Neoehrlichia mikurensis Causing Thrombosis and Relapsing Fever in a Lymphoma Patient Receiving Rituximab

Dual detection of Neoehrlichia mikurensis and Anaplasma phagocytophilum: How biplex PCR led in France to the diagnosis of neoehrlichiosis in post-tick bite fever

OBJECTIVES

Neoehrlichia mikurensis (NM) is an emerging intracellular bacterium member of the Anaplasmatacecae family. So far, only four cases have been described in France, all of them retrospectively.

METHODS

This study describes two new cases of NM discovered following implementation of a biplex PCR targeting both Anaplasma and NM.

RESULTS

Two immunocompetent patients developed a flu-like illness within 14 days after an identified tick bite. Both had negative Anaplasma PCR, but by using this biplex PCR NM, infection was diagnosed in both cases. One patient recovered spontaneously while the second was successfully treated by a seven-day course of doxycycline.

CONCLUSION

Present in Eastern France, NM is underdiagnosed. Biplex PCR screening of NM with A.phagocytophilum could effectively address this issue.

Ten years of detecting Neoehrlichia mikurensis infections in Sweden: demographic, clinical and inflammatory parameters

PURPOSE

To increase knowledge about the varied clinical manifestations of human infection with the emerging tick-borne pathogen Neoehrlichia mikurensis.

METHODS

All patients diagnosed in Sweden with N. mikurensis infection during a 10-year period (2013-2023) were investigated regarding their demographic factors, risk factors, comorbidities, clinical signs and symptoms, and laboratory results. Multivariate models were generated using "Orthogonal Projections to Latent Structures-Discriminant Analysis" to identify clinical and immune parameters associated with N. mikurensis infection.

RESULTS

During the 10-year period, 134 patients were diagnosed with N. mikurensis infection, 102 of whom were included in this study. Most of the patients (79%) were immunosuppressed. The main comorbidities were malignant B-cell lymphomas, multiple sclerosis, and rheumatoid arthritis. Rituximab therapy (59%) and splenectomy (14%) featured prominently. All patients resided in the southern tick-endemic part of Sweden, yet one-third of them were diagnosed in wintertime when ticks are inactive. Two asymptomatically infected blood donors were identified but transfusion-transmitted infection was not confirmed. Increased levels of C-reactive protein, orosomucoid, and total IgM in serum were associated with neoehrlichiosis. Previously unreported symptoms such as ankle edema, neck pain, numbness, and sudden deafness were detected in some patients. One case of aplastic anemia partially improved after eradication of the infection.

CONCLUSIONS

Neoehrlichiosis is a multi-faceted emerging infectious disease.

Fever of Unknown Origin, a Vascular Event, and Immunosuppression in Tick-Endemic Areas: Think About Neoehrlichiosis

Three patients were referred to our hospital because of fever of unknown origin (FUO) and thrombosis or thrombophlebitis. All of them had been under immunosuppression (IS) with rituximab. Intensive diagnostics for FUO and blood cultures remained negative. Finally, the association of fever, immunosuppression, and a vascular event led to the suspicion of Candidatus Neoehrlichia mikurensis (CNM) infection. The diagnosis was confirmed by species-specific polymerase chain reaction (PCR) in the peripheral blood. Therapy with doxycycline or rifampicin led to the resolution of the disease. A liver biopsy was performed in one patient due to hepatomegaly and elevated liver enzymes demonstrating hemophagocytosis. To our knowledge, this is the first histopathological study of liver tissue in CNM infection. The evidence of hemophagocytosis raises the question of whether symptomatic CNM infection might be in part related to host inflammatory and immune responses.

Tick-borne diseases under the radar in the North Sea Region

The impact of tick-borne diseases caused by pathogens such as Anaplasma phagocytophilum, Neoehrlichia mikurensis, Borrelia miyamotoi, Rickettsia helvetica and Babesia species on public health is largely unknown. Data on the prevalence of these pathogens in Ixodes ricinus ticks from seven countries within the North Sea Region in Europe as well as the types and availability of diagnostic tests and the main clinical features of their corresponding diseases is reported and discussed. Raised awareness is needed to discover cases of these under-recognized types of tick-borne disease, which should provide valuable insights into these diseases and their clinical significance.

Neoehrlichia mikurensis-A New Emerging Tick-Borne Pathogen in North-Eastern Poland?

Neoehrlichia mikurensis is a new emerging tick-borne Gram-negative bacterium, belonging to the family Anaplasmataceae, the main vector of which in Europe is the tick Ixodes ricinus. N. mikurensis is responsible for neoehrlichiosis, occurring mostly in patients with underlying diseases. In the present study, a total of 348 I. ricinus and Dermacentor reticulatus ticks collected in north-eastern Poland were analyzed for the prevalence of N. mikurensis. A total of 140 questing ticks (124 of I. ricinus ticks and 16 D. reticulatus) collected with the flagging method and 208 ticks (105 and 103 I. ricinus and D. reticulatus, respectively) removed from dogs were selected for the study. cDNA (questing ticks) and total DNA (questing and feeding ticks) were analyzed by qPCR targeting the 16S rRNA gene of N. mikurensis. Positive samples were further analyzed by nested PCR and sequencing. The prevalence differed between ticks collected from vegetation (19.3%; 27/140) and ticks removed from dogs (6.7%; 14/208). The presence of the pathogen in questing and feeding D. reticulatus ticks was proven in Poland for the first time. In summary, our research showed that infections of ticks of both the most common tick species I. ricinus and D. reticulatus in north-eastern Poland are present and ticks collected from urban areas were more often infected than ticks from suburban and natural areas. The detection of N. mikurensis in I. ricinus and D. reticulatus ticks from north-eastern Poland indicates potential transmission risk for tick-bitten humans at this latitude.

Spiroplasma ixodetis Infections in Immunocompetent and Immunosuppressed Patients after Tick Exposure, Sweden

We report 2 cases of Spiroplasma ixodetis infection in an immunocompetent patient and an immunocompromised patient who had frequent tick exposure. Fever, thrombocytopenia, and increased liver aminotransferase levels raised the suspicion of anaplasmosis, but 16S rRNA PCR and Sanger sequencing yielded a diagnosis of spiroplasmosis. Both patients recovered after doxycycline treatment.

Detection of Neoehrlichia mikurensis DNA in blood donors in southeastern Sweden

BACKGROUND

The tick-borne bacterium Neoehrlichia mikurensis can cause persistent asymptomatic bloodstream infections, but transfusion-mediated transmission has not been reported. This study aimed to investigate the prevalence of N. mikurensis in blood donors, and recipients of blood components from N. mikurensis-positive donors were traced.

METHODS

In 2019 and 2021, 1007 blood donors were recruited. Participants completed a questionnaire and additional blood samples were collected during blood donation. Detection of N. mikurensis was performed by PCR followed by sequencing. Positive donors were interviewed and retested. Look-back was performed on positive donations and on all subsequent donations.

RESULTS

N. mikurensis was detected in 7/1006 (0.7%) donors. A total of 380/1005 (38%) donors reported at least one noticed tick bite during the current season. The questionnaire could not detect any differences between negative and positive N. mikurensis-donors. Two of the positive donors were still positive on days 318 and 131 after the index donation, respectively. One donor with persistent N. mikurensis in blood experienced slight fatigue. All other had no symptoms attributable to neoehrlichiosis. Look-back included ten donations and 20 blood components. Eight components were discarded, and 12 recipients of N. mikurensis-positive donations were identified. PCR was negative in seven recipients. Five recipients had died, but their medical records gave no evidence for neoehrlichiosis.

CONCLUSIONS

Although N. mikurensis was found in 0.7% of blood donors, transfusion-mediated infection was not detected, despite several recipients being at high risk for severe neoehrlichiosis. The results warrant further studies as well as raised clinical awareness.