Emergence of ehrlichiosis by a new tick-borne Ehrlichia species in China.

OBJECTIVES: From March to June 2021, the reported number of clinically diagnosed endemic typhus in Anhui and Hubei provinces of China nearly increased four-fold compared with the monthly average numbers in last 5 years. An etiological and epidemiological investigation was initiated. METHODS: The clinical specimens from the reported patients and the potential vector ticks were collected for molecular and serological detection, as well as cell culturing assay to identify the potential pathogen. RESULTS: Polymerase chain reaction and sequence analysis of rrs and groEL showed that the pathogen from these patients was Ehrlichia sp., isolated from Haemaphysalis longicornis attached to these patients. The phylogenetic analysis based on 39 Ehrlichia genomes suggested that it should be taxonomically classified as a novel species, tentatively named "Candidatus Ehrlichia erythraense". A total of 19 of 106 cases were confirmed as Candidatus Ehrlichia erythraense infections by polymerase chain reaction, sequencing, and/or serological tests. The most frequent symptoms were fever (100%), rashes (100%), asthenia (100%), anorexia (100%), and myalgia (79%). CONCLUSION: The occurrence of the disease presenting with fever and rashes in Anhui and Hubei provinces was caused by a novel species of the genus Ehrlichia; physicians need to be aware of this newly-discovered pathogen to ensure appropriate testing, treatment, and regional surveillance.

Increased Incidence of Ehrlichia chaffeensis Infections in the United States, 2012 Through 2016.

Human ehrlichioses are tick-borne diseases that have been increasing in incidence in the United States during recent years. Ehrlichia chaffeensis is one of the primary bacteria that cause ehrlichiosis in humans, which typically results in fever-like symptoms, but may also be fatal if left untreated. E. chaffeensis infections are reported to the Centers for Disease Control and Prevention (CDC) through the National Notifiable Diseases Surveillance System (NNDSS). This study analyzed the cases of E. chaffeensis infections reported by the NNDSS from 2012 through 2016. There were 6786 cases and the incidence rate was 4.46 cases per million persons per year. The demographic group most commonly infected was white males between the ages of 40 and 64. Infections were most abundant in the southeast and midwest, particularly in Arkansas, Missouri, Tennessee, and Oklahoma, as well as much of the east coast. The number of cases reported each year from 2012 through 2016 was higher than the number reported in any of the previous 4 years. Ongoing surveillance and reporting of tick-borne diseases are critical to inform public health practice and guide disease treatment and prevention efforts.

Ehrlichioses: An Important One Health Opportunity.

Ehrlichioses are caused by obligately intracellular bacteria that are maintained subclinically in a persistently infected vertebrate host and a tick vector. The most severe life-threatening illnesses, such as human monocytotropic ehrlichiosis and heartwater, occur in incidental hosts. Ehrlichia have a developmental cycle involving an infectious, nonreplicating, dense core cell and a noninfectious, replicating reticulate cell. Ehrlichiae secrete proteins that bind to host cytoplasmic proteins and nuclear chromatin, manipulating the host cell environment to their advantage. Severe disease in immunocompetent hosts is mediated in large part by immunologic and inflammatory mechanisms, including overproduction of tumor necrosis factor α (TNF-α), which is produced by CD8 T lymphocytes, and interleukin-10 (IL-10). Immune components that contribute to control of ehrlichial infection include CD4 and CD8 T cells, natural killer (NK) cells, interferon-γ (IFN-γ), IL-12, and antibodies. Some immune components, such as TNF-α, perforin, and CD8 T cells, play both pathogenic and protective roles. In contrast with the immunocompetent host, which may die with few detectable organisms owing to the overly strong immune response, immunodeficient hosts die with overwhelming infection and large quantities of organisms in the tissues. Vaccine development is challenging because of antigenic diversity of E. ruminantium, the necessity of avoiding an immunopathologic response, and incomplete knowledge of the protective antigens.

Diagnóstico serológico y molecular de Ehrlichiosis humana en pacientes con sintomatologí­a clí­nica compatible con la enfermedad en el estado Zulia Venezuela 2004-2005 / Serological and molecular diagnosis of human Ehrlichiosis in patients with clinical manifestations associated with the disease in Zulia Venezuela 2004-2005

La Ehrlichiosis humana es una enfermedad zoonótica, transmitida al hombre por la picadura de garrapatas del perro y pocas veces del venado. E. chaffensis es el agente causal más relacionado con la Ehrlichiosis Humana, sin embargo, la ehrlichiosis en humanos puede ser causada por ehrlichiaspropias de los caninos como E. canis y E. ewingii. En 1992, en el estado Zulia se presenta el primer caso de Ehrlichiosis Humana, en una lactante de 17 meses de edad, en quien se detectaron anticuerpos frente a E. chaffensis. El objetivo de esta investigación fue estudiar la presencia de infección por Ehrlichia spp., en suero y sangre total de 30 sujetos con clínica sugestiva de esta patología. Se utilizaron las técnicas de IFI y ensayo nested PCR (Reacción en cadena de la polimerasa), usando primers derivados de la secuencia genética que codifica el ARN ribosomal 16S de Ehrlichia spp., que proporcionan información de género más no de especie, debido a que se necesitan primers de género que pusieran detectar Ehrlichias en cualquier huésped. Ninguna de las muestras fue positiva en la prueba IFI, no evidenciándose anticuerpos para Ehrilichia spp. El ensayo nested PCR de las muestras sanguíneas no mostró amplificación de las secuencias seleccionadas del gen del ARN ribosomal 16S en ninguna de las muestras. Los datos obtenidos no ponen en evidencia la infección por Ehrlichia spp. en los pacientes estudiados.

Human Ehrlichiosis is a zoonotic disease transmitted to humans through the bite of dog and occasionally, deer ticks. E. chaffeensis is the most common etiological agent related to human Ehrlichiosis; however, human Ehrlichiosis can be caused by canine ehrlichias such as E. canis and E. ewingii. In 1992, in the State of Zulia, the first case of human Ehrlichiosis appeared in a 17-month-old infant, in whom antibodies against E. chaffeensis were detected. The aim of this research was to study the presence of Ehrlichia spp. infection in the serum and whole blood of 30 persons with clinical symptoms associated with the disease. This was accomplished through techniques of indirect immunofluorescence and nested polymerase chain reaction assay (nested PCR), using primers derived from the genetic sequence that codify the ribosomal RNA 16S of Ehrlichia spp., which give information regarding gender but not species; due to this, gender primers are needed that could detect Ehrlichias in any host. None of the samples in the IFI assay was positive; no antibodies for Ehrilichia spp. were in evidence. The nested PCR test did not show amplification of the target sequence. The data did not support the evidence of Ehrlichia spp. infection in the patients studied.