Leptospirosis in the tropics and in travelers

Leptospira Lipid A Is a Potent Adjuvant That Induces Sterilizing Immunity against Leptospirosis

Leptospirosis is a globally significant zoonotic disease. The current inactivated vaccine offers protection against specific serovars but does not provide complete immunity. Various surface antigens, such as Leptospira immunoglobulin-like proteins (LigA and LigB), have been identified as potential subunit vaccine candidates. However, these antigens require potent adjuvants for effectiveness. Bacterial lipopolysaccharides (LPSs), including lipid A, are a well-known immunostimulant, and clinical adjuvants often contain monophosphoryl lipid A (MPLA). Being less endotoxic, we investigated the adjuvant properties of lipid A isolated from L. interrogans serovar Pomona (PLA) in activating innate immunity and enhancing antigen-specific adaptive immune responses. PLA activated macrophages to a similar degree as MPLA, albeit at a higher dose, suggesting that it is less potent in stimulation than MPLA. Mice immunized with a variable portion of LigA (LAV) combined with alum and PLA (LAV-alum-PLA) exhibited significantly higher levels of LAV-specific humoral and cellular immune responses compared to alum alone but similar to those induced by alum-MPLA. The adjuvant activity of PLA resembles that of MPLA and is primarily achieved through the increased recruitment, activation, and uptake of antigens by innate immune cells. Furthermore, like MPLA, PLA formulation establishes a long-lasting memory response. Notably, PLA demonstrated superior potency than MPLA formulation and provided sterilizing immunity against the leptospirosis in a hamster model. Overall, our study sheds light on the adjuvant properties of Leptospira lipid A and offers promising avenues for developing LPS-based vaccines against this devastating zoonotic disease.

Fatal acute undifferentiated febrile illness among clinically suspected leptospirosis cases in Colombia, 2016-2019

BACKGROUND

Acute undifferentiated febrile illness is a common challenge for clinicians, especially in tropical and subtropical countries. Incorrect or delayed diagnosis of febrile patients may result in medical complications or preventable deaths. Common causes of acute undifferentiated febrile illness in Colombia include leptospirosis, rickettsioses, dengue fever, malaria, chikungunya, and Zika virus infection. In this study, we described the acute undifferentiated febrile illness in postmortem patients reported as suspected cases of leptospirosis through the national leptospirosis surveillance in Colombia, 2016-2019.

METHODOLOGY/PRINCIPAL FINDINGS

We retrospectively analyze human fresh and formalin-fixed tissue samples from fatal suspected leptospirosis cases reported by the Public Health Laboratories in Colombia. Leptospirosis confirmation was made by immunohistochemistry, real-time polymerase chain reaction (PCR) in the tissue samples. In some cases, the serum sample was used for confirmation by Microagglutination test (MAT). Simultaneously, tissue samples were tested by PCR for the most common viral (dengue, Zika, and chikungunya), bacterial (Brucella spp., and Rickettsia spp.), and parasitic (malaria). Fresh tissue samples from 92 fatal suspected leptospirosis cases were reported to the National Reference Laboratory from 22/32 departments in Colombia. We confirmed leptospirosis in 27% (25/92) of cases. Other pathogens identified by real-time PCR were Brucella spp. (10.9%), Rickettsia spp. (14.1%), and dengue (2.2%). Dengue (6.9%), hepatitis (3.5%), and Yellow Fever cases (2.2%) were detected by the pathology. All patients were negative for chikungunya and Plasmodium spp. Most cases were classified as undifferentiated febrile illnesses (45.7%; 42/92).

CONCLUSIONS/SIGNIFICANCE

This study underscores the importance of early and accurate recognition of leptospirosis to prevent mortalities. Moreover, it draws attention to the existence of other febrile syndromes in Colombia, including rickettsiosis and brucellosis, that currently lack sufficient human surveillance and regular reporting. Expanding laboratory surveillance to include viruses such as Hantavirus, Mayaro virus, Oropouche virus, and West Nile virus is crucial.

Molecular and Serological Identification of Pathogenic Leptospira in Local and Imported Cattle from Lebanon

Leptospirosis is a worldwide bacterial zoonosis for which the risk increases in warm and wet climates. Despite the suitability of the local climate for the bacteria’s persistence, Lebanon lacks a formal system of prophylaxis for the prevention of Leptospira infection in both humans and animals, and the disease’s epidemiology is unknown so far. As a preliminary step, we focused on Leptospira infection in cattle, which is of public health and economic concern. We conducted a descriptive study in cattle from the governorate of Mount Lebanon (ML) and in imported cattle. A total of 187 blood and 135 serum samples were provided. Among the 187 blood samples, 135 were from randomly selected animals from 14 herds, while the remaining 52 were from imported livestock. Serum specimens (n = 135) were obtained exclusively from cattle in the ML governorate. DNA was extracted from all blood samples and subjected to real-time PCR targeting 16S rRNA. All Leptospira-positive DNA samples were then amplified using conventional PCR (cPCR), and Leptospira species were identified via Sanger sequencing. A microscopic agglutination test (MAT) was performed on the 135 serum samples from local cattle. The real-time PCR revealed Leptospira infection in 7 of 135 local animals and 1 of 52 imported animals. DNA from six of the seven local animals and the one imported animal were amplified by cPCR and successfully sequenced, identifying the pathogen as the species L. kirschneri. Seven animals located in five out of the 14 tested herds had MAT titers ≥1 : 100. Serogroup Grippotyphosa was predominant. This is the first study to provide epidemiological data on bovine Leptospira infection in Lebanon. Pathogenic Leptospira species and serogroups were identified in both local and imported cattle. These findings highlight the cattle associated risk of Leptospira infection in Lebanon, in the contexts of farming and trade. Summary. Leptospirosis is a severe zoonotic disease that can have critical consequences for people and animals. Within the country of Lebanon, this disease has been reported, but its epidemiology is unknown so far. The present study thus provides the first description of the existence of Leptospira in cattle in Lebanon (local and imported). It also highlights the existence of different pathogenic serogroups of Leptospira in local cattle. Our results should raise public health awareness of the threat posed by this underdiagnosed disease and serve as a starting point for control efforts in Lebanon.

Leptospirosis in Vietnam

Leptospirosis poses a serious public health problem in many countries because about 1 million people suffer annually from this severe, often fatal, infection. At present, its importance has been increasing due to development of integration processes, globalization and intensification of economic activities, inevitable anthropogenic transformation of landscapes as well as rise in number of people with occupational risk of pathogen exposure. The burden of human leptospirosis is expected to rise with demographic shifts and climate change that result in heavy rainfall and flooding. Regarding leptospirosis, Southeast Asia, including Vietnam, is among the most vulnerable global regions. The objective of the review was to analyze available published data on the spread of leptospirosis in Vietnam. More than 100 research articles were analyzed allowing to state that in Vietnam synanthropic rodents (rats), agricultural (buffaloes, cattle, pigs) and domestic animals (cats, dogs) are the main sources of leptospirosis infection in humans. It is essential that rats (cats and dogs also) in Vietnam are used for food. Among all farm animals, pigs are of maximal importance as a source of infection in humans. In Vietnam, Leptospira prevalence in pigs varies widely, up to 73%. It depends significantly on the location, farm size, age and gender of animals, etc. A large variety of Leptospira serovars have been identified in pigs in Vietnam: Tarassovi, Bratislava, Australis, Javanica, Autumnalis, Grippotyphosa, and some others. Official Vietnam reporting of leptospirosis cases based on clinical data does not reflect the real-life incidence rate in humans. However, the available seroprevalence studies reveal that, on average, about 10% of the Vietnamese population are infected with Leptospira. Work in agriculture is the dominant risk factor for acquiring this infection. The highest Leptospira seroprevalence rates were detected in farmers, 63.2%. Serovar diversity is typical for pathogenic Leptospira circulating in Vietnam. In humans, the most frequent are antibodies to Hebdomadis, Wolffi and Icterohaemorrhagiae, but the frequency varied markedly across the country depending on the site, possibly with relation to the environment, as well as with economic activity of the local population. In Vietnam, geographic, climatic and social differences between northern, central and southern regions contribute to the specificity of local leptospirosis epidemiology. This emphasizes the advisability of developing special measures for leptospirosis prevention taking into account regional peculiarities.

Triton X-114 Fractionated Subcellular Proteome of Leptospira interrogans Shows Selective Enrichment of Pathogenic and Outer Membrane Proteins in the Detergent Fraction

The Triton X-114-based solubilization and temperature-dependent phase separation of proteins is used for subcellular fractionation where, aqueous, detergent, and pellet fractions represents cytoplasmic, outer membrane (OM), and inner membrane proteins, respectively. Mass spectrometry-based proteomic analysis of Triton X-114 fractions of proteomic analysis of Leptospira interrogans identified 2957 unique proteins distributed across the fractions. The results are compared with bioinformatics predictions on their subcellular localization and pathogenic nature. Analysis of the distribution of proteins across the Triton X-114 fractions with the predicted characteristics is performed based on "number" of unique type of proteins, and "quantity" which represents the amount of unique protein. The highest number of predicted outer membrane proteins (OMPs) and pathogenic proteins are found in aqueous and pellet fractions, whereas detergent fraction representing the OM has the highest quantity of OMPs and pathogenic proteins though lower in number than the aqueous and pellet fractions. This leaves the possibility of an upsurge in pathogenic proteins and OMPs on the OM under pathogenic conditions suggesting their potential use to combat leptospirosis. Further, the Triton X-114 subcellular fractions are more correlated to enrichment of pathogenic proteins predicted by MP3 software than predicted localization.

Leptospira interrogans in mammals in Lviv Oblast, Ukraine, 2001-2015

This study describes changes in the prevalence of Leptospira interrogans infections among small mammals, including rats and larger domestic and wild mammals in Lviv Oblast, a region in western Ukraine from 2001–2015, using the microscopic agglutination test (MAT). A total of 439,948 domestic or wild animals were tested. We found the prevalence of Leptospira interrogans exposure varied among tested species and changed over the time. Infection was significantly less common in domestic animals, than in wild rodents. In swine the overall seroprevalence was 0.51%, while in cattle it was 0.19%. In dogs it was higher—2.75%. After 2006, evidence of infection was only observed in swine among domestic animals. The prevalence among large wild animals (0.25%) was similar to that among domestic animals. Among small mammals and rats, seroprevalence was most commonly observed among Rattus norvegicus (18.44%) and it was less common among other wild small mammals (8.74%). There were two dominant serogroups among large wild and domestic animals–L. icterohaemorrhagiae and L. hebdomadis while among wild small mammals the two most common were L. icterohaemorrhagiae and L. grippotyphosa. Wild animals with antibodies were found throughout the entire oblast.

Leptospirosis is one of the most prevalent bacterial zoonoses in the world. The main reservoir of the disease is rodents. Fur animals, domestic animals and livestock are an additional reservoir and also pose a threat of infection for humans. Therefore, the profound interest to Leptospira infection among the main and secondary reservoirs is important considering the direct threat for humans to get infection from these animals. We analyzed the official annual reports of the Lviv Regional State Laboratory of Veterinary Medicine of the Chief Administration of the State Service of Ukraine on Food Safety and Consumer Protection in the Lviv Oblast and the Laboratories of Especially Dangerous Infections of the Lviv Oblast Laboratory Center of the Ministry of Health of Ukraine for the period of 2001–2015 with regard to Leptospira infection rate in rodents, domestic animals and livestock, as well as wild animals in Lviv Oblast, Ukraine (Eastern Europe). During this period, no leptospirosis cases was recorded in cattle and horses. Cattle were infected only in 0.19% of samples, and Leptospira hebdomadis was identified in all cases. In contrast, all cases of infection among pigs (0.51%) and dogs (2.75%), as well as wild fauna (0.25%) were caused by L. icterohaemorrhagiae. Infection rates in rodents during the study period reached 8.74%, with L. grippotyphosa detected the most frequently (85.94%). While testing rats, we determined that almost every fifth rat (18.44%) was infected by Leptospira, and L. icterohaemorrhagiae was found the most frequently (71.83%). The results reveal that the main preventive measure against the potential threat of leptospirosis in humans is connected to eliminating the significant level of infection in rats and other rodents. Therefore, active deratization should remain a priority in the prevention of leptospirosis in Lviv Oblast of Ukraine.

Changing patterns in leptospirosis: a three-decade study in Brazil

BACKGROUND

This study was conducted to investigate changes in the clinical pattern of leptospirosis over time, analyzing its clinical and laboratory presentations in a metropolitan city of Brazil.

METHOD

This was a retrospective study including all patients with leptospirosis admitted to tertiary care hospitals in Fortaleza in the northeast of Brazil, between 1985 and 2015. Patients were divided into three groups according to the year of hospital admission: group I for the years 1985-1995, group II for 1996-2005, and group III for 2006-2015. Demographic, clinical, and laboratory data were compared between the groups.

RESULTS

A total of 507 patients were included. Their mean age was 37.3±15.9years and 82.4% were male. The mean time between symptom onset and admission was 7±4 days. There was a linear decrease in the levels of serum urea (190.1±92.7, 135±79.5, and 95.6±73.3mg/dl, respectively, p <0.0001) and creatinine (5.8±2.9, 3.8±2.6, and 3.0±2.5mg/dl, respectively, p <0.0001) in each decade, while levels of hemoglobin (10.31±1.9, 10.8±2.0, and 11.5±2.1g/dl, respectively, p <0.0001) and platelets (57.900±52.650, 80.130±68.836, and 107.101±99.699×10⁹/l, respectively, p<0.0001) increased. There was a tendency towards a linear decrease in mortality (22%, 14%, and 11.6%, respectively, p=0.060).

CONCLUSIONS

Leptospirosis showed significant changes over time in this region. The main changes point to a decrease in disease severity and complications, such as acute kidney injury. Mortality has decreased, being close to 11%.

Comparative analyses of transport proteins encoded within the genomes of Leptospira species

Select species of the bacterial genus Leptospira are causative agents of leptospirosis, an emerging global zoonosis affecting nearly one million people worldwide annually. We examined two Leptospira pathogens, Leptospira interrogans serovar Lai str. 56601 and Leptospira borgpetersenii serovar Hardjo-bovis str. L550, as well as the free-living leptospiral saprophyte, Leptospira biflexa serovar Patoc str. 'Patoc 1 (Ames)'. The transport proteins of these leptospires were identified and compared using bioinformatics to gain an appreciation for which proteins may be related to pathogenesis and saprophytism. L. biflexa possesses a disproportionately high number of secondary carriers for metabolite uptake and environmental adaptability as well as an increased number of inorganic cation transporters providing ionic homeostasis and effective osmoregulation in a rapidly changing environment. L. interrogans and L. borgpetersenii possess far fewer transporters, but those that they all have are remarkably similar, with near-equivalent representation in most transporter families. These two Leptospira pathogens also possess intact sphingomyelinases, holins, and virulence-related outer membrane porins. These virulence-related factors, in conjunction with decreased transporter substrate versatility, indicate that pathogenicity arose in Leptospira correlating to progressively narrowing ecological niches and the emergence of a limited set of proteins responsible for host invasion. The variability of host tropism and mortality rates by infectious leptospires suggests that small differences in individual sets of proteins play important physiological and pathological roles.

Comparative genomic analyses of transport proteins encoded within the genomes of Leptospira species

Select species of the bacterial genus Leptospira are causative agents of leptospirosis, an emerging global zoonosis affecting nearly one million people worldwide annually. We examined two Leptospira pathogens, Leptospira interrogans serovar Lai str. 56601 and Leptospira borgpetersenii serovar Hardjo-bovis str. L550, as well as the free-living leptospiral saprophyte, Leptospira biflexa serovar Patoc str. 'Patoc 1 (Ames)'. The transport proteins of these leptospires were identified and compared using bioinformatics to gain an appreciation for which proteins may be related to pathogenesis and saprophytism. L. biflexa possesses a disproportionately high number of secondary carriers for metabolite uptake and environmental adaptability as well as an increased number of inorganic cation transporters providing ionic homeostasis and effective osmoregulation in a rapidly changing environment. L. interrogans and L. borgpetersenii possess far fewer transporters, but those that they have are remarkably similar, with near-equivalent representation in most transporter families. These two Leptospira pathogens also possess intact sphingomyelinases, holins, and virulence-related outer membrane porins. These virulence-related factors, in conjunction with decreased transporter substrate versatility, indicate that pathogenicity was accompanied by progressively narrowing ecological niches and the emergence of a limited set of proteins responsible for host invasion. The variability of host tropism and mortality rates by infectious leptospires suggests that small differences in individual sets of proteins play important physiological and pathological roles.

Live imaging of bioluminescent leptospira interrogans in mice reveals renal colonization as a stealth escape from the blood defenses and antibiotics

Leptospira (L.) interrogans are bacteria responsible for a worldwide reemerging zoonosis. Some animals asymptomatically carry L. interrogans in their kidneys and excrete bacteria in their urine, which contaminates the environment. Humans are infected through skin contact with leptospires and develop mild to severe leptospirosis. Previous attempts to construct fluorescent or bioluminescent leptospires, which would permit in vivo visualization and investigation of host defense mechanisms during infection, have been unsuccessful. Using a firefly luciferase cassette and random transposition tools, we constructed bioluminescent chromosomal transformants in saprophytic and pathogenic leptospires. The kinetics of leptospiral dissemination in mice, after intraperitoneal inoculation with a pathogenic transformant, was tracked by bioluminescence using live imaging. For infective doses of 10⁶ to 10⁷ bacteria, we observed dissemination and exponential growth of leptospires in the blood, followed by apparent clearance of bacteria. However, with 2×10⁸ bacteria, the septicemia led to the death of mice within 3 days post-infection. In surviving mice, one week after infection, pathogenic leptospires reemerged only in the kidneys, where they multiplied and reached a steady state, leading to a sustained chronic renal infection. These experiments reveal that a fraction of the leptospiral population escapes the potent blood defense, and colonizes a defined number of niches in the kidneys, proportional to the infective dose. Antibiotic treatments failed to eradicate leptospires that colonized the kidneys, although they were effective against L. interrogans if administered before or early after infection. To conclude, mice infected with bioluminescent L. interrogans proved to be a novel model to study both acute and chronic leptospirosis, and revealed that, in the kidneys, leptospires are protected from antibiotics. These bioluminescent leptospires represent a powerful new tool to challenge mice treated with drugs or vaccines, and test the survival, dissemination, and transmission of leptospires between environment and hosts.

Leptospirosis is a worldwide neglected disease caused by the pathogenic bacterium named Leptospira interrogans. Some rodents, such as rats, do not get sick from leptospirosis and constitute a reservoir. They carry leptospires in their kidneys and excrete the bacteria in the environment. L. interrogans are mobile and penetrate their hosts through abraded skin or mucosa. Infected humans may develop mild to severe leptospirosis, potentially leading to death. Leptospires are difficult to cultivate and to genetically manipulate, impairing the study of leptospirosis. Here, we constructed bioluminescent leptospires, and monitored infection in live mice by tracking bioluminescence. In the first days after infection, a rapid dissemination and growth of bacteria was observed in the blood circulation, followed around one week after the infection by their apparent disappearance. However, the leptospires reemerged and multiplied in the kidneys, to reach sustained levels three weeks after infection. The use of antibiotics showed that antibiotic-susceptible L. interrogans are very difficult to eradicate once they are settled in the kidneys. Mice infected with bioluminescent leptospires represent a pertinent model to study leptospirosis. These bioluminescent leptospires are novel tools that will be useful to test the efficacy of treatments or vaccines against leptospirosis.

Globalization of leptospirosis through travel and migration

Leptospirosis remains the most widespread zoonotic disease in the world, commonly found in tropical or temperate climates. While previous studies have offered insight into intra-national and intra-regional transmission, few have analyzed transmission across international borders. Our review aimed at examining the impact of human travel and migration on the re-emergence of Leptospirosis. Results suggest that alongside regional environmental and occupational exposure, international travel now constitute a major independent risk factor for disease acquisition. Contribution of travel associated leptospirosis to total caseload is as high as 41.7% in some countries. In countries where longitudinal data is available, a clear increase of proportion of travel-associated leptospirosis over the time is noted. Reporting patterns is clearly showing a gross underestimation of this disease due to lack of diagnostic facilities. The rise in global travel and eco-tourism has led to dramatic changes in the epidemiology of Leptospirosis. We explore the obstacles to prevention, screening and diagnosis of Leptopirosis in health systems of endemic countries and of the returning migrant or traveler. We highlight the need for developing guidelines and preventive strategies of Leptospirosis related to travel and migration, including enhancing awareness of the disease among health professionals in high-income countries.

Leptospirosis: current situation and trends of specific laboratory tests

Leptospirosis is re-emerging as a worldwide zoonosis and is caused by bacteria of the genus Leptospira. Human leptospirosis is associated with high temperature and humidity. Laboratory tests are indispensible for the early diagnosis and proper disease management. The demand for suitable leptospirosis point-of-care diagnostic tests grows with the awareness and number of incidences. Confirmation is achieved by the microscopic agglutination test, bacterial cultivation, PCR or histopathologic methods. However, high costs, poor standardization and/or elaborate sample preparation prevent routine use at the point of care. Cost-efficient, but insensitive serological methods dominate the diagnostic landscape and, likewise, urgently need improvement toward greater compliance with some of the point-of-care criteria. Combined application of antigen and antibody detection methods increases accuracy, but also new development or transfer of diagnostic technologies should be considered useful. Nano- and microparticle technology may play a key role in improving future antigen detection methods.

Community-acquired acute kidney injury in tropical countries

Community-acquired acute kidney injury (AKI) in developing tropical countries is markedly different from AKI in developed countries with a temperate climate, which exemplifies the influence that environment can have on the epidemiology of human diseases. The aetiology and presentation of AKI reflect the ethnicity, socioeconomic factors, climatic and ecological characteristics in tropical countries. Tropical zones are characterized by high year-round temperatures and the absence of frost, which supports the propagation of infections that can cause AKI, including malaria, leptospirosis, HIV and diarrhoeal diseases. Other major causes of AKI in tropical countries are envenomation; ingestion of toxic herbs or chemicals; poisoning; and obstetric complications. These factors are associated with low levels of income, poor access to treatment, and social or cultural practices (such as the use of traditional herbal medicines and treatments) that contribute to poor outcomes of patients with AKI. Most causes of AKI in developing tropical countries are preventable, but strategies to improve the outcomes and reduce the burden of tropical AKI require both improvements in basic public health, achieved through effective interventions, and increased access to effective medical care (especially for patients with established AKI).

Severe leptospirosis: treatment with intravenous corticosteroids and supportive care

Leptospirosis is a common zoonotic infection worldwide and is recognized as an emerging public health problem. Although commonly thought of as a tropical disease, incidence in temperate climates is increasing, with recent outbreaks in the United States and Germany, among other countries. The disease presents with symptoms ranging from fever, headache, nausea, and vomiting to life-threatening multiorgan failure characterized by acute liver failure, nephritis, pulmonary hemorrhage, meningitis, and cardiac arrhythmia. We describe a case of an otherwise healthy 28-year-old man who had just returned from a 2-month trip to Southeast Asia. He presented to our emergency department twice after his return with the complaint of fever and malaise. Initially, he was treated with symptomatic measures and discharged home with malaria smears and blood cultures pending. On his final presentation before admission, he presented with severe fatigue, myalgia, acute renal failure, and marked thrombocytopenia. After several days, inpatient testing revealed the patient's leptospira antibody titer was markedly positive. Given the nonspecificity of patient symptoms, early diagnosis of leptospirosis can be challenging. Diagnostic uncertainty may lead to delay in recommended intravenous antibiotic treatment. We present a case of severe leptospirosis treated exclusively with supportive measures and intravenous corticosteroids.

Development of a magnetic bead fluorescence microscopy immunoassay to detect and quantify Leptospira in environmental water samples

Climate change, world population growth, and poverty have led to an increase in the incidence of leptospirosis. Leptospirosis is caused by pathogenic spirochaete bacteria that belong to the genus Leptospira. The bacteria are maintained in the renal tubules of the reservoir hosts (typically a rodent), then shed into the environment via the urine. Water is key for environmental survival and transmission, as leptospires can survive for several weeks in a moist environment. Therefore, environmental epidemiological studies are needed to study the contamination of environmental water sources. However, few such studies have been performed using cultivation of the isolates and PCR assays. But, leptospira cultivation can be easily contaminated by other organisms and takes usually several weeks. Moreover, PCR is a complex and costly analysis for the underdeveloped countries that have the highest incidence of leptospirosis. In this study, we describe two modifications of a fluorescence microscopy assay based on immuno-magnetic separation (IMS) to detect leptospires in environmental water samples that mainly differ in fluorescent dye staining. The first type uses acridine orange fluorescent dye staining combined with multiplexed IMS for sample screening. The detection limit ranged from 10(2) to 10(3) organisms per mL and largely depended on the capture efficiency (CE) of the immuno-magnetic particles. The second type uses serogroup-specific immuno-particles and direct fluorescence antibody staining (DFA) to detect leptospires; the detection limit of this second assay was approximately 10(1) cells per mL. Both assay types were applied to natural and experimentally infected water samples, which were also analysed with DFM and real-time PCR. Our data show that the fluorescent microscopy immunoassay successfully identified experimental leptospire contamination and was as sensitive as PCR. This modified immune-fluorescence assay may therefore enable epidemiological studies of leptospirosis.

Highly virulent Leptospira borgpetersenii strain characterized in the hamster model

Abstract. A recent study by our group reported the isolation and partial serological and molecular characterization of four Leptospira borgpetersenii serogroup Ballum strains. Here, we reproduced experimental leptospirosis in golden Syrian hamsters (Mesocricetus auratus) and carried out standardization of lethal dose 50% (LD50) of one of these strains (4E). Clinical disease features and histopathologic analyses of tissue lesions were also observed. As results, strain 4E induced lethality in the hamster model with inocula lower than 10 leptospires, and histopathological examination of animals showed typical lesions found in severe leptospirosis. Gross pathological findings were peculiar; animals that died early had more chance of presenting severe jaundice and less chance of presenting pulmonary hemorrhages (P < 0.01). L. borgpetersenii serogroup Ballum has had a considerable growth in human leptospirosis cases in recent years. This strain has now been thoroughly characterized and can be used in more studies, especially evaluations of vaccine candidates.

Acute kidney injury in the tropics

Acute kidney injury (AKI) is one of the most challenging problems faced by clinicians in the tropics owing to its fast-changing burden. AKI in the tropics is strikingly different from that in the developed world in terms of etiology and presentation. In addition, there is a stark contrast between well-developed and poor areas in the tropics. The true epidemiological picture of AKI in the tropics is not well understood due to the late presentation of patients to tertiary centers. Infections remain the major culprit in most cases of AKI, with high mortality rates in the tropics. Human immunodeficiency virus-related AKI, related to nephrotoxicity due to antiretroviral therapy, is on the rise. Acute tubular necrosis and thrombotic microangiopathy are the most common mechanisms of AKI. A notable problem in the tropics is the scarcity of resources in health centers to support patients who require critical care due to AKI. This article reviews the unique and contrasting nature of AKI in the tropics and describes its management in each situation.

Outpatient follow-up of patients hospitalized for acute leptospirosis

OBJECTIVE

The outcome of leptospirosis after the resolution of acute disease, either spontaneously or after treatment, is not well described. The aim of this study was to assess the possible sequelae of acute leptospirosis after hospital discharge.

METHODS

We report here a prospective study carried out in São Paulo, Brazil in which patients hospitalized for leptospirosis were followed in the outpatient setting.

RESULTS

Forty-seven patients were serially assessed: 32 severe and 15 mild cases. Early and late complications were not common in either group, but subjective complaints were common in the first few weeks after hospital discharge (53% of severe cases, 40% of mild cases). Two patients had continuing complaints: one had profound general malaise and the other developed new onset panic disorder. The sample analyzed represented 26% of the patients hospitalized with leptospirosis in the city of São Paulo during the study period. The duration of follow-up was an average of approximately 20 days at the first visit, and approximately 40 days at the second visit. Forty-seven patients came for one follow-up visit and 22 of the same patients had two follow-up visits.

CONCLUSIONS

While two of 47 patients reported continuing symptoms after hospitalization for acute leptospirosis, no definitive, objective evidence of chronic sequelae due to this infection was proven. While preliminary, these observations point to the need for a prospective, rigorous and systematic study to definitively determine and characterize late complications and chronic disease after acute leptospirosis.

Travel-related leptospirosis in Israel: a nationwide study

Leptospirosis is re-emerging in developed countries as a travel-related infection. In this nationwide study of travel-related leptospirosis in Israel, all cases diagnosed at the Central Reference Laboratory for Leptospirosis, during 2002-2008 were retrospectively reviewed and only travel-related cases were included. During the study years, 20 (42%) of 48 leptospirosis cases in Israel were travel-related. Exposure occurred in Southeast Asia in 15 (75%) of 20 cases. The estimated yearly incidence of travel-related leptospirosis was 1.78/100,000 travelers compared with an incidence of endemic cases of 0.06/100,000 inhabitants (risk ratio = 29.6, 95% confidence interval = 16.7-52.4). Most patients (89%) were infected during water-related activities. Severe disease was present in 10 (55%) of 18 patients; 7 of them were presumptively infected with the Icterohaemorrhagiae serogroup. Thus, travel-related leptospirosis is becoming increasingly important in the epidemiology of leptospirosis in Israel. Leptospirosis should be suspected in any traveler with undifferentiated febrile illness, especially when water exposure is reported.

LepBank: a Leptospira sequence repository and a portal for phylogenetic studies

Leptospirosis is a neglected infectious disease that constitutes a threat to both humans and animals. Comprehension about the epidemiological behavior and population dynamics of Leptospira may be helpful for the development of control measures. Thus, an effort was made to organize leptospiral sequences in a new and specific database. In addition, online bioinformatics tools were clustered in a web portal to facilitate sequences manipulation by scientists. LepBank (http://.lepbank.ufpel.edu.br) is a Leptospira sequences repository and a suite for systematics, which brings simplicity to leptospirosis research, integrating sophisticated online programs to a sequence database. We intend the database to be useful for the leptospirosis scientific community, providing standardized and high quality information and facilitating research into key aspects of the Leptospira taxonomy and phylogeny.

New hypothesis for cause of epidemic among native Americans, New England, 1616-1619

In the years before English settlers established the Plymouth colony (1616-1619), most Native Americans living on the southeastern coast of present-day Massachusetts died from a mysterious disease. Classic explanations have included yellow fever, smallpox, and plague. Chickenpox and trichinosis are among more recent proposals. We suggest an additional candidate: leptospirosis complicated by Weil syndrome. Rodent reservoirs from European ships infected indigenous reservoirs and contaminated land and fresh water. Local ecology and high-risk quotidian practices of the native population favored exposure and were not shared by Europeans. Reduction of the population may have been incremental, episodic, and continuous; local customs continuously exposed this population to hyperendemic leptospiral infection over months or years, and only a fraction survived. Previous proposals do not adequately account for signature signs (epistaxis, jaundice) and do not consider customs that may have been instrumental to the near annihilation of Native Americans, which facilitated successful colonization of the Massachusetts Bay area.

Overlapping clinical features of lupus and leptospirosis

Systemic manifestations of infectious disease may be confused with systemic lupus erythematosus (SLE), leading to potential patient morbidity and mortality. We report the case of a patient with severe renal failure and liver involvement who was initially diagnosed and treated for leptospirosis infection. It was later determined that his organ involvement was related to active SLE. We review the clinical and laboratory features common to both SLE and leptospirosis infection to highlight not only the importance of maintaining a high index of suspicion for infectious organisms in a patient with a suspect travel history but also the recognition of atypical features of a systemic autoimmune disease.

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.

The terminal portion of leptospiral immunoglobulin-like protein LigA confers protective immunity against lethal infection in the hamster model of leptospirosis

Subunit vaccines are a potential intervention strategy against leptospirosis, which is a major public health problem in developing countries and a veterinary disease in livestock and companion animals worldwide. Leptospiral immunoglobulin-like (Lig) proteins are a family of surface-exposed determinants that have Ig-like repeat domains found in virulence factors such as intimin and invasin. We expressed fragments of the repeat domain regions of LigA and LigB from Leptospira interrogans serovar Copenhageni. Immunization of Golden Syrian hamsters with Lig fragments in Freund's adjuvant induced robust antibody responses against recombinant protein and native protein, as detected by ELISA and immunoblot, respectively. A single fragment, LigANI, which corresponds to the six carboxy-terminal Ig-like repeat domains of the LigA molecule, conferred immunoprotection against mortality (67-100%, P<0.05) in hamsters which received a lethal inoculum of L. interrogans serovar Copenhageni. However, immunization with this fragment did not confer sterilizing immunity. These findings indicate that the carboxy-terminal portion of LigA is an immunoprotective domain and may serve as a vaccine candidate for human and veterinary leptospirosis.

Optimal treatment of leptospirosis: queries and projections

Although the global burden of leptospirosis remains enormous and new aspects of the disease are constantly recognised, little progress has been achieved in the field of leptospirosis therapeutics and queries regarding the utility of antibiotics in the late severe form of the disease remain. From the currently existing data, conclusions on the efficacy of antibiotic administration in severe or late disease cannot easily be drawn, since clinical trials have different selection criteria and may focus on Leptospira serovars with different virulence. However, as a rule the benefit of the doubt should apply. Moreover, new options, such as ceftriaxone, have a superior safety profile to penicillin. In vitro studies have outlined potential antimicrobial candidates such as macrolides and ketolides. Development of a globally accepted subunit vaccine for humans is warranted but is not expected in the near future.