Leptospirosis: re-emerging or re-discovered disease?

Assessment of the Current Surveillance System for Human Leptospirosis in Ecuador by Decision Analytic Modeling

Leptospirosis is a globally disseminated zoonotic disease with no national surveillance systems. On the other hand, surveillance is crucial for improving population health, and surveillance systems produce data that motivates action. Unfortunately, like many other countries, Ecuador put in place a monitoring system that has never been tested. The goal of this study was to use scenario tree modeling to assess the sensitivity of Ecuador's current national surveillance system to human leptospirosis as the basis for an economic assessment of the system. We created a decision-tree model to analyze the current system's sensitivity. The inputs were described as probabilities distributions, and the model assessed the program's sensitivity as an output. The model also considers the geographical and weather variations across Ecuador's three continental regions: Andean, Amazonia, and the Coast. Several data sources were used to create the model, including leptospirosis records from Ecuador's Ministry of Public Health, national and international literature, and expert elicitation, all of which were incorporated in a Bayesian framework. We were able to determine the most critical parameters influencing each scenario's output (CSU) sensitivity through sensitivity analysis. The Coast region had the best sensitivity scenario, with a median of 0.85% (IC 95% 0.41-0.99), followed by the Amazonia with a median of 0.54% (CI 95% 0.18-0.99) and the Andes with a median of 0.29% (CI 95% 0.02-0.89). As per the sensitivity study, the most influential criteria on the system's sensitivity were "Attendance or probability of going to a health center" and "probability of having symptoms," notably for the Coast and Amazonia Regions.

A NEW POSSIBILITY FOR SURVEILLANCE: DO WE IDENTIFY ALL CASES OF LEPTOSPIROSIS?

Leptospirosis is a febrile disease with a typically underestimated global incidence, especially in regions where dengue is endemic. Therefore, it is difficult to accurately determine the number of leptospirosis cases in these areas, which contributes to significant under-reporting this disease. In this study, we estimated the number of possible leptospirosis cases among dengue-like cases that were reported during 2008, 2010, and 2012 in the city of Fortaleza, northeast Brazil. Patients were evaluated for dengue and leptospirosis using immunoenzymatic tests for IgM antibodies that were specific to each pathogen. Among the suspected cases of dengue that resulted as negative in laboratory tests, 10.8% (2008), 19.2% (2010), and 30.8% (2012) were confirmed to be leptospirosis. Considering the cases reported by the surveillance authority as dengue that were subsequently discarded based on the laboratory test results, we estimate that the number of actual leptospirosis cases may be 26 to 49 times higher than those diagnosed and reported by the Health Services. Furthermore, we believe that approximately 20% of dengue-like cases may be leptospirosis cases in areas where the two diseases are endemic.

Leptospirosis in humans

Leptospirosis is a widespread and potentially fatal zoonosis that is endemic in many tropical regions and causes large epidemics after heavy rainfall and flooding. Infection results from direct or indirect exposure to infected reservoir host animals that carry the pathogen in their renal tubules and shed pathogenic leptospires in their urine. Although many wild and domestic animals can serve as reservoir hosts, the brown rat (Rattus norvegicus) is the most important source of human infections. Individuals living in urban slum environments characterized by inadequate sanitation and poor housing are at high risk of rat exposure and leptospirosis. The global burden of leptospirosis is expected to rise with demographic shifts that favor increases in the number of urban poor in tropical regions subject to worsening storms and urban flooding due to climate change. Data emerging from prospective surveillance studies suggest that most human leptospiral infections in endemic areas are mild or asymptomatic. Development of more severe outcomes likely depends on three factors: epidemiological conditions, host susceptibility, and pathogen virulence (Fig. 1). Mortality increases with age, particularly in patients older than 60 years of age. High levels of bacteremia are associated with poor clinical outcomes and, based on animal model and in vitro studies, are related in part to poor recognition of leptospiral LPS by human TLR4. Patients with severe leptospirosis experience a cytokine storm characterized by high levels of IL-6, TNF-alpha, and IL-10. Patients with the HLA DQ6 allele are at higher risk of disease, suggesting a role for lymphocyte stimulation by a leptospiral superantigen. Leptospirosis typically presents as a nonspecific, acute febrile illness characterized by fever, myalgia, and headache and may be confused with other entities such as influenza and dengue fever. Newer diagnostic methods facilitate early diagnosis and antibiotic treatment. Patients progressing to multisystem organ failure have widespread hematogenous dissemination of pathogens. Nonoliguric (high output) renal dysfunction should be supported with fluids and electrolytes. When oliguric renal failure occurs, prompt initiation of dialysis can be life saving. Elevated bilirubin levels are due to hepatocellular damage and disruption of intercellular junctions between hepatocytes, resulting in leaking of bilirubin out of bile caniliculi. Hemorrhagic complications are common and are associated with coagulation abnormalities. Severe pulmonary hemorrhage syndrome due to extensive alveolar hemorrhage has a fatality rate of >50 %. Readers are referred to earlier, excellent summaries related to this subject (Adler and de la Peña-Moctezuma 2010; Bharti et al. 2003; Hartskeerl et al. 2011; Ko et al. 2009; Levett 2001; McBride et al. 2005).

The dangers of living in a tent in London

A middle-aged patient was admitted severely unwell with acute liver and renal failure of unknown cause. After extensive investigation the patient was found to have leptospirosis. We examine the investigations and management and discuss the disease itself.

Prevalence of the Leptospira serovars bratislava, grippotyphosa, mozdok and pomona in French dogs

Although most French dogs are correctly vaccinated against leptospirosis with inactivated strains of canicola and icterohaemorrhagiae, the disease is still very prevalent in France raising the question of whether the vaccines used require updating. The aim of the present study was to provide serological data regarding circulation of the Leptospira serovars: grippotyphosa, bratislava, pomona and mozdok, which are contained in vaccines available in other parts of the world and which could be rapidly adapted for France. Results indicated that the epidemiology was consistent with the circulation of Leptospira belonging to the serogroups Australis and Grippotyphosa and that the case to support the inclusion of either pomona or mozdok in a dog vaccine for France was weak.

Geographic analysis on the occurrence of human and canine leptospirosis in the city of Maringá, state of Paraná, Brazil

INTRODUCTION

Leptospirosis is a zoonotic disease, the primary hosts of which are wild, synanthropic, and household animals. Humans behave as terminal and accidental hosts. The prevalence of leptospirosis depends on carrier animals that disseminate the agent, on the environmental survival of this agent, and on the contact of susceptible individuals. Each serovar has one or more hosts with different adaptation levels. The focuses of leptospirosis are infected, sick, and asymptomatic animals, which are considered to be sources of environmental infection. This study aimed to determine the risk areas for leptospiral infection in stray dogs and patients diagnosed with leptospirosis from 2006 to 2008 in Maringá, State of Paraná, Brazil.

METHODS

Three hundred and thirty-five stray dogs and 25 patients were studied. Serum from both animals and patients was examined by the microscopic serum agglutination test to study anti-leptospiral antibodies. To determine the risk areas and the spatial distribution of the disease, thematic maps were designed.

RESULTS

Forty-one (12.2%) dogs positive for one or more leptospire serovars were observed, the most frequent serovars being Pyrogenes (43.9%), Canícola (21.9%), and Copennhageni (19.5%). Among the humans, 2 (8%) were positive for serovars Pyrogenes and Hardjo Prajitno and for Pyrogenes and Cynopteri.

CONCLUSIONS

Spatial analysis showed that the risk for dogs and humans in the City of Maringá to become infected with leptospires exists in both the central and the peripheral areas, a fact that reinforces the relevance of this study and of continuous epidemiological and environmental surveillance actions to control the disease in animals and in humans.

Leptospirosis prevalence in Chinese populations in the last two decades

Leptospirosis is a common zoonotic disease in China. From 1991 to 2010, its average annual incidence was 0.70 cases per 100,000 population. During these two decades, three major outbreaks of leptospirosis occurred due to flooding and heavy rainfall. Leptospira interrogans serogroup Icterohaemorrhagiae serovar Lai is the predominant leptospire responsible for at least 60% of Chinese cases, and Apodemus agrarius serves as the major animal host. Based on the differences in predominant leptospiral serovars, epidemic features and incidence, there are three leptospirosis-prevalent regions in China. However, the incidence has significantly decreased in the last ten years.

A serosurvey for antibodies toLeptospirain dogs in the lower North Island of New Zealand

AIMS

To investigate the prevalence of antibodies to endemic and exotic Leptospira serovars in samples from a serum bank, collected from dogs in the lower North Island of New Zealand.

METHODS

Sera (n=466), which had been collected from apparently healthy dogs, were screened using the microscopic agglutination test (MAT) for antibodies to serovars L. borgpeterseni serovar hardjo, L. interrogans serovars pomona, copenhageni and canicola, and L. kirschneri serovar grippotyphosa.

RESULTS

Antibody to Leptospiral antigen was found in 14.2% of dogs tested. The highest level of reactivity was with serovar copenhageni, to which 9.5% (41/433) of sera were positive. Antibodies to serovars grippotyphosa and canicola were not detected in this population of dogs.

CONCLUSIONS

Leptospira infection is relatively common in dogs in the lower North Island .

CLINICAL RELEVANCE

Vaccination of dogs against leptospirosis should be considered using vaccine containing antigen to serovars hardjo, pomona and copenhageni. The presence of moderate levels of copenhageni antibody in dogs in the lower North Island raises the possibility that this serovar has become established in rodent populations in this region.

Serological surveillance of scrub typhus, murine typhus, and leptospirosis in small mammals captured at firing points 10 and 60, Gyeonggi province, Republic of Korea, 2001-2005

Soldiers from the Republic of Korea and the United States conducting peacetime military operations at various training sites and multiple range complexes located near the demilitarized zone separating North and South Korea are exposed to rodents and their potentially disease-carrying ectoparasites. These diseases include scrub typhus, murine typhus, and leptospirosis. Many of the training sites are rural or semi-rural, surrounded or co-located with various forms of agriculture, and are infested with rodents and insectivores (as well as their ectoparasites), which are commonly found in association with unmanaged tall grasses, scrub, and crawling vegetation habitats. For 5 years, rodents and insectivores were collected seasonally (spring, summer, fall, and winter) at firing points 10 and 60 near the demilitarized zone and serologically tested for the presence of scrub typhus, murine typhus, and leptospirosis antibodies. Of the nine species of small mammals collected, Apodemus agrarius, the common striped field mouse and known reservoir of scrub typhus, was the most frequently collected (90.6%). Only four of the nine species captured, A. agrarius (60.9%), Micromys minutus (100%), Mus musculus (55.6%), and Rattus norvegicus (46.7%), were positive for scrub typhus. Of all the small mammals captured, only A. agrarius was positive for murine typhus (0.3%) and leptospirosis (1.3%). Seasonal and annual prevalence rates based on weight and sex are presented.

[Anti-Leptospira antibodies in patients in the State of Mato Grosso do Sul with clinical suspicion of dengue or viral hepatitis]

In view of the lack of clinical and epidemiological data on human leptospirosis in the State of Mato Grosso do Sul, and the possibility of confounding it with other diseases, sera from patients with a preliminary clinical suspicion of dengue or viral hepatitis but without laboratory confirmation were examined by means of microscopic seroagglutination techniques for leptospirosis. The seroreactivity rates among the samples with clinically suspected dengue or viral hepatitis were 15.9% and 9%. The most frequent serovar was Hurstbridge (70.4%) and the serovar with the highest titer was Canicola (1:51,200). No association was found between seropositivity and the patients sex, age or occupation. This study demonstrated that, although the present notifications of leptospirosis cases in Mato Grosso do Sul are negligible, the prevalence of antibodies was high in the groups investigated. Therefore, the hypothesis that there is undernotification of human leptospirosis cases in this State and difficulties in the differential diagnosis between dengue and viral hepatitis should be considered.

NF-kB activation and p38 phosphorilation in microglial cells infected with Leptospira or exposed to partially purified leptospiral lipoproteins

Recently, we have shown a differential susceptibility of non-pathogenic vs. pathogenic leptospires to phagocytosis and killing by microglial cells. Although all ingested to some extent, only the pathogenic strains survived intracellularly while the non-pathogenic ones were killed in a time-dependent manner. By the same infection model, here we demonstrate that microglial cells respond to Leptospira infection with a time- and dose-dependent induction of molecular signals (p38 phosphorilation and NF-kB activation) and the production of soluble factors (cytokines and nitric oxide). Such bio-molecular response is predominantly observed against the pathogenic Leptospira; the phenomenon is reproduced by leptospiral lipoproteins and, to a lower extent, by leptospiral-derived LPS. These data provide initial evidence that Leptospira affects microglial cell response in a different manner depending upon the virulence of the infecting strain; specific bacterial components happen to be involved in the induction of such pathogen-induced immune response.

Evaluation of a commercial latex agglutination assay for serological diagnosis of leptospirosis

Leptospirosis is a febrile zoonosis of worldwide distribution. A latex agglutination assay was evaluated in two studies, the first using a panel of well-characterized sera from patients with leptospirosis and from patients with other disease states and the second, a prospective hospital-based study, evaluating sera from 186 consecutive patients admitted to hospital with acute febrile illness. The confirmed leptospirosis serum panel included paired acute- and convalescent-phase specimens from 40 cases, of which 34 gave positive latex tests (case sensitivity, 85%; 95% confidence interval [95% CI], 70 to 94%). The other diseases represented in the panel of 112 specimens from nonleptospirosis patients included autoimmune diseases, brucellosis, dengue, melioidosis, malaria, syphilis, toxoplasmosis, viral hepatitis, and a number of other viral infections. The specificity of latex agglutination using this panel was 81% (95% CI, 73 to 87%). Among the patients with acute febrile illness, there were 25 cases of leptospirosis and 161 patients with other diagnoses. The sensitivity and specificity of latex agglutination in this group were 88% (95% CI, 72 to 97%) and 98% (95% CI, 95 to 100%), respectively. In this evaluation, the two distinct groups of specimens gave similar results for sensitivity, but specificity was different in each study. The sensitivity and specificity observed for the hospital study were similar to those obtained in evaluations of other rapid tests in the same population. The results of this study suggest that multiple evaluations of new diagnostic assays should be performed, because performance characteristics may vary in different populations.

Seroepidemiology of leptospirosis in southern Vietnamese children

OBJECTIVE

To estimate the seroprevalence of human leptospirosis in southern Vietnam.

METHODS

All pupils (n=961) of two primary schools in two communes in southern Vietnam were screened for the presence of serum Leptospira immunoglobulin (Ig)G. Leptospira IgM was tested in 92 randomly selected samples. IgM and IgG were tested with a commercially available enzyme-linked immunosorbent assay (ELISA).

RESULTS

Leptospira IgG was found in 123 (12.8%, 95% CI: 10.8-15.1) children with a male:female ratio of 1.5:1. At the age of 7 years the prevalence was 11%. Log-linear binary regression of the IgG seroprevalence by age showed a mean seroconversion rate of 1.5% (95% CI: 1.23-1.75) per year. Five (5.4%, 95% CI: 2.3-12.1) samples were definitely positive for IgM. Presence of serum Leptospira IgG antibodies was significantly associated with swimming in rivers (RR: 1.745, 95% CI: 1.117-2.724) and wading through water (RR 1.793, 95% CI: 1.181-2.722).

CONCLUSION

Our data emphasize the importance of leptospirosis among children in Vietnam, despite the absence of severe disease, and stress the need for adequate and cheap diagnostics.

[Evidence of dog as a reservoir for human leptospirosis: a serovar isolation, molecular characterization and its use in a serological survey]

Canine leptospirosis has been known as Stuttgart disease since 1898, and dogs are considered to be the second principal source of infection in man. The isolation of a pathogenic serovar from dog urine that was diagnosed clinically and laboratorial as having leptospirosis and its utilization to test serological samples of human and canine cases of leptospirosis, has demonstrated its importance to the ecosystem of the southern region of Brazil. The results of the serological microscopic agglutination test indicated that 100% of human serum samples from 12 patients from the serum bank of 2001 at the Center for Control of Zoonoses, that had titers between 25 and 3,200 with the canicola serovar, and 72% of 105 canine serum samples from the same serum bank, also reacted with the new isolate. The mean and median titers of the human serum samples tested with the battery of antigens recommended by WHO was 630 and 100 respectively, and when tested with the isolate it was 1,823 and 400. In the dog sera, the values were respectively 347 and 100 with the battery, and 1,088 and 200 with the isolate.

Direct detection of leptospiral material in human postmortem samples

Leptospiral culture, direct immunofluorescence, and the polymerase chain reaction (PCR) were used to detect leptospiral material in postmortem specimens collected from eight patients who died of leptospirosis. Diagnosis of leptospiral infection was based on clinical summary (premortem) and confirmed by serological analysis and/or culture of leptospires. Leptospiral culture was the least sensitive technique, yielding two isolates (3%) from 65 samples. Both isolates were from the aqueous humour and cerebrospinal fluid of the same patient. Direct immunofluorescence was of intermediate sensitivity for detection of leptospires, confirming the presence of leptospires in 11% (2 of 18) of tissue samples from three patients. PCR analysis was the most sensitive technique for detection of leptospiral material in tissue samples, being positive in 20% (11 of 56) of samples from eight patients. Both samples (cerebellum and liver) positive by immunofluorescence were also positive by PCR. The sensitivity of the PCR assay was 1-10 leptospires ml(-1) sample, and the assay was specific for Leptospira pathogenic species. Multi-system involvement was indicated based on successful amplification of leptospiral DNA from more than one tissue sample, which corroborated with the clinical and pathologic findings. The results suggest that in acute and/or fatal leptospirosis, the pathogenesis of the pathologic features are related to the presence of the organisms in the tissues. In conclusion, PCR combined with serology appears to be a useful tool for diagnosis of leptospirosis and may be invaluable in epidemiological studies.

"Probable" versus "confirmed" leptospirosis: an epidemiologic and clinical comparison utilizing a surveillance case classification

PURPOSE

For surveillance purposes, the Centers for Disease Control and Prevention and Council of State and Territorial Epidemiologists (CDC/CSTE) have defined two case classifications for leptospirosis: "confirmed" and "probable." The objective of this study was to provide data to refine the current surveillance case classifications.

METHODS

All reported leptospirosis infections from exposures within the State of Hawaii, 1974 to 1998 meeting CDC/CSTE "confirmed" and "probable" case classifications were compared on a number of clinical and epidemiologic parameters.

RESULTS

Confirmed cases (n = 276) had more severe clinical manifestations than probable cases (n = 180); however, probable cases with higher peak microscopic agglutination test (MAT) titers (> or =1:800) were clinically and epidemiologically comparable to confirmed cases. In addition, 77 cases demonstrating fourfold or greater MAT titer increases in paired serum collected less than two weeks apart (currently excluded from the "confirmed" case classification) were also comparable to confirmed cases.

CONCLUSIONS

Our findings support amending the current CDC/CSTE surveillance confirmed case classification to include demonstration of a fourfold or greater MAT titer increase in paired serum, irrespective of the interval between specimen collection. Consideration should also be given to including single MAT titer > or =1:800 as a criterion for "confirmation." These changes would both simplify and expedite the surveillance confirmation of leptospirosis.

Ocular leptospirosis

Uveitis is a well-known late complication of systemic leptospirosis, a zoonotic disease caused by the water-borne spirochete Leptospira. Although it is one of the world's most widespread febrile diseases, it remains underdiagnosed, mainly because of protean manifestations, lack of awareness, and nonavailability of laboratory support. Systematic collection of published literature was conducted using Medline, the Cochrane library, and bibliographies of retrieved reports. Articles directly applicable to ocular leptospirosis and current reports on the epidemiology, basic research, clinical presentations, and management of leptospirosis were reviewed. Changing trends in risk factors and an expanding spectrum of ocular and systemic findings have been reported. Molecular research on leptospirosis has shown remarkable progress; several rapid diagnostic modalities are currently under study. Awareness of this entity is absolutely essential to arrive at an accurate diagnosis and to prevent its potential reversible and irreversible ocular complications.

Role of the coypu (Myocastor coypus) in the epidemiology of leptospirosis in domestic animals and humans in France

The coypu (Myocastor coypus), a rodent whose natural habitat is stagnant freshwater, has become a widespread pest in France within the last decade. This study investigated the prevalence of seropositivity and the renal carriage of leptospires in coypus in order to evaluate their role in terms of the risk of infection by Leptospira interrogans in domestic animals and humans. The study involved the application of serological and bacteriological methods to identify leptospires infection and/or carriage in 738 coypus trapped from 1996 to 1999 in six areas of France. Seroprevalence in samples ranged from 16.5 to 66%, and three field strains were isolated (two L. interrogans Icterohaemorrhagiae and one L. interrogans Sejroe). This first report on the isolation of leptospires from coypus in France emphasises the role of this animal in the epidemiology of leptospirosis.

Leptospirosis

Leptospirosis is a worldwide zoonotic infection with a much greater incidence in tropical regions and has now been identified as one of the emerging infectious diseases. The epidemiology of leptospirosis has been modified by changes in animal husbandry, climate, and human behavior. Resurgent interest in leptospirosis has resulted from large outbreaks that have received significant publicity. The development of simpler, rapid assays for diagnosis has been based largely on the recognition that early initiation of antibiotic therapy is important in acute disease but also on the need for assays which can be used more widely. In this review, the complex taxonomy of leptospires, previously based on serology and recently modified by a genotypic classification, is discussed, and the clinical and epidemiological value of molecular diagnosis and typing is also evaluated.

Two methods for rapid serological diagnosis of acute leptospirosis

Leptospirosis is a common and underdiagnosed zoonosis. Two rapid assays for serological diagnosis of acute leptospirosis in diagnostic laboratories, the immunoglobulin M (IgM)-dipstick assay and the indirect hemagglutination assay (IHA), were evaluated and compared with standard assays. Sera were examined from 104 patients admitted to a hospital for investigation in a leptospirosis diagnostic protocol. Specimens for serology were taken on days 1 and 4 of the patients' hospital stay. Antibodies were detected using an IgM-enzyme-linked immunosorbent assay (ELISA), microscopic agglutination test (MAT), an IgM-dipstick assay, and an IHA. Fifty-one patients were found to have leptospirosis. The sensitivity of the IgM-dipstick assay was 98%, its specificity was 90.6%, its positive predictive value was 90.9%, and its negative predictive value was 98%. The sensitivity of the IHA was 92.2%, its specificity was 94.4%, its positive predictive value was 95.9%, and its negative predictive value was 92.7%. The standard IgM-ELISA and MAT, were positive in the first samples tested from 67 and 55% of the cases, respectively, and the rapid IgM-dipstick assay and IHA were positive in 71 and 49%, respectively, in the first sample tested. Both rapid assays are highly sensitive and specific. Neither requires specialized equipment, and both are suitable for use in diagnostic laboratories.

Overview of the epidemiology, microbiology, and pathogenesis of Leptospira spp. in humans

Leptospirosis is probably the world's most widespread zoonosis. It remains underdiagnosed largely due to the broad spectrum of signs and symptoms attributable to this spirochetal pathogen. Leptospira spp. cause a diversity of diseases from flu-like illness to Weil's syndrome with multi-organ failure. Recent epidemics may herald a change in virulence or an alteration in the balance between humans and their interactions with other host species and the environment.