Neoehrlichia mikurensis is uncommon in rheumatological patients receiving tumour necrosis factor inhibitors and in blood donors: a retrospective cohort study.

INTRODUCTION: Neoehrlichia mikurensis is a tick-borne bacterium that primarily causes disease in immunocompromised patients. The bacterium has been detected in ticks throughout Europe, with a 0%-25% prevalence. N. mikurensis infection presents unspecific symptoms, which can easily be mistaken for inflammatory disease activity. We aimed to determine the prevalence of N. mikurensis in rheumatological patients receiving tumour necrosis factor inhibitors (TNFi) and a cohort of healthy individuals. MATERIALS AND METHODS: This retrospective cohort study included 400 rheumatological patients treated with TNFi and 400 healthy blood donors. Plasma samples were retrieved from the Danish Rheumatological Biobank and the Danish Blood Donor Study between 2015 and 2022. Age, sex, diagnosis and duration of TNFi treatment were recovered from the Danish Rheumatological Database, DANBIO. Data on age and sex were available for the blood donors. One plasma sample per individual was tested for N. mikurensis DNA-specific real-time PCR targeting the groEL gene. RESULTS: In the rheumatological patients, the median age was 61 years (IQR 55-68 years), 62% were women, and 44% had a diagnosis of seropositive rheumatoid arthritis. In total, 54% of the patients were treated with infliximab. The median time from TNFi initiation to blood sampling was 20 months (IQR, 5-60 months). N. mikurensis DNA was not detected in any samples from patients or blood donors. CONCLUSION: N. mikurensis infection does not appear to represent a prevalent risk in Danish rheumatological patients receiving TNFi or in blood donors.

Infection with Neoehrlichia mikurensis promotes the development of malignant B-cell lymphomas.

The tick-borne pathogen Neoehrlichia (N.) mikurensis is implicated in persistent infection of the vascular endothelium. B cells are crucial for the host defence to this infection. Chronic stimulation of B cells may result in B-cell transformation and lymphoma. Five patients with malignant B-cell lymphoma and concomitant N. mikurensis infection were investigated regarding clinical picture, lymphoma subtype, B-cell lymphoma immunophenotype and IGHV (variable region of the immunoglobulin heavy) gene repertoire. Three of the five patients improved markedly and ceased lymphoma treatment after doxycycline treatment to eliminate N. mikurensis. Sequencing the B-cell lymphoma IGHV genes revealed preferred usage of the IGHV1 (IGHV1-2, and -69) and IGHV3 (IGHV3-15, -21, -23) families. In conclusion, N. mikurensis infection may drive the development of malignant B-cell lymphomas. Eradication of the pathogen appears to induce remission with apparent curing of the lymphoma in some cases.

Cytokine responses of immunosuppressed and immunocompetent patients with Neoehrlichia mikurensis infection.

PURPOSE: The tick-borne bacterium Neoehrlichia mikurensis causes the infectious disease neoehrlichiosis in humans. Vascular endothelium is one of the target cells of the infection. Neoehrlichiosis patients with compromised B cell immunity present with more severe inflammation than immunocompetent patients. The aim of this study was to compare the cytokine profiles of immunocompetent and immunosuppressed patients with neoehrlichiosis. METHODS: Blood samples from Swedish and Norwegian immunosuppressed (N = 30) and immunocompetent (N = 16) patients with neoehrlichiosis were analyzed for the levels of 30 cytokines, using a multiplex cytokine assay and ELISA. A gender-matched healthy control group (N = 14) was analyzed in parallel. Data were analyzed using the multivariate method OPLS-DA. RESULTS: The multiplex cytokine analyses generated more cytokine results than did the uniplex ELISA analyses. Multivariate analysis of the multiplex cytokine results established that increased levels of FGF2, GM-CSF, CXCL10, and IFN-γ were associated with immunosuppressed patients, whereas increased levels of IL-15 and VEGF were associated with immunocompetent neoehrlichiosis patients. When multivariate analysis findings were confirmed with uniplex ELISA, it was found that both groups of patients had similarly elevated levels of VEGF, FGF2 and IFN-γ. In contrast, the immunosuppressed patients had clearly elevated levels of CXCL10, CXCL13 and BAFF, whereas the immunocompetent patients had the same levels as healthy controls. CONCLUSION: Pro-angiogenic and type 1 cytokines were produced as part of the host response of neoehrlichiosis independent of immune status, whereas immunosuppressed neoehrlichiosis patients produced cytokines required for B cell-mediated defense.

[Neoehrlichiosis as a cause of feaver of unknown origin]. / Neoehrlichiose als Ursache eines Fiebers unklarer Genese.

Establishing a diagnosis in cases of fever of unknown origin (FUO) in immunocompromised patients can be difficult. In 25-35% infectious diseases are the underlying cause. This article reports the case of a 74-year-old woman with a 5-month history of fever. Through open biopsy of the femoral shaft and microbiological analysis, a diagnosis of neoehrlichiosis could be established. After initiation of treatment with doxycycline, the symptoms quickly resolved resulting in a complete recovery.

A Novel Neorickettsial Infection in 3 Dogs in the Pacific Northwest.

The genus Neorickettsia includes obligate, intracellular bacteria responsible for diseases including Potomac horse fever caused by Neorickettsia risticii and salmon poisoning disease (SPD) caused by Neorickettsia helminthoeca. The Stellanchasmus falcatus (SF) agent is a member of this genus previously associated only with mild clinical signs in dogs. Between 2013 and 2016, 3 dogs in Washington State (USA) presented with disease suggestive of SPD, but N. helminthoeca was not detected by molecular techniques. Clinical signs included depression, anorexia, and diarrhea. Cytologic examination of aspirates supported a diagnosis of granulomatous lymphadenitis with organisms suggestive of Neorickettsia. Dogs either died or were humanely euthanized due to poor response to therapy. Necropsy findings included lymphadenomegaly and hepatomegaly. Histopathology identified granulomatous and lymphoplasmacytic splenitis, lymphadenitis, enteritis, and hepatitis with extensive necrosis. Neorickettsia DNA was detected using genus-specific primers and direct sequencing showed 100% sequence identity to the SF agent in all 3 dogs. This is the first clinicopathologic description of severe disease in dogs attributed to the SF agent. These findings may suggest the emergence of a novel neorickettsial disease in the Pacific Northwest.

Prevalence of selected rickettsial infections in cats in Southern Germany.

Prevalence of Anaplasma, Ehrlichia, Neorickettsia, and Wolbachia DNA in blood of 479 cats collected in different veterinary clinics in Southern Germany was determined using a previously published conventional PCR using 16S-23S intergenic spacer primers (5' CTG GGG ACT ACG GTC GCA AGA C 3' - forward; 5' CTC CAG TTT ATC ACT GGA AGT T 3' - reverse). Purified amplicons were sequenced to confirm genus and species. Associations between rickettsial infections, and feline immunodeficiency virus (FIV), as well as feline leukemia virus (FeLV) status were evaluated. Rickettsial prevalence was 0.4% (2/479; CI: 0.01-1.62%). In the two infected cats, Anaplasma phagocytophilum DNA was amplified. These cats came from different environment and had outdoor access. Both were ill with many of their problems likely related to other diseases. However, one cat had neutrophilia with left shift and the other thrombocytopenia potentially caused by their A. phagocytophilum infection. There was no significant difference in the FIV and FeLV status between A. phagocytophilum-negative and -positive cats. A. phagocytophilum can cause infection in cats in Southern Germany, and appropriate tick control is recommended.

Neorickettsia sennetsu as a Neglected Cause of Fever in South-East Asia.

Neorickettsia sennetsu infection is rarely recognized, with less than 100 globally reported patients over the last 50 years. The disease is thought to be contracted by eating raw fish, a staple of many South-East Asian cuisines. In 2009, the first patient with sennetsu was identified in the Lao PDR (Laos), raising the question as to how common this organism and related species are in patients presenting with fever. We investigated the frequency of N. sennetsu infection at hospitals in diverse areas of Laos. Consenting febrile hospital inpatients from central (Vientiane: n = 1,013), northern (Luang Namtha: n = 453) and southern (Salavan: n = 171) Laos were screened by PCR for N. sennetsu, if no previous positive direct diagnostic test was available. A PCR-restriction fragment length polymorphism assay was developed to differentiate between N. sennetsu, Ehrlichia chaffeensis and Anaplasma phagocytophilum. To allow more detailed studies of N. sennetsu, culture was successfully established using a reference strain (ATCC VR-367), identifying a canine-macrophage cell line (DH82) to be most suitable to visually identify infection. After screening, N. sennetsu was identified and sequence confirmed in four (4/1,637; 0.2%) Lao patients. Despite the previously identified high seroprevalence of N. sennetsu antibodies in the Lao population (~17%), acute N. sennetsu infection with sufficient clinical signs to prompt hospitalization appears to be rare. The reservoir, zoonotic cycle and pathogenicity of N. sennetsu remain unclear and require further investigations.

Detection of "Candidatus Neoehrlichia mikurensis" in two patients with severe febrile illnesses: evidence for a European sequence variant.

Recently, a new genus of Anaplasmataceae termed "Candidatus Neoehrlichia" was discovered in ticks and rodents. Here, we report on two patients who suffered from febrile bacteremia due to "Candidatus Neoehrlichia mikurensis" associated with thrombotic or hemorrhagic events. 16S rRNA and groEL gene sequencing provided evidence of three groups of sequence variants.

First case of human "Candidatus Neoehrlichia mikurensis" infection in a febrile patient with chronic lymphocytic leukemia.

An immunocompromised patient presented with febrile episodes, an erysipelas-like rash, and thromboembolic complications. Amplification of 16S rRNA gene sequences from blood and sequence analysis revealed "Candidatus Neoehrlichia mikurensis." We report the first case of human disease caused by "Ca. Neoehrlichia mikurensis."

Haemobartonella felis: recent developments in diagnosis and treatment.

Haemobartonella felis is a pleomorphic uncultivated wall-less haemotrophic bacterial parasite. Phylogenetic analysis of 16S rRNA gene sequences from a number of isolates of H felis has demonstrated that these bacteria are most closely related to species in the genus Mycoplasma, and Haemobartonella and related organisms are currently being reclassified as Mollicutes. Diagnosis by cytological examination of blood smears has been problematic, but recent molecular studies have led to the development of sensitive polymerase chain reaction (PCR) assays for diagnosis. Such studies have also resulted in the recognition of two distinct strains of H felis, which are divided into different groups based on phylogenetic analysis. This evolutionary divergence between strains is accompanied by differences in pathogenecity. This review discusses new developments in the diagnosis and treatment of H felis, focusing on the use of, and interpretation of, PCR assays.

Feline haemobartonellosis: clinical, haematological and pathological studies in natural infections and the relationship to infection with feline leukaemia virus.

Haemobartonella felis infection was demonstrated in 38 cats which could be divided into four groups as follows: group A, feline leukaemia virus (FeLV) free cats with H felis infection alone; group B, FeLV free cats with H felis infection and other clinical conditions; group C, FeLV positive cats with H felis infection but no clinical manifestation of FeLV related or any other intercurrent disease; and group D, FeLV positive cats with H felis infection and clinical manifestations of FeLV related or other diseases. Cats in group A were healthy carriers of the infection and none was anaemic, whereas some in group B had clinical haemobartonellosis and anaemia. This anaemia was mainly mild, normocytic and normochromic. Most of the cats in group C and all in group D were more severely ill and anaemic, the anaemia usually being macrocytic and hypochromic. Splenomegaly occurred only in groups C and D. Treatment with tetracyclines did not eliminate H felis from any of the cats and blood transfusions were ineffective in promoting long term recovery from anaemia in cats with intercurrent H felis and FeLV infections. The findings in the cats in groups C and D were further compared with those in a fifth group of cats which were infected with FeLV but free of H felis.

Fatal disseminated cryptococcosis and concurrent ehrlichiosis in a dog.

Laboratory findings in an adult bull terrier presented with a history of anorexia and weight loss included the following: severe anaemia, leukocytosis, neutrophilia, lymphopaenia, thrombocytopaenia, Ehrlichia canis morulae in monocytes, hypergammaglo-bulinaemia, a bleeding tendency, icterus and proteinuria. In addition, a high Haemobartonella canis parasitaemia, non-encapsulated yeasts on urinalysis and a localised Demodex canis infestation were present. Treatment for ehrlichiosis was initiated but the dog died. Lesions found were a severe cryptococcal granulomatous pneumonia and cryptococcal colonies in the lungs, bronchial lymph nodes, kidneys, liver, spleen, heart, meninges, eyes and thoracic cavity. In addition, hyphal forms resembling Filobasidiella neoformans, the teleomorph of Cryptococcus neoformans, were seen in lung fine needle aspiration smears, impression smears and lung sections. C. neoformans was cultured from urine, lung and liver. Lung and kidney also yielded Salmonella typhimureum. Cortical atrophy with T-cell depletion of lymph nodes as well as splenic lymphoid follicular atrophy, typical of chronic ehrlichiosis-induced cell mediated immunosuppression, could have predisposed to the fatal disseminated cryptococcis.

Susceptibility of the female reproductive tract of mice to Tyzzer's organism.

Susceptibility of the reproductive tract of ICR adult female mice to Tyzzer's organisms was examined by intravenous and intravaginal inoculation at various stage of pregnancy. After intravenous inoculation, the uterus was most severely affected when inoculation was made at the midpregnancy. Severe involvement of the uterus was also seen after intravaginal inoculation made either at late-pregnancy or shortly before and after parturition. While non-pregnant female mice were less susceptible to intravenous or intravaginal inoculation, the growth of organisms in the uterine epithelium was recognized after intrauterine inoculation. In 4CS adult female mice showing a constant 4-day-estrous cycle the endometrium was found to be the most susceptible at the estrus phase. Such difference in susceptibility of the female reproductive tract depending upon stage of pregnancy and estrous cycle might be related to metabolic changes of the endometrium controlled by sex hormones, whereas increased blood circulation and modified immune response during pregnancy and estrous cycle might be also involved.

Sequestration and phagocytosis of Haemobartonella felis in the spleen.

Spleens of two cats infected with Haemobartonella felis were examined by electron microscopy to determine the means by which the organism was sequestered in this organ. The principal means of sequestration occurred when H felis, located on the erythrocytes was removed by phagocytosis by a cordal macrophage, apparently preceded by the adhesion of extended processes of the macrophage to H felis. The second and least frequent means of removal of H felis was by pitting, a process that did not cause destruction of the host erythrocyte. The H felis was pitted from the parasitized erythrocyte when H felis passed through gaps between reticular cells or when the parasitized erythrocyte passed among the cytoplasmic processes of the reticular cells in the splenic cords. Some H felis were closely associated with the plasmalemma of cordal reticular cells and also were located in intracytoplasmic vacuoles of the cells without being influenced by the phagocytic process.