Childhood leptospirosis in an industrialized country: Population-based study in Okinawa, Japan

Imported Infectious Diseases, Tropical Diseases and Local Endemic Infectious Diseases in Japan

We aimed to describe the historical perspectives and the current epidemiology of tropical, imported and local endemic infectious diseases in Japan in this review. Public health legislation for infectious diseases and immigration statistics were overviewed to provide the background of the infectious disease situation in Japan. Many tropical diseases were successfully controlled and eliminated in the latter half of the 20th century and the majority of those diseases are imported today. The trend of the main 15 imported infectious diseases before the advent of COVID-19 was summarized as well as local endemic infectious diseases in Japan. Transmission risks of traditional cuisines, lifestyles and nature exposures in Japan are introduced to guide clinicians for travel advice to prevent those local infectious diseases.

[Kidney injury in children and adolescents with leptospirosis in France]

INTRODUCTION

Leptospirosis is an anthropozoonosis with polymorphic clinical symptoms and a high variability of severity, ranging from flu-like syndrome to severe acute kidney injury. This disease is highly incident in tropical regions but there is a trend towards increasing incidence in metropolitan France and in Reunion Island. The objective of this study was to describe the epidemiological, clinical, laboratory and therapeutic characteristics of the pediatric leptospirosis in metropolitan France and in Reunion Island.

PATIENTS AND METHODS

We performed a retrospective analysis of leptospirosis cases hospitalized in University hospitals where members of the Paediatric Nephrology Society work in France between January 2008 and December 2020, 6 centers reported leptospirosis cases, one center had one patient in consultation but lack of available data and 10 centers did not find any case.

RESULTS

A total of 21 cases were reported (mean age 13.4±3.4years), mostly boys (ratio 6:1). Out of 21 patients, 95% had fever, 71% were presenting with myalgia, 81% with thrombocytopenia, and 76% with gastrointestinal symptoms. Regarding kidney impairment, 18 patients (86%) had acute kidney injury, including 4 (19%) with oligoanuria, but none of them required acute dialysis. About 30% of patients had biological signs of tubulopathy including hypophosphatemia, hypokalemia, or tubular proteinuria. No death due to the disease occurred. The therapeutic management followed the current guidelines with the use of antibiotic therapy by amoxicillin or 3rd generation cephalosporins with symptomatic treatment. When there was biological control after exit, creatinine decreased.

DISCUSSION

In this multicenter retrospective study, we report 21 children with leptospirosis with a significant proportion of acute kidney injury, the outcome was favorable. Children do not seem to be at high risk of chronic kidney disease progression but nephrology follow-up has not been systematically carried out. Compared to studies performed in adults, the prognosis was better and hepatic impairment was rare. Compared to other pediatric studies, conjunctivitis was not a common symptom but kidney injury and survival appeared to be similar. Children were presenting with anicteric renal presentation. The casebook wasn't exhaustive and didn't include the other overseas territories, which account for the highest proportion of leptospirosis infection.

CONCLUSION

Leptospirosis is an infection which may lead to multivisceral failure with kidney involvement conditioning the outcome. Despite a better prognosis in children, it remains important to quickly diagnose this infection in order to start appropriate antibiotic therapy and perform a kidney function monitoring.

Analysis of human clinical and environmental Leptospira to elucidate the eco-epidemiology of leptospirosis in Yaeyama, subtropical Japan

Background

Leptospirosis, a zoonosis caused by species in the spirochete genus Leptospira, is endemic to the Yaeyama region in Okinawa, subtropical Japan. Species of the P1 subclade “virulent” group, within the genus Leptospira, are the main etiological agents of leptospirosis in Okinawa. However, their environmental persistence is poorly understood. This study used a combination of bacterial isolation and environmental DNA (eDNA) metabarcoding methods to understand the eco-epidemiology of leptospirosis in this endemic region.

Findings

Polymerase chain reaction (PCR) characterized twelve human clinical L. interrogans isolates belonging to the P1 subclade “virulent” subgroup and 11 environmental soil isolates of the P1subclade “low virulent” subgroup (genetically related to L. kmetyi, n = 1; L. alstonii, n = 4; L. barantonii, n = 6) from the Yaeyama region targeting four virulence-related genes (lipL32, ligA, ligB and lpxD1). Clinical isolates were PCR positive for at least three targeted genes, while all environmental isolates were positive only for lipL32. Analysis of infected renal epithelial cells with selected clinical and environmental strains, revealed the disassembly of cell-cell junctions for the Hebdomadis clinical strain serogroup. Comparison of leptospiral eDNA during winter and summer identified operational taxonomic units corresponding to the species isolated from soil samples (L. kmetyi and L. barantonii) and additional P2 subclade species (L. licerasiae, L. wolffii-related, among others) that were not detected by soil cultivation. Total Leptospira read counts were higher in summer than in winter and the analysis of leptospiral/animal eDNA relationship suggested Rattus spp. as a potential reservoir animal.

Conclusion

Our study demonstrated high environmental Leptospira diversity in the Yaeyama region, particularly during summer, when most of the leptospirosis cases are reported. In addition, several Leptospira species with pathogenic potential were identified that have not yet been reported in Yaeyama; however, the environmental persistence of P1 subclade species previously isolated from human clinical cases in this region was absent, suggesting the need of further methodology development and surveillance.

Leptospirosis is a widespread bacterial zoonosis and one of the most important acute febrile infectious disease in tropical and subtropical regions, which is difficult to differentiate from other infectious diseases common in these regions. Leptospirosis is endemic to Okinawa prefecture, the southernmost prefecture of Japan, where the infection occurs mainly after recreational activities in rivers in the northern part of Okinawa Main Island and the Yaeyama region. This study combined several methods such as bacterial isolation from soil and environmental DNA metabarcoding from river water samples to understand the persistence of Leptospira outside the human host, leptospiral diversity in the environment, and their potential reservoir animals in the wild environment of the Yaeyama region. Although this study didn’t confirm the environmental persistence of Leptospira species previously isolated from clinical cases, several newly reported Leptospira species with pathogenic potential from the Yaeyama region suggested the need for continual surveillance to improve leptospirosis control and prevention in this region.

Laboratory diagnostic, epidemiological, and clinical characteristics of human leptospirosis in Okinawa Prefecture, Japan, 2003-2020

BACKGROUND

Leptospirosis is considered an endemic disease among agricultural workers in Okinawa Prefecture, which is the southernmost part of Japan and has a subtropical climate, but data on the current status and trend of this disease are scarce.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted a retrospective study of clinically suspected leptospirosis patients whose sample and information were sent to the Okinawa Prefectural Institute of Health and Environment from November 2003 to December 2020. Laboratory diagnosis was established using culture, nested polymerase chain reaction (PCR), and/or microscopic agglutination test (MAT) with blood, cerebrospinal fluid, and/or urine samples. Statistical analyses were performed to compare the epidemiological information, clinical features, and sensitivities of diagnostic methods among laboratory-confirmed cases. Serogroups and the species of Leptospira isolates were determined by MAT using 13 antisera and flaB sequencing. A total of 531 clinically suspected patients were recruited, among whom 246 (46.3%) were laboratory confirmed to have leptospirosis. Among the confirmed cases, patients aged 20-29 years (22.4%) and male patients (85.7%) were the most common. The most common estimated sources of infection were recreation (44.5%) and labor (27.8%) in rivers. Approximately half of the isolates were of the L. interrogans serogroup Hebdomadis. The main clinical symptoms were fever (97.1%), myalgia (56.3%), and conjunctival hyperemia (52.2%). Headache occurred significantly more often in patients with Hebdomadis serogroup infections than those with other serogroup infections. The sensitivities of culture and PCR exceeded 65% during the first 6 days, while the sensitivity of MAT surpassed that of culture and PCR in the second week after onset. PCR using blood samples was a preferable method for the early diagnosis of leptospirosis.

CONCLUSIONS/SIGNIFICANCE

The results of this study will support clinicians in the diagnosis and treatment of undifferentiated febrile patients in Okinawa Prefecture as well as patients returning from Okinawa Prefecture.

Is the Rattus norvegicus Population Playing a Role in the Transmission of Zoonotic Diseases to Children? A Pilot Study in Tehran, Iran

Background: Due to frequent exposure to surface water and contact with animals, children represent a group susceptible to zoonotic diseases. Objectives: The present study aims to determine the presence and prevalence of the main zoonotic agents in R. norvegicus populations in Tehran, Iran. Methods: In the present study, 100 R. norvegicus were captured within a time span of one year from five districts of Tehran, Iran. Fecal and blood samples were collected from rodents and serum was recovered after centrifugation. The presence of specific IgG antibodies against Leptospira spp. and Rabies virus was detected using a commercial qualitative rat ELISA kit. A conventional PCR assay was employed to detect the presence of Vibrio vulnificus in the commensal R. norvegicus population. Results: In general, 80% (n = 80/100) and 20% (n = 20/100) of rats were males and females, respectively. The results of the ELSA assay showed that of the 100 R. norvegicus captured in Tehran, 7% (n = 7/100) and 1% (n = 1/100) were positive for Leptospira spp. and Rabies virus, respectively. Leptospira spp. revealed the highest frequency (20%; 4/20) among R. norvegicus collected from the eastern part of Tehran. Rabies virus was detected only from the southern (5%; 1/20) part of Tehran. Results of the PCR method showed that the percentage of the rats tested positive for V. vulnificus was 5%. Overall, the surveyed zoonotic microorganisms had the highest (n = 5/20; 25%) and lowest (n = 1/20; 5%) frequency rates in the eastern and northern parts of Tehran, respectively. Conclusions: The results accentuate the necessity of implementing rodent control programs and regular disinfection as well as avoiding contact with rodent populations in urban environments.

Leptospiral Infection, Pathogenesis and Its Diagnosis-A Review

Leptospirosis is a perplexing conundrum for many. In the existing literature, the pathophysiological mechanisms pertaining to leptospirosis is still not understood in full. Considered as a neglected tropical zoonotic disease, leptospirosis is culminating as a serious problem worldwide, seemingly existing as co-infections with various other unrelated diseases, including dengue and malaria. Misdiagnosis is also common as non-specific symptoms are documented extensively in the literature. This can easily lead to death, as the severe form of leptospirosis (Weil's disease) manifests as a complex of systemic complications, especially renal failure. The virulence of Leptospira sp. is usually attributed to the outer membrane proteins, including LipL32. With an armament of virulence factors at their disposal, their ability to easily adhere, invade and replicate within cells calls for a swift refinement in research progress to establish their exact pathophysiological framework. As an effort to reconstitute the current knowledge on leptospirosis, the basis of leptospiral infection, including its risk factors, classification, morphology, transmission, pathogenesis, co-infections and clinical manifestations are highlighted in this review. The various diagnostic techniques are also outlined with emphasis on their respective pros and cons.

Age-specific epidemiology of human leptospirosis in New Caledonia, 2006-2016

With over one million cases worldwide annually and a high fatality in symptomatic forms, human leptospirosis is a growing public health concern for the most vulnerable populations, especially in the context of global warming and unplanned urbanization. Although the Asia-Pacific region is particularly affected, accurate epidemiological data are often lacking. We conducted an eleven-year retrospective laboratory-based epidemiological survey of human leptospirosis in New Caledonia. From 2006 to 2016, 904 cases were laboratory-confirmed, including 29 fatalities, corresponding to an average annual incidence of 30.6/100,000 and a case fatality rate of 3.2%. Over the period, there was a major shift from indirect serological diagnosis by MAT to direct diagnosis by real-time PCR, a more specific and sensitive test when performed early in the course of the disease. The systematic implementation of genotyping informed on the variety of the infective strains involved, with a predominance of serogroups Icterohaemorrhagiae and Pyrogenes. The epidemiological pattern showed a marked seasonality with an annual peak in March-April. Interestingly, the seasonal peak in children of school age was significantly earlier and corresponded to school holidays, suggesting that attending school from February on could protect children from environment-borne leptospirosis.

A systematic literature review of leptospirosis outbreaks worldwide, 1970-2012

Objective.

This review describes the geographic and temporal distribution of, detection methods for, and other epidemiological features of published leptospirosis outbreaks, with the aim of informing efforts to standardize outbreak-reporting practices.

Methods.

We conducted a systematic review of leptospirosis outbreaks reported in the scientific literature and ProMED during 1970–2012. Predefined criteria were used to identify and classify outbreaks and a standard form was used to extract information.

Results.

During 1970–2012, we identified 318 outbreaks (average: 7 outbreaks/year; range: 1–19). Most outbreaks were reported in the Latin America and the Caribbean region (36%), followed by Southern Asia (13%), and North America (11%). Most outbreaks were located in tropical and subtropical ecoregions (55%). Quality classification showed that there was clear description of laboratory-confirmed cases in 40% of outbreaks. Among those, the average outbreak size was 82 cases overall (range: 2–2 259) but reached 253 cases in tropical/subtropical ecoregions. Common risk factors included outdoor work activities (25%), exposure to floodwaters (23%), and recreational exposure to water (22%). Epidemiologic investigation was conducted in 80% of outbreaks, mainly as case interviews. Case fatality was 5% overall (range: 0%–60%).

Conclusions.

Outbreak reporting increased over the study period with outbreaks covering tropical and non-tropical regions. Outbreaks varied by size, setting, and risk factors; however, data reviewed often had limited information regarding diagnosis and epidemiology. Guidelines are recommended to develop standardized procedures for diagnostic and epidemiological investigations during an outbreak and for reporting.

Novel genotypes of Leptospira interrogans serogroup Sejroe isolated from human patients in Okinawa Prefecture, Japan

Leptospirosis is a zoonotic disease caused by pathogenic spirochetes of Leptospira species. It is a public health issue in the tropics, including Okinawa, the southernmost prefecture of Japan. This study reports the first isolation of L. interrogans serogroup Sejroe from two human patients in Japan, and describes its molecular characterization using multilocus sequence typing (MLST) and multiple-locus variable-number tandem repeat analysis (MLVA). MLST on the two isolates, 168036 and 178129, showed that pfkB in 178129 is a novel allele, and that both isolates constitute novel sequence types (STs); ST286 for 168036 and ST287 for 178129. A minimum spanning tree based on seven alleles of L. interrogans indicates that both isolates are genetically close, but are distinct from known L. interrogans serogroup Sejroe strains. MLVA using 11 loci demonstrated that seven of the 11 loci were identical between the two isolates, whereas the identity between the isolates and the seven reference strains of L. interrogans serogroup Sejroe was zero to three loci. These results indicate that the isolates investigated in this study have novel genotypes, and are genetically closest to each other among the known L. interrogans serogroup Sejroe strains.

Environmental DNA metabarcoding to detect pathogenic Leptospira and associated organisms in leptospirosis-endemic areas of Japan

Leptospires, which cause the zoonotic disease leptospirosis, persist in soil and aqueous environments. Several factors, including rainfall, the presence of reservoir animals, and various abiotic and biotic components interact to influence leptospiral survival, persistence, and pathogenicity in the environment. However, how these factors modulate the risk of infection is poorly understood. Here we developed an approach using environmental DNA (eDNA) metabarcoding for detecting the microbiome, vertebrates, and pathogenic Leptospira in aquatic samples. Specifically, we combined 4 sets of primers to generate PCR products for high-throughput sequencing of multiple amplicons through next-generation sequencing. Using our method to analyze the eDNA of leptospirosis-endemic areas in northern Okinawa, Japan, we found that the microbiota in each river shifted over time. Operating taxonomic units corresponding to pathogenic L. alstonii, L. kmetyi, and L. interrogans were detected in association with 12 nonpathogenic bacterial species. In addition, the frequencies of 11 of these species correlated with the amount of rainfall. Furthermore, 10 vertebrate species, including Sus scrofa, Pteropus dasymallus, and Cynops ensicauda, showed high correlation with leptospiral eDNA detection. Our eDNA metabarcoding method is a powerful tool for understanding the environmental phase of Leptospira and predicting human infection risk.