Potent Innate Immune Response to Pathogenic Leptospira in Human Whole Blood

Background: Leptospirosis is caused by pathogenic spirochetes of the genus Leptospira. The bacteria enter the human body via abraded skin or mucous membranes and may disseminate throughout. In general the clinical picture is mild but some patients develop rapidly progressive, severe disease with a high case fatality rate. Not much is known about the innate immune response to leptospires during haematogenous dissemination. Previous work showed that a human THP-1 cell line recognized heat-killed leptospires and leptospiral LPS through TLR2 instead of TLR4. The LPS of virulent leptospires displayed a lower potency to trigger TNF production by THP-1 cells compared to LPS of non-virulent leptospires. Methodology/Principal Findings: We investigated the host response and killing of virulent and non-virulent Leptospira of different serovars by human THP-1 cells, human PBMC's and human whole blood. Virulence of each leptospiral strain was tested in a well accepted standard guinea pig model. Virulent leptospires displayed complement resistance in human serum and whole blood while in-vitro attenuated non-virulent leptospires were rapidly killed in a complement dependent manner. In vitro stimulation of THP-1 and PBMC's with heat-killed and living leptospires showed differential serovar and cell type dependence of cytokine induction. However, at low, physiological, leptospiral dose, living virulent complement resistant strains were consistently more potent in whole blood stimulations than the corresponding non-virulent complement sensitive strains. At higher dose living virulent and non-virulent leptospires were equipotent in whole blood. Inhibition of different TLRs indicated that both TLR2 and TLR4 as well as TLR5 play a role in the whole blood cytokine response to living leptospires. Conclusions/Significance: Thus, in a minimally altered system as human whole blood, highly virulent Leptospira are potent inducers of the cytokine response

Syndromic approach to arboviral diagnostics for global travelers as a basis for infectious disease surveillance

Background Arboviruses have overlapping geographical distributions and can cause symptoms that coincide with more common infections. Therefore, arbovirus infections are often neglected by travel diagnostics. Here, we assessed the potential of syndrome-based approaches for diagnosis and surveillance of neglected arboviral diseases in returning travelers. Method To map the patients high at risk of missed clinical arboviral infections we compared the quantity of all arboviral diagnostic requests by physicians in the Netherlands, from 2009 through 2013, with a literature-based assessment of the travelers’ likely exposure to an arbovirus. Results 2153 patients, with travel and clinical history were evaluated. The diagnostic assay for dengue virus (DENV) was the most commonly requested (86%). Of travelers returning from Southeast Asia with symptoms compatible with chikungunya virus (CHIKV), only 55% were tested. For travelers in Europe, arbovirus diagnostics were rarely requested. Over all, diagnostics for most arboviruses were requested only on severe clinical presentation. Conclusion Travel destination and syndrome were used inconsistently for triage of diagnostics, likely resulting in vast under-diagnosis of arboviral infections of public health significance. This study shows the need for more awareness among physicians and standardization of syndromic diagnostic algorithm

Soluble ST2 Levels Are Associated with Bleeding in Patients with Severe Leptospirosis

Leptospirosis is a bacterial disease that is mainly spread by rodents and other small mammals. Transmission frequently occurs in (sub-) tropical countries, where environmental circumstances are most favourable. Severe leptospirosis can cause bleeding and vital organ dysfunction. An exaggerated immune response is thought to play an important role in the pathophysiology of leptospirosis. Soluble ST2 (sST2) is thought to inhibit negative regulatory pathways of this response. Soluble ST2 is produced by cells that surround, for example, blood vessels, and several of these blood cells play an important part in the host immune response. In an observational study, we measured the extent of sST2 release in patients suffering from severe leptospirosis. We found that patients that died from leptospirosis displayed higher levels of sST2. Moreover, from this study we have seen that sST2 levels were associated with bleeding, whereas other markers of infection were not. In an experiment, we showed that (white) blood cells did not seem to be the source of sST2 production. Damage to blood vessels is likely to cause bleeding in leptospirosis patients, exposing sST2 producing cells like fibroblasts to the blood stream. Hence, we believe that sST2 may be used as a marker for tissue damage in patients suffering from severe leptospirosis

Under-diagnosis of rickettsial disease in clinical practice: A systematic review

Rickettsial diseases present as acute febrile illnesses, sometimes with inoculation eschars. We performed a systematic review of studies published between 1997 and 2017 to assess the underestimation of non-eschar rickettsial disease (NERD) relative to eschar rickettsial disease (ERD), as a cause of acute fever in patients with rickettsial diseases that commonly present with eschar(s): scrub typhus (ST), Mediterranean spotted fever (MSF), and African tick-bite fever. We compared ERD/NERD ratios according to study design: 'complete approach' studies, with testing performed in all patients with 'unspecified febrile illness'; versus 'clinical judgement' studies, with testing performed if patients presented with specific symptoms. In 'complete approach' studies, ERD/NERD ratios were significantly lower, suggesting a considerable under-diagnosis of NERD in 'clinical judgement' studies. Based on these results, we estimate that the diagnosis of rickettsial disease was missed in 66.5% of patients with ST, and in 57.9% of patients with MSF. Study design influences the reported eschar rates in ST and MSF significantly. NERD is likely to be a vastly underdiagnosed entity, and clinicians should consider and test for the disease more often. CRD 4201605334

Searching and Finding the Hidden Treasure: A Retrospective Analysis of Rickettsial Disease Among Dutch International Travelers

BACKGROUND: Rickettsial disease (RD) is a prevalent and underestimated cause of febrile illness worldwide, especially in the absence of an inoculation eschar. We attempted to quantify this underestimation at our clinic, by investigating past cases of febrile illness in travelers who had tested negative for leptospirosis, a disease that can initially present similarly to non-eschar RD, and which we routinely consider when other important causes of unspecified febrile illness have tested negative. METHODS: We performed a retrospective analysis in febrile returned travelers from Asia, Africa, or the Americas between 2010 and 2017, who had tested negative for leptospirosis. Serologic immunofluorescence assays were performed for Orientia tsutsugamushi (scrub typhus), typhus group, and spotted fever group RD. We performed a medical records review of all patients who tested positive. In case of a fitting medical history, cases were deemed either confirmed (based on convalescent serology) or suspected (based on single serology). RESULTS: Among 97 patients, convalescent serology was available in 16 (16.5%) patients, and a single serology in 81 (83.5%) patients. RD was the likely diagnosis in 8 of 16 (50.0%) patients with convalescent serology, and in 8 of 81 (9.9%) with single serology. Of the 16 confirmed/suspected cases, 11 (69%) had been missed and 7 (44%) had not received adequate empiric antibiotic therapy. CONCLUSIONS: This study shows that non-eschar RD is an important and poorly recognized cause of illness in travelers, even in a specialized travel clinic. A lower threshold to test and treat for RD is warranted in returning travelers with febrile illness

Prospective Evaluation of Three Rapid Diagnostic Tests for Diagnosis of Human Leptospirosis

<div><p>Background</p><p>Diagnosis of leptospirosis by the microscopic agglutination test (MAT) or by culture is confined to specialized laboratories. Although ELISA techniques are more common, they still require laboratory facilities. Rapid Diagnostic Tests (RDTs) can be used for easy point-of-care diagnosis. This study aims to evaluate the diagnostic performance of the RDTs LeptoTek Dri Dot, LeptoTek Lateral Flow, and Leptocheck-WB, prospectively.</p><p>Methodology</p><p>During 2001 to 2012, one or two of the RDTs at the same time have been applied prior to routine diagnostics (MAT, ELISA and culture) on serum specimens from participants sent in for leptospirosis diagnosis. The case definition was based on MAT, ELISA and culture results. Participants not fulfilling the case definition were considered not to have leptospirosis. The diagnostic accuracy was determined based on the 1^st submitted sample and paired samples, either in an overall analysis or stratified according to days post onset of illness.</p><p>Results</p><p>The overall sensitivity and specificity for the LeptoTek Dri Dot was 75% respectively 96%, for the LeptoTek Lateral Flow 78% respectively 95%, and for the Leptocheck-WB 78% respectively 98%. Based on the 1^st submitted sample the sensitivity was low (51% for LeptoTek Dri Dot, 69% for LeptoTek Lateral Flow, and 55% for Leptocheck-WB), but substantially increased when the results of paired samples were combined, although accompanied by a lower specificity (82% respectively 91% for LeptoTek Dri Dot, 86% respectively 84% for LeptoTek Lateral Flow, and 80% respectively 93% for Leptocheck-WB).</p><p>Conclusions</p><p>All three tests present antibody tests contributing to the diagnosis of leptospirosis, thus supporting clinical suspicion and contributing to awareness. Since the overall sensitivity of the tested RDTs did not exceed 80%, one should be cautious to rely only on an RDT result, and confirmation by reference tests is strongly recommended.</p></div

Towards the burden of human leptospirosis: duration of acute illness and occurrence of post-leptospirosis symptoms of patients in the Netherlands.

BACKGROUND:Leptospirosis is a global zoonotic disease. Although important for the assessment of the burden of leptospirosis, data on the duration of the illness and the occurrence of post-leptospirosis complaints are not well documented. Hence the main objective of this study was to estimate the occurrence of persistent complaints and duration of hospital stay in laboratory confirmed leptospirosis patients in the Netherlands during 1985 to 2010. Additionally, several risk factors potentially impacting on the occurrence of post-leptospirosis complaints were investigated. METHODS/PRINCIPAL FINDINGS:The duration of the acute phase of leptospirosis was 16 days (IQR 12-23); 10 days (IQR 7-16) were spent hospitalized. Eighteen fatal cases were excluded from this analysis. Complaints of leptospirosis patients by passive case investigations (CPC) derived from files on ambulant consultations occurring one month after hospital discharge, revealed persistent complaints in 108 of 236 (45.8%) laboratory confirmed cases. Data on persistent complaints after acute leptospirosis (PCAC), assessed in 225 laboratory confirmed leptospirosis cases collected through questionnaires during 1985-1993, indicated 68 (30.2%) PCAC cases. Frequently reported complaints included (extreme) fatigue, myalgia, malaise, headache, and a weak physical condition. These complaints prolonged in 21.1% of the cases beyond 24 months after onset of disease. There was no association between post-leptospirosis complaints and hospitalization. However, individuals admitted at the intensive care unit (ICU) were twice as likely to have continuing complaints after discharge adjusting for age and dialysis (OR 2.0 95% CI 0.8-4.8). No significant association could be found between prolongation of complaints and infecting serogroup, although subgroup analysis suggest that infection with serogroups Sejroe (OR 4.8, 95%CI 0.9-27.0) and icterohaemorrhagiae (OR 2.0, 95%CI 0.9-4.3 CI) are more likely to result in CPC than infections with serogroup Grippotyphosa. CONCLUSION/SIGNIFICANCE:In addition to the acute disease, persistent complaints have an impact on the burden of leptospirosis

Long pentraxin PTX3 is associated with mortality and disease severity in severe Leptospirosis

To evaluate the long pentraxin PTX3 in patients with severe leptospirosis and to compare the results with the widely used short pentraxin C-reactive protein and the pro-inflammatory cytokines IL-6 and IL-8. This observational cohort study was carried out in Semarang, Indonesia, where leptospirosis is endemic and mortality is high. Consecutive patients with severe leptospirosis were sampled on admission and during follow-up. A total number of 52 patients entered the study, the mortality was 27%. Severe leptospirosis patient yielded elevated plasma PTX3 levels. PTX3 correlated with IL-8 and to a lesser extent with CRP and IL-6 levels. High levels of PTX3, IL-6 and IL-8 were associated with mortality (OR 5.6, 95%CI: 1.2-26; OR 3.2, 95%CI: 1.2-8.1; OR 6.5, 95%CI: 1.5-28). Moreover, PTX3 levels were associated with disease severity (OR 9.5; 95%CI: 2.9-45). This association was unique, since none of the other markers showed this relation. C-reactive protein was not able to differentiate the severe from the severest cases. The long pentraxin PTX3 is elevated in patients with severe leptospirosis and is associated with fatal disease and disease severity. PTX3 may be used as a marker to monitor disease severity in severe leptospirosis or predict outcom

Travel-related leptospirosis in the Netherlands 2009–2016: An epidemiological report and case series

Background: Leptospirosis is a potentially fatal zoonotic disease that is prevalent in travellers. Here, we describe epidemiological and diagnostic characteristics of all returning travellers diagnosed with leptospirosis in the Netherlands between 2009 and 2016. Furthermore, we present a detailed clinical case series of all travellers with leptospirosis who presented at the Academic Medical Center (AMC) in the same period. Method: We extracted data from the records of the Dutch Leptospirosis Reference Center (NRL) of all cases of leptospirosis in travellers in the Netherlands from 2009 to 2016. Patients who presented at the AMC were identified and clinical data were extracted from the hospital records. Results: 224 cases of travel-related leptospirosis were included. An increase of cases was observed from 2014 onwards. The majority of cases were male (78.1%), and had travelled to South-East Asia (62.1%). Of 41 AMC cases, 53.7% were hospitalised, but most patients had a relatively mild disease course, with no fatalities. A longer delay in diagnosis and treatment initiation existed in hospitalised compared to non-hospitalised patients, suggesting a benefit of early recognition and treatment. Conclusions: Leptospirosis was increasingly observed in returning travellers in the Netherlands, and is a diagnosis that should be considered in any returning febrile traveller