Leptospirosis in the Asia Pacific region

Solution structure of a bacterial immunoglobulin-like domain of the outer membrane protein (LigB) from Leptospira

Leptospiral immunoglobulin-like (Lig) proteins are surface proteins expressed in pathogenic strains of Leptospira. LigB, an outer membrane protein containing tandem repeats of bacterial Ig-like (Big) domains and a no-repeat tail, has been identified as a virulence factor involved in adhesion of pathogenic Leptospira interrogans to host cells. A Big domain of LigB, LigBCen2R, was reported previously to bind the GBD domain of fibronectin, suggesting its important role in leptospiral infections. In this study, we determined the solution structure of LigBCen2R by nuclear magnetic resonance (NMR) spectroscopy. LigBCen2R adopts a canonical immunoglobulin-like fold which is comprised of a beta-sandwich of ten strands in three sheets. We indicated that LigBCen2R is able to bind to Ca(2+) with a high affinity by isothermal titration calorimetry assay. NMR perturbation experiment identified a number of residues responsible for Ca(2+) binding. Structural comparison of it with other Big domains demonstrates that they share a similar fold pattern, but vary in some structural characters. Since Lig proteins play a vital role in the infection to host cells, our study will contribute a structural basis to understand the interactions between Leptospira and host cells.

Comparative genomic analysis of eight Leptospira strains from Japan and the Philippines revealing the existence of four putative novel genomic islands/islets in L. interrogans serovar Lai strain 56601

Leptospirosis is one of the most widespread zoonotic diseases worldwide and can be considered an emerging health problem to both human and animal. Despite the importance of the disease, complete genome sequences are currently available for only three Leptospira interrogans strains: 56601, Fiocruz L1-130, and IPAV. Therefore, intra- and inter-species comparative genomic analyses of Leptospira are limited. Here, to advance current knowledge of the genomic differences within Leptospira species, next-generation sequencing technology was used to examine the genomes of eight L. interrogans strains belonging to six different serogroups isolated from humans and dogs in Japan and the Philippines. The genomic sequences were mapped to that of the reference strain, L. interrogans serovar Lai strain 56601. The results revealed the presence of four novel genomic islands/islets (GIs) in strain 56601. This study provides a deeper insight into the molecular basis and evolutionary perspective of the virulence of leptospires.

Role of India's wildlife in the emergence and re-emergence of zoonotic pathogens, risk factors and public health implications

Evolving land use practices have led to an increase in interactions at the human/wildlife interface. The presence and poor knowledge of zoonotic pathogens in India's wildlife and the occurrence of enormous human populations interfacing with, and critically linked to, forest ecosystems warrant attention. Factors such as diverse migratory bird populations, climate change, expanding human population and shrinking wildlife habitats play a significant role in the emergence and re-emergence of zoonotic pathogens from India's wildlife. The introduction of a novel Kyasanur forest disease virus (family flaviviridae) into human populations in 1957 and subsequent occurrence of seasonal outbreaks illustrate the key role that India's wild animals play in the emergence and reemergence of zoonotic pathogens. Other high priority zoonotic diseases of wildlife origin which could affect both livestock and humans include influenza, Nipah, Japanese encephalitis, rabies, plague, leptospirosis, anthrax and leishmaniasis. Continuous monitoring of India's extensively diverse and dispersed wildlife is challenging, but their use as indicators should facilitate efficient and rapid disease-outbreak response across the region and occasionally the globe. Defining and prioritizing research on zoonotic pathogens in wildlife are essential, particularly in a multidisciplinary one-world one-health approach which includes human and veterinary medical studies at the wildlife-livestock-human interfaces. This review indicates that wild animals play an important role in the emergence and re-emergence of zoonotic pathogens and provides brief summaries of the zoonotic diseases that have occurred in wild animals in India.

Risk of infection and associated influenza-like disease among abattoir workers due to two Leptospira species

The aims of this study were to determine the annual incidence of infection with Leptospira interrogans serovar Pomona and/or Leptospira borgpetersenii serovar Hardjo and its association with influenza-like illness (ILI) in meat workers in New Zealand. Sera were collected twice, 50-61 weeks apart, from 592 workers at eight abattoirs slaughtering sheep (n = 4), cattle (n = 2) and deer (n = 2), and tested by the microscopic agglutination test for Hardjo and Pomona. Forty-nine (8·3%) participants either seroconverted or had at least a twofold increased serological titre against either serovar. The worker infection risk was higher in sheep abattoirs (11·9%) than in abattoirs processing deer (0%) or cattle (1·2%) (P < 0·01). The annualized risk of mild (ILI) or severe clinical disease attributable to the two Leptospira serovars was 2·7%. This study has demonstrated that meat workers are at substantial risk of infection and clinical disease, suggesting further investigation of infection sources and preventive measures are warranted.

Isolation and characterization of two novel plasmids from pathogenic Leptospira interrogans serogroup Canicola Serovar Canicola strain Gui44

Background

Previous genomic analysis of pathogenic Leptospira has identified two circular chromosomes but no plasmid. This study aims to investigate potential extrachromosomal elements of L.interrogans serovar Canicola strain Gui44.

Methodology

Two novel plasmids, pGui1 and pGui2, were isolated from the pathogenic strain Gui44, using a modified alkaline lysis method. Southern blotting was performed to determine the presence and size of them. Then, 454 and Hiseq sequencing were applied to obtain and analyze the complete sequences of the two plasmids. Furthermore, real-time quantitative PCR and next-generation sequencing were used to compare relative copy numbers of the two plasmids with that of the chromosomes. Finally, after serial passages in vitro for more than 2 years, the strain Gui44 was subsequently re-sequenced to estimate stability of the two plasmids.

Principal Findings

The larger plasmid, pGui1, 74,981 base pairs (bp) in length with GC content of 34.63%, possesses 62 open reading frames (ORFs). The smaller plasmid, pGui2, is 66,851 bp in length with GC content of 33.33%, and contains 63 ORFs. The replication initiation proteins encoded by pGui1 and pGui2 demonstrate significant sequence similarity with LA1839 (86% and 88%), a well-known replication protein in another pathogenic L.interrogans serovar Lai strain Lai, suggesting the ability for autonomous plasmid replication. Quantitative PCR and next-generation sequencing confirms a single copy of both plasmids and their stable presence in the strain Gui44 with in vitro serial passages after more than 2 years. Interestingly, the two plasmids both contain a significant number of novel genes (35 in pGui1 and 52 in pGui2).

Conclusions

This report confirms the presence of two separate circular plasmids in serovar Canicola strain Gui44 and provides a new understanding of genomic organization, adaptation, evolution and pathogenesis of Leptospira, which will aid in the development of in vivo genetic manipulation systems in pathogenic Leptospira species.

Leptospira species are the causative agent of leptospirosis, one of the most common animal to human transmitted diseases. Previous genomic analysis of L.interrogans serovar Lai and Copenhageni has identified the presence of large (4.33 mega base) and small (350 kilo base) circular chromosomes without evidence of any plasmids. Detailed understanding of Leptospira and its pathogenicity was delayed by the lack of available genetic tools. In this study we confirm the existence of two novel plasmids in L.interrogans serovar Canicola strain Gui44, an epidemic strain in China. Some novel genes identified in the two plasmids may play important roles in the characterization of the strain. The two plasmids will provide useful information in understanding the diversity of Leptospira genome and markedly improve our understanding of the evolution and pathogenesis of L.interrogans. In particular, it will contribute to the development of genetic manipulation systems in pathogenic Leptospira species.

Study on the Prevalence of Leptospirosis among Fever Cases Reported from Private Clinics in the Urban areas of Villupuram District, Tamil Nadu, India

Objectives

To know the prevalence of leptospirosis cases reported in private clinics among fever cases in Villupuram District, Tamil Nadu, India to know its real magnitude of the problem and to diagnose Leptospirosis among fever cases from differential diagnosis.

Methods

1502 Blood serum samples collected from three urban towns namely Kallakurichi (Latitude: 11° 73′ N; Longitude: 78° 97′ E), Villupuram (Latitude: 11° 75′ N; Longitude: 79° 92′ E) and Thindivanam (Latitude: 12° 25′ N; Longitude: 79° 65′ E) in fifteen clinics based on case definition of leptospirosis delineated by the National Vector Borne Disease Control Programme (NVBDCP), Government of India. Samples were tested in the laboratory of the Zonal Entomological Team (ZET), Cuddalore with Macroscopic Slide Agglutination Test (MSAT) and Ig-M ELISA.

Result

There were 65 positive cases detected from 1502 blood serum samples in both MSAT and Ig-M ELISA. It could be known that there was 4% cases contributed from private clinics among fever cases. From this study, further it was known that all age groups of people affected irrespective of sexes based on their living condition associated with the environment prevailed of the disease.

Conclusion

From this study, it was quantified that 4% of cases reported in private clinics among fever cases and its findings ascertained both the importance of differential diagnosis as well as reports that should be included to the Government for knowing its real magnitude for planning.

'Leptorapide' - a one-step assay for rapid diagnosis of human leptospirosis

SUMMARY

Leptospirosis is a globally important zoonotic infection caused by spirochaetes of the genus Leptospira. It is transmitted to humans by direct contact with infected animals or indirectly via contaminated water. It is mainly a problem of the resource-poor developing countries of the tropical and sub-tropical regions of the world but outbreaks due to an increase in travel and recreational activities have been reported in developed and more industrialized areas of the world. Current methods of diagnosis are costly, time-consuming and require the use of specialized laboratory equipment and personnel. The purpose of this paper is to report the validation of the 'Leptorapide®' test (Linnodee Ltd, Northern Ireland) for the diagnosis of human leptospirosis. It is a simple one-step latex agglutination assay performed using equal volumes of serum sample and antigen-bound latex beads. Evidence of leptospiral antibodies is determined within minutes. Agglutination is scored on a scale of 1-5 and the results interpreted using a score card provided with the kit. Validation has been performed with a large sample size obtained from individuals originating from various parts of the world including Brazil and India. The test has shown sensitivity and specificity values of 97·1% and 94·0%, respectively, relative to the microscopic agglutination test. The results demonstrate that Leptorapide offers a cost-effective and accurate alternative to the more historical methods of antibody detection.

Production and characterization of a polyclonal antibody of anti-rLipL21-IgG against leptospira for early detection of acute leptospirosis

Leptospirosis is one of the zoonotic diseases in animals and humans throughout the world. LipL21 is one of the important surface-exposed lipoproteins in leptospires and the most effective cross protective immunogenic antigen. It is widely considered as a diagnostic marker for leptospirosis. In this study, we evaluated the serodiagnostic potential of LipL21 protein of Leptospira interrogans serovar Pomona. We have successfully amplified, cloned, and expressed LipL21 in E. coli and evaluated its specificity by immunoblotting. Purified recombinant LipL21 (rLipL21) was inoculated into rabbits for the production of polyclonal antibody. Characterization of the purified IgG antibody against rLipL21 was performed by cross reactivity assay. Only sera from leptospirosis patients and rabbit hyperimmune sera recognized rLipL21 while the nonleptospirosis control sera showed no reaction in immunoblotting. We confirmed that anti-rLipL21-IgG antibody cross reacted with and detected only pathogenic leptospiral species and it did not react with nonpathogenic leptospires and other bacterial species. Results observed showed that anti-rLipL21-IgG antibody has high specificity and sensitivity to leptospires. The findings indicated that the antibody could be used in a diagnostic assay for detection of leptospires or their proteins in the early phase of infection.

El Niño Southern Oscillation and leptospirosis outbreaks in New Caledonia

Leptospirosis is an important cause of seasonal outbreaks in New Caledonia and the tropics. Using time series derived from high-quality laboratory-based surveillance from 2000-2012, we evaluated whether climatic factors, including El Niño Southern Oscillation (ENSO) and meteorological conditions allow for the prediction of leptospirosis outbreaks in New Caledonia. We found that La Niña periods are associated with high rainfall, and both of these factors were in turn, temporally associated with outbreaks of leptospirosis. The sea surface temperature in El Niño Box 4 allowed forecasting of leptospirosis outbreaks four months into the future, a time lag allowing public health authorities to increase preparedness. To our knowledge, our observations in New Caledonia are the first demonstration that ENSO has a strong association with leptospirosis. This association should be tested in other regions in the South Pacific, Asia or Latin America where ENSO may drive climate variability and the risk for leptospirosis outbreaks.

Though not reservoirs, dogs might transmit Leptospira in New Caledonia

Leptospira has been a major public health concern in New Caledonia for decades. However, few multidisciplinary studies addressing the zoonotic pattern of this disease were conducted so far. Here, pig, deer and dog samples were collected. Analyses were performed using molecular detection and genotyping. Serological analyses were also performed for dogs. Our results suggest that deer are a reservoir of L. borgpetersenii Hardjobovis and pigs a reservoir of L. interrogans Pomona. Interestingly, 4.4% of dogs were renal carriers of Leptospira. In dog populations, MAT results confirmed the circulation of the same Leptospira serogroups involved in human cases. Even if not reservoirs, dogs might be of significance in human contamination by making an epidemiological link between wild or feral reservoirs and humans. Dogs could bring pathogens back home, shedding Leptospira via their urine and in turn increasing the risk of human contamination. We propose to consider dog as a vector, particularly in rural areas where seroprevalence is significantly higher than urban areas. Our results highlight the importance of animal health in improving leptospirosis prevention in a One Health approach.

Human leptospirosis in The Federated States of Micronesia: a hospital-based febrile illness survey

BACKGROUND

Human leptospirosis is an emerging infectious disease of global significance, and is endemic to several countries in the Pacific. Zoonotic transmission dynamics combined with diagnostic challenges lead to difficulties in prevention and identification of cases. The Federated States of Micronesia (FSM) lacks surveillance data for human leptospirosis. This hospital-based serologic survey sought to estimate the burden of leptospirosis, collect information relating to associated factors, and assess the leptospirosis point-of-care rapid diagnostic test (RDT) commonly used in FSM.

METHODS

A four-month hospital-based survey was conducted in Pohnpei State, FSM in 2011. Patients with undifferentiated fevers presenting to hospital were referred for enrolment by physicians. Consenting participants provided paired blood specimens 10-30 days apart, and responded to interview questions regarding demographics, clinical symptoms, exposure to animals, and environmental exposure. Blood samples were subjected to immunochromatographic RDT and confirmed by microscopic agglutination test (MAT).

RESULTS

Of 54 participants tested by MAT, 20.4% (95% confidence interval [CI] 10.1-30.6%) showed serologic evidence of acute infection. Occupation student (odds ratio [OR], 17.5; 95% CI: 1.9-161.1) and recreational gardening (OR, 8.6; 95% CI: 1.0-73.8), identified by univariate logistic regression, were associated with infection. The local rapid diagnostic test (RDT) performed with a sensitivity of 69.2 (42.3-89.3 CI) and specificity of 90.0 (81.6-95.6 CI) compared to MAT.

CONCLUSIONS

This study demonstrated a high burden of leptospirosis in Pohnpei. Further work is warranted to identify additional risk factors and opportunities to control leptospirosis in Pohnpei and other Pacific settings.

Sero-prevalence and risk factors for leptospirosis in abattoir workers in New Zealand

Leptospirosis is an important occupational disease in New Zealand. The objectives of this study were to determine risk factors for sero-prevalence of leptospiral antibodies in abattoir workers. Sera were collected from 567 abattoir workers and tested by microscopic agglutination for Leptospira interrogans sv. Pomona and Leptospira borgpetersenii sv. Hardjobovis. Association between prevalence and risk factors were determined by species specific multivariable analysis. Eleven percent of workers had antibodies against Hardjobovis or/and Pomona. Workers from the four sheep abattoirs had an average sero-prevalence of 10%–31%, from the two deer abattoirs 17%–19% and the two beef abattoirs 5%. The strongest risk factor for sero-positivity in sheep and deer abattoirs was work position. In sheep abattoirs, prevalence was highest at stunning and hide removal, followed by removal of the bladder and kidneys. Wearing personal protective equipment such as gloves and facemasks did not appear to protect against infection. Home slaughtering, farming or hunting were not significantly associated with sero-prevalence. There is substantial risk of exposure to leptospires in sheep and deer abattoirs in New Zealand and a persisting, but lower risk, in beef abattoirs. Interventions, such as animal vaccination, appear necessary to control leptospirosis as an occupational disease in New Zealand.

Emerging Zoonoses in Domesticated Livestock of Southeast Asia

Southeast Asia, identified as one of the hotspot for emerging and reemerging diseases is an area of emerging market with doubling population size within the next few years. The livestock industry is growing rapidly to cater for the population need via intensification and various diversification methods. This article discusses a few relevant emerging and emerging zoonoses within the past two decades and highlights the impact of these diseases to the animal industry and public health in the region.

Improvement of leptospirosis surveillance in remote Pacific islands using serum spotted on filter paper

OBJECTIVES

Leptospirosis is a serious neglected disease in the Pacific. Because sensitive and specific laboratory tests are largely unavailable, the burden of disease and epidemiological data are often unreliable and do not allow informed disease prioritization and efficient control. We report the use of serum spotted on filter paper to improve the surveillance of leptospirosis in remote and resource-limited settings.

METHODS

A total of 172 acute-phase serum samples collected from patients with suspected dengue at Yap State Hospital, Federated States of Micronesia, were spotted on filter paper and sent by regular mail to the Institut Louis Malardé, French Polynesia. Real-time PCR protocols for dengue and leptospirosis confirmation were performed on all specimens.

RESULTS

A total of five leptospirosis infections were detected amongst the patients with suspected dengue.

CONCLUSIONS

This study confirms the use of filter paper as a convenient tool to improve leptospirosis surveillance capacity in remote areas. New surveillance strategies, notably based on the regular use of this type of tool, are essential to more adequately describe the epidemiology and burden of neglected diseases.

Detection of Leptospira-specific antibodies using a recombinant antigen-based enzyme-linked immunosorbent assay

We produced three highly purified recombinant antigens rLipL32, rLipL41, and rLigA-Rep (leptospiral immunoglobulin-like A repeat region) for the detection of Leptospira-specific antibodies in an enzyme-linked immunosorbent assay (ELISA). The performance of these recombinant antigens was evaluated using 121 human sera. Among them, 63 sera were microscopic agglutination test (MAT)-confirmed positive sera from febrile patients in Peru, 22 sera were indigenous MAT-negative febrile patient sera, and 36 sera were from patients with other febrile diseases from Southeast Asia, where leptospirosis is also endemic. Combining the results of immunoglobulin M (IgM) and IgG detection from these three antigens, the overall sensitivity is close to 90% based on the MAT. These results suggest that an ELISA using multiple recombinant antigens may be used as an alternative method for the detection of Leptospira-specific antibodies.

Risk Factors for Leptospirosis Infection in Humans and Implications for Public Health Intervention in Indonesia and the Asia-Pacific Region

Prevention and control of leptospirosis require an understanding of risk factors. This review identifies risk factors associated with leptospirosis infection from countries in the Asia-Pacific region, and compares and contrasts these data with those available from Indonesia. MEDLINE, PubMed, and Scopus databases were used to search for relevant articles. Indonesian gray literature was searched for leptospirosis risk factor studies in Indonesia. A total of 34 articles were included in this review. The contrast between peer-reviewed publications and Indonesian gray literature revealed that the variety of risk factors associated with leptospirosis infection is region or area specific. The presence of skin wounds, the existence of rodents, especially rats, and activities related to contact with contaminated surface water are factors frequently reported to have significant association with leptospirosis infection in human in Indonesia and in other Asia-Pacific 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.

Valuing human leptospirosis prevention using the opportunity cost of labor

Leptospirosis is a serious public health concern in the Philippines, not only because of its increasing incidence rate, but also because of its significant health and economic impacts. Despite its relatively high seroprevalence, knowledge on the economic burden of disease, particularly on the value that the society places on disease prevention remains limited. Obtaining such information is important within the context of public health policy. This study was conducted in Metro Manila to determine the economic burden of leptospirosis, by asking respondents about their willingness to contribute to labor (WTCL) for the prevention of leptospirosis. The respondents pledged an average labor contribution of 10.66 h/month. The average WTCL corresponded to a monetary value of US$4.01 per month when valued using the opportunity cost of labor (leisure rate of time). From the monetized labor contribution, the total economic value of preventing leptospirosis was estimated at US$124.97 million per annum, which represents 1.13% of Metro Manila's gross domestic product (GDP). Estimates from a Tobit regression model identified the respondents' knowledge regarding leptospirosis, the susceptibility of their homes to flooding, and the proximity of their homes to sewers as significant factors to consider when developing resource contribution programs for leptospirosis prevention. More efforts need to be made in developing community level preventive programs, and in improving public's knowledge and awareness about leptospirosis.

Laboratory diagnosis of leptospirosis: a challenge

Leptospirosis is caused by pathogenic bacteria called leptospires that are transmitted directly or indirectly from animals to humans. It occurs worldwide but is most common in tropical and subtropical areas. It is a potentially serious but treatable disease. Its symptoms may mimic those of a number of other unrelated infections such as influenza, meningitis, hepatitis, dengue, or other viral hemorrhagic fevers. The spectrum of the disease is extremely wide, ranging from subclinical infection to a severe syndrome of multiorgan infection with high mortality. Laboratory diagnosis tests are not always available, especially in developing countries. Numerous tests have been developed, but availability of appropriate laboratory support is still a problem. Direct observation of leptospires by darkfield microscopy is unreliable and not recommended. Isolation of leptospires can take up to months and does not contribute to early diagnosis. Diagnosis is usually performed by serology; enzyme-linked immunosorbent assay and the microscopic agglutination tests are the laboratory methods generally used, rapid tests are also available. Limitation of serology is that antibodies are lacking at the acute phase of the disease. In recent years, several real-time polymerase chain reaction assays have been described. These can confirm the diagnosis in the early phase of the disease prior to antibody titers are at detectable levels, but molecular testing is not available in restricted resources areas.

Leptospirosis risk increases with changes in species composition of rat populations

Rats are major reservoirs of leptospirosis and considered as a main threat to biodiversity. A recent introduction of Rattus rattus to the island of Futuna (Western Polynesia) provided the opportunity to test if a possible change in species composition of rat populations would increase the risk of leptospirosis to humans. We trapped rodents on Wallis and Futuna and assessed Leptospira carriage in 357 rodents (Rattus norvegicus, R. rattus, Rattus exulans, and Mus domesticus) from 2008 to 2012. While Leptospira prevalence in rodents and the composition of rat populations on Futuna fluctuated with rainfall, the biomass of Leptospira-carrying rodents has been continuously rising from 2008 to 2012. Our results suggest that the introduction of R. rattus increases the risk to humans being infected with leptospirosis by rats.

Zoonoses in South-East Asia: a regional burden, a global threat

Zoonoses are an issue of growing interest in South-East Asia, where environmental factors and socio-economic context favor the endemization of well-known diseases and the emergence of new pathogens at the human-wildlife interface. However, the health status of the region with respect to many zoonotic diseases remains poorly defined, despite the high overall burden of zoonoses on the countries of the area, and the global risk of new biological threats in the region. The first objective of this paper was to provide an update of data on the zoonoses commonly described by the scientific community and reported by governmental institutions and international organizations in continental South-East Asia. The analysis of the available data led to the identification of some trends in the evolution of the diseases, as well as some gaps in knowledge and in the current surveillance and control networks. In light of these findings, we discuss measures for effectively addressing zoonotic disease issues in South-East Asia, such as the allocation of funds for research and for surveillance and control programs, and a multi-sectoral and multi-disciplinary approach at various levels.

Pathogenic and saprophytic Leptospira species in water and soils from selected urban sites in peninsular Malaysia

Leptospira species were studied in water and soils from selected urban sites in Malaysia. A total of 151 water (n=121) and soil (n=30) samples were collected from 12 recreational lakes and wet markets. All samples were filtered and inoculated into semi-solid Ellinghausen and McCullough modified by Johnson and Harris (EMJH) media supplemented with additional 5-fluorouracil. The cultures were then incubated at 30°C and observed under a dark field microscope with intervals of 10 days. A PCR assay targeting the rrs gene was used to confirm the genus Leptospira among the isolates. Subsequently, the pathogenic status of the isolates was determined using primer sets G1/G2 and Sapro1/Sapro2, which target the secY and rrs genes, respectively. The isolates were identified at serogroup level using the microscopic agglutination test (MAT) while their genetic diversity was assessed by pulsed field gel electrophoresis (PFGE). Based on dark field microscopy, 23.1% (28/121) water and 23.3% (7/30) soil cultures were positive for Leptospira spp. Of the 35 positive cultures, only 8 were pure and confirmed as Leptospira genus by PCR assay. Two out of 8 isolates were confirmed as pathogenic, 5 were saprophytic and one was intermediate. These 8 isolates were negative for the 25 reference hyperimmune rabbit sera tested in the MAT. PFGE showed that all 8 of these environmental Leptospira spp. were genetically diverse. In conclusion, the presence of pathogenic Leptospira spp. in the urban Malaysian environment may indicate and highlight the importance of water screening, especially in recreational lakes, in order to minimize any chance of Leptospira infection.

Isolation and molecular characterization of Leptospira interrogans and Leptospira borgpetersenii isolates from the urban rat populations of Kuala Lumpur, Malaysia

Rats are considered the principal maintenance hosts of Leptospira. The objectives of this study were isolation and identification of Leptospira serovars circulating among urban rat populations in Kuala Lumpur. Three hundred urban rats (73% Rattus rattus and 27% R. norvegicus) from three different sites were trapped. Twenty cultures were positive for Leptospira using dark-field microscopy. R. rattus was the dominant carrier (70%). Polymerase chain reaction (PCR) confirmed that all isolates were pathogenic Leptospira species. Two Leptospira serogroups, Javanica and Bataviae, were identified using microscopic agglutination test (MAT). Pulsed-field gel electrophoresis (PFGE) identified two serovars in the urban rat populations: L. borgpetersenii serovar Javanica (85%) and L. interrogans serovar Bataviae (15%). We conclude that these two serovars are the major serovars circulating among the urban rat populations in Kuala Lumpur. Despite the low infection rate reported, the high pathogenicity of these serovars raises concern of public health risks caused by rodent transmission of leptospirosis.

Public health needs assessments of Tutuila Island, American Samoa, after the 2009 tsunami

OBJECTIVE

An 8.3 magnitude earthquake followed by tsunami waves devastated American Samoa on September 29, 2009, resulting in widespread loss of property and public services. An initial and a follow-up Community Needs Assessment for Public Health Emergency Response (CASPER) objectively quantified disaster-affected population needs.

METHODS

Using a 2-stage cluster sampling method of CASPER, a household questionnaire eliciting information about medical and basic needs, illnesses, and injuries was administered. To assess response efforts, percent changes in basic and medical needs, illnesses, and injuries between the initial and follow-up CASPER were calculated.

RESULTS

During the initial CASPER (N = 212 households), 47.6% and 51.6% of households reported needing a tarpaulin and having no electricity, respectively. The self-reported greatest needs were water (27.8%) and financial help with cleanup (25.5%). The follow-up CASPER (N = 207 households) identified increased vector problems compared to pre-tsunami, and food (26%) was identified as the self-reported greatest need. As compared to the initial CASPER, the follow-up CASPER observed decreases in electricity (-78.3%), drinking water (-44.4%), and clothing (-26.6%).

CONCLUSION

This study highlights the use of CASPER during the response and recovery phases following a disaster. The initial CASPER identified basic needs immediately after the earthquake, whereas the follow-up CASPER assessed effectiveness of relief efforts and identified ongoing community needs.

Leptospira and rodents in Cambodia: environmental determinants of infection

We investigated infection of rodents and shrews by Leptospira spp. in two localities of Cambodia (Veal Renh, Kaev Seima) and in four types of habitat (forests, non-flooded lands, lowland rain-fed paddy fields, houses) during the wet and the dry seasons. Habitat preference was common, and rodent and shrew species were found only in houses or in rain-fed paddy fields or in forests. Among 649 small mammals trapped belonging to 12 rodent species and 1 shrew species, 71 of 642 animals tested were carriers of Leptospira according to the 16S ribosomal RNA marker used. Rodent infection was higher in low-slope locations, corresponding to rain-fed paddy fields, especially in the rainy season and in Kaev Seima. Rodents (Rattus exulans) and shrews (Suncus murinus) inhabiting households showed significantly low levels of infections, whereas rodents living in and near to forests (shrubby wasteland, orchards) showed high levels of infection.

Modeling seasonal leptospirosis transmission and its association with rainfall and temperature in Thailand using time-series and ARIMAX analyses

OBJECTIVE

To study the number of leptospirosis cases in relations to the seasonal pattern, and its association with climate factors.

METHODS

Time series analysis was used to study the time variations in the number of leptospirosis cases. The Autoregressive Integrated Moving Average (ARIMA) model was used in data curve fitting and predicting the next leptospirosis cases.

RESULTS

We found that the amount of rainfall was correlated to leptospirosis cases in both regions of interest, namely the northern and northeastern region of Thailand, while the temperature played a role in the northeastern region only. The use of multivariate ARIMA (ARIMAX) model showed that factoring in rainfall (with an 8 months lag) yields the best model for the northern region while the model, which factors in rainfall (with a 10 months lag) and temperature (with an 8 months lag) was the best for the northeastern region.

CONCLUSION

The models are able to show the trend in leptospirosis cases and closely fit the recorded data in both regions. The models can also be used to predict the next seasonal peak quite accurately.

Leptospirosis in American Samoa--estimating and mapping risk using environmental data

Background

The recent emergence of leptospirosis has been linked to many environmental drivers of disease transmission. Accurate epidemiological data are lacking because of under-diagnosis, poor laboratory capacity, and inadequate surveillance. Predictive risk maps have been produced for many diseases to identify high-risk areas for infection and guide allocation of public health resources, and are particularly useful where disease surveillance is poor. To date, no predictive risk maps have been produced for leptospirosis. The objectives of this study were to estimate leptospirosis seroprevalence at geographic locations based on environmental factors, produce a predictive disease risk map for American Samoa, and assess the accuracy of the maps in predicting infection risk.

Methodology and Principal Findings

Data on seroprevalence and risk factors were obtained from a recent study of leptospirosis in American Samoa. Data on environmental variables were obtained from local sources, and included rainfall, altitude, vegetation, soil type, and location of backyard piggeries. Multivariable logistic regression was performed to investigate associations between seropositivity and risk factors. Using the multivariable models, seroprevalence at geographic locations was predicted based on environmental variables. Goodness of fit of models was measured using area under the curve of the receiver operating characteristic, and the percentage of cases correctly classified as seropositive. Environmental predictors of seroprevalence included living below median altitude of a village, in agricultural areas, on clay soil, and higher density of piggeries above the house. Models had acceptable goodness of fit, and correctly classified ∼84% of cases.

Conclusions and Significance

Environmental variables could be used to identify high-risk areas for leptospirosis. Environmental monitoring could potentially be a valuable strategy for leptospirosis control, and allow us to move from disease surveillance to environmental health hazard surveillance as a more cost-effective tool for directing public health interventions.

Leptospirosis is the most common bacterial infection transmitted from animals to humans. Infected animals excrete the bacteria in their urine, and humans can become infected through contact with animals or a contaminated environment such as water and soil. Environmental factors are important in determining the risk of human infection, and differ between ecological settings. The wide range of risk factors include high rainfall and flooding; poor sanitation and hygiene; urbanisation and overcrowding; contact with animals (including rodents, livestock, pets, and wildlife); outdoor recreation and ecotourism; and environmental degradation. Predictive risk maps have been produced for many infectious diseases to identify high-risk areas for transmission and guide allocation of public health resources. Maps are particularly useful where disease surveillance and epidemiological data are poor. The objectives of this study were to estimate leptospirosis seroprevalence at geographic locations based on environmental factors, produce a predictive disease risk map for American Samoa, and assess the accuracy of the maps in predicting infection risk. This study demonstrated the value of geographic information systems and disease mapping for identifying environmental risk factors for leptospirosis, and enhancing our understanding of disease transmission. Similar principles could be used to investigate the epidemiology of leptospirosis in other areas.

Outbreak of leptospirosis after flood, the Philippines, 2009

After a typhoon in September 2009, an outbreak of leptospirosis occurred in Metro Manila, the Philippines; 471 patients were hospitalized and 51 (10.8%) died. A hospital-based investigation found risk factors associated with fatal infection to be older age, hemoptysis, anuria, jaundice, and delayed treatment with antimicrobial drugs.

Serum profiling of leptospirosis patients to investigate proteomic alterations

Leptospirosis is a zoonotic infectious disease of tropical, subtropical and temperate zones, which is caused by the pathogenic spirochetes of genus Leptospira. Although this zoonosis is generally not considered as fatal, the pathogen can eventually cause severe infection with septic shock, multi-organ failure and lethal pulmonary hemorrhages leading to mortality. In this study, we have performed a proteomic analysis of serum samples from leptospirosis patients (n = 6), febrile controls (falciparum malaria) (n = 8) and healthy subjects (n = 18) to obtain an insight about disease pathogenesis and host immune responses in leptospiral infections. 2DE and 2D-DIGE analysis in combination with MALDI-TOF/TOF MS revealed differential expression of 22 serum proteins in leptospirosis patients compared to the healthy controls. Among the identified differentially expressed proteins, 8 candidates exhibited different trends compared to the febrile controls. Functional analysis suggested the involvement of differentially expressed proteins in vital physiological pathways, including acute phase response, complement and coagulation cascades and hemostasis. This is the first report of analysis of human serum proteome alterations in leptospirosis patients, which revealed several differentially expressed proteins, including α-1-antitrypsin, vitronectin, ceruloplasmin, G-protein signaling regulator, apolipoprotein A-IV, which have not been reported in context of leptospirosis previously. This study will enhance our understanding about leptospirosis pathogenesis and provide a glimpse of host immunological responses. Additionally, a few differentially expressed proteins identified in this study may further be investigated as diagnostic or prognostic serum biomarkers for leptospirosis.

This article is part of a Special Issue entitled: Integrated omics.

Leptospirosis in American Samoa 2010: epidemiology, environmental drivers, and the management of emergence

Leptospirosis has recently been reported as an emerging disease worldwide, and a seroprevalence study was undertaken in American Samoa to better understand the drivers of transmission. Antibodies indicative of previous exposure to leptospirosis were found in 15.5% of 807 participants, predominantly against three serovars that were not previously known to occur in American Samoa. Questionnaires and geographic information systems data were used to assess behavioral factors and environmental determinants of disease transmission, and logistic regression was used to identify factors associated with infection. Many statistically significant factors were consistent with previous studies, but we also showed a significant association with living at lower altitudes (odds ratio [OR] = 1.53, 95% confidence interval [CI]: 1.03-2.28), and having higher numbers of piggeries around the home (OR = 2.63, 95% CI: 1.52-4.40). Our findings support a multifaceted approach to combating the emergence of leptospirosis, including modification of individual behavior, but importantly also managing the evolving environmental drivers of risk.

Leptospirosis after typhoon

Leptospirosis is a zoonotic disease with protean manifestations. A 35-year-old male presented with pneumonia after the Typhoon Morakot. Skin rash, conjunctival suffusion, and subconjunctival hemorrhage led us to the diagnosis of leptospirosis and the microscopic agglutination test confirmed the diagnosis. This patient well demonstrated the picture of conjunctival suffusion and reminded us of the alertness of leptospirosis after a typhoon.

Herd-level risk factors associated with Leptospira Hardjo seroprevalence in Beef/Suckler herds in the Republic of Ireland

Background

The aim of the present study was to investigate risk factors for herd seropositivity to Leptospira Hardjo in Irish suckler herds. Herds were considered eligible for the study if they were unvaccinated and contained ≥ 9 breeding animals of beef breed which were ≥ 12 months of age. The country was divided into six regions using county boundaries. Herd and individual animal prevalence data were available from the results of a concurrent seroprevalence study. Herds were classified as either "Free from Infection" or "Infected" based on a minimum expected 40% within-herd prevalence.

Questionnaires were posted to 320 farmers chosen randomly from 6 regions, encompassing 25 counties, of the Republic of Ireland. The questionnaire was designed to obtain information about vaccination; reproductive disease; breeding herd details; the presence of recognized risk factors from previous studies; and husbandry on each farm. Data collected from 128 eligible herds were subjected to statistical analysis.

Results

Following the use of Pearson's Chi-Square Test, those variables associated with a herd being "infected" with a significance level of P < 0.2 were considered as candidates for multivariable logistic regression modelling. Breeding herd size was found to be a statistically significant risk factor after multivariable logistic regression. The odds of a herd being positive for leptospiral infection were 5.47 times higher (P = 0.032) in herds with 14 to 23 breeding animals compared with herds with ≤ 13 breeding animals, adjusting for Region, and 7.08 times higher (P = 0.033) in herds with 32.6 to 142 breeding animals.

Conclusions

Breeding herd size was identified as a significant risk factor for leptospiral infection in Irish suckler herds, which was similar to findings of previous studies of leptospirosis in dairy herds.

A new loop-mediated isothermal amplification method for rapid, simple, and sensitive detection of Leptospira spp. in urine

We developed a new loop-mediated isothermal amplification (LAMP) method to detect rrs, a 16S rRNA gene of pathogenic Leptospira spp. in urine. The method enables detection of two leptospiral cells per reaction mixture following boiling of urine specimens. The sensitivity of this method is higher than that of culture or of flaB nested PCR.

Leptospirosis as frequent cause of acute febrile illness in southern Sri Lanka

TOC summary: Clinical impression and serologic tests of acute-phase specimens are insensitive, and rapid, pathogen-based tests are needed.

To determine the proportion of fevers caused by leptospirosis, we obtained serum specimens and epidemiologic and clinical data from patients in Galle, Sri Lanka, March–October 2007. Immunoglobulin M ELISA was performed on paired serum specimens to diagnose acute (seroconversion or 4-fold titer rise) or past (titer without rise) leptospirosis and seroprevalence (acute). We compared (individually) the diagnostic yield of acute-phase specimens and clinical impression with paired specimens for acute leptospirosis. Of 889 patients with paired specimens, 120 had acute leptosoirosis and 241 had past leptospirosis. The sensitivity and specificity of acute-phase serum specimens were 17.5% (95% confidence interval [CI] 11.2%–25.5%) and 69.2% (95% CI 65.5%–72.7%), respectively, and of clinical impression 22.9% (95% CI 15.4%–32.0%) and 91.7% (95% CI 89.2%–93.8%), respectively. For identifying acute leptospirosis, clinical impression is insensitive, and immunoglobulin M results are more insensitive and costly. Rapid, pathogen-based tests for early diagnosis are needed.

Serologic evidence of human leptospirosis in and around Kolkata, India: a clinico-epidemiological study

OBJECTIVE

To investigate the prevalence of leptospirosis among patients from within and outside Kolkata, India, attending the Calcutta School of Tropical Medicine, for treatment during August 2002 to August 2008.

METHODS

The leptospirosis cases were determined on the basis of clinical, epidemiological, and biochemical factors, and were tested for leptospiral antibodies using IgM ELISA. Serum samples with absorbance ratio ≥ 1.21 were interpreted as reactive.

RESULTS

The commonest presentation involved fever, headache and jaundice. The male-female ratio was 61:46. A total of 65(64.20%) cases had abnormal liver and renal functions respectively, and 57.1% had both the abnormalities. The highest incidence (75, 35.04%) was recorded in September-October followed by July-August (53, 24.77%). The reactive cases had absorbance ratios between 1.21 and 8.21, and 53 showed equivocal result, while IgM non reactivity were seen in 90 patients (absorbance ratios 0.10-0.90). The patients responded to treatment with parenteral antibiotics, penicillin, ceftriaxone and cefotaxime; follow up did not reveal case fatality.

CONCLUSIONS

The cardinal signs of leptospirosis help in making clinical diagnosis, but in any hyper-endemic situation any patient reporting with acute fever and signs of pulmonary, hepatic or renal involvement should be suspected to have leptospirosis and investigated accordingly. Increased awareness, and early diagnosis and treatment, can reduce mortality due to leptospirosis.

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.

Different patterns in a cohort of patients with severe leptospirosis (Weil syndrome): effects of an educational program in an endemic area

The aim of this study is to investigate the changes in clinical pattern and therapeutic measures in leptospirosis-associated acute kidney injury; a retrospective study with 318 patients in Brazil. Patients were divided according to the time of admission: 1985-1996 (group I) and 1997-2010 (group II). Patients were younger in group I (36 ± 13 versus 41 ± 16 years, P = 0.005) and the numbers of oliguria increased (21% versus 41% in group II, P = 0.014). Higher frequency of lung manifestations was observed in group II (P < 0.0001). Although increased severity, there was a significant reduction in mortality (20% in group I versus 12% in group II, P = 0.03). Mortality was associated with advanced age, low diastolic blood pressure, oliguria, arrhythmia, and peritoneal dialysis, besides a trend to better mortality with penicillin administration. Leptospirosis is occurring in an older population, with a higher number of oliguria and lung manifestations. However, mortality is decreasing and can be the result of changes in treatment.

Recombinant vaccines against leptospirosis

Leptospirosis is an important neglected infectious disease that occurs in urban environments, as well as in rural regions worldwide. Rodents, the principal reservoir hosts of pathogenic Leptospira spp., and other infected animals shed the bacteria in their urine. During occupational or even recreational activities, humans that come into direct contact with infected animals or with a contaminated environment, particularly water, are at risk of infection. Prevention of urban leptospirosis is largely dependent on sanitation measures that are often difficult to implement, especially in developing countries. Vaccination with inactivated whole-cell preparations (bacterins) has limited efficacy due to the wide antigenic variation of the pathogen. Intensive efforts towards developing improved recombinant vaccines are ongoing. During the last decade, many reports on the evaluation of recombinant vaccines have been published. Partial success has been obtained with some surface-exposed protein antigens. The combination of protective antigens and new adjuvants or delivery systems may result in the much-needed effective vaccine.

Spatial epidemiology of suspected clinical leptospirosis in Sri Lanka

Leptospirosis is one of the most widespread zoonoses in the world. A large outbreak of suspected human leptospirosis began in Sri Lanka during 2008. This study investigated spatial variables associated with suspected leptospirosis risk during endemic and outbreak periods. Data were obtained for monthly numbers of reported cases of suspected clinical leptospirosis for 2005–2009 for all of Sri Lanka. Space–time scan statistics were combined with regression modelling to test associations during endemic and outbreak periods. The cross-correlation function was used to test association between rainfall and leptospirosis at four locations. During the endemic period (2005–2007), leptospirosis risk was positively associated with shorter average distance to rivers and with higher percentage of agriculture made up of farms <0·20 hectares. Temporal correlation analysis of suspected leptospirosis cases and rainfall revealed a 2-month lag in rainfall-case association during the baseline period. Outbreak locations in 2008 were characterized by shorter distance to rivers and higher population density. The analysis suggests the possibility of household transmission in densely populated semi-urban villages as a defining characteristic of the outbreak. The role of rainfall in the outbreak remains to be investigated, although analysis here suggests a more complex relationship than simple correlation.

Leptospirosis in Hawaii, USA, 1999-2008

Although infrequently diagnosed in the United States, leptospirosis is a notable reemerging infectious disease throughout developing countries. Until 1995, when the disease was eliminated from the US list of nationally notifiable diseases, Hawaii led the nation in reported annual incidence rates. Leptospirosis remains a notifiable disease in Hawaii. To ascertain the status of leptospirosis in Hawaii since the most recent US report in 2002, we reviewed 1999–2008 data obtained from case investigation reports by the Hawaii State Department of Health. Of the 345 case reports related to in-state exposures, 198 (57%) were laboratory confirmed. Our findings indicate a change in seasonal disease occurrence from summer to winter and in the infective serogroup from Icterohemorrhagiae to Australis. Also, during the past 20 years, recreational exposures have plateaued, while occupational exposures have increased. Ongoing surveillance is needed to clarify and track the dynamic epidemiology of this widespread zoonosis.