. Considering the AUC, the XGBoost and decision tree valued with 0.867 and 0.787, whereas logistic regression showed 0.877. Therefore, the application of XGBoost for accurate prediction and decision-making in the categorization of pre-treatment in patients with cervical SCI has reached better development with this study.

The 2022 Society for Vascular Surgery, American Venous Forum, and American Vein and Lymphatic Society clinical practice guidelines for the management of varicose veins of the lower extremities. Part I. Duplex Scanning and Treatment of Superficial Truncal Reflux: Endorsed by the Society for Vascular Medicine and the International Union of Phlebology.

The Society for Vascular Surgery, American Venous Forum, and American Vein and Lymphatic Society collaborated to update the 2011 Society for Vascular Surgery/American Venous Forum clinical practice guidelines and provide new evidence-based recommendations on critical issues affecting the care of patients with varicose veins. Each recommendation is based on a recent, independent systematic review and meta-analysis of the diagnostic tests and treatments options for patients with lower extremity varicose veins. Part I of the guidelines includes evidence-based recommendations for the evaluation of patients with CEAP (Clinical Class, Etiology, Anatomy, Pathology) class 2 varicose vein using duplex ultrasound scanning and other diagnostic tests, open surgical treatment (ligation and stripping) vs endovenous ablation techniques, thermal vs nonthermal ablation of the superficial truncal veins, and management of incompetent perforating veins in CEAP class 2 disease. We have also made recommendations on the concomitant vs staged treatment of varicose tributaries using phlebectomy or liquid or foam sclerotherapy (with physician-compounded foam or commercially prepared polidocanol endovenous microfoam) for patients undergoing ablation of incompetent superficial truncal veins.

Genealogy of an in-vivo passaged isolate of western Canadian bovine respiratory syncytial virus.

Bovine respiratory syncytial virus (BRSV) is a primary respiratory pathogen in calves. Clinical infection with this pathogen has been experimentally modelled to assess vaccine efficacy using a field isolate (Asquith) of BRSV that has been sequentially passaged in vivo in neonatal calves to maintain virulence. The objective of this retrospective cumulative analysis of passages over approximately 20 years was to determine if there have been any changes in the viral genome of this isolate because of this process. Sequence analyses indicated that the Asquith isolate placed genetically in a clade comprising US and some European isolates and a recently described Chinese BRSV isolate (DQ). Furthermore, there were rare changes in bases over time in the N, G, and F gene segments examined when comparing among different passages ranging from 1996 to 2019. These results indicated the absence of significant mutations in the absence of significant adaptive immunological pressure.

Le virus respiratoire syncitial bovin (BRSV) est un agent pathogène respiratoire primaire chez les veaux. Une infection clinique avec cet agent pathogène a été expérimentalement modélisée pour évaluer l'efficacité vaccinale en utilisant un isolat de champ (Asquith) de BRSV qui a été passé séquentiellement in vivo chez des veaux nouveau-nés pour maintenir sa virulence. L'objectif de cette analyse rétrospective cumulative des passages sur une période d'approximativement 20 ans était de déterminer s'il y avait eu des changements dans le génome viral de cet isolat à cause de ce processus. L'analyse des séquences indiquaient que l'isolat Asquith se positionnait génétiquement dans un clade comprenant des isolats américains et quelques isolats européens et un isolat chinois de BRSV récemment décrit (DQ). Également, il y avait de rares changements de bases dans le temps dans les segments de gènes N, G et F examinés lors de la comparaison parmi les différents passages allant de 1996 à 2019. Ces résultats indiquent l'absence de mutation significative en absence de pression immunologique adaptative significative.(Traduit par Docteur Serge Messier).

Unexpected clinical case of Pasteurella multocida infectious endocarditis in a patient with iv drug abuse: why epidemiological history matters.

Introduction: Right-sided lesions caused by staphylococci are the most common clinical entity of infectious endocarditis (IE) among iv drug abusers. But some aspects of the epidemiological history are critical in terms of early detection of uncommon pathogens. Case report: We describe a clinical observation of native aortic valve IE caused by Pasteurella multocida in a 37-year-old female with a history of heroin addiction, alcohol abuse and liver cirrhosis.She presented herself at our hospital with acute fever, chills, subconjunctival petechial hemorrhages, traces of scratches on the hands, splenomegaly, peripheral edema, elevated WBC and inflammatory serum markers. Initial transthoracic echocardiography was negative, but the patient was put on oxacillin for suspected right-sided IE. The transesophageal echocardiography revealed vegetation on noncoronary leaflet of aortic valve. Blood culture was positive with the growth of P. multocida in 4/4 samples.On detailed questioning, a close domestic contact with cats was revealed. Oxacillin was switched to meropenem and tigecycline with a prompt clinical response. The P. multocida isolate was found to be susceptible to penicillins, so the patient was discharged after 3 weeks with recommendations to take amoxicillin for up to 4 weeks. At 3 and 6 months follow-up there were no signs of IE relapse revealed. Conclusions: P. multocida is a rare causative agent of IE. In our case, this pathogen was identified in a patient with injection drug use, where such etiology is not usually assumed. The close contact with cats was not taken into account, which caused late diagnosis and delayed therapy.

Intradialytic acid-base changes and organic anion production during high versus low bicarbonate hemodialysis.

The use of high dialysate bicarbonate for hemodialysis in end-stage renal disease is associated with increased mortality, but potential physiological mediators are poorly understood. Alkalinization due to high dialysate bicarbonate may stimulate organic acid generation, which could lead to poor outcomes. Using measurements of ß-hydroxybutyrate (BHB) and lactate, we quantified organic anion (OA) balance in two single-arm studies comparing high and low bicarbonate prescriptions. In study 1 (n = 10), patients became alkalemic using 37 meq/L dialysate bicarbonate; in contrast, with the use of 27 meq/L dialysate, net bicarbonate loss occurred and blood bicarbonate decreased. Total OA losses were not higher with 37 meq/L dialysate bicarbonate (50.9 vs. 49.1 meq using 27 meq/L, P = 0.66); serum BHB increased in both treatments similarly (P = 0.27); and blood lactate was only slightly higher with the use of 37 meq/L dialysate (P = 0.048), differing by 0.2 meq/L at the end of hemodialysis. In study 2 (n = 7), patients achieved steady state on two bicarbonate prescriptions: they were significantly more acidemic when dialyzed against a 30 meq/L bicarbonate dialysate compared with 35 meq/L and, as in study 1, became alkalemic when dialyzed against the higher bicarbonate dialysate. OA losses were similar to those in study 1 and again did not differ between treatments (38.9 vs. 43.5 meq, P = 0.42). Finally, free fatty acid levels increased throughout hemodialysis and correlated with the change in serum BHB (r = 0.81, P < 0.001), implicating upregulation of lipolysis as the mechanism for increased ketone production. In conclusion, lowering dialysate bicarbonate does not meaningfully reduce organic acid generation during hemodialysis or modify organic anion losses into dialysate.

Validation of apixaban anti-factor Xa assay and impact of body weight.

BACKGROUND: Direct oral anticoagulants (DOACs) are widely used as therapies for venous thromboembolism and other cardiovascular diseases. However, routine coagulation monitoring is not required, but may be clinically indicated in high risk populations including obese patients. OBJECTIVES: The aims of this study were two fold; to validate a chromogenic assay for anti-factor Xa measurement in patients taking apixaban, and correlate it with PT/INR and PTT, and to measure anti-factor Xa levels in patients who weighed >120 kg. PATIENTS/METHODS: Patients who were taking apixaban had 3 blood samples drawn over a 4 h period. Apixaban levels were determined using an anti-factor Xa activity assay (STA-Liquid Anti-Xa) using STA-Apixaban Calibrator and STA-Apixaban Controls. The PT/INR was determined using standard methodology. Apix MS, using manufacturer provided apixaban standard, was performed on plasma. RESULTS AND CONCLUSIONS: 18 normal weight patients, 39 obese patients and 14 controls were enrolled. There was a strong correlation between apixaban anti-factor Xa activity compared to plasma Apix MS (r = 0.95). In patients >120 kg, there was a statistically significant decreased rate of change in anti-factor Xa levels after ingestion. Further, the area under the curve for apixaban anti-factor Xa levels was significantly lower in patients over 120 kg. While INR correlated with apixaban MS and apixaban anti-factor Xa activity in both normal weight and obese patients, the association was not sufficiently strong to clinically manage patients, normal weight or obese. Given these findings, research is necessary to investigate the clinical utility of apixaban anti-factor Xa activity measurement in selected populations.

Validation of the STA-Liatest DDi assay for exclusion of proximal deep vein thrombosis according to the latest Clinical and Laboratory Standards Institute/Food and Drug Administration guideline: results of a multicenter management study.

: Recommended strategy for venous thromboembolism (VTE) diagnosis includes the use of sensitive D-dimer (DDi) assays along with pretest probability (PTP) assessment. The Clinical and Laboratory Standards Institute (CLSI) recently issued a guideline (US FDA endorsed) on DDi in VTE exclusion. Such guideline specifies the ideal D-dimer assay characteristics and target population. Demonstrate STA-LiatestD-Di performance combined with a PTP score for proximal deep vein thrombosis (pDVT) exclusion in a CLSI compliant study. International, multicenter, prospective nonrandomized, noninterventional clinical outcome management study conducted in a standard-of-care setting. DDi was measured in DVT-suspected consecutive low/moderate PTP outpatients, without conditions possibly impacting DDi values independently of thrombosis presence (age >80, pregnancy, postoperative, cancer) using a 0.5 µg/ml (FEU) threshold for DVT exclusion. Results were used to determine test performance. One thousand two hundred and thirty-four patients (17 centers) signed informed consent. Nine hundred and eighty (mean age: 55) with valid results (494 negative DDi) completed the study (DVT prevalence: 8.7%). STA-LiatestD-Di performance exceeded CLSI/FDA requirements: sensitivity: 100% (95% CI 95.8-100%), NPV: 100% (95% CI 99.3-100%). STA-LiatestD-Di associated with PTP score showed excellent performance for pDVT exclusion, as recently demonstrated for pulmonary embolism. The assay allows safe VTE exclusion, avoiding unnecessary imaging tests.

Antibody recognition of cathepsin L1-derived peptides in Fasciola hepatica-infected and/or vaccinated cattle and identification of protective linear B-cell epitopes.

Fasciola hepatica infection causes important economic losses in livestock and food industries around the world. In the Republic of Ireland F. hepatica infection has an 76% prevalence in cattle. Due to the increase of anti-helminthic resistance, a vaccine-based approach to control of Fasciolosis is urgently needed. A recombinant version of the cysteine protease cathepsin L1 (rmFhCL1) from F. hepatica has been a vaccine candidate for many years. We have found that vaccination of cattle with this immunodominant antigen has provided protection against infection in some experimental trials, but not in others. Differential epitope recognition between animals could be a source of variable levels of vaccine protection. Therefore, we have characterised for first time linear B-cell epitopes recognised within the FhCL1 protein using sera from F. hepatica-infected and/or vaccinated cattle from two independent trials. Results showed that all F. hepatica infected animals recognised the region 19-31 of FhCL1, which is situated in the N-terminal part of the pro-peptide. Vaccinated animals that showed fluke burden reduction elicited antibodies that bound to the regions 120-137, 145-155, 161-171 of FhCL1, which were not recognised by non-protected animals. This data, together with the high production of specific IgG2 in animals showing vaccine efficacy, suggest important targets for vaccine development.

The evidence supporting treatment of reflux and obstruction in chronic venous disease.

On July 20, 2016, a Medicare Evidence Development and Coverage Advisory Committee panel convened to assess the evidence supporting treatment of chronic venous disease. Several societies addressed the questions posed to the panel. A multidisciplinary coalition, representing nine societies of venous specialists, reviewed the literature and presented a consensus opinion regarding the panel questions. The purpose of this paper is to present our coalition's consensus review of the literature and recommendations for chronic venous disease.

Multiresidual LC-MS analysis of plasticizers used in PVC gaskets of lids and assessment of their migration into food sauces.

Plasticizers may migrate from polyvinyl chloride (PVC) gaskets into the foodstuffs mainly by direct contact during the packaging and sterilization procedure, but also by means of occasional contacts occurring during shipment and storage. The present work reports a reliable liquid chromatography-mass spectrometry (LC-MS) method able to quantify the main plasticizers used in the PVC closure gaskets for metal lids to verify their compliance in both food contact materials and foodstuffs. The atmospheric pressure chemical ionization in the positive ion mode resulted the best performing interface for the multiresidual detection of the plasticizers taken into account, followed by selected/multiple reaction monitoring, selected ion monitoring or full scan experiments, depending on the compounds to detect. The method was single-laboratory validated, demonstrating to reach a good sensitivity, thus making possible to perform analysis without any preliminary sample purification or concentration step. It proved to be effectively applicable not only for the determination of plasticizers in PVC gaskets but also in complex food matrices. In particular, it was applied for monitoring plasticizer migration into sauces placed in contact with the lids in worst storage conditions, observing therefore their trend during the shelf-life. Copyright © 2016 John Wiley & Sons, Ltd.

Efficacy of intranasal vaccination with a multivalent vaccine containing temperature-sensitive modified-live bovine herpesvirus type 1 for protection of seronegative and seropositive calves against respiratory disease.

OBJECTIVE To evaluate efficacy and duration of immunity of the bovine herpesvirus type 1 (BHV-1) fraction of a trivalent vaccine also containing parainfluenza virus-3 and bovine respiratory syncytial virus fractions administered intranasally (IN) for protection of calves against infectious bovine rhinotracheitis (IBR). DESIGN Controlled challenge study. ANIMALS 120 dairy calves (3 to 8 days old) seronegative for antibody against BHV-1 (experiments 1 and 2) or seropositive for maternally derived antibody against BHV-1 (experiment 3). PROCEDURES In 3 separate experiments, calves were vaccinated IN via 2 nostrils (experiment 1) or 1 nostril (experiments 2 and 3) with a vaccine containing or not containing a BHV-1 fraction. For seronegative calves, the test vaccine contained a minimum immunizing dose of BHV-1; for seropositive calves, it contained a commercial dose of BHV-1. Calves were challenged IN with virulent BHV-1 on day 28 or 193 (seronegative calves) or day 105 (seropositive calves) after vaccination to evaluate vaccine efficacy. Frequency and duration of clinical signs, rectal temperatures, virus shedding, and serologic responses were compared between treatment groups within experiments. RESULTS In all experiments, BHV-1 vaccinated calves had lower frequencies or shorter durations of clinical signs of IBR than did control calves. Following viral challenge, peak rectal temperatures and degrees of virus shedding were lower and serologic responses were higher in vaccinated versus control calves. CONCLUSIONS AND CLINICAL RELEVANCE IN vaccination against BHV-1 protected all calves against clinical IBR disease, regardless of serologic status at the time of vaccination, and suppressed virus shedding. A single dose of this IN vaccine has the potential to protect seronegative calves for at least 193 days and override maternally derived antibody to protect seropositive calves for at least 105 days.

Implementing the global health security agenda: lessons from global health and security programs.

The Global Health Security Agenda (GHSA) describes a vision for a world that is safe and secure from infectious disease threats; it underscores the importance of developing the international capacity to prevent, detect, and respond to pandemic agents. In February 2014, the United States committed to support the GHSA by expanding and intensifying ongoing efforts across the US government. Implementing these goals will require interagency coordination and harmonization of diverse health security elements. Lessons learned from the Global Health Initiative (GHI), the President's Emergency Program for AIDS Relief (PEPFAR), and the Cooperative Threat Reduction (CTR) program underscore that centralized political, technical, and fiscal authority will be key to developing robust, sustainable, and integrated global health security efforts across the US government. In this article, we review the strengths and challenges of GHI, PEPFAR, and CTR and develop recommendations for implementing a unified US global health security program.

Differential endometrial cell sensitivity to a cholesterol-dependent cytolysin links Trueperella pyogenes to uterine disease in cattle.

Purulent disease of the uterus develops in 40% of dairy cows after parturition, when the epithelium of the endometrium is disrupted to expose the underlying stroma to bacteria. The severity of endometrial pathology is associated with isolation of Trueperella pyogenes. In the present study, T. pyogenes alone caused uterine disease when infused into the uterus of cattle where the endometrial epithelium was disrupted. The bacterium secretes a cholesterol-dependent cytolysin, pyolysin (PLO), and the plo gene was identical and the plo gene promoter was highly similar amongst 12 clinical isolates of T. pyogenes. Bacteria-free filtrates of the T. pyogenes cultures caused hemolysis and endometrial cytolysis, and PLO was the main cytolytic agent, because addition of anti-PLO antibody prevented cytolysis. Similarly, a plo-deletion T. pyogenes mutant did not cause hemolysis or endometrial cytolysis. Endometrial stromal cells were notably more sensitive to PLO-mediated cytolysis than epithelial or immune cells. Stromal cells also contained more cholesterol than epithelial cells, and reducing stromal cell cholesterol content using cyclodextrins protected against PLO. Although T. pyogenes or plo-deletion T. pyogenes stimulated accumulation of inflammatory mediators, such as IL-1beta, IL-6, and IL-8, from endometrium, PLO did not stimulate inflammatory responses by endometrial or hematopoietic cells, or in vitro organ cultures of endometrium. The marked sensitivity of stromal cells to PLO-mediated cytolysis provides an explanation for how T. pyogenes acts as an opportunistic pathogen to cause pathology of the endometrium once the protective epithelium is lost after parturition.

Development and validation of a liquid chromatography/linear ion trap mass spectrometry method for the quantitative determination of deoxynivalenol-3-glucoside in processed cereal-derived products.

Cereal-based food can be frequently contaminated by the presence of mycotoxins derived from Fusarium fungus, and, in particular, by deoxynivalenol (DON). Nowadays, analytical strategies for the detection of DON are well developed, but there are gaps for what concerns a correct identification, quantification and toxicological evaluation of the respective metabolites, mainly related to detoxifying actions via plant metabolism or to processing technologies and also referred to as "masked" mycotoxins. Here, we report the development of a liquid chromatography/linear ion trap mass spectrometry method capable of determining deoxynivalenol-3-glucoside (DON-3G), which is the main known DON metabolite, in different processed cereal-derived products. Samples were extracted with a mixture of methanol/water (80:20; v/v) and cleaned up using immunoaffinity columns. Chromatographic separation was performed using a core-shell C(18) column with an aqueous acetic acid/methanol mixture as the mobile phase under gradient conditions. The method was in-house validated on a bread matrix as follows: matrix-matched linearity (r(2)>0.99) was established in the range of 10-200 µg kg(-1); trueness expressed as recovery was close to 90%; good intermediate precision (overall RSD<9%) and adequate detection quantitation limits (4 and 11 µg kg(-1), respectively) were achieved. Furthermore, applying a metrology approach based on intralaboratory data, the estimated measurement expanded uncertainty was determined to be equal to 29%. The reliability of the method was finally demonstrated in bread, cracker, biscuit and minicake commodities, resulting in relatively low levels of DON-3G, which were not higher than 30 µg kg(-1).

Characterization of an established endothelial cell line from primary cultures of fetal sheep hypothalamus.

Immortalized cell lines from fetal brain are an experimental model for studying the in vitro molecular pathways regulating neural cell differentiation and the development of neural networks. The procedures are described to obtain an established cell line from the 90-day old fetal sheep hypothalamus. Viral oncogene LT-SV40 transformation was used to isolate a stable cell line (ENOS-01) that was characterized immunocytochemically. Immortalized cells can be classified as an endothelial cell line of hypothalamic microvasculature. Furthermore, mRNA expression and immunocytochemical of estrogen receptors α and ß were also evaluated. Since it is known that cerebral vessels are directly targeted by sex steroids, our established cell line represents an alternative system to study estradiol/receptor interactions during brain development. Our in vitro model can provide a tool to investigate the complex relationships among the cell types forming the blood-brain barrier, which is known to be involved in the pathogenesis of sheep transmissible neurological diseases.

Structure of the type IV secretion system in different strains of Anaplasma phagocytophilum.

BACKGROUND: Anaplasma phagocytophilum is an intracellular organism in the Order Rickettsiales that infects diverse animal species and is causing an emerging disease in humans, dogs and horses. Different strains have very different cell tropisms and virulence. For example, in the U.S., strains have been described that infect ruminants but not dogs or rodents. An intriguing question is how the strains of A. phagocytophilum differ and what different genome loci are involved in cell tropisms and/or virulence. Type IV secretion systems (T4SS) are responsible for translocation of substrates across the cell membrane by mechanisms that require contact with the recipient cell. They are especially important in organisms such as the Rickettsiales which require T4SS to aid colonization and survival within both mammalian and tick vector cells. We determined the structure of the T4SS in 7 strains from the U.S. and Europe and revised the sequence of the repetitive virB6 locus of the human HZ strain. RESULTS: Although in all strains the T4SS conforms to the previously described split loci for vir genes, there is great diversity within these loci among strains. This is particularly evident in the virB2 and virB6 which are postulated to encode the secretion channel and proteins exposed on the bacterial surface. VirB6-4 has an unusual highly repetitive structure and can have a molecular weight greater than 500,000. For many of the virs, phylogenetic trees position A. phagocytophilum strains infecting ruminants in the U.S. and Europe distant from strains infecting humans and dogs in the U.S. CONCLUSIONS: Our study reveals evidence of gene duplication and considerable diversity of T4SS components in strains infecting different animals. The diversity in virB2 is in both the total number of copies, which varied from 8 to 15 in the herein characterized strains, and in the sequence of each copy. The diversity in virB6 is in the sequence of each of the 4 copies in the single locus and the presence of varying numbers of repetitive units in virB6-3 and virB6-4. These data suggest that the T4SS should be investigated further for a potential role in strain virulence of A. phagocytophilum.