Leptospira in Slaughtered Fattening Pigs in Southern Italy: Serological Survey and Molecular Typing

Simple Summary

In this study, serological and molecular assays in 55 pigs in Sicily were conducted in order to investigate Leptospira spp. prevalence and to carry out strain characterization. A seropositivity rate of 16.4% was determined; 3.64% of kidney samples tested positive for pathogenic Leptospiral DNA. Obtained data showed that Leptospira infection is common among pigs in southern Italy, confirming the importance of Leptospiral infection in pigs and reaffirming the potential role of these animals as a source of infection for humans (occupational risk) and other animals. Our study delivers a comprehensive overview based on up-to-date data to deepen the knowledge of swine leptospiral infections, characterize new potential emerging strains, and reinforce control measures able to reduce the infection risk in swine herds.

Abstract

Leptospirosis is a re-emerging zoonosis of worldwide significance; a wide spectrum of wild and domestic animal species act as natural or accidental hosts. Swine can act as maintenance or accidental hosts of pathogenic Leptospira spp. This study aimed at investigation of Leptospira spp. prevalence and diversity in slaughtered pigs in southern Italy (Sicily). In total, 55 samples of kidneys and blood were collected. Microscopic agglutination test and real-time PCR were performed to detect pathogenic and intermediately pathogenic Leptospira. Partial rpoB gene sequencing and multi-locus sequence typing (MLST) were performed to characterize Leptospira species. The analysis showed a seropositivity rate of 16.4%, with Australis representing the most frequently identified serogroup (63.64%); Pomona and Sejroe were detected with a prevalence of 27.27% and 9.09%, respectively. Pathogenic Leptospiral DNA was detected in 2 kidney samples (3.64%). Leptospira were identified through MLST as L. borgpetersenii serovar Tarassovi (serogroup Tarassovi). Obtained data confirmed the presence of Leptospira infection among pigs in southern Italy, suggesting that management of these animals may be considered an occupational risk for humans.

Presence of <em>Leptospira</em> sp. and leptospirosis risk factor analysis in Boyolali district, Indonesia

BACKGROUND

Leptospirosis is a health problem that causes death in Indonesia. In 2017, Boyolali District was reported that the number of leptospirosis cases reached 40.62 per 100,000 population with a CFR of 23.52%. The determination of risk factors and Leptospira bacteria's presence in the body of water plays an essential role in the transmission of leptospirosis.

DESIGN AND METHODS

This study aims to determine the risk factors and Leptospira bacteria's presence in water bodies in Boyolali District. This research is descriptive research with a survey method using a cross-sectional design and an analytical study using an observational method with a case-control approach. The sample was 100 water samples from wells, rivers, and paddy fields in endemic and non-endemic areas of leptospirosis. This study's population was 34 people with leptospirosis in Boyolali Regency in January 2017 - August 2018.

RESULTS

There was a significant relationship between leptospirosis incidence in the Boyolali Regency with garbage, the pet presence, a history of injuries, and field activity. Leptospira bacteria are found in rivers (18.18%) and rice fields (6.67%), while in sub-districts with cases occur almost every year. Leptospira are found in wells (18.18%) and rice fields (6.67%).

CONCLUSIONS

People should pay more attention to home sanitation and the surrounding environment to avoid leptospirosis.

Dissemination kinetics and pathology of canine Leptospira icterohaemorrhagiae isolate in a guinea pig infection model

Despite significant progress made in elucidating the mechanism of acute human leptospirosis in different organs, there is a paucity of information in organs such as the heart, pancreas, brain, and adrenal gland. This study was designed to establish leptospire dissemination kinetics and patho-morphological changes associated with these orangs in the guinea pig infection model using cultural isolation (CI), polymerase chain reaction (PCR), Warthin Starry silver stain (WSss), immunohistochemistry (IH), and transmission electron microscopy (TEM). Twenty guinea pigs were inoculated intra-peritoneally with a low dosage of 1 × 10⁷ Leptospira interrogans serovar Icterohaemorrhagiae and 10 as control using distilled water. The guinea pigs were sacrificed at post-infection day (p.i.d.) ½, 1, 3, 5, and 7 followed by the harvest of the brain, pancreas, adrenal gland, heart, lungs, liver, kidneys, and spleen for CI, PCR, HE, WSss, IH, and TEM evaluations. The study revealed early dissemination of Leptospira organism in the brain, heart, pancreas, and adrenal gland and exerted various histopathological changes that were not explicitly elucidated in previous studies. This study revealed that the virulent pathogenic isolate of Leptospira organism obtained from clinically infected dog mimicked the same clinical manifestations, gross and histopathological changes especially in organs that were not previously evaluated.

Serological Survey and Molecular Typing Reveal New Leptospira Serogroup Pomona Strains among Pigs of Northern Italy

Swine act as both maintenance and incidental hosts of pathogenic Leptospira spp. Here, a serological test was performed on 131,660 pig sera collected between 2002 and 2017 from 4715 farms in Northern Italy. A positivity rate of 13.05% was determined. Australis was the most frequently identified serogroup (77.29%), followed by Pomona (18.47%), Tarassovi (1.51%) and Icterohaemorrhagie (1.40%). Culture isolation and real-time Polymerase chain reaction (PCR) were carried out on 347 kidneys and 470 clinical samples, respectively. Overall, 133 strains were cultured successfully and 43 randomly chosen isolates were identified as serogroup Pomona. Multi-locus sequence typing (MLST) revealed that 41 isolates and 8 DNA extracted from biological samples belonged to sequence type 140. Using a multiple-locus, variable-number tandem repeat analysis, 43 samples produced identical profiles but, after 2014, three new Leptospira interrogans serogroup Pomona genotypes were observed. Interestingly, two isolates showed new MLST profiles and an unclassified identification by monoclonal antibodies. The 16S rRNA gene sequencing clustered them into L. kirschneri species and a core genome MLST analysis revealed an allelic identity of 96% compared with Mozdok strains. Genotyping allowed us to discriminate leptospires and to identify new emerging strains. The accurate identification of infective strains is required for formulating preventive methods and intervention strategies.

Evidence of multiple intraspecific transmission routes for Leptospira acquisition in Norway rats (Rattus norvegicus)

Infectious diseases frequently have multiple potential routes of intraspecific transmission of pathogens within wildlife and other populations. For pathogens causing zoonotic diseases, knowing whether these transmission routes occur in the wild and their relative importance, is critical for understanding maintenance, improving control measures and ultimately preventing human disease. The Norway rat (Rattus norvegicus) is the primary reservoir of leptospirosis in the urban slums of Salvador, Brazil. There is biological evidence for potentially three different transmission routes of leptospire infection occurring in the rodent population. Using newly obtained prevalence data from rodents trapped at an urban slum field site, we present changes in cumulative risk of infection in relation to age-dependent transmission routes to infer which intra-specific transmission routes occur in the wild. We found that a significant proportion of animals leave the nest with infection and that the risk of infection increases throughout the lifetime of Norway rats. We did not observe a significant effect of sexual maturity on the risk of infection. In conclusion, our results suggest that vertical and environmental transmission of leptospirosis both occur in wild populations of Norway rats.

Rapid, actionable diagnosis of urban epidemic leptospirosis using a pathogenic Leptospira lipL32-based real-time PCR assay

Background

With a conservatively estimated 1 million cases of leptospirosis worldwide and a 5–10% fatality rate, the rapid diagnosis of leptospirosis leading to effective clinical and public health decision making is of high importance, and yet remains a challenge.

Methodology

Based on parallel, population-based studies in two leptospirosis-endemic regions in Brazil, a real-time PCR assay which detects lipL32, a gene specifically present in pathogenic Leptospira, was assessed for the diagnostic effectiveness and accuracy. Patients identified by active hospital-based surveillance in Salvador and Curitiba during large urban leptospirosis epidemics were tested. Real-time PCR reactions were performed with DNA-extracted samples obtained from 127 confirmed and 23 unconfirmed cases suspected of leptospirosis, 122 patients with an acute febrile illness other than leptospirosis, and 60 healthy blood donors.

Principal findings

The PCR assay had a limit of detection of 280 Leptospira genomic equivalents/mL. Sensitivity for confirmed cases was 61% for whole blood and 29% for serum samples. Sensitivity was higher (86%) for samples collected within the first 6 days after onset of illness compared to those collected after 7 days (34%). The real-time PCR assay was able to detect leptospiral DNA in blood from 56% of serological non-confirmed cases. The overall specificity of the assay was 99%.

Conclusions

These findings indicate that real-time PCR may be a reliable tool for early diagnosis of leptospirosis, which is decisive for clinical management of severe and life-threatening cases and for public health decision making.

In this study, we describe the performance testing and diagnostic accuracy assessment of a previously described real-time PCR assay aiming at the validation for early diagnosis of human leptospirosis. We found that diagnostic sensitivity was higher for EDTA whole blood samples (61%) than for serum samples (29%). We demonstrated that the molecular diagnosis was optimal when performed with EDTA whole samples collected within the first 6 days with symptoms, condition in which the sensitivity was 86%. The real-time PCR assay was able to detect leptospiral DNA in EDTA whole blood from 56% of serological non-confirmed cases for whom a convalescent sample was not available. The test overall specificity was 99%. Our findings demonstrate that real-time PCR is a reliable diagnostic tool suited for early diagnosis, and its results could support early medical interventions that could have a decisive impact on clinical outcome and thus decrease both the severity and fatality of cases.

Leptospira spp. in Small Mammals from Areas with Low and High Human Hantavirus Incidences in South-West Germany

INTRODUCTION

Leptospirosis is caused by Leptospira spp. and is considered the most widespread zoonotic disease worldwide. It mimics nephropathia epidemica in humans, a disease mainly caused by Puumala hantavirus (PUUV). Small mammals are reservoirs for Leptospira spp. and PUUV. Seewis virus (SWSV) is a shrew-borne hantavirus with unknown pathogenicity. The objective of this study was to estimate the prevalence for Leptospira spp. and the frequency of Leptospira-hantavirus co-infections in small mammals collected at locations with high and low incidences in humans.

MATERIALS AND METHODS

In 2012 and 2013, 736 small mammals belonging to seven species (Apodemus flavicollis, Microtus agrestis, Microtus arvalis, Myodes glareolus, Sorex araneus, S. coronatus, and S. minutus) were collected at four high incidence sites (H1-H4) and four low (L1-L4) incidence sites for PUUV infection in humans. Kidney-derived DNA samples were tested for Leptospira spp. by real-time PCR targeting the lipl 32 gene and further analyzed by duplex PCR targeting the flaB and the secY genes. For the detection of Seewis virus, lung-derived DNA was tested via RT-PCR targeting the nucleocapsid gene.

RESULTS

Altogether, 42 of the 736 small mammals including 27 of 660 bank voles and 11 of 66 shrews, were positive for Leptospira spp., while Sorex spp. (14.7%) showed significantly higher prevalences compared to bank voles (4.1%). Detected Leptospira spp. were pathogenic species other than L. kirschneri. Significantly more Leptospira-positive bank voles were found at H sites than at L sites. Altogether 22.2% of positive bank voles were infected with PUUV. Double infection of PUUV and Leptospira spp. occurrence in bank voles is 1.86 times (OR = 1.86; 95% CI: 0.72-4.73) more likely than infections with each pathogen separately.

DISCUSSION

Leptospira- positive bank voles are focally positively associated with PUUV infection in bank voles and with human hantavirus cases. It should be considered that shrews may serve as Leptospira spp. reservoirs.

An Extended Multilocus Sequence Typing (MLST) Scheme for Rapid Direct Typing of Leptospira from Clinical Samples

Background

Rapid typing of Leptospira is currently impaired by requiring time consuming culture of leptospires. The objective of this study was to develop an assay that provides multilocus sequence typing (MLST) data direct from patient specimens while minimising costs for subsequent sequencing.

Methodology and Findings

An existing PCR based MLST scheme was modified by designing nested primers including anchors for facilitated subsequent sequencing. The assay was applied to various specimen types from patients diagnosed with leptospirosis between 2014 and 2015 in the United Kingdom (UK) and the Lao Peoples Democratic Republic (Lao PDR). Of 44 clinical samples (23 serum, 6 whole blood, 3 buffy coat, 12 urine) PCR positive for pathogenic Leptospira spp. at least one allele was amplified in 22 samples (50%) and used for phylogenetic inference. Full allelic profiles were obtained from ten specimens, representing all sample types (23%). No nonspecific amplicons were observed in any of the samples. Of twelve PCR positive urine specimens three gave full allelic profiles (25%) and two a partial profile. Phylogenetic analysis allowed for species assignment. The predominant species detected was L. interrogans (10/14 and 7/8 from UK and Lao PDR, respectively). All other species were detected in samples from only one country (Lao PDR: L. borgpetersenii [1/8]; UK: L. kirschneri [1/14], L. santarosai [1/14], L. weilii [2/14]).

Conclusion

Typing information of pathogenic Leptospira spp. was obtained directly from a variety of clinical samples using a modified MLST assay. This assay negates the need for time-consuming culture of Leptospira prior to typing and will be of use both in surveillance, as single alleles enable species determination, and outbreaks for the rapid identification of clusters.

Leptospirosis is a zoonotic disease with more than 1 million cases per year globally and epidemics are increasingly reported. In this setting rapid typing is essential to identify potential clusters and transmission pathways. Typing of bacteria commonly requires bacterial isolates but culturing Leptospira is difficult and time consuming and requires invasive samples, such as blood or cerebrospinal fluid. We modified an existing typing scheme to lower the limit of detection and were able to amplify and sequence alleles directly from clinical specimens. Samples included blood (whole blood, serum, or buffy coat) and urine from patients diagnosed by PCR with leptospirosis between 2014 and 2015 in the United Kingdom and the Lao Peoples Democratic Republic. Using the sequences in phylogenetic analysis we identified the predominant Leptospira species in both countries as L. interrogans. With its increased sensitivity the modified assay allows for typing and species determination of Leptospira directly from blood or urine. It will be of use during epidemics and outbreaks for rapid identification of clusters and can support surveillance without the need to culture fastidious isolates.

Leptospira in breast tissue and milk of urban Norway rats (Rattus norvegicus)

Leptospirosis is a zoonosis caused by bacteria of the genus Leptospira. The disease is globally distributed and a major public health concern. The Norway rat (Rattus norvegicus) is the main reservoir of the pathogen in urban slums of developing and developed countries. The potential routes of intra-specific leptospire transmission in rats are largely unknown. Herein, we identified pathogenic Leptospira spp. in breast tissue and milk of naturally infected rats. We examined kidney, breast tissue and milk from 24 lactating rats for the presence of leptospires using immunofluorescence, immunohistochemistry, polymerase chain reaction (PCR) and scanning electronic microscopy. All 24 rats had evidence for Leptospira in the kidneys, indicating chronic carriage. The majority of kidney-positive rats had detectable leptospires in milk (18, 75%) and breast tissue (16, 67%), as evidenced by immunofluorescence assay and immunohistochemistry. Four (17%) milk samples and two (8%) breast tissue samples were positive by quantitative real-time PCR. Scanning electron microscopy confirmed the presence of leptospires in breast tissue. No major pathological changes in breast tissue were found. This study, for the first time, identified leptospires in the milk and breast tissue of wild Norway rats, suggesting the possibility of milk-borne transmission of leptospirosis to neonates.

Comparison of Mucosal, Subcutaneous and Intraperitoneal Routes of Rat Leptospira Infection

Leptospirosis is a zoonosis found worldwide that is caused by a spirochete. The main reservoirs of Leptospira, which presents an asymptomatic infection, are wild rodents, including the brown rat (Rattus norvegicus). Experimental studies of the mechanisms of its renal colonization in rats have previously used an intraperitoneal inoculation route. However, knowledge of rat-rat transmission requires the use of a natural route of inoculation, such as a mucosal or subcutaneous route. We investigated for the first time the effects of subcutaneous and mucosal inoculation routes compared to the reference intraperitoneal route during Leptospira infection in adult rats. Infection characteristics were studied using Leptospira renal isolation, serology, and molecular and histological analyses. Leptospira infection was asymptomatic using each inoculation route, and caused similar antibody production regardless of renal colonization. The observed renal colonization rates were 8 out of 8 rats, 5 out of 8 rats and 1 out of 8 rats for the intraperitoneal, mucosal and subcutaneous inoculation routes, respectively. Thus, among the natural infection routes studied, mucosal inoculation was more efficient for renal colonization associated with urinary excretion than the subcutaneous route and induced a slower-progressing infection than the intraperitoneal route. These results can facilitate understanding of the infection modalities in rats, unlike the epidemiological studies conducted in wild rats. Future studies of other natural inoculation routes in rat models will increase our knowledge of rat-rat disease transmission and allow the investigation of infection kinetics.

Leptospirosis (infection with pathogenic Leptospira spp.) is a public health concern worldwide. The brown rat (Rattus norvegicus), as the most ubiquitous animal of urban wildlife, is potentially the primary source of Leptospira spp. for humans, dogs and livestock. For understanding the Leptospira maintenance in rat colonies, the experimental studies required the use of natural route of transmission between the rats. We investigated the effects of the mucosal and bite’s transmission (conjunctival-mucosal and subcutaneous routes) compared to the reference route (intraperitoneal) during infection in adult rats. With serology, we showed that the antibody production was independent of the inoculation route. By isolation, molecular and histological analyses, we found that the mucosal route was more efficient at renal colonization and leptospires excretion than the subcutaneous route. These results can be useful in understanding the infection modalities in rat that could prevent the human leptospirosis.

Prevalence and Genotype Allocation of Pathogenic Leptospira Species in Small Mammals from Various Habitat Types in Germany

Small mammals serve as most important reservoirs for Leptospira spp., the causative agents of Leptospirosis, which is one of the most neglected and widespread zoonotic diseases worldwide. The knowledge about Leptospira spp. occurring in small mammals from Germany is scarce. Thus, this study's objectives were to investigate the occurrence of Leptospira spp. and the inherent sequence types in small mammals from three different study sites: a forest in southern Germany (site B1); a National Park in south-eastern Germany (site B2) and a renaturalised area, in eastern Germany (site S) where small mammals were captured. DNA was extracted from kidneys of small mammals and tested for Leptospira spp. by real-time PCR. Positive samples were further analysed by duplex and conventional PCRs. For 14 positive samples, multi locus sequence typing (MLST) was performed. Altogether, 1213 small mammals were captured: 216 at site B1, 456 at site B2 and 541 at site S belonging to following species: Sorex (S.) araneus, S. coronatus, Apodemus (A.) flavicollis, Myodes glareolus, Microtus (Mi.) arvalis, Crocidura russula, Arvicola terrestris, A. agrarius, Mustela nivalis, Talpa europaea, and Mi. agrestis. DNA of Leptospira spp. was detected in 6% of all small mammals. At site B1, 25 small mammals (11.6%), at site B2, 15 small mammals (3.3%) and at site S, 33 small mammals (6.1%) were positive for Leptospira spp. Overall, 54 of the positive samples were further determined as L. kirschneri, nine as L. interrogans and four as L. borgpetersenii while five real-time PCR-positive samples could not be further determined by conventional PCR. MLST results revealed focal occurrence of L. interrogans and L. kirschneri sequence type (ST) 117 while L. kirschneri ST 110 was present in small mammals at all three sites. Further, this study provides evidence for a particular host association of L. borgpetersenii to mice of the genus Apodemus.

Patterns in Leptospira Shedding in Norway Rats (Rattus norvegicus) from Brazilian Slum Communities at High Risk of Disease Transmission

BACKGROUND

We address some critical but unknown parameters of individuals and populations of Norway rats (Rattus norvegicus) that influence leptospiral infection, maintenance and spirochetal loads shed in urine, which contaminates the environment ultimately leading to human infection.

METHODOLOGY/PRINCIPAL FINDINGS

Our study, conducted in Salvador, Brazil, established the average load of leptospires in positive kidneys to be 5.9 x 10(6) per mL (range 3.1-8.2 x10(6)) genome equivalents (GEq), similar to the 6.1 x 10(6) per ml (range 2.2-9.4 x10(6)) average obtained from paired urines, with a significant positive correlation (R2=0.78) between the two. Based on bivariate and multivariate modeling, we found with both kidney and urine samples that leptospiral loads increased with the age of rats (based on the index of body length to mass), MAT titer and the presence of wounding/scars, and varied with site of capture. Some associations were modified by sex but trends were apparent. Combining with data on the demographic properties and prevalence of leptospiral carriage in rat populations in Salvador, we estimated that daily leptospiral loads shed in the urine of a population of 82 individuals exceeded 9.1 x 10(10) leptospires.

CONCLUSIONS/SIGNIFICANCE

These factors directly influence the risk of leptospiral acquisition among humans and provide essential epidemiological information linking properties of rat populations with risk of human infection.

Bacteria isolated from conspecific bite wounds in Norway and black rats: implications for rat bite-associated infections in people

Bites associated with wild and domestic Norway and black rats (Rattus norvegicus and Rattus rattus) may have a variety of health consequences in people. Bite-related infections are among the most significant of these consequences; however, there is little data on the infectious agents that can be transmitted from rats to people through biting. This is problematic because without an accurate understanding of bite-related infection risks, it is difficult for health professionals to evaluate the adequacy of existing guidelines for empirical therapy. The objectives of this study were to increase our knowledge of the bacterial species associated with rat bites by studying bite wounds that wild rats inflict upon one another and to review the literature regarding rat bites and bite wound management. Wild Norway and black rats (n=725) were trapped in Vancouver, Canada, and examined for bite wounds in the skin. All apparently infected wounds underwent aerobic and anaerobic culture, and isolated bacteria were identified. Thirty-six rats had bite wound-related infections, and approximately 22 different species of bacteria belonging to 18 genera were identified. Staphylococcus aureus was the most common isolate; however, the majority of infections (72.5%) were polymicrobial. Rat bites can result in infection with a number of aerobic and anaerobic Gram-positive and Gram-negative bacteria. In humans, these wounds are best managed through early recognition and cleansing. The benefit of prophylactic antimicrobial treatment is debatable, but given the deep puncturing nature of rodent bites, we suggest that they should be considered a high risk for infection. Antibiotics selected should include coverage for a broad range of bacterial species.

The first case in Japan of severe human leptospirosis imported from Vietnam

Leptospirosis is a worldwide zoonosis and common in tropical and subtropical areas with high rainfall. It should be noted as an imported infectious disease although it is sporadic in Japan. Some imported cases already have been reported in Japan and these cases occurred mainly in Southeast Asia. The case discussed in this article is the first reported Japanese case infected in Vietnam. Four days after returning back to Japan after a two-week stay in the mountain area near Hue, in the middle part of Vietnam, the patient suddenly experienced chills, a high fever, sore throat, gastrocnemius pain, and headache. Conjunctival jaundice, renal function disorder, and proteinuria were observed on the third day of onset. Significant increase in antibody titers against serovar Australis and Autumnalis strains was observed in paired serum samples by microscopic agglutination test (MAT). Consequently we recognized this case as a diagnosis of severe leptospirosis (Weil’s disease). Finally, renal function disorder did not deteriorate further, and then the patient recovered after the tenth day of onset with the administration of antibiotics and supportive care without sequelae. We experienced the first imported Japanese case of severe human leptospirosis infection from Vietnam that was successfully treated with ceftriaxone and minocycline.

Detection of pathogenic Leptospira spp. through real-time PCR (qPCR) targeting the LipL32 gene

Rapid diagnosis of leptospirosis, through culture and/or serology, can be difficult without proper expertise and is often delayed due to the length of time required to obtain results. Polymerase chain reaction (PCR), more specifically the real-time detection of the amplified PCR product, is a methodology that can provide a diagnosis in a timelier manner compared to culture and serology. There are a limited number of real-time PCR (qPCR) assays for detecting Leptospira and not all of these assays are able to distinguish pathogenic from nonpathogenic species. In addition, there are a variety of probe technologies and qPCR instruments that are utilized with these assays. This chapter presents a qPCR assay that targets lipL32, a gene which is present only in pathogenic Leptospira spp. This assay utilizes a TaqMan probe and instructions for use on either the Lightcycler 1.2 (Roche Diagnostics, Indianapolis, IN) or the ABI 7500 (Applied Biosystems, Foster City, CA) are provided.

Effects of recent Leptospira vaccination on whole blood real-time PCR testing in healthy client-owned dogs

BACKGROUND

Bacterin-based canine Leptospira vaccines could present a challenge for the use of whole blood real-time polymerase chain reaction (PCR) as a diagnostic tool. Recent vaccination could induce positive results if the targeted DNA fragment is present within the vaccine and in the blood of the recently vaccinated dog.

OBJECTIVES

The objective of this study was to assess whether 2 available 4-serovar vaccines induce a positive real-time PCR reaction in the blood of healthy recently vaccinated dogs.

ANIMALS

Twenty healthy dogs.

METHODS

This was a prospective study. Dogs were assigned to 1 of 2 vaccine groups. Both vaccines were culture-based and include Leptospira interrogans serovars Pomona, Canicola, and Icterohaemorrhagiae and Leptospira kirschneri serovar Grippotyphosa. Whole blood for real-time PCR and serum for the microscopic agglutination test (MAT) were collected prior to and 3 and 7 days after vaccination and weekly thereafter for 8 weeks. Two real-time PCR tests targeting 2 different genes were performed independently in a blinded fashion.

RESULTS

Both Leptospira vaccines produced positive real-time PCR reactions when assayed undiluted or diluted 1 : 100 in canine blood. However, blood samples drawn from all dogs at all time points after vaccination were negative on PCR. All dogs developed MAT titers.

CONCLUSIONS AND CLINICAL IMPORTANCE

Recent vaccination with 2 commercially available vaccines does not interfere with the use of real-time PCR for the identification of acute Leptospira infection in dogs.

Use of quantitative real-time PCR for studying the dissemination of Leptospira interrogans in the guinea pig infection model of leptospirosis

The dynamics of leptospirosis infection have been poorly studied. The purpose of this study was to determine the LD50, rate of bacterial dissemination, histopathology and antibody responses against leptospira following inoculation with the highly virulent Leptospira interrogans Fiocruz L1-130 strain in a guinea pig model of leptospirosis. Three routes of infection (intraperitoneal, conjunctival and subcutaneous inoculation) were used to establish disease in guinea pigs. The size and kinetics of leptospiral burdens in the blood and tissues of infected animals were determined over a 1 week course of infection using quantitative real-time PCR (qPCR). Bacteraemia peaked at day 5 post-infection reaching more than 5×104 leptospires ml−1. The highest spirochaetal load was found in the liver and kidneys, and was associated with alterations in organ tissues and a decline in liver and kidney functions. In contrast, lesions and bacteria were not detected in guinea pigs infected with an avirulent strain derived from a high-passage-number in vitro-passaged variant of the Fiocruz L1-130 strain. The use of qPCR supports the findings of earlier studies and provides an easy and reliable method for the quantification of L. interrogans in the tissues of infected animals. qPCR will be used in future studies to evaluate the efficacy of vaccine candidates against leptospirosis and the virulence of selected L. interrogans mutants relative to the parental strain.

Detection of pathogenic Leptospira spp. through TaqMan polymerase chain reaction targeting the LipL32 gene

Rapid diagnosis of leptospirosis, through culture and/or serology, can be difficult without proper expertise and is often delayed because of the length of time required to obtain results. In this study, we developed a real-time polymerase chain reaction (PCR) assay using a TaqMan probe targeting lipL32, which is present only in pathogenic Leptospira spp. Using Leptospira interrogans serovar Icterohaemorrhagiae DNA, the lower limit of detection was found to be 20 genomic equivalents/reaction with a 95% cutoff value. The assay detected pathogenic Leptospira strains, but not intermediately pathogenic or nonpathogenic strains. When testing the assay on spiked clinical specimens, whole blood and plasma were better specimens for detecting the same initial number of leptospires compared with serum from clotted and centrifuged blood. Leptospira spiked at the same concentration was better detected in centrifuged urine. This real-time PCR assay with high specificity and sensitivity may prove to be a rapid method for diagnosing acute leptospirosis.