An Improved Enzyme-Linked Immunoassay for the Detection of Leptospira-Specific Antibodies

Molecular Diagnosis as an Alternative for Public Health Surveillance of Leptospirosis in Colombia

Leptospirosis represents a public health problem in Colombia. However, the underreporting of the disease is an unfortunate reality, with a clear trend towards a decrease in cases since 2019, when the guidelines for its confirmatory diagnosis changed with the requirement of two paired samples. The purpose of this review is to highlight the importance of leptospirosis. While the access to rapid diagnosis is available at practically all levels of care for dengue and malaria, leptospirosis-a doubly neglected disease-deserves recognition as a serious public health problem in Colombia. In this manner, it is proposed that molecular tests are a viable diagnostic alternative that can improve the targeted treatment of the patient and the timeliness of data and case reporting to SIVIGILA, and reduce the underreporting of the disease. Taking advantage of the strengthened technological infrastructure derived from the SARS-CoV-2 pandemic for molecular diagnosis in Colombia, with a network of 227 laboratories distributed throughout the national territory, with an installed capacity for PCR testing, it is proposed that molecular diagnosis can be used as an alternative for early diagnosis. This would allow case confirmation through the public health network in Colombia, and, together with the microagglutination (MAT) technique, the epidemiological surveillance of this disease in this country would be strengthened.

Enzyme immunoassays (EIA) for serodiagnosis of human leptospirosis: specific IgG3/IgG1 isotyping may further inform diagnosis of acute disease

The laborious microscopic agglutination test (MAT) is the gold standard serologic test for laboratory diagnosis of leptospirosis. We developed EIA based serologic assays using recombinant proteins (rLigA, rLigB, rLipL32) and whole-cell extracts from eight Leptospira serovars as antigen and assessed the diagnostic performance of the new assay within each class, against MAT positive (MAT+) human sera panels from Portugal/PT (n = 143) and Angola/AO (n = 100). We found that a combination of recombinant proteins rLigA, rLigB and rLipL32 correctly identified antigen-specific IgG from patients with clinical and laboratory confirmed leptospirosis (MAT+) with 92% sensitivity and ~ 97% specificity (AUC 0.974) in serum from the provinces of Luanda (LDA) and Huambo (HBO) in Angola. A combination of whole cell extracts of L. interrogans sv Copenhageni (LiC), L. kirschneri Mozdok (LkM), L. borgpetersenii Arborea (LbA) and L. biflexa Patoc (LbP) accurately identified patients with clinical and laboratory confirmed leptospirosis (MAT+) with 100% sensitivity and ~ 98% specificity for all provinces of Angola and Portugal (AUC: 0.997 for AO/LDA/HBO, 1.000 for AO/HLA, 0.999 for PT/AZ and 1.000 for PT/LIS). Interestingly, we found that MAT+ IgG+ serum from Angola had a significantly higher presence of IgD and that IgG3/IgG1 isotypes were significantly increased in the MAT+ IgG+ serum from Portugal. Given that IgM/IgD class and IgG3/IgG1 specific isotypes are produced in the earliest course of infection, immunoglobulin G isotyping may be used to inform diagnosis of acute leptospirosis. The speed, ease of use and accuracy of EIA tests make them excellent alternatives to the laborious and expensive MAT for screening acute infection in areas where circulating serovars of pathogenic Leptospira are well defined.

Leptospirosis and Rickettsial Diseases Sero-Conversion Surveillance Among U.S. Military Personnel in Honduras

INTRODUCTION

Leptospirosis and rickettsial diseases are global zoonotic diseases. In severe infection cases, mortality can range from 10% to 30%. Currently most epidemiological data available are based on outbreak investigations and hospital-based studies from endemic countries. The U.S. soldiers at military bases in these countries are highly vulnerable due to the fact that most of them are immunologically naïve to these pathogens. No risk assessment of leptospirosis and rickettsial diseases among U.S. military personnel in Honduras is currently available. This study was aimed at determining the prevalence of leptospirosis and rickettsial diseases in U.S. military personnel deployed to Honduras using serological assays.

MATERIALS AND METHODS

A cohort of pre- and post-deployment sera from the most recent 1,000 military personnel stationed in Honduras for at least 6 months between 2000 and 2016 was identified for this study. Serum specimens from these eligible subjects were retrieved. All post-deployment serum specimens were screened at a dilution of 1:100 for the presence of IgG antibodies to Leptospira and Rickettsia pathogens. The pre-deployment sera from those individuals with post-deployment IgG antibodies above cutoff (i.e., seropositive) were tested to determine seroconversion. Seroconversion was defined as conversion of an optical density value from below the cutoff (i.e., negative) in a pre-deployed specimen to above the cutoff (i.e., positive) in a post-deployed specimen at a titer of 100.

RESULTS

The seropositive post-deployment specimens for antibodies against Leptospira (causing leptospirosis), Rickettsia typhi (causing murine typhus [MT]), spotted fever group rickettsioses (SFGR, causing SFG Rickettsia), Orientia tsutsugamushi (causing scrub typhus [ST]), and Coxiella burnetii (causing Q fever [QF]) were 11.6%, 11.3%, 6%, 5.6%, and 8.0%, respectively. The seroconverted rate in those assigned to Honduras from 2000 to 2016 was 7.3%, 1.9%, 3.9%, 4.3%, and 2.7% for leptospirosis, MT, SFGR, ST, and QF, respectively. Among the seroconverted specimens, 27 showed seroconversion of at least two antibodies. These seroconverted individuals accounted for 8.8% (3 out of 34) of the personnel who looked for medical attention during their deployment.

CONCLUSIONS

Our results suggest a leptospirosis seroconversion rate of 7.3%, which is higher than the 0.9% and 3.9% seroconversion in Korea and Japan, respectively. The higher rate of seroconversion indicates potential risk of Leptospira exposure. Additional testing of water samples in the pools and pits around the training sites to locate the infected areas is important to eliminate or reduce future exposure to Leptospira during trainings. The rates of seroconversion for ST, MT, spotted fever Rickettsia, and QF were 4.3%, 1.9%, 3.9%, and 2.7%, respectively, indicating the potential exposure to a variety of rickettsial-related pathogens. Testing of vectors for rickettsial pathogens in the areas could inform effective vector control countermeasures to prevent exposure. Proper precaution and protective measures are needed to better protect military personnel deployed to Honduras.

Laboratory Diagnosis of Leptospirosis

The diagnosis of leptospirosis depends on specific laboratory tests because nonspecific and diverse clinical manifestations make clinical diagnosis difficult and it is easily confused with other infectious diseases in the tropics. Suitable laboratory diagnostic tests vary depending on the stage of the disease, requiring the combination of diagnostic tests using appropriate specimens at each disease stage.

An Observational Study of Sepsis in Takeo Province Cambodia: An in-depth examination of pathogens causing severe infections

The world's most consequential pathogens occur in regions with the fewest diagnostic resources, leaving the true burden of these diseases largely under-represented. During a prospective observational study of sepsis in Takeo Province Cambodia, we enrolled 200 patients over an 18-month period. By coupling traditional diagnostic methods such as culture, serology, and PCR to Next Generation Sequencing (NGS) and advanced statistical analyses, we successfully identified a pathogenic cause in 46.5% of our cohort. In all, we detected 25 infectious agents in 93 patients, including severe threat pathogens such as Burkholderia pseudomallei and viral pathogens such as Dengue virus. Approximately half of our cohort remained undiagnosed; however, an independent panel of clinical adjudicators determined that 81% of those patients had infectious causes of their hospitalization, further underscoring the difficulty of diagnosing severe infections in resource-limited settings. We garnered greater insight as to the clinical features of severe infection in Cambodia through analysis of a robust set of clinical data.

Update on molecular diagnosis of human leptospirosis

Background

Leptospirosis, caused by pathogenic Leptospira spp., is a widespread zoonotic disease worldwide. Early diagnosis is required for proper patient management and reducing leptospirosis morbidity and mortality.

Objective

To summarize current literature regarding commonly used and new promising molecular approaches to Leptospira detection and diagnostic tests of human leptospirosis.

Method

The relevant articles in Leptospira and leptospirosis were retrieved from MEDLINE (PubMed) and Scopus.

Results

Several molecular techniques have been developed for diagnosis of human leptospirosis. Polymerase chain reaction-based techniques targeting on either lipL32 or 16S rRNA (rrs) gene are most commonly used to detect leptospiral DNA in various clinical specimens. Whole blood and urine are recommended specimens for suspected cases in the first (acute) and the second (immune) phases, respectively. Isothermal amplification with less expensive instrument is an alternative DNA detection technique that may be suitable for resource-limited laboratories.

Conclusion

Detection of leptospiral DNA in clinical specimens using molecular techniques enhances sensitivity for diagnosis of leptospirosis. The efficient and robust molecular detection especially in the early leptospiremic phase may prompt early and appropriate treatment leading to reduced morbidity and mortality of patients with leptospirosis.