Development and Clinical Validation of a Multiplex Real-Time Quantitative PCR Assay for Human Infection by Anaplasma phagocytophilum and Ehrlichia chaffeensis

Challenges of Diagnosing Severe Ehrlichiosis in Orthotopic Liver Transplant Recipients

In recent solid organ transplant recipients, acute febrile illness is usually a source of grave concern and a diagnostic dilemma, especially if no response is noted after initiation of broad antimicrobial therapy. Human Monocytic Ehrlichiosis (HME) is a tick-borne illness caused by Ehrlichia chaffeensis and is not considered an opportunistic infection in immunocompromised patients such as solid organ transplant patients. Ehrlichiosis in immunocompromised patients can be life-threatening, and a strong index of suspicion is needed, especially in patients who live in endemic areas, for proper treatment initiation with doxycycline. We report a case of a 40-year-old male who received an orthotopic liver transplant six months earlier secondary to primary sclerosing cholangitis, on chronic immunosuppressive medication, who presented with complaints of sudden onset fever associated with nausea, vomiting, and diarrhea. Initial extensive infectious workup was negative and no response to empiric antimicrobials. There was suspicion for ehrlichiosis prompting empiric doxycycline use. Subsequently, E. chaffeensis polymerase chain reaction (PCR) was positive, and the antibiotic regimen was de-escalated to only doxycycline with complete resolution of his symptoms and progressive improvement in previously abnormal biochemical indices.

Discovery and Surveillance of Tick-Borne Pathogens

Within the past 30 yr molecular assays have largely supplanted classical methods for detection of tick-borne agents. Enhancements provided by molecular assays, including speed, throughput, sensitivity, and specificity, have resulted in a rapid increase in the number of newly characterized tick-borne agents. The use of unbiased high throughput sequencing has enabled the prompt identification of new pathogens and the examination of tick microbiomes. These efforts have led to the identification of hundreds of new tick-borne agents in the last decade alone. However, little is currently known about the majority of these agents beyond their phylogenetic classification. Our article outlines the primary methods involved in tick-borne agent discovery and the current status of our understanding of tick-borne agent diversity.

Rhabdomyolysis and Multisystem Organ Failure Due to Fulminant Ehrlichiosis Infection

A previously healthy 51-y-old male presented to his local emergency department with subjective fevers, myalgias, dyspnea, and generalized weakness that had been progressive for several weeks. He was initially diagnosed with bilateral pneumonia, septic shock, and rhabdomyolysis requiring transfer to a tertiary care facility. He was treated for sepsis with broad-spectrum antibiotics, steroids, and a fluid bolus before transfer. Once he arrived at the tertiary care facility, he developed respiratory failure requiring intubation and ventilatory support. Ceftriaxone and metronidazole were started in the intensive care unit to cover common causes of community-acquired versus aspiration pneumonia, and doxycycline was included to cover tick-borne disease based on a history of tick exposure from working in his rural yard. Blood polymerase chain reaction testing later confirmed ehrlichiosis. The patient had a prolonged hospital course requiring ventilatory support and vasopressors, followed by a 4-wk stay in a rehabilitation unit after discharge. Wilderness medical providers should counsel their patients on prevention of tick bites and keep tickborne illness in the differential for acute illness, based on local epidemiology.

Molecular and serological detection of arthropod-borne pathogens in carnivorous birds from Brazil

Rickettsiales, Haemosporida and Rhizobiales agents can cause diseases that affect various animal species, including humans. Due to predation behaviour, carnivorous birds may play an important role in spreading these etiological agentes across geographically distant areas, specially if they are migratory. The aim of this study was to investigate the occurrence and to access the phylogenetic relations among Anaplasmataceae (Ehrlichia, Anaplasma, Neorickettsia), Bartonellaceae (Bartonella spp.), and Haemosporida (Plasmodium, Haemoproteus and Leucocytozoon) agents in blood samples from 121 carnivorous birds sampled in the states of São Paulo and Rio de Janeiro, Brazil. Inclusions resembling hemoparasites were not observed in Giemsa-stained preparations. While three animals were seropositive for E. chaffeensis (3.41% [3/88]; 95% CI:1.17-9.55%), five showed antibodies to A. phagocytophilum (5.68% [5/88]; 95% CI: 2.45-12.62%). Despite the detection of rrs gene fragments closely related to E. chaffeensis (4.13% [5/121]; 95% CI: 1.78-9.31%), no positivity was observed in the qPCR based on the genes vlpt for the organism. Similarly, 12 (9.91% [12/121]; 95% CI: 5.76-16.74%) samples were positive in the qPCR for Anaplasma spp. based on groEL gene, but negative in the qPCR for A. phagocytophilum based on msp-2 gene. Three samples were positive in the nPCR for E. canis based on rrs gene. Three samples were positive for Haemoproteus spp. and one for Plasmodium spp. in the nPCR based on cytB gene. Four birds (3.3% [4/121]; 95% CI: 1.29-8.19%) presented co-positivity by Ehrlichia sp. and Anaplasma sp. in molecular assays. One (0.82% [1/121]; 95% CI:0.15-4.53%) bird showed to be seropositive for E. chaffeensis and and positive in PCR for Haemoproteus sp. All birds were negative in the qPCR assay for Bartonella spp. (nuoG). The present work showed the occurrence of Anaplasmataceae agents and hemosporidians in carnivorous birds from southeastern Brazil. The role of these animals in the dispersion of Anaplasmataceae agents should be further investigated.

Tick-borne zoonoses and commonly used diagnostic methods in human and veterinary medicine

Around the world, human health and animal health are closely linked in terms of the One Health concept by ticks acting as vectors for zoonotic pathogens. Animals do not only maintain tick cycles but can either be clinically affected by the same tick-borne pathogens as humans and/or play a role as reservoirs or sentinel pathogen hosts. However, the relevance of different tick-borne diseases (TBDs) may vary in human vs. veterinary medicine, which is consequently reflected by the availability of human vs. veterinary diagnostic tests. Yet, as TBDs gain importance in both fields and rare zoonotic pathogens, such as Babesia spp., are increasingly identified as causes of human disease, a One Health approach regarding development of new diagnostic tools may lead to synergistic benefits. This review gives an overview on zoonotic protozoan, bacterial and viral tick-borne pathogens worldwide, discusses commonly used diagnostic techniques for TBDs, and compares commercial availability of diagnostic tests for humans vs. domestic animals, using Germany as an example, with the aim of highlighting existing gaps and opportunities for collaboration in a One Health framework.

Recurrent Fevers in a Triathlete

Human granulocytic anaplasmosis (HGA) is a tick-borne illness that typically causes a self-limited febrile illness. We describe herein a healthy triathlete who had recurrent fevers for six weeks as a result of HGA and discuss the impact of this patient’s HGA on his metabolic fitness during training over a three month time period. We also review the literature for other cases of Ehrlichia and Anaplasma with prolonged courses.

A Brief History of the Major Rickettsioses in the Asia-Australia-Pacific Region: A Capstone Review for the Special Issue of TMID

The rickettsioses of the "Far East" or Asia-Australia-Pacific region include but are not limited to endemic typhus, scrub typhus, and more recently, tick typhus or spotted fever. These diseases embody the diversity of rickettsial disease worldwide and allow us to interconnect the various contributions to this special issue of Tropical Medicine and Infectious Disease. The impact of rickettsial diseases-particularly of scrub typhus-was substantial during the wars and "police actions" of the last 80 years. However, the post-World War II arrival of effective antibiotics reduced their impact, when recognized and adequately treated (chloramphenicol and tetracyclines). Presently, however, scrub typhus appears to be emerging and spreading into regions not previously reported. Better diagnostics, or higher population mobility, change in antimicrobial policies, even global warming, have been proposed as possible culprits of this phenomenon. Further, sporadic reports of possible antibiotic resistance have received the attention of clinicians and epidemiologists, raising interest in developing and testing novel diagnostics to facilitate medical diagnosis. We present a brief history of rickettsial diseases, their relative importance within the region, focusing on the so-called "tsutsugamushi triangle", the past and present impact of these diseases within the region, and indicate how historically, these often-confused diseases were ingeniously distinguished from each another. Moreover, we will discuss the importance of DNA-sequencing efforts for Orientia tsutsugamushi, obtained from patient blood, vector chiggers, and rodent reservoirs, particularly for the dominant 56-kD type-specific antigen gene (tsa56), and whole-genome sequences, which are increasing our knowledge of the diversity of this unique agent. We explore and discuss the potential of sequencing and other effective tools to geographically trace rickettsial disease agents, and develop control strategies to better mitigate the rickettsioses.

Targeted Metagenomics for Clinical Detection and Discovery of Bacterial Tick-Borne Pathogens

Tick-borne diseases, due to a diversity of bacterial pathogens, represent a significant and increasing public health threat throughout the Northern Hemisphere. A high-throughput 16S V1-V2 rRNA gene-based metagenomics assay was developed and evaluated using >13,000 residual samples from patients suspected of having tick-borne illness and >1,000 controls. Taxonomic predictions for tick-borne bacteria were exceptionally accurate, as independently validated by secondary testing. Overall, 881 specimens were positive for bacterial tick-borne agents. Twelve tick-borne bacterial species were detected, including two novel pathogens, representing a 100% increase in the number of tick-borne bacteria identified compared to what was possible by initial PCR testing. In three blood specimens, two tick-borne bacteria were simultaneously detected. Seven bacteria, not known to be tick transmitted, were also confirmed to be unique to samples from persons suspected of having tick-borne illness. These results indicate that 16S V1-V2 metagenomics can greatly simplify diagnosis and accelerate the discovery of bacterial tick-borne pathogens.

Optimization and Evaluation of a Multiplex Quantitative PCR Assay for Detection of Nucleic Acids in Human Blood Samples from Patients with Spotted Fever Rickettsiosis, Typhus Rickettsiosis, Scrub Typhus, Monocytic Ehrlichiosis, and Granulocytic Anaplasmosis

Spotted fever group rickettsioses (SFGR), typhus group rickettsioses (TGR), scrub typhus (caused by Orientia tsutsugamushi), ehrlichiosis, and anaplasmosis often present as undifferentiated fever but are not treated by agents (penicillins and cephalosporins) typically used for acute febrile illness. Inability to diagnose these infections when the patient is acutely ill leads to excess morbidity and mortality. Failure to confirm these infections retrospectively if a convalescent blood sample is not obtained also impairs epidemiologic and clinical research. We designed a multiplex real-time quantitative PCR (qPCR) assay to detect SFGR, TGR, O. tsutsugamushi, and infections caused by Anaplasma phagocytophilum and Ehrlichia chaffeensis with the ompA, 17-kDa surface antigen gene, tsa56, msp2 (p44), and vlpt gene targets, respectively. Analytical sensitivity was ≥2 copies/μl (linear range, 2 to 2 × 10⁵) and specificity was 100%. Clinical sensitivities for SFGR, TGR, and O. tsutsugamushi were 25%, 20%, and 27%, respectively, and specificities were 98%, 99%, and 100%, respectively. Clinical sensitivities for A. phagocytophilum and E. chaffeensis were 93% and 84%, respectively, and specificities were 99% and 98%, respectively. This multiplex qPCR assay could support early clinical diagnosis and treatment, confirm acute infections in the absence of a convalescent-phase serum sample, and provide the high-throughput testing required to support large clinical and epidemiologic studies. Because replication of SFGR and TGR in endothelial cells results in very low bacteremia, optimal sensitivity of qPCR for these rickettsioses will require use of larger volumes of input DNA, which could be achieved by improved extraction of DNA from blood and/or extraction of DNA from a larger initial volume of blood.

Ehrlichia spp. and Anaplasma spp. in Xenarthra mammals from Brazil, with evidence of novel 'Candidatus Anaplasma spp.'

Anaplasmataceae agents are obligatory intracellular Gram-negative α-proteobacteria that are transmitted mostly by arthropod vectors. Although mammals of the Superorder Xenarthra (sloths, anteaters, and armadillos) have been implicated as reservoirs for several zoonotic agents, only few studies have sought to detect Anaplasmataceae agents in this group of mammals. This study aimed to investigate the occurrence and genetic diversity of Anaplasma spp. and Ehrlichia spp. in blood and spleen samples of free-living Xenarthra from four different states in Brazil (São Paulo, Mato Grosso do Sul, Rondônia, and Pará). Nested and conventional PCR screening assays were performed to detect the rrs and dsb genes of Anaplasma spp. and Ehrlichia spp., respectively. The assays were positive in 27.57% (91/330) of the Anaplasma spp. and 24.54% (81/330) of the Ehrlichia spp. Of the 91 positive Anaplasma spp. samples, 56.04% were positive in a conventional PCR assay targeting the 23S–5S intergenic region. Phylogenetic and distance analyses based on the rrs gene allocated Anaplasma sequences from sloths captured in Rondônia and Pará states in a single clade, which was closely related to the A. marginale, A. ovis, and A. capra clades. The sequences detected in southern anteaters from São Paulo were allocated in a clade closely related to sequences of Anaplasma spp. detected in Nasua nasua, Leopardus pardalis, and Cerdocyon thous in Brazil. These sequences were positioned close to A. odocoilei sequences. Genotype analysis corroborated previous findings and demonstrated the circulation of two distinct Anaplasma genotypes in animals from north and southeast Brazil. The first genotype was new. The second was previously detected in N. nasua in Mato Grosso do Sul state. The intergenic region analyses also demonstrated two distinct genotypes of Anaplasma. The sequences detected in Xenarthra from Pará and Rondônia states were closely related to those in A. marginale, A. ovis, and A. capra. Anaplasma spp. sequences detected in Xenarthra from São Paulo and were allocated close to those in A. phagocytophilum. The analyses based on the dsb gene grouped the Ehrlichia spp. sequences with sequences of E. canis (São Paulo, Mato Grosso do Sul, and Pará) and E. minasensis (Rondônia and Pará). The data indicate the occurrence of E. canis and E. minasensis and two possible new Candidatus species of Anaplasma spp. in free-living mammals of the Superorder Xenarthra in Brazil.