Sporadic Cases and an Outbreak of Leptospirosis Probably Associated with Recreational Activities in Rivers in the Northern Part of Okinawa Main Island

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.

Molecular epidemiology of Leptospira spp. among wild mammals and a dog in Amami Oshima Island, Japan

Leptospirosis is a worldwide zoonosis caused by the pathogenic Leptospira spp. Canine and human leptospirosis sometimes occur on Amami Oshima Island, located in the Nansei Archipelago, southwestern Japan; however, information on the causative Leptospira spp. on this island is quite limited. This study aimed to investigate the molecular and serological characteristics of Leptospira spp. isolated from wild animals and a dog in Amami Oshima Island. We obtained seven Leptospira strains by culturing kidney tissues of wild animals, such as black rats (2), wild boars (3), and rabbit (1) as well as blood from a symptomatic dog. Using flaB sequencing and microscopic agglutination test with antisera for 18 serovars, the isolates were identified as Leptospira borgpetersenii serogroups Javanica (black rat), L. interrogans serogroup Australis (black rat and dog), and L. interrogans serogroup Hebdomadis (wild boar and rabbit). The sequence type (ST) of L. borgpetersenii serogroup Javanica was determined to be ST143 via multilocus sequence typing (MLST) using seven housekeeping genes. For L. interrogans, MLST and multiple-locus variable-tandem repeat analysis (MLVA) revealed identical ST and MLVA types in rat and canine isolates, whereas two STs and MLVA types were identified in wild boar isolates. The STs and MLVA types of rabbit and one of the wild boars were identical. Bacterial culture and flaB-nested polymerase chain reaction demonstrated a high rate of Leptospira infection in wild boars (58.3%, 7/12), whereas Leptospira spp. were detected in 4.8% of black rats (2/42). This study revealed diverse Leptospira genotype and serotype maintenance in wild mammals on Amami Oshima Island. MLST and MLVA indicated that black rats were a source of canine infection. Wild boars carry L. interrogans and are considered an important maintenance host because antibodies against serogroup Hebdomadis were detected in human and canine leptospirosis patients on this island.

Transbronchial Invasion and Proliferation of Leptospira interrogans in Lung without Inflammatory Cell Infiltration in a Hamster Model

Leptospirosis caused by pathogenic Leptospira is one of the most common zoonoses in the world. It is believed that humans become infected with it mainly through their skin and mucous membranes by contact with water or soil that is contaminated with urine excreted from infected animals. Recently, outbreaks have frequently occurred in the tropics, especially after flooding, but how leptospires cause mass infection remains poorly understood. In this study, we injected leptospires into the tracheas of hamsters under direct view and prove for the first time that leptospires can infect through the respiratory tract. We determined that a 50% lethal dose (LD₅₀) of the Leptospira interrogans strain UP-MMC-SM (L495) for hamsters in transtracheal infection was 3.2 × 10² cells. The results of culture, macroscopic findings, and histopathological analysis suggested that intratracheally injected leptospires invaded the lung tissue, proliferated in the collagen-rich stroma adjacent to the bronchus and blood vessels, and then spread throughout the body via the bloodstream. In the lung, leptospires continuously infiltrated the alveolar wall without inflammatory cell infiltration, spread throughout the lung, and finally caused pulmonary hemorrhage. Our results revealed that the respiratory tract might be a portal of entry for leptospires. We speculate that some cases of leptospirosis might be caused by transbronchial infection from inhaling infectious aerosols containing leptospires during floods. Leptospira was also confirmed to be a unique pathogen that invades through the bronchus, proliferates in the collagen-rich lung stroma, and spreads through the alveolar interstitium throughout the lung without causing pneumonia.

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.

Clinical characteristics of laboratory-confirmed leptospirosis in Okinawa, Japan, 1974-2015: high incidence of Jarisch-Herxheimer reaction

BACKGROUND

Leptospirosis is a zoonotic disease known to have wide-ranging clinical manifestations. Despite a number of published case series, culture-confirmed series are few and there is a paucity of data on Jarisch-Herxheimer reaction (JHR) associated with treatment of leptospirosis. Our objective was to describe the clinical and epidemiological factors associated with leptospirosis in an endemic area of Japan, with a focus on the occurrence of JHR, an often unrecognized and likely underestimated phenomenon.

METHODS

We performed a retrospective observational study of laboratory-confirmed leptospirosis at a single center over a 40-year period.

RESULTS

We report 100 leptospirosis cases in 99 patients during the period 1974-2015. Seventy-four cases were diagnosed by culture, representing eight different serovars. JHR was seen in 23 (82%) of 28 cases, including 19 (90%) of 21 cases treated with bactericidal antibiotics compared to 4 (57%) of seven cases with bacteriostatic antibiotics (p=0.08).

CONCLUSIONS

We found a wide variety of clinical manifestations, epidemiological exposures, and causative serovars of disease in an endemic region of Japan. We also found that JHR occurs frequently, and its recognition may be important for the diagnosis and management of leptospirosis in the early stage when laboratory confirmation is pending.

Waterborne Leptospirosis: Survival and Preservation of the Virulence of Pathogenic Leptospira spp. in Fresh Water

Many studies have implicated fresh water as a source of leptospirosis outbreaks. To estimate the survival and the preservation of the virulence of pathogenic Leptospira spp. maintained in water, we selected five still waters with various pH and mineral profiles. The water samples were artificially inoculated with a culture of a pathogenic strain belonging to serovar Icterohaemorrhagiae. Samples were stored for 20 months at 4, 20 or 30 °C. The survival and preservation of virulence of this pathogenic strain was estimated by subculturing these stored samples. After 14 and 20 months of storage, the strain Icterohaemorrhagiae was re-isolated, and its virulence was determined using an animal model. In these waters, the mean survival was 130 days for storage at 4 °C, 263 days at 20 °C, and 316 days at 30 °C. Unexpectedly, the mean survival was 344 days for a final pH < 7 and 129 days for pH ≥ 7. Moreover, the pathogenic strain remained fully virulent and was able to induce a lethal disease in gerbils even when the pH of the contaminated waters decreased to <6. These data showed that despite unfavourable storage conditions such as cold, nutrient-poor acidic waters, the survival and virulence of pathogenic Leptospira spp. was fully preserved over at least 20 months.

[Leptospirosis now-the centennial of the discovery of Weil's disease pathogen]

This year, 2014, marks the centennial of the discovery of Leptospira as the Weil's disease pathogen by Ryokichi Inada, Yutaka Ido and their colleagues. Leptospirosis is a worldwide zoonosis especially in countries with tropical and subtropical climates. Recently, the number of patients with leptospirosis dramatically decreased in Japan because public hygiene has greatly improved, the mechanization of agriculture was introduced, and farmers started using rubber boots and gloves while working in the field. The opportunities for percutaneous infection with Leptospira was reduced, but have not been totally eliminated in Japan.We previously reported a novel combination of five antimicrobial agents for selective isolation of Leptospira from contaminated samples. This cocktail, after being incorporated into Leptospira growth medium, inhibited the growth of contaminants and allowed successful detection of leptospires in environmental samples. We collected soil and environmental water and cultured them using this selective medium. It was revealed that not only saprophytic Leptospira but also pathogenic Leptospira are widely living in the environment. We hypothesized that soil serves as reservoir for Leptospira and infectious source for leptospirosis. In this review, we also discuss the Leptospira-rat-human relationship in the Philippines, natural defense of host against oral and percutaneous infection by Leptospira, the mechanism of jaundice in leptospirosis, and the development of immunochromatography-based methods for detection of leptospiral antigen in urine.

Leptospirosis in a Japanese urban area: a case report and literature review

Leptospirosis is not a major disease in urban areas of Japan. We describe a 49-year-old man with leptospirosis, who lived in an urban area and had no history of living in endemic area of leptospirosis. As he worked at a fish market infested with rats, he was suspected of having contracted leptospirosis and received antimicrobial agent treatment. Serum and urinary tests confirmed the diagnosis of leptospirosis. Although it took six days from the onset until treatment initiation, the patient improved in response to receiving ceftriaxone for seven days. Analyzing past reports of Japanese patients with leptospirosis who had no history of overseas travel, we identified 90 patients with courses similar to that of our patient, and the period from onset to treatment initiation was about six days on average (described in 46 cases). Health care providers as well as patients need to recognize that even people with no history of being in an endemic area of leptospirosis may still be at risk of developing this disease depending on occupations and activities.

Risk factors of leptospirosis among febrile hospital admissions in northeastern Malaysia

BACKGROUND

Leptospirosis is a worldwide zoonotic disease. Risk factors for the disease may vary among countries.

OBJECTIVE

This study was conducted to determine the risk factors of leptospirosis among febrile cases.

MATERIALS AND METHODS

A hospital-based cross-sectional study was conducted among 999 febrile patients admitted to 10 hospitals in northeastern Malaysia, from August 2010 to February 2011. An interviewer-guided proforma sheet on sociodemography, type of occupation and social history data was distributed to all adult patients with fever on admission. Serum sample for leptospirosis was screened by IgM Enzyme-linked Immunosorbent Assay (IgM ELISA) test and confirmed by Microscopic Agglutination Test (MAT). The cut-off point for positive MAT was ≥ 1:400 titer in single acute specimens.

RESULTS

Seroprevalence of leptospirosis was 8.4% (95% CI: 6.8, 10.3) (n=84/999) by MAT. Multiple logistic regression analysis showed that the high risk occupation group (OR: 1.95, 95% CI: 1.22, 3.13) (p=0.005) and history of recent recreational activity (OR: 2.36, 95% CI: 1.46, 3.85) (p<0.001) were significant associated factors for leptospirosis.

CONCLUSION

This study shows a relatively high seroprevalence of leptospirosis in northeastern Malaysia. Identification of high risk occupational group and history of recent recreational activity will help to increase the index of suspicion to diagnose leptospirosis among febrile inpatients due to its mimicking other common febrile illnesses in Malaysia.

Evaluation of ‘white-spotted kidneys’ associated with leptospirosis by polymerase chain reaction based LipL32 gene in slaughtered cows

The presence of white spots in the kidneys of cattle at slaughter (so-called white-spotted kidneys) can be an indication of infection with Leptospira, a spirochaete of public health concern because it causes zoonotic disease. In this study, 24 kidneys of 180 slaughtered cows (13.3%) showed focal to multifocal white spots at inspection. These kidneys, together with matching urine (n = 18) and blood (n = 24) samples, were examined by polymerase chain reaction (PCR) targeting the LipL32 gene. Leptospiral deoxyribonucleic acid (DNA) was detected in 19 (79.2%) out of 24 kidneys, as well as 7 (29.2%) blood and 10 (55.5%) urine samples of cows with white spots in their kidneys. Histopathological findings revealed multifocal infiltration of mononuclear cells, including lymphocytes and a few plasma cells in the renal interstitial tissues. In addition, 14 apparently normal kidneys and associated urine and blood samples were similarly examined by PCR but did not provide any positive results. In this study, high detection of leptospirosis in kidneys with interstitial nephritis suggests that Leptospira spp. are associated with white spotted kidneys. The present findings indicate that white spotted kidneys can be due to leptospirosis in this region in southwestern Iran, which indicates an increased risk of zoonotic disease. The data show that LipL32-based primers are useful for PCR-based diagnosis of leptospirosis.

Human leptospirosis cases and the prevalence of rats harbouring Leptospira interrogans in urban areas of Tokyo, Japan

Thirteen patients with leptospirosis were identified, as confirmed by laboratory analysis during the last 5 years in our laboratory, who came from urban areas of Tokyo, Japan. All of the patients came into contact with rats before the onset of illness. Seventeen per cent of Norway rats captured in the inner cities of Tokyo carried leptospires in their kidneys. Most of these rat isolates were Leptospira interrogans serovar Copenhageni/Icterohaemorrhagiae. Antibodies against these serovars and their DNA were detected in the patients. This suggests that rats are important reservoirs of leptospirosis, and that rat-borne leptospires occur in urban areas of Tokyo.

The kidney in leptospirosis

Leptospirosis is a worldwide zoonosis. Typically, patients are young men, although children can be affected. In children, this disease causes mainly alterations of sensorium. Acute renal failure and jaundice (Weil's syndrome) are less common in children than in adults. The main renal histological findings are acute interstitial nephritis and acute tubular necrosis. Acute renal failure is characterized by hypokalemia and nonoliguria. Many factors are involved in its physiopathology: hypotension, hypovolemia, rhabdomyolysis, hyperbilirubinemia, and, primarily, the direct action of leptospiral proteins. Antibiotic administration (especially early administration) reduces length of hospitalization and leptospiruria. For children, even late antibiotic treatment has been shown to reduce the extent of acute renal failure and thrombocytopenia. Although the best method of dialysis is not yet established, early and intensive dialysis can decrease mortality. Mortality in patients with acute renal failure is approximately 15-20% in association with the presence of oliguria, higher levels of creatinine, and older age. Functional recovery is fast and complete; however, abnormal urinary concentration can persist.

The globalization of leptospirosis: worldwide incidence trends

OBJECTIVES

Leptospirosis continues to be a significant zoonosis of the developing world. Globalization, in the context of international travel, particularly for recreational activities and military expeditions, has led to increased exposure of individuals from the developed world to the disease, as recent outbreaks show.

METHODS

We evaluated the trends in annual leptospirosis incidence for individual countries worldwide through reports from national and international organizations, the published medical literature on the subject, and web searches with the terms 'leptospirosis' and the individual country names. Inter-country variations in leptospirosis incidence, when relevant official data were available, were also analyzed.

RESULTS

The Caribbean and Latin America, the Indian subcontinent, Southeast Asia, Oceania, and to a lesser extent Eastern Europe, are the most significant foci of the disease, including areas that are popular travel destinations.

CONCLUSIONS

Leptospirosis is a re-emerging zoonosis of global importance and unique environmental and social correlations. Attempts at global co-ordination and recognition of the true burden of an infectious disease with significant mortality should be encouraged.