Association of rodent-borne Leptospira spp. with urban environments in Malaysian Borneo

Leptospira infection and carrier survey on rats from wet market areas in Kuala Lumpur, Malaysia

BACKGROUND OBJECTIVES

Leptospirosis is an important zoonotic infection that has caused significant mortality and morbidity worldwide. This disease is endemic in Malaysia and as a developing tropical country, leptospirosis is concerning as it threatens Malaysian public health and the country's economic sectors. However, there is limited information on leptospirosis in Malaysia, especially regarding leptospiral seroepidemiology among carriers in Malaysia. Therefore, more epidemiological information on the source of the disease and reservoir are needed for better disease control and source intervention. The objectives of this study are to gather information on Leptospira infection and the carrier status of rats captured from selected wet markets of Kuala Lumpur metropolitan city in Malaysia.

METHODS

Live rat trappings were performed in four major wet markets in Kuala Lumpur, namely, Pudu, Chow Kit, Datuk Keramat, and Petaling Street. Animal samplings were performed for 12 months in 2017, where blood and kidney samples were collected and tested for anti-leptospiral antibodies via Microscopic Agglutination Test (MAT) and pathogenic Leptospira screening via Polymerase Chain Reaction (PCR) amplification offlaB gene.

RESULTS

MAT showed that 34.7% (n = 50/144) of the captured rats were positive for anti-leptospiral antibody of which the most prominent serovar was Malaya followed by a local strain, IMR LEP 175. In parallel, 50 rats were also positive for pathogenic Leptospira DNA.

INTERPRETATION CONCLUSION

This study showed that there are persistent Leptospira infections among rats in Kuala Lumpur wet markets and these rats are important reservoir hosts for the bacteria.

Leptospirosis in Malaysia: current status, insights, and future prospects

Among zoonotic infections, leptospirosis has a worldwide distribution and high prevalence in tropical regions. It has a broad clinical presentation from mild to severe, life-threatening infection. Leptospires, the etiological agent of leptospirosis, are found in varied ecological niches and animal species, providing a significant source of human infection. This review aims to provide the current status of leptospirosis in Malaysia and the direction for future studies. The literature search for this review was performed using PubMed, Web of Sciences, and Google Scholar databases. The incidence of leptospirosis in Malaysia from 2004 to 2020 varied; however, a large number of cases occurred during floods. Leptospira has been isolated from wild and domestic animals as well as from the environment; among them, several novel species have been identified. In Malaysia, leptospirosis infection and death were mostly associated with recreational and non-recreational water activities. Despite the endemicity of leptospirosis, the public's knowledge, attitude, and practice level are relatively low in this country. More studies are needed in Malaysia to explore the extent of leptospirosis in different settings and locations.

Pathological and molecular study of kidneys in apparently healthy cattle and sheep with special reference to Leptospira species in central and northern Jordan

Background and Aim

Renal pathological conditions can cause significant economic losses for livestock owners. This study investigated and described the gross pathology and histopathology of lesions found in the kidneys of sheep and cattle, with particular attention to the presence of Leptospira spp.

Materials and Methods

Three hundred and sixty kidneys from apparently healthy sheep and cattle (208 and 152, respectively) were collected from slaughterhouses in Jordan for gross and histopathological examinations, multiplex polymerase chain reaction (PCR) analysis, and gene sequencing of Leptospira spp.

Results

Histopathological analysis of the samples revealed the following conditions: interstitial nephritis (4.44%), glomerulonephritis (4.16%), acute tubular necrosis (17.22%), and renal congestion (4.72%). In addition, in 26.9% of the samples, hyaline material was observed in the interstitium of the cortex and medulla. The PCR results revealed that 83 (23.1%) of the 360 samples were positive for Leptospira spp. 16S rRNA, 42/152 (28%) of cattle, and 41/208 (20%) of sheep. Four samples (two sheep and two cattle) were sequenced and deposited in GenBank with accession numbers from OL701310 to OL701313. Basic Local Alignment Search Tool search and nucleotide similarities between OL701311 and OL701313 resulted in the highest similarities with different Leptospira borgpetersenii strains, whereas OL701310 showed the highest nucleotide similarity (99.2%) with the Leptospira interrogans strain. Similarly, phylogenetic analysis revealed that OL701311 to OL701313 clustered together with different serovars of L. borgpetersenii, whereas OL701310 clustered with the L. interrogans clade.

Conclusion

This is the first study to reveal a close association between pathogenic Leptospira spp. and kidney disorders in Jordanian cattle and sheep. These findings may help expand the current understanding of the causes and mechanisms of renal disease in cattle and sheep and contribute to developing more effective prevention and treatment programs.

Leptospirosis in humans and selected animals in Sub-Saharan Africa, 2014-2022: a systematic review and meta-analysis

BACKGROUND

Leptospirosis is an emerging neglected tropical zoonotic disease of public health importance causing substantial morbidities and mortalities among humans. The infection is maintained within the population through interactions between humans, animals, and the environment. Understanding the burden of disease in both humans and animals is necessary for effective prevention and control in Sub-Saharan Africa (SSA). Therefore, we aimed to determine the seroprevalence of leptospirosis in humans, selected domestic animals, and rodents in SSA.

METHODS

A comprehensive search was done in six databases: Scopus, PubMed, Google Scholar, CINAHL, Web of Science, and African Journals Online databases for articles published between 01 January 2014 and 30 August 2022. Thirty-seven articles distributed across 14 out of 46 countries in SSA were included. The random effects meta-analysis model was used to pool the extracted seroprevalence data.

RESULTS

The overall pooled seroprevalence of leptospirosis among humans was 12.7% (95% CI: 7.5,20.8), 15.1% (95% CI: 9.4,23.5), and 4.5% (95% CI: 0.4, 35.6) based on results obtained using ELISA, MAT, and PCR diagnostic methods respectively. The pooled seroprevalence estimates among cattle were 29.2%, 30.1%, and 9.7% based on ELISA, MAT, and PCR respectively. Further, the pooled seroprevalence in goats was 30.0% for studies that used MAT, and among rodents, the pooled seroprevalence estimates were 21.0% for MAT and 9.6% for PCR diagnostic criteria. The seroprevalence of leptospirosis varied extensively between studies, across SSA regions and study setting (rural or urban).

CONCLUSION

Leptospirosis is widespread in SSA in both humans and animals based on the current results of the pooled seroprevalence in the limited studies available. The burden is high in animals and humans and underestimated due to limited studies and challenges with limited diagnostic capacity in most healthcare settings in SSA. Hence, we recommend that leptospirosis should be listed as a disease of concern and be included on the list of routine diagnostics among patients presenting with febrile illness in healthcare settings. Further, we recommend the enhancement of surveillance of leptospirosis in all countries in SSA and the development of strategies with a One Health perspective to effectively prevent and control leptospirosis.

Influence of landscape structure on previous exposure to Leptospira spp. and Brucella abortus in free-living neotropical primates from southern Brazil

The environments in which neotropical primates live have been undergoing an intense fragmentation process, constituting a major threat to the species' survival and causing resource scarcity, social isolation, and difficulty in dispersal, leaving populations increasingly vulnerable. Moreover, the proximity of wild environments to anthropized landscapes can change the dynamics of pathogens and the parasite-host-environment relationship, creating conditions that favor exposure to different pathogens. To investigate the previous exposure of free-living primates in Rio Grande do Sul State (RS), southern Brazil, to the bacterial agents Leptospira spp. and Brucella abortus, we investigated agglutinating antibodies against 23 serovars of Leptospira spp. using the microscopic agglutination test and B. abortus acidified antigen test in primate serum samples; 101 samples from primates captured between 2002 and 2016 in different forest fragments were used: 63 Alouatta caraya, 36 Alouatta guariba clamitans, and 02 Sapajus nigritus cucullatus. In addition, the forest remnants where the primates were sampled were characterized in a multiscale approach in radii ranging from 200 to 1400 m to investigate the potential relationship of previous exposure to the agent with the elements that make up the landscape structure. The serological investigation indicated the presence of antibodies for at least one of the 23 serovars of Leptospira spp. in 36.6% (37/101) of the samples analyzed, with titers ranging from 100 to 1600. The most observed serovars were Panama (17.8%), Ballum (5.9%), Butembo (5.9%), Canicola (5.9%), Hardjo (4.9%), and Tarassovi (3.9%); no samples were seropositive for Brucella abortus. Decreased forest cover and edge density were the landscape factors that had a significant relationship with Leptospira spp. exposure, indicating that habitat fragmentation may influence contact with the pathogen. The data generated in this study demonstrate the importance of understanding how changes in landscape structure affect exposure to pathogenic microorganisms of zoonotic relevance. Hence, improving epidemiological research and understanding primates' ecological role in these settings can help improve environmental surveillance and conservation strategies for primate populations in different landscapes.

Application of Multilocus Sequence Typing for the Characterization of Leptospira Strains in Malaysia

Leptospirosis is a common zoonotic disease in tropical and subtropical countries. It is considered an emerging disease in Malaysia and is a notifiable disease. This study was conducted to characterize Malaysian isolates from human, animal and environmental samples via MLST and rrs2 sequencing in an attempt to develop a Malaysian genotypic database. An existing polymerase chain reaction (PCR)-based MLST scheme was performed to facilitate subsequent sequencing. Out of 46 extracted DNA, 36 had complete MLST profiles whereby all six genes were amplified and sequenced. Most of the pathogenic Leptospira genotypes with full MLST profiles were L. interrogans serogroup Bataviae (n = 17), followed by L. borgpetersenii serogroup Javanica (n = 9), L. interrogans serogroup Sejroe (n = 2), L. interrogans serogroup Australis (n = 2), L. kirschneri (n = 2), L. interrogans serogroup Grippotyphosa (n = 1) and L. interrogans serogroup Pyrogenes (n = 3). Two samples (R3_SER/17 and R4_SER/17) were not closely related with any of the reference strains. For the samples with incomplete MLST profiles, leptospiral speciation was conducted through rrs2 analysis, in which four samples were identified as L. borgpetersenii, five samples were closely related to L. kmetyi and one sample was known as L. yasudae. This study shows that molecular approaches that combine both MLST and rrs2 sequencing have great potential in the comprehensive characterization of pathogenic Leptospira because they can be performed directly from cultured and clinical samples.

An Overview of Anthropogenic Actions as Drivers for Emerging and Re-Emerging Zoonotic Diseases

Population growth and industrialization have led to a race for greater food and supply productivity. As a result, the occupation and population of forest areas, contact with wildlife and their respective parasites and vectors, the trafficking and consumption of wildlife, the pollution of water sources, and the accumulation of waste occur more frequently. Concurrently, the agricultural and livestock production for human consumption has accelerated, often in a disorderly way, leading to the deforestation of areas that are essential for the planet's climatic and ecological balance. The effects of human actions on other ecosystems such as the marine ecosystem cause equally serious damage, such as the pollution of this habitat, and the reduction of the supply of fish and other animals, causing the coastal population to move to the continent. The sum of these factors leads to an increase in the demands such as housing, basic sanitation, and medical assistance, making these populations underserved and vulnerable to the effects of global warming and to the emergence of emerging and re-emerging diseases. In this article, we discuss the anthropic actions such as climate changes, urbanization, deforestation, the trafficking and eating of wild animals, as well as unsustainable agricultural intensification which are drivers for emerging and re-emerging of zoonotic pathogens such as viral (Ebola virus, hantaviruses, Hendravirus, Nipah virus, rabies, and severe acute respiratory syndrome coronavirus disease-2), bacterial (leptospirosis, Lyme borreliosis, and tuberculosis), parasitic (leishmaniasis) and fungal pathogens, which pose a substantial threat to the global community. Finally, we shed light on the urgent demand for the implementation of the One Health concept as a collaborative global approach to raise awareness and educate people about the science behind and the battle against zoonotic pathogens to mitigate the threat for both humans and animals.

Prevalence of Pathogenic Leptospira spp. in Non-Volant Small Mammals of Hutan Lipur Sekayu, Terengganu, Malaysia

Leptospirosis is an important zoonotic disease that is transmitted worldwide through infected small mammals such as rodents. In Malaysia, there is a paucity of information on the animal reservoirs that are responsible for leptospirosis transmission, with only a few studies focusing on leptospirosis risk in recreational areas. Therefore, in this study we characterized the species composition and the prevalence of pathogenic Leptospira spp. in non-volant small mammals of Hutan Lipur Sekayu, Terengganu. We performed ten trapping sessions totaling 3000 trappings between September 2019 and October 2020. Kidney samples from captured individuals were extracted for the PCR detection of pathogenic Leptospira spp. Overall, we captured 45 individuals from 8 species (1.56% successful trapping effort), with 9 individuals testing positive for pathogenic Leptospira, that is, a 20% (n = 9/45) prevalence rate. Rattus tiomanicus (n = 22) was the most dominant captured species and had the highest positive individual with pathogenic Leptospira (44.4%, n = 4/9). Despite the low successful trapping effort in this study, the results show the high diversity of non-volant small mammals in Hutan Lipur Sekayu, and that they could also maintain and transmit pathogenic Leptospira.

Rats and the city: Implications of urbanization on zoonotic disease risk in Southeast Asia

Urbanization is rapidly transforming Southeast Asia, altering the landscape and the interactions between people, animals, and the environment. These changes have the potential to exacerbate many existing health challenges in the region, including those posed by zoonoses. Here, we used a novel, multidisciplinary, ecosystem-level approach to examine the influence of urbanization on zoonotic disease risk in a Southeast Asian city. We infer that urbanization alters the ecology of animal reservoirs, arthropod vectors, and pathogens in a manner that may increase transmission risk from multiple zoonotic diseases in urban areas. This effect was particularly strong for pathogens associated with environmental or tick-borne transmission, providing targets for the development of low-cost interventions to reduce zoonotic disease risk in tropical cities.

Urbanization is rapidly transforming much of Southeast Asia, altering the structure and function of the landscape, as well as the frequency and intensity of the interactions between people, animals, and the environment. In this study, we explored the impact of urbanization on zoonotic disease risk by simultaneously characterizing changes in the ecology of animal reservoirs (rodents), ectoparasite vectors (ticks), and pathogens across a gradient of urbanization in Kuching, a city in Malaysian Borneo. We sampled 863 rodents across rural, developing, and urban locations and found that rodent species diversity decreased with increasing urbanization—from 10 species in the rural location to 4 in the rural location. Notably, two species appeared to thrive in urban areas, as follows: the invasive urban exploiter Rattus rattus (n = 375) and the native urban adapter Sundamys muelleri (n = 331). R. rattus was strongly associated with built infrastructure across the gradient and carried a high diversity of pathogens, including multihost zoonoses capable of environmental transmission (e.g., Leptospira spp.). In contrast, S. muelleri was restricted to green patches where it was found at high densities and was strongly associated with the presence of ticks, including the medically important genera Amblyomma, Haemaphysalis, and Ixodes. Our analyses reveal that zoonotic disease risk is elevated and heterogeneously distributed in urban environments and highlight the potential for targeted risk reduction through pest management and public health messaging.

Internalization of Leptospira interrogans via diverse endocytosis mechanisms in human macrophages and vascular endothelial cells

Leptospirosis, one of the leading global causes of morbidity and mortality, is an emerging public health problem, particularly in large urban centers of developing countries. Leptospirosis results from infection with an organism belonging to the Leptospira genus L. interrogans. The extensive invasive ability has previously been documented, however a mechanism that describes how the organism is internalized by human macrophages and transmigrates through human blood vessel remains poorly understood. In the present study, we utilized a human macrophage and vascular endothelial cell line to study the diverse invasive mechanisms by which L. interrogans infections occur. We found that THP-1 and HUVEC had a diverse expression of cell receptors and L. interrogans entered THP-1 and HUVEC by different pathways. In the macrophage model cell line, ITGB1/FAK-signaling mediated microfilament dependent endocytosis with lysosome fusion, whereas ITGB1/CAV-1/PI3K-signaling mediated microfilament dependent endocytosis and transcytosis without lysosome fusion in the endothelial cell model. Shedding of pathogenic leptospires from HUVEC displayed higher viability than those from THP-1. The monolayer of HUVEC maintained integrity during the infection, while 3D imaging showed that leptospires were transmigrated both intra- and intercellularly. These results indicate that endocytosis of leptospires in human macrophages and human vascular endothelial cells are quite different, macrophages are responsible for eliminating leptospires in the human body during the infection while vascular endothelial cells facilitate dissemination of leptospires from blood vessels into target organs where they cause injury.

Leptospirosis is a zoonotic bacterial disease which causes 1.03 million cases and 58,900 deaths each year. Human infections occur when the primary reservoir hosts, such as rodents, contaminate food and water with leptospires. Unlike other bacterial pathogens, leptospires invade the human body through mucosal barriers and enter the bloodstream, which can result in septicemia. Left untreated, leptospirosis can spread into multiple organs and tissues such as lungs, liver and kidneys. Pathological features of this disease include high fever, myalgia, lymphadenectasis, hemorrhaging and jaundice. Human macrophages and vascular endothelial cells play important roles in eliminating and preventing the transmission of this pathogen. We speculated that leptospires could be neutralized in macrophages and subsequently transported by vascular endothelial cells throughout the human body. In this research, the diverse mechanisms of human macrophages and vascular endothelial cells infected by leptospires were explored. Our findings can be used to improve the treatment, prevention, and supervision regarding leptospire transmission and infection.

Leptospirosis in rats and livestock in Bantul and Gunungkidul district, Yogyakarta, Indonesia

Background and Aim:

The animal reservoir of leptospirosis is comprised of both domestic and wild mammals, with rats known as the most important in the spread of the disease. The occurrence of this reservoir in residential areas increases the potential for leptospirosis transmission. This study aimed to investigate the type of reservoirs and estimate the prevalence of leptospirosis in rats and livestock animals in Bantul and Gunungkidul districts, Special Region of Yogyakarta Province, Indonesia.

Materials and Methods:

This research utilized a cross-sectional study design. Rat trapping and livestock (cattle, goat, and sheep) blood surveys were conducted at four locations in each district. Samples of rat renal and livestock blood serum were examined using the polymerase chain reaction technique to determine the presence of Leptospira bacteria. The data were analyzed descriptively by describing the species of rats trapped, the types of cattle, and the prevalence of Leptospira in the sample.

Results:

The rat species infected with Leptospira in Bantul district consisted of Rattus tanezumi 4.8% (3/63); Rattus norvegicus 12.5% (2/16); Bandicota indica 28.6% (2/7); and Bandicota bengalensis 50.0% (1/2). No rats were found to be positive for Leptospira in Gunungkidul district. The prevalence of Leptospira in cattle was 63.64% (7/11) in Bantul district and 50.00% (8/16) in Gunungkidul district. In goats and sheep, the prevalence of Leptospira was 22.22% (2/9) in Bantul district and 45.16% (14/31) in Gunungkidul district.

Conclusion:

The potential exists for transmission of leptospirosis from rats and cattle in Bantul and Gunungkidul Districts. It is necessary to increase leptospirosis awareness. Community education, especially for livestock farmers, needs to be improved to prevent the transmission of leptospirosis from livestock.

Presence of Leptospira spp. and absence of Bartonella spp. in urban rodents of Buenos Aires province, Argentina

Big cities of Argentina are characterized by a strong social and economic fragmentation. This context enables the presence of urban rodents in close contact to the human population, mostly in the peripheral areas of the cities. Urban rodents can harbor a large variety of zoonotic pathogens. The aim of this study was to molecularly characterize Leptospira spp. and Bartonella spp. in urban rodents from the area of Gran La Plata, Buenos Aires province, Argentina. The species of urban rodents captured and tested were Rattus norvegicus, Rattus rattus, and Mus musculus. Leptospira interrogans and L. borgpetersenii were detected in R. norvegicus and M. musculus respectively. Bartonella spp. DNA was not detected in any of the kidney samples tested. No significant differences were observed between the prevalence of bacteria and rodent and environmental variables such as host sex, presence of stream and season by Generalized Linear Model analysis. These results confirm the role of urban rodents as infection sources of Leptospira spp., suggesting the need to implement public health measures to prevent the transmission of Leptospira spp. and other zoonotic pathogens from rodents to humans. Bartonella was not detected in this set of samples.

Zoonotic Pathogens in Wildlife Traded in Markets for Human Consumption, Laos

We tested animals from wildlife trade sites in Laos for the presence of zoonotic pathogens. Leptospira spp. were the most frequently detected infectious agents, found in 20.1% of animals. Rickettsia typhi and R. felis were also detected. These findings suggest a substantial risk for exposure through handling and consumption of wild animal meat.

Leptospira interrogans Serogroup Pomona in a Dairy Cattle Farm in a Multi-Host Zootechnical System

Bovine leptospirosis is an infectious zoonotic disease causing reproductive problems and economic losses in livestock. This work reports, for the first time in Sicily (South Italy), an outbreak of Leptospira interrogans serogroup Pomona that occurred in cattle farms within the Nebrodi Park and was mainly characterized by full-term abortion. Blood and urine samples were collected at different time points from animals of six different farms (Farms A–F) sharing the same grazing area. Research of antibodies against pathogenic Leptospira species in serum samples was carried out via Micro Agglutination Test (MAT). Urine samples were subjected to pathogen isolation and molecular analyses via TaqMan Real Time-PCR. Genotyping of Leptospira species was obtained by Multi-locus sequence typing. MAT detected antibodies against Leptospira interrogans serogroup Pomona in serum samples of all the farms. Pathogenic Leptospira spp. DNA and culture isolation was obtained from urine samples. Genotyping confirmed the excretion of L. interrogans serogroup Pomona. This study describes clinical manifestations, diagnostic implications and epidemiological characteristics of an outbreak in cattle due to L. interrogans Pomona in a protected multi-host area, where domestic and wild animals share the same habitat, suggesting a role of wild species in transmission and persistence of Pomona serogroup among cattle.

Influence of Climatic Factors on Human Hantavirus Infections in Latin America and the Caribbean: A Systematic Review

BACKGROUND

With the current climate change crisis and its influence on infectious disease transmission there is an increased desire to understand its impact on infectious diseases globally. Hantaviruses are found worldwide, causing infectious diseases such as haemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS)/hantavirus pulmonary syndrome (HPS) in tropical regions such as Latin America and the Caribbean (LAC). These regions are inherently vulnerable to climate change impacts, infectious disease outbreaks and natural disasters. Hantaviruses are zoonotic viruses present in multiple rodent hosts resident in Neotropical ecosystems within LAC and are involved in hantavirus transmission.

METHODS

We conducted a systematic review to assess the association of climatic factors with human hantavirus infections in the LAC region. Literature searches were conducted on MEDLINE and Web of Science databases for published studies according to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) criteria. The inclusion criteria included at least eight human hantavirus cases, at least one climatic factor and study from > 1 LAC geographical location.

RESULTS

In total, 383 papers were identified within the search criteria, but 13 studies met the inclusion criteria ranging from Brazil, Chile, Argentina, Bolivia and Panama in Latin America and a single study from Barbados in the Caribbean. Multiple mathematical models were utilized in the selected studies with varying power to generate robust risk and case estimates of human hantavirus infections linked to climatic factors. Strong evidence of hantavirus disease association with precipitation and habitat type factors were observed, but mixed evidence was observed for temperature and humidity.

CONCLUSIONS

The interaction of climate and hantavirus diseases in LAC is likely complex due to the unknown identity of all vertebrate host reservoirs, circulation of multiple hantavirus strains, agricultural practices, climatic changes and challenged public health systems. There is an increasing need for more detailed systematic research on the influence of climate and other co-related social, abiotic, and biotic factors on infectious diseases in LAC to understand the complexity of vector-borne disease transmission in the Neotropics.

Effect of Sewerage on the Contamination of Soil with Pathogenic Leptospira in Urban Slums

Leptospirosis is an environmentally transmitted zoonotic disease caused by pathogenic Leptospira spp. that affects poor communities worldwide. In urban slums, leptospirosis is associated with deficient sanitary infrastructure. Yet, the role of sewerage in the reduction of the environmental contamination with pathogenic Leptospira has not been explored. Here, we conducted a survey of the pathogen in soils surrounding open and closed sewer sections in six urban slums in Brazil. We found that soils surrounding conventionally closed sewers (governmental interventions) were 3 times less likely to contain pathogenic Leptospira (inverse OR 3.44, 95% CI = 1.66-8.33; p < 0.001) and contained a 6 times lower load of the pathogen (0.82 log₁₀ units difference, p < 0.01) when compared to their open counterparts. However, no differences were observed in community-closed sewers (poor-quality closings performed by the slum dwellers). Human fecal markers (BacHum) were positively associated with pathogenic Leptospira even in closed sewers, and rat presence was not predictive of the presence of the pathogen in soils, suggesting that site-specific rodent control may not be sufficient to reduce the environmental contamination with Leptospira. Overall, our results indicate that sewerage expansion to urban slums may help reduce the environmental contamination with the pathogen and therefore reduce the risk of human leptospirosis.

Leptospirosis infections among hospital patients, Sarawak, Malaysia

Background

Leptospirosis diagnoses have increased in Sarawak, Malaysia in recent years.

Methods

To better understand the burden of disease and associated risk factors, we evaluated 147 patients presenting with clinical leptospirosis to local hospitals in Sarawak, Malaysia for the presence of Leptospira and associated antibodies. Sera and urine specimens collected during the acute illness phase were assessed via a commercially available rapid diagnostic test (Leptorapide, Linnodee Ltd., Antrim, Northern Ireland), an ELISA IgM assay (Leptospira IgM ELISA, PanBio, Queensland, Australia) and a pan-Leptospira real-time PCR (qPCR) assay to estimate disease prevalence and diagnostic accuracy of each method. Microagglutination testing was performed on a subset of samples.

Results

Overall, 45 out of 147 patients (30.6%) showed evidence of leptospires through qPCR in either one or both sera (20 patients) or urine (33 patients), and an additional ten (6.8%) were considered positive through serological testing, for an overall prevalence of 37.4% within the study population. However, each diagnostic method individually yielded disparate prevalence estimates: rapid test 42.2% for sera and 30.5% for urine, ELISA 15.0% for sera, qPCR 13.8% for sera and 23.4% for urine. Molecular characterization of a subset of positive samples by conventional PCR identified the bacterial species as Leptospira interrogans in 4 specimens. A multivariate risk factor analysis for the outcome of leptospirosis identified having completed primary school (OR = 2.5; 95 CI% 1.0–6.4) and weekly clothes-washing in local rivers (OR = 10.6; 95 CI% 1.4–214.8) with increased likelihood of leptospirosis when compared with those who had not.

Conclusion

Overall, the data suggest a relatively high prevalence of leptospirosis in the study population. The low sensitivities of the rapid diagnostic test and ELISA assay against qPCR highlight a need for better screening tools.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40794-021-00154-2.

Leptospirosis and Coinfection: Should We Be Concerned?

Pathogenic Leptospira is the causative agent of leptospirosis, an emerging zoonotic disease affecting animals and humans worldwide. The risk of host infection following interaction with environmental sources depends on the ability of Leptospira to persist, survive, and infect the new host to continue the transmission chain. Leptospira may coexist with other pathogens, thus providing a suitable condition for the development of other pathogens, resulting in multi-pathogen infection in humans. Therefore, it is important to better understand the dynamics of transmission by these pathogens. We conducted Boolean searches of several databases, including Google Scholar, PubMed, SciELO, and ScienceDirect, to identify relevant published data on Leptospira and coinfection with other pathogenic bacteria. We review the role of the host-microbiota in determining the synanthropic interaction of Leptospira sp. with other bacteria, thus creating a suitable condition for the leptospira to survive and persist successfully. We also discuss the biotic and abiotic factors that amplify the viability of Leptospira in the environment. The coinfection of leptospira with pathogenic bacteria has rarely been reported, potentially contributing to a lack of awareness. Therefore, the occurrence of leptospirosis coinfection may complicate diagnosis, long-lasting examination, and mistreatment that could lead to mortality. Identifying the presence of leptospirosis with other bacteria through metagenomic analysis could reveal possible coinfection. In conclusion, the occurrence of leptospirosis with other diseases should be of concern and may depend on the success of the transmission and severity of individual infections. Medical practitioners may misdiagnose the presence of multiple infections and should be made aware of and receive adequate training on appropriate treatment for leptospirosis patients. Physicians could undertake a more targeted approach for leptospirosis diagnosis by considering other symptoms caused by the coinfected bacteria; thus, more specific treatment could be given.

Agro-Environmental Determinants of Leptospirosis: A Retrospective Spatiotemporal Analysis (2004-2014) in Mahasarakham Province (Thailand)

Leptospirosis has been recognized as a major public health concern in Thailand following dramatic outbreaks. We analyzed human leptospirosis incidence between 2004 and 2014 in Mahasarakham province, Northeastern Thailand, in order to identify the agronomical and environmental factors likely to explain incidence at the level of 133 sub-districts and 1982 villages of the province. We performed general additive modeling (GAM) in order to take the spatial-temporal epidemiological dynamics into account. The results of GAM analyses showed that the average slope, population size, pig density, cow density and flood cover were significantly associated with leptospirosis occurrence in a district. Our results stress the importance of livestock favoring leptospirosis transmission to humans and suggest that prevention and control of leptospirosis need strong intersectoral collaboration between the public health, the livestock department and local communities. More specifically, such collaboration should integrate leptospirosis surveillance in both public and animal health for a better control of diseases in livestock while promoting public health prevention as encouraged by the One Health approach.

Evaluation of the Panbio Leptospira IgM ELISA among Outpatients Attending Primary Care in Southeast Asia

Despite estimates suggesting Leptospira spp. being endemic in Southeast Asia, evidence remains limited. Diagnostic accuracy evaluations based on Leptospira ELISA mainly rely on hospitalized and severe patients; therefore, studies measuring the pathogen burden may be inaccurate in the community. We evaluated the Panbio Leptospira ELISA IgM among 656 febrile outpatients attending primary care in Chiangrai, Thailand, and Hlaing Tha Yar, Yangon, Myanmar. ELISA demonstrated limited diagnostic accuracy for the detection of acute leptospiral infection using the manufacturer recommended cutoff, with a sensitivity of 71.4% and specificity of 36.4%, and an area under the receiver operator characteristic curve value of 0.65 (95% CI: 0.41-0.89), compared with our reference test, the PCR assay. ELISA also performed poorly as a screening tool for detecting recent exposure to Leptospira spp. compared with the "gold-standard" microscopic agglutination test, with a specificity of 42.7%. We conclude that the utility of the Leptospira IgM ELISA for both serodiagnosis and seroprevalence is limited in our setting.

First detection of a novel 'unknown host' flavivirus in a Malaysian rodent

Current phylogenetic analysis of the flavivirus genus has identified a group of mosquito-borne viruses for which the vertebrate hosts are currently unknown. Here we report the identification of a novel member of this group from a peridomestic rodent species (Sundamys muelleri) collected in Sarawak, Malaysia in 2016. We propose to name this novel flavivirus Batu Kawa virus after the location in which it was identified, with the abbreviation BKWV. Characterization of the BKWV genome allowed identification of putative mature peptides, potential enzyme motifs and conserved structural elements. Phylogenetic analysis found BKWV to be most closely related to Nhumirim virus (from Brazil) and Barkedji virus (from Senegal and Israel). Both of these viruses have been identified in Culex mosquitoes and belong to a group of viruses with unknown vertebrate hosts. This is the first known report of a member of this group of viruses from a potential mammalian host.

Leptospiral Infection, Pathogenesis and Its Diagnosis-A Review

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

Insight into the Epidemiology of Leptospirosis: A Review of Leptospira Isolations from "Unconventional" Hosts

Leptospirosis is a re-emerging worldwide zoonotic disease. Even though the primary serological test for diagnosis and surveying is the microscopic agglutination test (MAT), isolation remains the gold-standard test to detect Leptospira infections. The leptospirosis transmission is linked to maintenance and accidental hosts. In the epidemiology of Leptospira some serovar are strictly related to specific maintenance hosts; however, in recent years, the bacterium was isolated from an even wider spectrum of species. The aim of this review is to report the isolation of Leptospira strains in animals which could be recognized as "unconventional" hosts, analyzing studies from 1960 to 2020 that highlighted the Leptospira isolation. This scientific literature aimed to provide evidence of infection in several animal species including of the Carnivora, Didelphimorphia, Rodentia, Cetacea, Cingulata, Afrosoricida, Chiroptera and Primate orders, as well as in Reptilia and Amphibia classes. In conclusion, the spreading of Leptospira is attention-worthy because the infection could occur in all the animal species ranging in a specific area. Further screening and isolations are needed to collect all necessary data to gain a complete understanding of leptospirosis epidemiology and its modifications.

Amplification of pathogenic Leptospira infection with greater abundance and co-occurrence of rodent hosts across a counter-urbanizing landscape

Land use change can elevate disease risk by creating conditions beneficial to species that carry zoonotic pathogens. Observations of concordant global trends in increased pathogen prevalence or disease incidence and landscape change have generated concerns that urbanization could increase transmission risk of some pathogens. Yet host-pathogen relationships underlying transmission risk have not been well characterized within cities, even where contact between humans and species capable of transmitting pathogens of concern occurs. We addressed this deficit by testing the hypothesis that areas in cities experiencing greater population loss and infrastructure decline (i.e., counter-urbanization) can support a greater diversity of host species and a larger and more diverse pool of pathogens. We did so by characterizing pathogenic Leptospira infection relative to rodent host richness and abundance across a mosaic of abandonment in post-Katrina New Orleans (Louisiana, USA). We found that Leptospira infection loads were highest in areas that harboured increased rodent species richness (which ranged from one to four rodent species detected). Areas with greater host co-occurrence also harboured a greater abundance of hosts, including the host species most likely to carry high infection loads, indicating that Leptospira infection can be amplified by increases in overall and relative host abundance. Evidence of shared infection among rodent host species indicates that cross-species transmission of Leptospira probably increases infection at sites with greater host richness. Additionally, evidence that rodent co-occurrence and abundance and Leptospira infection load parallel abandonment suggests that counter-urbanization can elevate zoonotic disease risk within cities, particularly in underserved communities that are burdened with disproportionate concentrations of derelict properties.

Multi-locus sequence analyses reveal a clonal L. borgpetersenii genotype in a heterogeneous invasive Rattus spp. community across the City of Johannesburg, South Africa

BACKGROUND

Rattus spp. are frequently implicated as key reservoir hosts for leptospirosis, one of the most common, but neglected, bacterial zoonoses in the world. Although leptospirosis is predicted to be a significant public health threat in Africa, studies from the continent are limited.

METHODS

Rattus spp. (n = 171) were sampled (January-May 2016) across the City of Johannesburg, South Africa's largest inland metropole. Rattus spp. genetic diversity was evaluated by full length (1140 bp) cyt b sequencing of 42 samples. For comparison, a further 12 Rattus norvegicus samples collected in Cape Town, South Africa's largest coastal metropole, were also genotyped. Leptospira infections were identified and genotyped using real-time PCR and multi-locus (lfb1, secY and lipL41) DNA sequencing.

RESULTS

Five R. norvegicus haplotypes were identified across Johannesburg, four of which have not previously been detected in South Africa, and one in Cape Town. Across Johannesburg we identified a Leptospira spp. infection prevalence of 44% (75/171) and noted significant differences in the prevalence between administrative regions within the metropole. Multi-locus sequence analyses identified a clonal genotype consistent with L. borgpetersenii serogroup Javanica (serovar Ceylonica).

DISCUSSION

The prevalence of infection identified in this study is amongst the highest detected in Rattus spp. in similar contexts across Africa. Despite the complex invasion history suggested by the heterogeneity in R. norvegicus haplotypes identified in Johannesburg, a single L. borgpetersenii genotype was identified in all infected rodents. The lack of L. interrogans in a rodent community dominated by R. norvegicus is notable, given the widely recognised host-pathogen association between these species and evidence for L. interrogans infection in R. norvegicus in Cape Town. It is likely that environmental conditions (cold, dry winters) in Johannesburg may limit the transmission of L. interrogans. Spatial heterogeneity in prevalence suggest that local factors, such as land use, influence disease risk in the metropole.

CONCLUSIONS

In South Africa, as in other African countries, leptospirosis is likely underdiagnosed. The high prevalence of infection in urban rodents in Johannesburg suggest that further work is urgently needed to understand the potential public health risk posed by this neglected zoonotic pathogen.

High incidence of asymptomatic leptospirosis among urban sanitation workers from Kota Kinabalu, Sabah, Malaysian Borneo

Leptospirosis is a public health challenge in Sabah State of Malaysian Borneo. Rapid urbanization, rural-to-urban migration, and undocumented immigration in Sabah have increased the pressure on the urban garbage disposal system. Rodents and other small animals thrive under these conditions. We hypothesized that urban sanitation workers would be at risk of developing leptospirosis. In total, 303 urban sanitation workers with a mean age of 42.6 years were enrolled in this study. The serum samples collected from these workers were subjected to the microscopic agglutination test (MAT), PCR and nucleotide sequencing of the amplicons to confirm the presence of Leptospira. The phylogenetic analysis using the neighbor joining method was performed to assess whether they were pathogenic. In this study 43.8% (133/303) of the samples were MAT-seropositive and among them, 29 (21.8%) were positive by PCR. Nucleotide sequencing of the amplicons confirmed the presence of Leptospira. Phylogenetic analysis showed that our strains belonged to the pathogenic group of Leptospira. A high proportion of urban sanitation workers were seropositive for leptospirosis, and a considerable number were PCR positive for Leptospira, thereby indicating asymptomatic infections. Further research is needed to confirm whether this is a transient phenomenon or antibiotic therapy is required.

Isolation of Leptospira serovar Pomona from a crested porcupine (Hystrix cristata, L., 1758)

Pathogenic Leptospira is widespread in rodents, the most studied reservoir and the main hosts involved in its transmission. In Italy, among rodents, Hystrix cristata (crested porcupine) is the largest species and it is distributed all over the country. In this paper, the isolation and characterization of pathogenic Leptospira spp. from the kidney of H. cristata is reported for the first time. During Autumn 2018, Leptospira detection by real-time PCR and isolation were performed from kidneys of two died female porcupines (an adult and a porcupette). Only for porcupette kidney sample, real-time PCR for pathogenic Leptospira tested positive. The isolated strain was identified as Leptospira interrogans serogroup Pomona serovar Pomona, using the three schemes of multilocus sequence typing. The results show that H. cristata could be a Leptospira host. The infection of serovars Pomona could be related to the habitat shared with wild boar, a typical reservoir host for this serovar.

Helminth fauna of small mammals from public parks and urban areas in Bangkok Metropolitan with emphasis on community ecology of infection in synanthropic rodents

In 2018, extensive field studies of diversity and prevalence of helminth infection in synanthropic rodents and non-rodent small mammals from public parks and citified areas in the Bangkok Metropolitan were conducted. Rattus rattus complex was the dominant small mammal in public parks. Of the 197 animals, 147 individuals were infected with one or more species of helminths, yielding an infection prevalence of 74.6%. Twenty-five species of helminths were recovered during necropsy. Pterygodermatites tani was the most prevalent (36.2%); other encountered species included Raillietina celebensis, Hydatigera taeniaformis (metacestode in liver tissue), Gongylonema neoplasticum and Hymenolepis diminuta. Different helminth assemblages infected three different host taxa, i.e. synanthropic Rattus spp., Tupaia belangeri (Northern treeshrew) and Suncus murinus (Asian house shrew). Nine species of possible zoonotic helminths were identified. The focus on synanthropic rats influenced the findings of helminth diversity by either host intrinsic or extrinsic factors. A significant positive correlation was found between host body mass and helminth species richness. Greater helminth species richness was found in rats from public parks compared with animals from citified areas (e.g. inside buildings or offices). Also, helminth species richness was negatively correlated with the proportion of post-flooding/rain-fed land. These results provide essential information for assessing the incidence of potential zoonotic health threats in Bangkok and updating research in parasite ecology.

Bacteriostatic and Bactericidal Effect of Tigecycline on Leptospira spp

Tigecycline is a relatively new antimicrobial, belonging to glycylcyclines with antimicrobial activity against a large spectrum of bacteria. Very few data are available on its effect on Leptospira spp., which consist in a bacteriostatic mechanism. The aim of this investigation was to evaluate the bacteriostatic and bactericidal effect of tigecycline on reference Leptospira strains belonging to 16 serovars. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined through the microdilutions method, and tetracycline was used as the control. Results showed that tigecycline had higher MIC and MBC values than tetracycline. Obtained MIC values were between 4 and 32 µg/mL, while MBC values between 16 and >128 µg/mL. Patoc (MIC: 4 µg/mL; MBC: 16 µg/mL) resulted in the most susceptible serovar, while the most resistant were Bataviae (MIC: 32 µg/mL; MBC: 64 µg/mL), Bratislava (MIC: 8 µg/mL; MBC 128 µg/mL), and Tarassovi (MIC: 8 µg/mL; MBC: >128 µg/mL). This is the first investigation focused on the effect of tigecycline against Leptospira spp. reference strains. Since tigecycline is used as a treatment for bacteremia and urinary tract disease, and these symptoms could be linked to Leptospira infection, the possibility of using this antibiotic as a treatment for leptospirosis should be evaluated. Further studies are needed to explore the possibility to use tigecycline for in vivo application against Leptospira.

Leptospira Infections in Domestic and Wild Animals

Leptospirosis is a worldwide-distributed, re-emerging zoonosis due to the large variety of wild and domestic animal species that can play the role of natural or accidental host. Currently, specific animal species play an important role as the reservoir for particular Leptospira serovars, although recent investigations have highlighted new host–pathogen interactions involved in Leptospira epidemiology. Furthermore, the constant modification of ecosystems and wildlife habitats and the constantly increasing number of animal species moving towards urban or peri-urban areas are increasing the possibility of direct or indirect contacts between wildlife and domestic animals; furthermore, the constant modification of animal leptospirosis also causes problems for human health. The studies published in this Special Issue have evidenced and confirmed the hidden role of a large variety of animal species, domestic and wild, in the leptospirosis epidemiology. They highlighted the necessity for continuous monitoring and large-scale surveillance studies to better understand this neglected and re-emerging zoonosis.

Emerging zoonotic diseases originating in mammals: a systematic review of effects of anthropogenic land-use change

Zoonotic pathogens and parasites that are transmitted from vertebrates to humans are a major public health risk with high associated global economic costs. The spread of these pathogens and risk of transmission accelerate with recent anthropogenic land-use changes (LUC) such as deforestation, urbanisation, and agricultural intensification, factors that are expected to increase in the future due to human population expansion and increasing demand for resources.We systematically review the literature on anthropogenic LUC and zoonotic diseases, highlighting the most prominent mammalian reservoirs and pathogens, and identifying avenues for future research.The majority of studies were global reviews that did not focus on specific taxa. South America and Asia were the most-studied regions, while the most-studied LUC was urbanisation. Livestock were studied more within the context of agricultural intensification, carnivores with urbanisation and helminths, bats with deforestation and viruses, and primates with habitat fragmentation and protozoa.Research into specific animal reservoirs has improved our understanding of how the spread of zoonotic diseases is affected by LUC. The behaviour of hosts can be altered when their habitats are changed, impacting the pathogens they carry and the probability of disease spreading to humans. Understanding this has enabled the identification of factors that alter the risk of emergence (such as virulence, pathogen diversity, and ease of transmission). Yet, many pathogens and impacts of LUC other than urbanisation have been understudied.Predicting how zoonotic diseases emerge and spread in response to anthropogenic LUC requires more empirical and data synthesis studies that link host ecology and responses with pathogen ecology and disease spread. The link between anthropogenic impacts on the natural environment and the recent COVID-19 pandemic highlights the urgent need to understand how anthropogenic LUC affects the risk of spillover to humans and spread of zoonotic diseases originating in mammals.

Epidemiology and genetic diversity of zoonotic pathogens in urban rats (Rattus spp.) from a subtropical city, Guangzhou, southern China

Commensal rats (Rattus spp.), which are globally distributed, harbour many pathogens responsible for significant human diseases. Despite this, we have a poor understanding of the epidemiology and genetic diversity of some recently neglected zoonotic pathogens, such as Leptospira spp., Bartonella spp. and hepatitis E virus (HEV), which constitute a major public health threat. Thus, we surveyed the occurrences, co-infection and genetic diversity of these pathogens in 129 urban rats from China. For Rattus tanezumi, the prevalences of Leptospira spp., Bartonella spp. and HEV infection were 6.67%, 0% and 46.67%, respectively. The prevalences of Leptospira spp., Bartonella spp. and HEV infection were 57.89%, 9.65% and 57.89% for Rattus norvegicus respectively. Leptospira spp. and HEV infections were more likely to occur in mature R. norvegicus. Phylogenetic analyses showed that pathogenic Leptospira interrogans and Leptospira borgpetersenii might exist. We also found that Bartonella spp. showed high similarity to Bartonella elizabethae, Bartonella rochalimae and Bartonella tribocorum, which are implicated in human disease. Dual and triple infections were both detected. Moreover, dual infections with Leptospira spp. and HEV represented the most frequent co-infection, and there was a significantly positive association between them. High genetic diversity was observed in genes segments from Leptospira, Bartonella and HEV. Our results first discover the occurrence of multiple co-infections and genetic diversity of Leptospira, Bartonella and HEV in commensal rats from China. Altogether, the present study provides an insight into evaluating the risk of rat-borne zoonoses in urban China.

Crested Porcupine (Hystrix cristata L.): A New Potential Host for Pathogenic Leptospira Among Semi-Fossorial Mammals

Wildlife plays a pivot role in the epidemiology of leptospirosis and rodents have a reservoir function for several Leptospira serogroups. The crested porcupine is the largest rodent of the Italian fauna and shares the same environment with red foxes, badgers, coypus and wild boars that are known to be infected by Leptospira. Between 2018 and 2019 the seroprevalence of Leptospira in crested porcupine was investigated for the first time. Overall 7 out of 14 sera (50 %) were found positive to Leptospira. Icterohaemorrhagiae resulted as the most detected serogroup (57 %) followed by Pomona, Australis and Sejroe. The highest titer (1:1600) was detected for the serogroup Australis. These results indicate that porcupines could be infected by several serogroup of Leptospira and the role of reservoir or accidental host need to be addressed. Further investigations are necessary in order to clarify the leptospirosis - epidemiology - wildlife framework in light of its potential zoonotic source.

Impacts of flood on health of Iranian population: Infectious diseases with an emphasis on parasitic infections

Background

Outbreaks of infectious diseases are the major concern after flooding. Flood makes people displacement which would be more complicated with inadequate sanitation. Settling in crowded shelters in absence of clean water and inaccessibility to health care services makes people more vulnerable to get infection. This review aimed to discuss about potential undesirable outcomes of flooding occurred in 2019 in Iran.

Methods

A comprehensive search was carried out in databases including PubMed, Google scholar, Scopus, Science Direct, Iran medex, Magiran and SID (Scientific information database) from 2000 to 2019. All original descriptive articles on flood were concerned. Related articles on flood disturbance were considered. Also, publication of red cross society was considered as only reliable reference in evaluation of consequences of flood occurred in 2019 in Iran.

Results

Flooding in Iran, was started in March 2019 and lasted to April 2019. Flood affected 31 provinces and 140 rivers burst their banks, and southwestern Iran being hit most severely. According the reports of international federation of red cross society, 3800 cities and villages were affected by the floods with 65,000 destroyed houses and 114,000 houses partially damaged. Also 70 hospitals or health care centers with 1200 schools were damaged along with many infrastructures including 159 main roads and 700 bridges.

Conclusions

Considering 365,000 displaced persons and estimation of mentioned damages, it was one of the greatest natural disaster during the last 20 years. Various risk factors in favor of infectious diseases such as overcrowding, disruption of sewage disposal, poor standards of hygiene, poor nutrition, negligible sanitation and human contact among refugees provide suitable conditions for increased incidence of infectious diseases after flooding and also cause epidemics.More attention is needed to provide hygienic situation for people after natural disasters including flood.

Leptospira infection in rats: A literature review of global prevalence and distribution

Background

The role of rodents in Leptospira epidemiology and transmission is well known worldwide. Rats are known to carry different pathogenic serovars of Leptospira spp. capable of causing disease in humans and animals. Wild rats (Rattus spp.), especially the Norway/brown rat (Rattus norvegicus) and the black rat (R. rattus), are the most important sources of Leptospira infection, as they are abundant in urban and peridomestic environments. In this study, we compiled and summarized available data in the literature on global prevalence of Leptospira exposure and infection in rats, as well as compared the global distribution of Leptospira spp. in rats with respect to prevalence, geographic location, method of detection, diversity of serogroups/serovars, and species of rat.

Methods

We conducted a thorough literature search using PubMed without restrictions on publication date as well as Google Scholar to manually search for other relevant articles. Abstracts were included if they described data pertaining to Leptospira spp. in rats (Rattus spp.) from any geographic region around the world, including reviews. The data extracted from the articles selected included the author(s), year of publication, geographic location, method(s) of detection used, species of rat(s), sample size, prevalence of Leptospira spp. (overall and within each rat species), and information on species, serogroups, and/or serovars of Leptospira spp. detected.

Findings

A thorough search on PubMed retrieved 303 titles. After screening the articles for duplicates and inclusion/exclusion criteria, as well as manual inclusion of relevant articles, 145 articles were included in this review. Leptospira prevalence in rats varied considerably based on geographic location, with some reporting zero prevalence in countries such as Madagascar, Tanzania, and the Faroe Islands, and others reporting as high as >80% prevalence in studies done in Brazil, India, and the Philippines. The top five countries that were reported based on number of articles include India (n = 13), Malaysia (n = 9), Brazil (n = 8), Thailand (n = 7), and France (n = 6). Methods of detecting or isolating Leptospira spp. also varied among studies. Studies among different Rattus species reported a higher Leptospira prevalence in R. norvegicus. The serovar Icterohaemorrhagiae was the most prevalent serovar reported in Rattus spp. worldwide. Additionally, this literature review provided evidence for Leptospira infection in laboratory rodent colonies within controlled environments, implicating the zoonotic potential to laboratory animal caretakers.

Conclusions

Reports on global distribution of Leptospira infection in rats varies widely, with considerably high prevalence reported in many countries. This literature review emphasizes the need for enhanced surveillance programs using standardized methods for assessing Leptospira exposure or infection in rats. This review also demonstrated several weaknesses to the current methods of reporting the prevalence of Leptospira spp. in rats worldwide. As such, this necessitates a call for standardized protocols for the testing and reporting of such studies, especially pertaining to the diagnostic methods used. A deeper understanding of the ecology and epidemiology of Leptospira spp. in rats in urban environments is warranted. It is also pertinent for rat control programs to be proposed in conjunction with increased efforts for public awareness and education regarding leptospirosis transmission and prevention.

The role of rodents in the transmission of many diseases, including leptospirosis, is widely known. Rats abundant in urban and peridomestic environments are the most important reservoirs and sources of Leptospira infection in humans and animals. Leptospirosis is a significant but neglected disease of humans and animals that is increasing in incidence in regions affected by natural disasters. This paper summarizes the global prevalence and distribution of Leptospira infection in rats and will add to the literature that supports research, education, and public awareness regarding leptospirosis transmission and prevention.

Weil's disease with haemoptysis and acute respiratory distress syndrome

A 35-year-old male patient reached the emergency department after an episode of massive haemoptysis a few hours ago. Fever and dyspnea were mentioned to be present the last 5 days. His medical history included only malaria, successfully treated 2 years ago. Clinical examination revealed high fever, jaundice, cyanosis, tachypnea and bilateral rales on pulmonary auscultation. Laboratory investigation showed high erythrocyte sedimentation rate and C reactive protein, leucocytosis, anaemia, mild thrombocytopaenia, renal impairment, hyperbilirubinaemia and abnormal liver function tests; arterial blood gas analysis showed respiratory alkalosis with severe hypoxia. Thoracic X-ray revealed bilateral pulmonary infiltrates, whereas abdominal and heart ultrasound detected hepatomegaly and small pericardial infusion, respectively. The diagnosis of leptospirosis along with acute respiratory distress syndrome was confirmed by positive IgM Leptospira antibodies. Empirical treatment with triple antibiotic therapy and corticosteroids was applied. The patient was discharged after 1 week, without any symptoms and with almost normal laboratory tests.