Leptospirosis diagnosis among patients suspected of dengue fever in Brazil

Why do Doctors Miss the Diagnosis of Leptospiral Uveitis? Emergence of New Serovars and Challenges in Diagnosis

PURPOSE

Leptospirosis is an endemic disease in India and uveitis is its late complication. Several Indian reports showed diversity of serovars, changing patterns and existence of new serovars. Failure to add new serovars in testing panel result in increased false-negativity in serology.

AIM

To analyse seroprevalence, changing patterns and to discuss the resulting challenges in diagnosis.

METHODS

In this retrospective study covering the period from 1994 to 2020, we analysed data from laboratory records of patients diagnosed with leptospiral uveitis in South India. Microscopic agglutination Test (MAT) and/or Enzyme-Linked Immunosorbent Assay (ELISA) were performed on clinically diagnosed leptospiral uveitis cases from our hospital, as well as on systemic leptospirosis patients from government and private hospitals.

RESULTS

Out of a total of 87 216 new uveitis cases with varying causes over 27 years, 3,658 (4.1%) were clinically diagnosed as leptospiral uveitis. Among them, 1,268 (34.7%) patients were seropositive. In 1994, 92% of clinically diagnosed leptospirosis patients were seropositive in the MAT performed at the Centers for Disease Control and Prevention in Atlanta. However, the positivity rate gradually declined to 35% over the years. The predominant serovars identified were L. autumnalis, L. icterohaemorrhagiae, and L. australis. There were notable variations in the distribution of serovars over the years.

CONCLUSIONS

The data suggest a declining sensitivity of MAT and ELISA, possibly due to the emergence of new serovars. Customizing the panel based on local isolates could enhance the performance of MAT. Critical need is the addition of advanced molecular techniques to improve the diagnosis.

Utility of demographic and clinical signs as diagnostic predictors for leptospiral uveitis: A retrospective study

PURPOSE

Leptospirosis is a waterborne zoonotic disease prevalent in tropical regions, causing significant morbidity and mortality. It can involve any organ in its primary stage, and uveitis is its late complication. While advanced laboratory diagnosis is available only in tertiary care centers globally, a cost-effective bedside assessment of clinical signs and their scoring could offer a provisional diagnosis.

AIM

To analyze the diagnostic potential of demographic and clinical signs in a large cohort of serologically confirmed leptospiral uveitis patients.

METHODS

In this retrospective study, demographic and clinical parameters of 876 seropositive leptospiral uveitis patients and 1042 nonleptospiral uveitis controls were studied. Multivariable logistic regression analysis with bootstrap confidence interval (CI) characterized the diagnostic predictors. The performance of the model was evaluated using the area under the receiver operating curve (AUROC).

RESULTS

Presence of nongranulomatous uveitis (odds ratio [OR] = 6.9), hypopyon (OR = 4.6), vitreous infiltration with membranous opacities (OR = 4.3), bilateral involvement (OR = 4), panuveitis (OR = 3.3), vasculitis (OR = 1.9), disc hyperemia (OR = 1.6), absence of retinochoroiditis (OR = 15), and absence of cystoid macular edema (OR = 8.9) emerged as predictive parameters. The AUROC value was 0.86 with 95% CI of 0.846-0.874. At a cut-off score of 40, the sensitivity and specificity were 79.5 and 78.4, respectively.

CONCLUSION

The study demonstrates that ocular signs can serve as diagnostic predictors for leptospiral uveitis, enabling primary care ophthalmologists to make bedside diagnosis. This can be further confirmed by laboratory methods available at tertiary care centers.

Detection of Pathogenic Leptospira in Captive Chelonians (Kinosternon scorpioides-Linnaeus, 1766) in the Brazilian Amazon

Leptospirosis is a zoonosis of great importance for One Health. In this context, the Amazonian biome may harbor numerous hosts for Leptospira spp. that contribute to the maintenance of the pathogen in the environment. Some reptiles, such as chelonians, have been little studied in terms of their involvement with leptospires. The objective of this study was to detect Leptospira spp. DNA in Kinosternon scorpioides turtles kept in captivity in a region of the Brazilian Amazon. A total of 147 samples of blood (n = 40), cloacal fluid (n = 27), cloacal lavage (n = 40), and stomach (n = 40) were collected from 40 chelonians. After DNA extraction, the samples were subjected to amplification of a 331 base pair product of the 16S rRNA gene using the Lep1 and Lep2 primers. PCR products were Sanger sequenced, assembled, and subjected to online blast search and phylogenetic analysis. Of the animals tested, 40% (16/40, 95% confidence interval [CI]: 25-55) had at least one or two samples positive for Leptospira spp. Considering the total number of samples collected, 12.93% (19/147) were positive, being blood clots (27.5%; 11/40), followed by cloacal washings (10%; 4/40), cloacal fluid (11.11%; 3/27) and gastric washings (2.5%; 1/40). Of these, 11 samples were sequenced and showed 99% to 100% identity with Leptospira interrogans sequences, which was confirmed by phylogenetic analysis. This is the first study to detect pathogenic Leptospira DNA in chelonians in a region of the Brazilian Amazon. It has been concluded that K. scorpioides turtles in captivity have been exposed to pathogenic Leptospira.

The Diagnostic Potential of RNA Aptamers against the NS1 Protein of Dengue Virus Serotype 2

Dengue infection, caused by the dengue virus, is a global threat which requires immediate attention and appropriate disease management. The current diagnosis of dengue infection is largely based on viral isolation, RT-PCR and serology-based detection, which are time-consuming and expensive, and require trained personnel. For early diagnosis of dengue, the direct detection of a dengue antigenic target is efficacious, and one such target is NS1. NS1-based detection is primarily antibody-centric and is beset by drawbacks pertaining to antibodies such as the high cost of synthesis and large batch-to-batch variation. Aptamers are potential surrogates of antibodies and are much cheaper, without exhibiting batch-to-batch variation. Given these advantages, we sought to isolate RNA aptamers against the NS1 protein of dengue virus serotype 2. A total of 11 cycles of SELEX were carried out, resulting in two potent aptamers, DENV-3 and DENV-6, with dissociation constant values estimated at 37.57 ± 10.34 nM and 41.40 ± 9.29 nM, respectively. These aptamers can be further miniaturized to TDENV-3 and TDENV-6a with an increased LOD upon their usage in direct ELASA. Moreover, these truncated aptamers are highly specific against the dengue NS1 while showing no cross-reactivity against the NS1 of the Zika virus, the E2 protein of the Chikungunya virus or the LipL32 protein of Leptospira, with target selectivity retained even in human serum. The usage of TDENV-3 as the capturing probe and TDENV-6a as the detection probe underpinned the development of an aptamer-based sandwich ELASA for the detection of dengue NS1. The sensitivity of the sandwich ELASA was further improved with the stabilization of the truncated aptamers and the repeated incubation strategy, which enabled a LOD of 2 nM when used with the target NS1 spiked in human serum diluted at 1:2000.

Role of Diagnostics in Epidemiology, Management, Surveillance, and Control of Leptospirosis

A One Health approach to the epidemiology, management, surveillance, and control of leptospirosis relies on accessible and accurate diagnostics that can be applied to humans and companion animals and livestock. Diagnosis should be multifaceted and take into account exposure risk, clinical presentation, and multiple direct and/or indirect diagnostic approaches. Methods of direct detection of Leptospira spp. include culture, histopathology and immunostaining of tissues or clinical specimens, and nucleic acid amplification tests (NAATs). Indirect serologic methods to detect leptospiral antibodies include the microscopic agglutination test (MAT), the enzyme-linked immunosorbent assay (ELISA), and lateral flow methods. Rapid diagnostics that can be applied at the point-of-care; NAAT and lateral flow serologic tests are essential for management of acute infection and control of outbreaks. Culture is essential to an understanding of regional knowledge of circulating strains, and we discuss recent improvements in methods for cultivation, genomic sequencing, and serotyping. We review the limitations of NAATs, MAT, and other diagnostic approaches in the context of our expanding understanding of the diversity of pathogenic Leptospira spp. Novel approaches are needed, such as loop mediated isothermal amplification (LAMP) and clustered regularly interspaced short palindromic repeats (CRISPR)-based approaches to leptospiral nucleic acid detection.

Clinical profile, management and outcome of patients with leptospirosis during the times of COVID-19 pandemic: A prospective study from a tertiary care centre in South India

Leptospirosis is a rodent-borne acute febrile illness, classically seen after heavy rainfall and floods. This study aimed to describe the clinical profile, management strategies and outcome of patients with leptospirosis amidst the Coronavirus disease-2019 outbreak. A prospective study of adult patients with undifferentiated fever (5-15 days) was conducted in South India between October 2020 and February 2021. The demographic, clinical details, laboratory details, treatment and outcome of leptospirosis positive (based on serology) and negative patients were compared. A chisquare test was used for qualitative variables, while an independent t-test or Mann Whitney U test was used for continuous variables. Of the 206 patients with suspected acute febrile illness, a total of 63 patients were diagnosed with leptospirosis based on serology results. The median sequential organ failure assessment score was higher in those with leptospirosis (p<0.001). Myalgia, abdominal pain, jaundice, decreased urine output, myocarditis, and dialysis requirement were more common in patients with leptospirosis. Leucocytosis and raised procalcitonin/C-reactive protein were more common in patients with leptospirosis. The duration of stay and antibiotic consumption was higher in patients with leptospirosis. Acute febrile illness such as leptospirosis should be suspected in tropical areas with significant risk factors. The presence of conjunctival suffusion, hepatic and renal dysfunction should warrant a serology test for leptospirosis.