Leptospira and leptospirosis

Gut microbiota involved in leptospiral infections

Leptospirosis is a re-emerging zoonotic disease worldwide. Intestinal bleeding is a common but neglected symptom in severe leptospirosis. The regulatory mechanism of the gut microbiota on leptospirosis is still unclear. In this study, we found that Leptospira interrogans infection changed the composition of the gut microbiota in mice. Weight loss and an increased leptospiral load in organs were observed in the gut microbiota-depleted mice compared with those in the control mice. Moreover, fecal microbiota transplantation (FMT) to the microbiota-depleted mice reversed these effects. The phagocytosis response and inflammatory response in bone marrow-derived macrophages and thioglycolate-induced peritoneal macrophages were diminished in the microbiota-depleted mice after infection. However, the phagocytosis response and inflammatory response in resident peritoneal macrophage were not affected in the microbiota-depleted mice after infection. The diminished macrophage disappearance reaction (bacterial entry into the peritoneum acutely induced macrophage adherence to form local clots and out of the fluid phase) led to an increased leptospiral load in the peritoneal cavity in the microbiota-depleted mice. In addition, the impaired capacity of macrophages to clear leptospires increased leptospiral dissemination in Leptospira-infected microbiota-depleted mice. Our study identified the microbiota as an endogenous defense against L. interrogans infection. Modulating the structure and function of the gut microbiota may provide new individualized preventative strategies for the control of leptospirosis and related spirochetal infections.

Evaluation of LipL32 and LigA/LigB Knockdown Mutants in Leptospira interrogans Serovar Copenhageni: Impacts to Proteome and Virulence

Leptospirosis is a worldwide zoonosis caused by pathogenic species of the genus Leptospira. The recent application of CRISPR interference (CRISPRi) to Leptospira facilitates targeted gene silencing and provides a new tool to investigate pathogenic mechanisms of leptospirosis. CRISPRi relies on the expression of a catalytically “dead” Cas9 (dCas9) and a single-guide RNA (sgRNA). Previously, our group generated a LipL32 and a double LigA/LigB (LigAB) mutant, which, in the current study, are characterized by whole-cell proteomics in comparison with control leptospires harboring plasmid expressing dCas9 alone. Comparison of control and LigAB mutant leptospires identified 46 significantly differentially expressed (DE) proteins, including 27 proteins that were less abundant and 19 proteins that were more abundant in the LigAB mutant compared with the control. Comparison of the control and LipL32 mutant leptospires identified 243 DE proteins, of which 84 proteins were more abundant and 159 were less abundant in the LipL32 mutant strain. Significantly increased amounts of known virulence impactors and surface membrane receptors, including LipL45, LipL31, LigB, and LipL41, were identified. The virulence of LipL32 and LigAB mutants were evaluated in the hamster model of leptospirosis; the LigAB mutant was unable to cause acute disease although mutant leptospires could still be recovered from target organs, albeit at a significantly lower bacterial burden (<850 and <16-fold in liver and kidney, respectively, in comparison with control), indicating attenuation of virulence and a shift to chronic bacterial persistence. Notably, the LipL32 mutant displayed augmented virulence as evidenced by early onset of clinical symptoms and increased numbers of circulating foamy macrophages. Validation of LipL32 and LigAB mutants recovered from liver and kidney in the presence or absence of antibiotic selection revealed high plasmid stability and, by extension, gene silencing in vivo. Collectively, this work emphasizes the advantages and feasibility of using CRISPRi technology to evaluate and characterize virulence factors of leptospires and their respective host–pathogen interactions in animal models of leptospirosis. Importantly, it also provides insight into the requirements of LigA and LigB for acute disease and explores the impact of silencing expression of lipL32, which resulted in substantial changes in amounts of outer membrane proteins.

A lethal model of Leptospira infection in hamster nasal mucosa

Leptospirosis is a fatal zoonosis caused by contact between skin or a mucosal surface and contaminated soil or water. Hamsters were infected by intraperitoneal injection fto establish experimental leptospirosis, which is not a natural route of infection. There are no reports of nasal mucosal infection in hamsters. In this study, infection of the nasal mucosa was performed to establish a model of natural infection. Both methods of infection can cause lethal models with similar symptoms in the later stages of infection, such as weight loss, blood concentration, increased neutrophils (GRAN), and decreased lymphocytes (LYM) in the blood, severe organ damage and liver function obstruction. The burden of Leptospira in the organs and blood was lower in the mucosal inoculation groups at 1 day after infection. However, mucosal infection induced a higher Leptospira burden in urine than intraperitoneal infection in the late stages of infection. After nasal mucosal infection, antibody levels were higher and lasted longer. These results indicated that the route of nasal mucosal infection is a good choice for studying leptospirosis in hamsters.

The establishment of a leptospirosis experimental model is still key to elucidating the pathogenesis of leptospirosis. Hamsters were infected by intraperitoneal injection to establish experimental leptospirosis, although this is not a natural route of infection. The transmission characteristics of Leptospira and the disease progression in hamsters infected by a natural transmission route (e.g. through mucosal surfaces) had not been explored. In this study, we compared the dynamics of Leptospira infection in hamsters inoculated via the nasal mucosa or by intraperitoneal inoculation, and compared the burden of Leptospira and the level of antibodies produced with disease progression, such as body weight, serology, haematological changes and histopathological changes. Our data suggested that there are significant differences in the dynamics of infection between intraperitoneal and mucosal infection pathways. Although the result was the same in the later stage of infection, the course of mucosal infection was slower, which may better recapitulate the natural history of the disease, assist in studying kidney disease caused by Leptospira, and provide an animal model for the study of leptospirosis mucosal immunity.

The role of small ruminants in the epidemiology of leptospirosis

Leptospirosis is a common global zoonotic disease of man and all farm animals. Although most leptospiral infections in sheep and goats are asymptomatic, they may play a role in the epidemiology of the disease by the spread of Leptospira through the urine. This study was carried out to evaluate the role of sheep and goats in the epidemiology of leptospirosis. Blood and urine samples were taken from 210 goats and 246 sheep. To detect antibodies, sera samples were tested with 8 live serovars of L. interrogans (Hardjo, Pomona, Grippotyphosa, Canicola, Ballum, Icterhemorrhagiae, Tarasovi, and Australis) by MAT. Then, urine samples were tested by Nested PCR targeting 16S rRNA gene for detection of pathogenic Leptospira. Results of MAT showed that 10.95% of goats and 8.53% of sheep had antibodies against at least one examined serovars. In both species, the highest reacting was L. i. Pomona with a rate of 68.18% and 56% in sheep and goats, respectively. Moreover, in PCR, 2 (0.95%) urine samples of goat and 12 (4.87%) urine samples of sheep were positive. All of the MAT positive studied animals were PCR negative and, statistical analysis showed that there was no relationship and agreement between the results of PCR and MAT in sheep (kappa = − 0.07, p > 0.05) and goats (kappa = − 0.02, p > 0.05). Finally, it is concluded that sheep and goats can excrete L. interrogans in the urine and thus transmit them to other animals and humans.

Motility of the Zoonotic Spirochete Leptospira: Insight into Association with Pathogenicity

If a bacterium has motility, it will use the ability to survive and thrive. For many pathogenic species, their motilities are a crucial virulence factor. The form of motility varies among the species. Some use flagella for swimming in liquid, and others use the cell-surface machinery to move over solid surfaces. Spirochetes are distinguished from other bacterial species by their helical or flat wave morphology and periplasmic flagella (PFs). It is believed that the rotation of PFs beneath the outer membrane causes transformation or rolling of the cell body, propelling the spirochetes. Interestingly, some spirochetal species exhibit motility both in liquid and over surfaces, but it is not fully unveiled how the spirochete pathogenicity involves such amphibious motility. This review focuses on the causative agent of zoonosis leptospirosis and discusses the significance of their motility in liquid and on surfaces, called crawling, as a virulence factor.

Integrated Lateral Flow Electrochemical Strip for Leptospirosis Diagnosis

LipL32 is an outer membrane protein present only on pathogenic Leptospira species, which is the causative agent of leptospirosis. Leptospirosis symptoms are often misdiagnosed with other febrile illnesses as the clinical manifestations are non-specific. Therefore, an accurate diagnostic tool for leptospirosis is indeed critical for proper and prompt treatment. Typical diagnosis via serological assays is generally performed to assess the antibodies produced against Leptospira. However, their delayed antibody response and complicated procedure undoubtedly limit the practical utilization especially in a primary care setting. Here, we demonstrate for the first time an early-stage detection of LipL32 by an integrated lateral-flow immunoassay with an electrochemical readout (eLFIA). A ferrocene trace tag was monitored via differential pulse voltammetry operated on a smartphone-based device, thus allowing for on-field testing. A superior performance in terms of the lowest detectable limit of detection of 8.53 pg/mL and broad linear dynamic range (5 orders of magnitude) among other sensors available thus far was established. Additionally, the developed test strip provided a straightforward yet sensitive approach for diagnosis of leptospirosis using the collected human sera from patients, in which the results were comparable to the real-time polymerase chain reaction technique.

Revisiting the Development of Vaccines Against Pathogenic Leptospira: Innovative Approaches, Present Challenges, and Future Perspectives

Human vaccination against leptospirosis has been relatively unsuccessful in clinical applications despite an expressive amount of vaccine candidates has been tested over years of research. Pathogenic Leptospira encompass a great number of serovars, most of which do not cross-react, and there has been a lack of genetic tools for many years. These obstacles have hampered the understanding of the bacteria's biology and, consequently, the identification of an effective antigen. Thus far, many approaches have been used in an attempt to find a cost-effective and broad-spectrum protective antigen(s) against the disease. In this extensive review, we discuss several strategies that have been used to develop an effective vaccine against leptospirosis, starting with Leptospira-inactivated bacterin, proteins identified in the genome sequences of pathogenic Leptospira, including reverse vaccinology, plasmid DNA, live vaccines, chimeric multi-epitope, and toll- and nod-like receptors agonists. This overview should be able to guide scientists working in the field to select potential antigens and to choose the appropriate formulation to administer the candidates.

Galleria mellonella infection model to evaluate pathogenic and nonpathogenic Leptospira strains

The Galleria mellonella larvae infection model is emerging as a valuable tool for studying various characteristics of infectious agents and host-pathogen interaction. This system has been widely recognized as a high throughput, ethical, and cost-effective invertebrate infection model to study the virulence and pathogenesis of various bacterial pathogens. In this study, we compared the effect of Leptospira infection in G. mellonella larvae infected with Leptospira interrogans serovar Copenhageni (pathogenic) or Leptospira biflexa serovar Patoc (saprophytic) strains. We observed significant pathologic changes such as decreased activity, complete melanization, and lower survival rate in the G. mellonella larvae infected with a pathogenic strain L. interrogans serovar Copenhageni compared to those infected with a nonpathogenic strain L. biflexa serovar Patoc. Our study demonstrates the feasibility and the potential of using G. mellonella larvae as an alternative model to study virulence mechanisms and pathogenesis of Leptospira strains. Once optimized, the G. mellonella infection model can be a potential substitute for hamsters to explore various host and pathogen-related mechanistic events in Leptospira infection.

Development of Human Recombinant Leptospirosis Vaccines

Leptospirosis is a bacterial zoonotic disease with significant impact on health all over the world. Currently, bacterins are the only vaccines available for prevention of this disease, despite several drawbacks. In an effort to develop a more effective vaccine against leptospirosis, reverse and structural vaccinology have been applied to design recombinant constructions composed of leptospiral surface-exposed antigens. Herein, we describe a protocol for design and development of Leptospirosis recombinant vaccines using immunoinformatic approaches.

A serological survey of canine leptospirosis in the city of Belgrade, Serbia

Canine leptospirosis is a zoonosis caused by bacteria belonging to the genus Leptospira. Dogs are one of the animal species involved in the cycle of preservation and transmission of leptospirosis in urban areas. Serological testing for the presence of specific antibodies against Leptospira spp. in dogs was continuously performed between 2010 and 2020 in the city of Belgrade. At the request of the owners themselves, other veterinary laboratories or laboratory clinics, 179 blood sera from 179 dogs were examined in the Laboratory for Immunology, Scientific Institute of Veterinary Medicine of Serbia. Blood sera samples from dogs were examined using the standard microscopic agglutination test (MAT) for the presence of specific antibodies against seven different serovars of Leptospira: Pomona, Icterohaemorrhagiae, Grippotyphosa, Sejroe, Canicola, Bataviae, and Australis. The number of seropositive dogs was 17/179 (9.5%). Among all examined sera, the highest titre of seropositive samples was to serovar Icterohaemorrhagiae (10/17, 58.8%), followed by Pomona (4/17, 23.5%), and serovar Canicola (3/17, 17.6%). Specific antibodies for serovars Grippotyphosa, Sejroe, Bataviae and Australis were not detected in any of the dog sera. Cross-reaction (the presence of two or three titres with different values where one of them was higher than others) between different serovars was diagnosed in a low number of sera (n=4), with the following serovars: Icterohaemorrhagiae and Pomona (n=3) and Pomona and Canicola (n=1). The confirmed specific antibody titres for Leptospira spp. were between 1:100 to 1:3000 (5 sera had titres of 1:100, 7 had titres of 1:300, 4 had titres of 1:1000, and 1 serum had a titre 1:3000). Monitoring canine leptospirosis is a useful tool in preventing leptospirosis in Belgrade.

The association between natural drinking water sources and the emergence of zoonotic leptospirosis among grazing beef cattle herds during a human outbreak

Leptospirosis is a zoonotic bacterial disease associated with water abundance in tropical and temperate climate zones. Bacterial spread may also occur in dry and warm weather conditions when humans and animals are forced to share depleted water sources. In such settings, farm animals such as beef cattle, which may be present in large numbers in natural water sources, can play a major role in disease spread. However, the risk factors for their infection and the potential control measures to prevent the disease spread have not been adequately studied.

In the face of an emerging human leptospirosis outbreak in the dry and warm Israeli 2018 summer, we tested seropositivity to Leptospira serovar Pomona in grazing beef cattle and wild boars located in proximity to the contaminated streams. Additionally, we used the natural setting of the outbreak to identify risk factors for seropositivity in beef cattle.

We found high seropositivity to serovar Pomona in grazing beef cattle (233/845), and in wild boars (7/13). Seropositivity was significantly associated with beef cattle drinking from natural water sources compared to beef cattle drinking from water troughs with fresh water supply (Multivariable logistic regression; odds ratio = 18.6, 95% confidence interval = 3–116, p-value<0.01).

One Health approach is necessary for mitigating zoonotic Leptospira infections, in which interactions between humans, animals, and the environment play a major role. As the global warming crisis results in severe climate changes, dry and warm weather conditions may become more common worldwide. Under such conditions, reducing inter-species interactions in contaminated natural water sources is essential for protecting public health. Our study demonstrates the role of natural water as a source for beef cattle infection and disease spread. Furthermore, we suggest using water troughs with freshwater supply for preventing future outbreaks in animals and humans in such settings.

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Leptospirosis spread through depleted water sources shared by humans and animals

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Dry and warm weather may become more common due to global warming crisis

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During human outbreak, high seropositivity was found in beef cattle and wild boars

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Drinking sources were significantly associated with seropositivity in beef cattle

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Using water troughs with freshwater supply may prevent future outbreaks

Immunoinformatics-Based Designing of a Multi-Epitope Chimeric Vaccine From Multi-Domain Outer Surface Antigens of Leptospira

Accurate information on antigenic epitopes within a multi-domain antigen would provide insights into vaccine design and immunotherapy. The multi-domain outer surface Leptospira immunoglobulin-like (Lig) proteins LigA and LigB, consisting of 12–13 homologous bacterial Ig (Big)-like domains, are potential antigens of Leptospira interrogans. Currently, no effective vaccine is available against pathogenic Leptospira. Both the humoral immunity and cell-mediated immunity of the host play critical roles in defending against Leptospira infection. Here, we used immunoinformatics approaches to evaluate antigenic B-cell lymphocyte (BCL) and cytotoxic T-lymphocyte (CTL) epitopes from Lig proteins. Based on certain crucial parameters, potential epitopes that can stimulate both types of adaptive immune responses were selected to design a chimeric vaccine construct. Additionally, an adjuvant, the mycobacterial heparin-binding hemagglutinin adhesin (HBHA), was incorporated into the final multi-epitope vaccine construct with a suitable linker. The final construct was further scored for its antigenicity, allergenicity, and physicochemical parameters. A three-dimensional (3D) modeled construct of the vaccine was implied to interact with Toll-like receptor 4 (TLR4) using molecular docking. The stability of the vaccine construct with TLR4 was predicted with molecular dynamics simulation. Our results demonstrate the application of immunoinformatics and structure biology strategies to develop an epitope-specific chimeric vaccine from multi-domain proteins. The current findings will be useful for future experimental validation to ratify the immunogenicity of the chimera.

A Review on Host-Leptospira Interactions: What We Know and Future Expectations

Leptospirosis is a widespread zoonosis caused by pathogenic Leptospira spp. It is considered a neglected infectious disease of human and veterinary concern. Our group has been investigating proteins annotated as hypothetical, predicted to be located on the leptospiral surface. Because of their location, these proteins may have the ability to interact with various host components, which could allow establishment of the infection. These proteins act as adherence factors by binding to host receptor molecules, such as the extracellular matrix (ECM) components laminin and glycosaminoglycans to help bacterial colonization. Leptospira also interacts with the host fibrinolytic system, which has been demonstrated to be a powerful tool for invasion mechanisms. The interaction with fibrinogen and thrombin has been shown to reduce fibrin clot formation. Additionally, the degradation of coagulation cascade components by secreted proteases or by acquired surface plasmin could also play a role in reducing clot formation, hence facilitating dissemination during infection. Interaction with host complement system regulators also plays a role in helping bacteria to evade the immune system, facilitating invasion. Interaction of Leptospira to cell receptors, such as cadherins, can contribute to investigate molecules that participate in virulence. To achieve a better understanding of the host-pathogen interaction, leptospiral mutagenesis tools have been developed and explored. This work presents several proteins that mediate binding to components of the ECM, plasma, components of the complement system and cells, to gather research achievements that can be helpful in better understanding the mechanisms of leptospiral-host interactions and discuss genetic manipulation for Leptospira spp. aimed at protein function validation.

IL-10 deficiency protects hamsters from Leptospira infection

Leptospirosis is a globally spread zoonotic disease with outcomes ranging from subclinical infection to fatal Weil syndrome. In addition to antibiotics, some immune activators have shown protective effects against leptospirosis. However, the unclear relationship between Leptospira and cytokines, has limited the development of antileptospiral immunomodulators. In this study, the particular role of IL-10 in leptospirosis was explored by using IL-10 defective (IL-10^-/-) hamsters. After Leptospira infection, an improved survival rate, reduced leptospiral burden and alleviation of organ lesions were found in IL-10^-/- hamsters compared with WT hamsters. In addition, the gene expression levels of IL-1β, IL-6 and TNF-α and the NO level were higher in IL-10^-/- hamsters than in WT hamsters. Our results indicate that IL-10 deficiency protects hamsters from Leptospira infection.

Seroprevalence and risk factors for Leptospira spp. in small ruminants of semi-arid zone in northeastern Colombia

Leptospirosis in small ruminants is an economically important disease that causes important losses by pathologies of the reproductive tract. The present study aimed to estimate the seroprevalence and risk factors associated with Leptospira spp. in small ruminants under traditional husbandry systems. A cross-sectional epidemiological study was carried out in a sample of 1039 animals which included 793 sheep and 245 goats from 49 farms of 10 municipalities of northeastern areas of Colombia. The MAT test using a panel of 13 laboratory serovars was performed to diagnose the Leptospira spp. antibodies in the serum samples of animals. A structured questionnaire was filled in each farm to obtain information on putative risk factors, and its association with Leptospira spp. infection was detected by univariate and multivariate logistic regression. The general seroprevalence showed a rate of 13.9%, the 79.6% of farms showed at least one positive animal, the 14.2% and 0.4% of positive animals showed titers ≥ 1:100 and 1:200, respectively. The seroprevalence in sheep and goats showed a rate of 13.1% and 16.2%, respectively. The most common serovars in positive animals were Autumnalis (3.6%), Tarassovi (3.4%), Bratislava (2.9%), Mini (2.9%), Bataviae (1.4%), Canicola (0.3%), and Grippotyphosa (0.3%). The univariate and multivariate analysis showed as risk factors the absence of housing system (OR = 3.412 CI: 1.347-8.152), the absence of quarantine measures to new animals (OR = 1.371 CI: 0.943-1.978), and the protective factor identified was the use of Toggenburg breed (OR = 0.571 CI: 0.249-1.074). This exploratory study showed the Leptospira spp. positive small ruminants located in the northeastern areas of Colombia with titer associated with chronic and subclinical infection.

The FUR-like regulators PerRA and PerRB integrate a complex regulatory network that promotes mammalian host-adaptation and virulence of Leptospira interrogans

Leptospira interrogans, the causative agent of most cases of human leptospirosis, must respond to myriad environmental signals during its free-living and pathogenic lifestyles. Previously, we compared L. interrogans cultivated in vitro and in vivo using a dialysis membrane chamber (DMC) peritoneal implant model. From these studies emerged the importance of genes encoding the Peroxide responsive regulators PerRA and PerRB. First described in in Bacillus subtilis, PerRs are widespread in Gram-negative and -positive bacteria, where regulate the expression of gene products involved in detoxification of reactive oxygen species and virulence. Using perRA and perRB single and double mutants, we establish that L. interrogans requires at least one functional PerR for infectivity and renal colonization in a reservoir host. Our finding that the perRA/B double mutant survives at wild-type levels in DMCs is noteworthy as it demonstrates that the loss of virulence is not due to a metabolic lesion (i.e., metal starvation) but instead reflects dysregulation of virulence-related gene products. Comparative RNA-Seq analyses of perRA, perRB and perRA/B mutants cultivated within DMCs identified 106 genes that are dysregulated in the double mutant, including ligA, ligB and lvrA/B sensory histidine kinases. Decreased expression of LigA and LigB in the perRA/B mutant was not due to loss of LvrAB signaling. The majority of genes in the perRA and perRB single and double mutant DMC regulons were differentially expressed only in vivo, highlighting the importance of host signals for regulating gene expression in L. interrogans. Importantly, the PerRA, PerRB and PerRA/B DMC regulons each contain multiple genes related to environmental sensing and/or transcriptional regulation. Collectively, our data suggest that PerRA and PerRB are part of a complex regulatory network that promotes host adaptation by L. interrogans within mammals.

Molecular detection and characterization of pathogenic Leptospira species in bats (Chiroptera) roosting in human habitats in Nigeria, West Africa

Leptospirosis is a neglected zoonosis with a nearly global distribution. In order to determine the role of bats in the epidemiology of leptospirosis in Nigeria, a total of 231 bats belonging to three families, Pteropodidae (n = 117), Molossidae (n = 107) and Nycteridae (n = 17), roosting in human habitats were screened by PCR and sequencing for the detection of pathogenic Leptospira species. DNA extracted from the kidneys of bats were subjected to conventional PCR targeting the rrs1, rrs2, flaB and secY genes for the detection of pathogenic Leptospira spp. Overall, 27 out of the 231 (11.7%) of the samples screened were positive for Leptospira spp. High prevalence (>80%) of Leptospira spp. DNA was detected in Chaerophon and Nycteris bat species captures in an abandoned well located within a human habitation. Sequences generated in this study were highly identical to Leptospira borgpetersenii and Leptospira interrogans and clustered with sequences of pathogenic species in GenBank. The detection of pathogenic Leptospira spp. was significantly associated (p < .001) with the bat species, feeding habit, roosting site and study location. To the best of our knowledge, this is the first molecular detection and characterization of pathogenic Leptospira spp. in bats from Nigeria. Results show that bats in Nigeria are infected with diverse Leptospira genotypes phylogenetically related to known pathogenic, including zoonotic taxa. Together, these findings reinforce bats' roles as potential reservoirs of Leptospira spp. and should be considered as a starting point for future comparative studies to improve our understanding of the epidemiology of this bacterial pathogen in Nigeria.

Pituitary apoplexy and panhypopituitarism following acute leptospirosis

Leptospirosis is a common tropical febrile illness which may manifest with the hepatorenal syndrome and systemic hemorrhagic manifestations. Pituitary apoplexy is a rare but life-threatening condition characterized by a hemorrhage within the pituitary gland or a pituitary adenoma. Apoplexy is very rarely associated with some inducing events such as infectious diseases such as dengue hemorrhagic fever, Hantaan virus, Puumala virus have also been reported to cause pituitary apoplexy. We present the first case of pituitary apoplexy in a patient who was being treated for leptospirosis and discuss the possible mechanisms of apoplexy in the scenario presented. We also review other reports of infectious causes that may result in pituitary apoplexy.

Risk and Predictive Factors of Leptospirosis in Dogs Diagnosed with Kidney and/or Liver Disease in Selangor, Malaysia

Simple Summary

Canine leptospirosis is commonly associated with kidney and/or liver disease. The current study identified the potential risk and predictive factors of dogs diagnosed with kidney and/or liver disease due to leptospirosis. A total of 124 client-owned dogs were recruited and the samples collected were directly tested using polymerase chain reaction (PCR) and subsequently inoculated for bacterial isolation. Statistical analyses were descriptively analyzed, and risk analyses were performed using Pearson chi-square tests and logistic regression. The different breeds of dog with history of exposure to rats and those managed outdoors had a greater risk of leptospirosis (p < 0.05). The significant predictors for the dogs’ positivity were presence of rats and acute clinical illness (p < 0.05). Administration of antibiotics and detection of clinical illness at an early stage of the disease improved the survivability of the dogs (p < 0.05).

Abstract

Canine leptospirosis is commonly associated with kidney and/or liver disease. It has been widely reported and causes public health concerns due to its zoonotic potential and its re-emergence, resulting from close contact between humans and dogs. The current study identified potential risk and predictive factors for dogs diagnosed with kidney and/or liver disease due to leptospirosis. A total of 124 client-owned dogs were recruited, and information such as signalment, medical history, management, and clinical findings were documented. Samples collected from the recruited dogs were directly tested using polymerase chain reaction (PCR) and subsequently inoculated for bacterial isolation. Statistical analyses were descriptively analyzed, and risk analyses were performed using Pearson chi-square tests and logistic regression. A total of 53 dogs (42.7%) were positive for leptospiral infection based on PCR, and 10 leptospiral isolates were successfully recovered from eight dogs. The mortality rate of infected dogs was 34.0% (18/53). Medium and large dog breeds, with a history of exposure to rats, and managed outdoors had a greater risk for leptospirosis (p < 0.05). The significant predictors for the dogs’ positivity were the presence of rats and acute clinical illness (p < 0.05). Administration of antibiotics and the detection of clinical illness at an early stage of the disease improved the survivability of the dogs (p < 0.05). Identifying the profile of dogs that are at risk to leptospirosis could be useful in the design of diagnostic and treatment strategies, as well as to increase awareness for prevention of the disease.

Microorganisms associated with the North African hedgehog Atelerix algirus and its parasitizing arthropods in Algeria

Hedgehogs are small mammals. They are potential reservoirs of various zoonotic agents. This study was conducted in Bouira, a north-central region of Algeria. A total of 21 Atelerix algirus corpses were picked up on roadsides and gardens. Hedgehog kidneys, spleens and ectoparasites were collected. Twelve hedgehogs were infested with ectoparasites, including Archaeopsylla erinacei, Rhipicephalus sanguineus s.l. and Haemaphysalis erinacei. Hedgehog organs and randomly selected arthropods were screened for microorganisms using molecular methods. Coxiella burnetii was detected in kidneys, spleens, A. erinacei, Hae. erinacei and Rh. sanguineus s.l. Leptospira interrogans was detected in kidneys. Rickettsia felis and Rickettsia massiliae were detected respectively in A. erinacei and in Rh. sanguineus s.l. DNA of an uncultivated Rickettsia spp. was found in Hae. erinacei. Wolbachia spp. DNA was detected in fleas. The DNA of potential new Bartonella and Ehrlichia species were found respectively in fleas and ticks. This study highlights the presence of DNA from a broad range of microorganisms in hedgehogs and their ectoparasites that may be responsible for zoonoses in Algeria.

Serologic titers to Leptospira in vaccinated pigs and interpretation for surveillance

Diagnosis and surveillance of pathogenic Leptospira is difficult as organisms may be intermittently shed and in small numbers. Therefore, serologic testing by the microscopic agglutination test (MAT) is the primary screening method for leptospirosis. While a MAT titer ≥1:100 is considered to be a positive result, interpretation is complicated by the use of commercial vaccines in pigs. Most guidelines for interpretation of MAT titers in pigs were published in the 1970’s and 1980’s, prior to the development of the current multivalent vaccines. We evaluated MAT titers in routinely vaccinated healthy research pigs compared to their unvaccinated cohorts. Our study confirmed previous reports that the Pomona serovar elicits minimal antibody response even after a second booster 6 months after initial vaccination. However, MAT titers of ≥1:3,200 were detected as early as 4 weeks post initial vaccination for serovars Bratislava and Icterohaemorrhagiae and remained as high as ≥1:1,600 prior to booster at 24 weeks post vaccination. Our study determined that high levels of MAT titers can occur from vaccination alone and high titers are not necessarily indicative of infection. Therefore, the interpretation of MAT titers as indicators of Leptospira infection should be readdressed.

The viability of Leptospira is related to physicochemical properties of the surface water surrounding an agricultural area and HemO and LipL32 gene expression in response to iron in water

BACKGROUND

The pathogenic Leptospira can survive and contaminate surface water based on physicochemical factors. This study aimed to determine how the physicochemical properties of water sources influence the growth and effect of iron on the gene expression of Leptospira spp. P47.

METHODS

Surface water samples (n=55) were collected and used for Leptospira spp. P47 cultivation. Physicochemical factors, including iron, calcium, magnesium and pH, were analyzed. The association between Leptospira spp. P47 viability at days 5, 10 and 15 with the physicochemical factors were analyzed. In addition, this bacterium was cultured in six selected water samples. The effect of iron in water on HemO and LipL32 gene expression was determined by relative quantification real-time PCR.

RESULTS

Leptospira viability at day 5 was not significantly correlated with physicochemical factors, while Leptospira viability at day 10 was associated with both pH and iron. The Leptospira viability rate at day 15 had a significantly positive association with pH and iron and a negative association with calcium. HemO expression was significantly increased, mostly in selected water samples and under iron-depleted conditions. Conversely, LipL32 expression was significantly decreased in all water samples.

CONCLUSIONS

Physicochemical factors in natural surface waters are key factors for bacterial survival in the environment, which may increase the chance of Leptospira infection in humans.

Cross-sectional survey for sheep leptospirosis in the northeast region of Brazil

Sheep farming has shown expressive growth, even in the Northeast region of Brazil, with rainfall below expectations in the last decade. This growth has been observed not only in the number of herds, but also in the number of properties involved in sheep farming. Although expressive, the production of small ruminants still presents low levels of performance, mainly due to the occurrence of diseases, which constitute an obstacle to this activity. The aim of this study was to determine the factors associated with the seroprevalence of leptospirosis in sheep in Northeastern Brazil. Blood samples were collected from 3438 sheep in 190 herds from 48 municipalities, belonging to the states of Ceará, Paraíba, Piauí, Rio Grande do Norte and Sergipe. Serological diagnosis was performed using the microscopic agglutination test (MAT). In 76.3 % (95 % CI = 69.79-81.81) of the herds there was at least one animal seropositive for at least one of the Leptospira spp. serogroups and 14.94 % (95 %CI = 13.8-16.18) of the animals were seropositive. The state of Paraíba had the highest herd (95.7 %) and animal (26.6 %) prevalences, followed by Ceará (93.9 % and 23.7 %, respectively). The most frequent serogroups were Autumnalis (18.68 %), Australis (17.9 %) and Pyrogenes (15.18 %). There was no association between the studied variables and the herd-level prevalence of leptospirosis. High herd and animal-level seroprevalences was found for sheep leptospirosis in the semiarid region of Northeastern Brazil, and there is a need to implement control and prevention measures, such as quarantine, serology, vaccination and adequate treatment, in addition to the introduction of proven healthy animals, mainly in the states of Paraíba and Ceará, aiming to reduce the prevalence of disease.

Pathogens with potential impact on reproduction in captive and free-ranging European bison (Bison bonasus) in Poland - a serological survey

BACKGROUND

The European bison is an endangered species, and as such it is extremely important to monitor herds for pathogens which can lead to reproductive failure. The aim of the present study was to determine the current prevalence of antibodies to pathogens known to potentially influence reproduction in European bison. Serum samples from 183 bison, originating from different parts of Poland, were tested using commercial ELISA tests for antibodies to Chlamydia spp., Coxiella burnetti, Leptospira interrogans, Neospora caninum and Toxoplasma gondii; the findings were compared between captive and main free-ranging herds, and with regard to the influence of demographic factors such as age and sex. The prevalence of seropositivity was also checked with regard to location and the animal species sharing it.

RESULTS

Chlamydia spp. antibodies were present in 48 out of 130 (36.9%) tested samples. Coxiella burnetii was found in one sample out of 178 (0.58%). N. caninum in 36 out of 172 (20.9%) and T. gondii in 23 out of 172 (13.4%). No sample was positive for leptospirosis. Neither sex nor age appeared to have a significant effect on the occurrence of antibodies to the identified species. The prevalence of Chlamydia spp. in the samples varied significantly according to location; however, similar frequency ranges were observed between free ranging and captive herds. In contrast, antibodies to N. caninum were more common in free-ranging herds than captive herds, with the highest frequency observed in the Bieszczady Mountains.

CONCLUSIONS

Chlamydia spp., N. caninum and T. gondii might have a similar impact on the reproductive potential of European bison as they have on cattle. The high occurrence of antibodies to N. caninum in bison from the Bieszczady Mountains may be associated with the relatively high density of the wolf population in the area.

Pathogenic Leptospira spp. Seroprevalence and Herd-Level Risk Factors Associated with Chilean Dairy Cattle

Leptospirosis is a ubiquitous distributed zoonotic infectious disease present in wild and domestic animals. This study aimed to estimate within-herd and herd-level seroprevalence against pathogenic Leptospira spp. in dairy cows from southern Chile and identify risk factors associated with the herd-level status. We used a multi-stage strategy combined with a stratified sample strategy for randomly sampling 147 herds and 4876 lactating cows. We considered as infected a herd with at least one positive reactor to MAT. In addition, an epidemiological survey was applied to the herd's owners and a logistic regression (LR) model was constructed to analyze it. The overall within-herd prevalence was 5.9% (95% CI 4.9-6.8), the overall herd-level prevalence was 42.2% (95% CI 9.2-47.9), and there was variation in both between different herd sizes. L.&nbsp;borgpetersenii serovars Hardjo and Tarassovi and L. interrogans serovar Pomona were the more frequent serovars in non-vaccinated herds. A factor that decreases the risk of a farm being infected was Leptospira vaccine usage (OR = 0.04; 95% CI = 0.02-0.11), and variables that increase risk were using bulls for mating (OR = 3.43; 95% CI = 1.1-10.1) and continuous calving distribution (OR = 3.4; 95% CI = 1.3-8.8). The study's results will contribute to unravelling the infection burden in the main dairy area of the country and designing control strategies.

Surface proteomics and label-free quantification of Leptospira interrogans serovar Pomona

Leptospirosis is a re-emerging zoonosis with a global distribution. Surface-exposed outer membrane proteins (SE-OMPs) are crucial for bacterial-host interactions. SE-OMPs locate and expose their epitope on cell surface where is easily accessed by host molecules. This study aimed to screen for surface-exposed proteins and their abundance profile of pathogenic Leptospira interrogans serovar Pomona. Two complementary approaches, surface biotinylation and surface proteolytic shaving, followed by liquid chromatography tandem-mass spectrometry (LC-MS/MS) were employed to identify SE-OMPs of intact leptospires. For quantitative comparison, in-depth label-free analysis of SE-OMPs obtained from each method was performed using MaxQuant. The total number of proteins identified was 1,001 and 238 for surface biotinylation and proteinase K shaving, respectively. Among these, 39 were previously known SE-OMPs and 68 were predicted to be localized on the leptospiral surface. Based on MaxQuant analysis for relative quantification, six known SE-OMPs including EF- Tu, LipL21, LipL41, LipL46, Loa22, and OmpL36, and one predicted SE-OMPs, LipL71 were found in the 20 most abundant proteins, in which LipL41 was the highest abundant SE-OMP. Moreover, uncharacterized LIC14011 protein (LIP3228 ortholog in serovar Pomona) was identified as a novel predicted surface βb-OMP. High-abundance leptospiral SE-OMPs identified in this study may play roles in virulence and infection and are potential targets for development of vaccine or diagnostic tests for leptospirosis.

SEROSURVEY FOR SELECTED PARASITIC AND BACTERIAL PATHOGENS IN DARWIN'S FOX (LYCALOPEX FULVIPES): NOT ONLY DOG DISEASES ARE A THREAT

The Darwin's fox (Lycalopex fulvipes) is one of the most endangered carnivores worldwide, with the risk of disease spillover from domestic dogs being a major conservation threat. However, lack of epidemiologic information about generalist, non-dog-transmission-dependent protozoal and bacterial pathogens may be a barrier for disease prevention and management. To determine the exposure of some of these agents in Darwin's fox populations, 54 serum samples were collected from 47 Darwin's foxes in Southern Chile during 2013-18 and assessed for the presence of antibodies against Brucella abortus, Brucella canis, Coxiella burnetii, pathogenic Leptospira (serovars Grippotyphosa, Pomona, Canicola, Hardjo, and Copehageni), Toxoplasma gondii, and Neospora caninum. The highest seroprevalence was detected for T. gondii (78%), followed by pathogenic Leptospira (14%). All the studied Leptospira serovars were confirmed in at least one animal. Two foxes seroconverted to Leptospira and one to T. gondii during the study period. No seroconversions were observed for the other pathogens. No risk factors, either intrinsic (sex, age) or extrinsic (season, year, and degree of landscape anthropization), were associated with the probability of being exposed to T. gondii. Our results indicate that T. gondii exposure is widespread in the Darwin's fox population, including in areas with minimal anthropization, and that T. gondii and pathogenic Leptospira might be neglected threats to the species. Further studies identifying the causes of morbidity and mortality in Darwin's fox are needed to determine if these or other pathogens are having individual or population-wide effects in this species.

Seroprevalence of Leptospira among Selected Mammals on a Wildlife Management Area in Louisiana, USA

From August to December 2018, we collected blood samples from 98 individuals of 11 mammal species to examine seroprevalence of leptospirosis at the Sherburne Wildlife Management Area in central Louisiana, USA. Overall, 21.4% of individuals tested positive for antibodies of at least one Leptospira interrogans serovar and six individuals were reactive for two or more serovars. The most prevalent serovar we detected was serovar Bratislava (19.4%), followed by serovar Grippotyphosa (6.1%), serovar Icterohaemorrhagiae and serovar Pomona (2.0%), and serovar Canicola and serovar Hardjo (1.0%). We detected the highest prevalence in fox squirrels (Sciurus niger), hispid cotton rats (Sigmodon hispidus), and feral swine (Sus scrofa), with serovar Bratislava being the most reactive for these three species. Positive samples returned titer results of 100-400 for all species and serovars, with the exception of one feral swine that returned a titer of 1,600 to serovar Bratislava, indicating an active infection. Although the potential effects of leptospirosis on our study species remains unclear, our data contribute information necessary to understand and manage potential risks of Leptospira exposure to wildlife, domestic animals, and humans.

Risk Factors for Hospitalisation amongst Leptospirosis Patients in New Zealand

Leptospirosis is a neglected zoonotic disease that is widespread in tropical and subtropical regions such as Oceania, which includes New Zealand. The incidence rate of leptospirosis in New Zealand remains high in comparison to other high-income countries, with over half of the notified patients hospitalised, and the factors associated with hospitalisation are poorly understood. This study aimed to estimate the risk factors for hospitalisation amongst leptospirosis patients using passive surveillance data: notifications from 1 January 1999 to 31 December 2017 extracted from New Zealand’s notifiable disease database. There were 771 hospitalised and 673 non-hospitalised patients. Multivariable logistic regression was used to identify risk factors. The year of notification was significantly and positively associated with hospitalisation, with adjusted (adj.) OR 1.03 (95% CI:1.01–1.05). Occupation was significantly associated with hospitalisation, with the adjusted odds of hospitalisation amongst dairy farmers notified with leptospirosis at adj. OR 1.44 (95% CI: 1.02–2.02) times the adjusted odds of hospitalisation amongst farmers that worked with other livestock. Seropositivity for Leptospira interrogans Copenhageni (adj. OR 5.96, 95% CI: 1.68–21.17) and Pomona (adj. OR 1.14, 95% CI: 0.74–1.74)) was more likely to result in hospitalisation when compared to Leptospira borgpetersenii Ballum (baseline). Seropositivity for Leptospira borgpetersenii Hardjo (adj. OR 0.71, 95% CI: 0.49–1.01) and Tarassovi (adj. OR 0.39, 95% CI: 0.23–0.66) was less likely to result in hospitalisation when compared to Ballum (baseline). All the estimates were additionally adjusted for the effect of sex, age, ethnicity, reported occupational exposure, geographical location, reported season, and deprivation status Although passive surveillance data has limitations we have been able to identify that the New Zealand dairy farming population may benefit from a targeted awareness campaign.

Detection of Anti-LipL32 Antibodies in Serum Samples from Horses with Chronic Intraocular Infection with Leptospira spp

Equine recurrent uveitis (ERU) is typically caused by chronic intraocular leptospiral infection in warm-blooded horses in central Europe. The most effective therapy for leptospiral-induced ERU is the surgical removal of diseased vitreous (vitrectomy). Since vitrectomy is a highly specialized and invasive surgery, the indication must be determined very carefully. In order to obtain evidence of intraocular leptospiral infection by laboratory diagnostics in questionable leptospiral ERU-cases, sampling of aqueous humor is required, because serum tests using microscopic agglutination test (MAT) are too unspecific. The SNAP Lepto is a cross-species rapid test for the detection of anti-Lipl32 antibodies that has a high sensitivity (0.97) and specificity (1.00) for the detection of anti-leptospiral antibodies using aqueous humor or vitreous samples, which is comparable to MAT. To evaluate sensitivity and specificity of SNAP Lepto using serum, serum samples from 90 horses with confirmed leptospiral ERU and from 103 ocularly healthy horses were tested by both MAT and SNAP Lepto. Sensitivity was similar for both tests (0.82 vs. 0.79), but specificity was lower for MAT (0.52 vs. 0.95). Sensitivity and specificity are therefore lower in serum samples compared to intraocular samples, however, the SNAP Lepto is far superior to MAT and suitable as a screening method using equine serum.

Comparative genome characterization of Leptospira interrogans from mild and severe leptospirosis patients

Leptospirosis is a zoonotic disease caused by spirochetes from the genus Leptospira. In Thailand, Leptospira interrogans is a major cause of leptospirosis. Leptospirosis patients present with a wide range of clinical manifestations from asymptomatic, mild infections to severe illness involving organ failure. For better understanding the difference between Leptospira isolates causing mild and severe leptospirosis, illumina sequencing was used to sequence genomic DNA in both serotypes. DNA of Leptospira isolated from two patients, one with mild and another with severe symptoms, were included in this study. The paired-end reads were removed adapters and trimmed with Q30 score using Trimmomatic. Trimmed reads were constructed to contigs and scaffolds using SPAdes. Cross-contamination of scaffolds was evaluated by ContEst16s. Prokka tool for bacterial annotation was used to annotate sequences from both Leptospira isolates. Predicted amino acid sequences from Prokka were searched in EggNOG and David gene ontology database to characterize gene ontology. In addition, Leptospira from mild and severe patients, that passed the criteria e-value < 10e-5 from blastP against virulence factor database, were used to analyze with Venn diagram. From this study, we found 13 and 12 genes that were unique in the isolates from mild and severe patients, respectively. The 12 genes in the severe isolate might be virulence factor genes that affect disease severity. However, these genes should be validated in further study.

Evaluation of a genus-specific rGroEL1-524 IgM-ELISA and commercial ELISA kits during the course of leptospirosis in Thailand

In the present study, we developed a genus-specific rGroEL_1-524 IgM-ELISA assay for use in screening diagnosis of suspected leptospirosis among acute undifferentiated febrile illness patients during acute fever. The diagnostic accuracies of the rGroEL_1–524 IgM-ELISA, commercial Panbio IgM-ELISA, and Virion-Serion Classic IgG-ELISA were evaluated using 133 Thai leptospirosis sera and 210 controls. Sensitivities were 91.7%, 59.6%, and 17.7% for acute infection, and the specificities were 92.6%, 90.2%, and 88.3% for the non-leptospirosis control, respectively. The rGroEL_1-524 IgM-ELISA had high sensitivity, at 92.3% and 91.7%, among culture-positive and MAT-negative cases at 1–3 days post-onset of symptoms (DPO1–3), respectively. Impaired specificity on scrub typhus was found, possibly from antibody cross-reaction to ortholog GroEL. Commercial Panbio IgM-ELISA had sensitivities at DPO1–3 of 30.8% and 41.7% for culture-positive and MAT-negative cases whereas Virion-Serion IgG-ELISA showed sensitivities of 5.9% and 13.3%, respectively. The rGroEL_1-524 IgM-ELISA could be useful as a screening test for early diagnosis. The performance of the commercial ELISA suggests the applicability of IgM-ELISA for diagnosis, while IgG-ELISA is useful for seroprevalence surveys. However, confirmation by reference tests is recommended.

Seroprevalence and Associated Risk Factors of Leptospira interrogans Serogroup Sejroe Serovar Hardjo in Dairy Farms in and around Jimma Town, Southwestern Ethiopia

A cross-sectional study was conducted on selected dairy farms in and around Jimma town, Oromia, southwestern Ethiopia from November 2019 to May 2020 to determine the seroprevalence of Leptospira interrogans serogroup Sejroe serovar Hardjo (L. hardjo). Furthermore, information was gathered on individual animal and herd level by using pretested semistructured questionnaire to assess associated risk factors. A stratified and simple random sampling procedure was used for the selection of dairy farms and individual animal's, respectively. Indirect enzyme-linked immunosorbent assay (I-ELISA) was used in this study to detect antibody against L. hardjo. Out of 384 animal's sera, 94 animals were seropositive against L. hardjo antibodies. From 77 dairy farms selected for the study, 57 of them were distinguished as positive for L. hardjo. The overall seroprevalence of leptospirosis caused by L. hardjo was 24.48% (95% CI: 20.18%–28.78%) and 74.03% (95% CI: 64.23%–83.82%) at individual animal and farm level, respectively. The result of multilogistic regression analysis revealed that management system (p < 0.05; OR = 4.25 (95% CI: 2.31–7.82)), hygienic status of the farm (p < 0.05; OR = 0.35 (95% CI: 0.20–0.61)), age of animals (p < 0.05; OR = 8.30 (95% CI: 1.87–36.89)), history of abortion (p < 0.05; OR = 8.37 (95% CI: 1.73–40.42)), herd size (p < 0.05; OR = 2.32 (95% CI: 1.17–4.61)), and access of rodents to the farm (p < 0.05; OR = 0.17 (95% CI: 0.03–0.86)) were significantly associated with the occurrence of L. hardjo infection. However, breed, parity, and introduction of new animals to the farm were insignificantly associated (p > 0.05). Management system of the animal, hygienic status of the farm, herd size, age of animals, previous history of abortion, and access of rodents to the farm were identified as potential risk factors of L. hardjo disease occurrence. Thus, limiting rodents contact with cattle and their feed and water as well as good sanitary practices and husbandry management should be undertaken.

Protective efficacy of whole-cell inactivated Leptospira vaccines made using virulent or avirulent strains in a hamster model

Whole-cell inactivated vaccines remain the only licensed vaccines used to control human and animal leptospirosis worldwide. Although they are protective against lethal infections, the efficacy of these vaccines has been divergent. The manufacturing process often involves the use of standard bacterial strains subjected to serial in vitro passages, with a risk of loss of virulence, and may affect the immunogenicity and consequently decrease protection. Thus, the objective of this study was to perform a comparative analysis of the efficacy of in-house bacterins produced with standard (avirulent) and virulent strains. Hamsters were immunized with killed bacteria produced using avirulent and virulent strains of L. interrogans serovars Copenhageni and Canicola. Vaccine efficacy was determined in terms of protection against lethal homologous or heterologous challenges. The results showed that immunization with both avirulent and virulent Canicola strains resulted in 100% protection against homologous challenge. Conversely, Copenhageni bacterins produced using an avirulent strain conferred only 25-37.5% protection against homologous challenge (P > 0.05), while virulent Copenhageni bacterin conferred 100% protection (P < 0.001). A single vaccine dose was sufficient to induce protection, and administration of a prime boost significantly reduced the bacterial load in the kidneys and improved the humoral immune response to the virulent Copenhageni strain. These findings suggest that the maintenance of virulent strains in bacterin formulations is essential for improving the immunogenicity and efficacy of leptospirosis vaccines.

Control and Eradication Programs for Non-EU Regulated Cattle Diseases in the Netherlands

Within the European Union, infectious cattle diseases are categorized in the Animal Health Law. No strict EU regulations exist for control, evidence of disease freedom, and surveillance of diseases listed other than categories A and B. Consequently, EU member states follow their own varying strategies for disease control. The aim of this study was to provide an overview of the control and eradication programs (CPs) for six cattle diseases in the Netherlands between 2009 and 2019 and to highlight characteristics specific to the Dutch situation. All of these diseases were listed as C,D or E in the New Animal Health Law. In the Netherlands, CPs are in place for six endemic cattle diseases: bovine viral diarrhea, infectious bovine rhinotracheitis, salmonellosis, paratuberculosis, leptospirosis, and neosporosis. These CPs have been tailored to the specific situation in the Netherlands: a country with a high cattle density, a high rate of animal movements, a strong dependence on export of dairy products, and a high-quality data-infrastructure. The latter specifically applies to the dairy sector, which is the leading cattle sector in the Netherlands. When a herd enters a CP, generally the within-herd prevalence of infection is estimated in an initial assessment. The outcome creates awareness of the infection status of a herd and also provides an indication of the costs and time to achieve the preferred herd status. Subsequently, the herd enrolls in the control phase of the CP to, if present, eliminate the infection from a herd and a surveillance phase to substantiate the free or low prevalence status over time. The high-quality data infrastructure that results in complete and centrally registered census data on cattle movements provides the opportunity to design CPs while minimizing administrative efforts for the farmer. In the CPs, mostly routinely collected samples are used for surveillance. Where possible, requests for proof of the herd status are sent automatically. Automated detection of risk factors for introduction of new animals originating from a herd without the preferred herd status i.e., free or unsuspected, is in place using centrally registered data. The presented overview may inspire countries that want to develop cost-effective CPs for endemic diseases that are not (yet) regulated at EU level.

High Diversity of Leptospira Species Infecting Bats Captured in the Urabá Region (Antioquia-Colombia)

Leptospirosis is a globally distributed zoonotic disease caused by pathogenic bacteria of the genus Leptospira. This zoonotic disease affects humans, domestic animals and wild animals. Colombia is considered an endemic country for leptospirosis; Antioquia is the second department in Colombia, with the highest number of reported leptospirosis cases. Currently, many studies report bats as reservoirs of Leptospira spp. but the prevalence in these mammals is unknown. The goal of this study was to better understand the role of bats as reservoir hosts of Leptospira species and to evaluate the genetic diversity of circulating Leptospira species in Antioquia-Colombia. We captured 206 bats in the municipalities of Chigorodó (43 bats), Carepa (43 bats), Apartadó (39 bats), Turbo (40 bats), and Necoclí (41 bats) in the Urabá region (Antioquia-Colombia). Twenty bats tested positive for Leptospira spp. infection (20/206—9.70%) and the species of infected bats were Carollia perspicillata, Dermanura rava, Glossophaga soricina, Molossus molossus, Artibeus planirostris, and Uroderma convexum. These species have different feeding strategies such as frugivorous, insectivores, and nectarivores. The infecting Leptospira species identified were Leptospira borgpetersenii (3/20–15%), Leptospira alexanderi (2/20–10%), Leptospira noguchii (6/20–30%), Leptospira interrogans (3/20–15%), and Leptospira kirschneri (6/20–30%). Our results showed the importance of bats in the epidemiology, ecology, and evolution of Leptospira in this host-pathogen association. This is the first step in deciphering the role played by bats in the epidemiology of human leptospirosis in the endemic region of Urabá (Antioquia-Colombia).

Sperm viability, serological, molecular, and modified seminal plasma agglutination tests in the diagnosis of Leptospira in the semen and serum of bovine bulls

The present study investigated the serum microscopic agglutination test (MAT) among 203 bovine bulls with reproduction by natural means, without apparent signs of orchitis or inflammation of accessory reproductive glands. Simultaneously, the semen of all bulls was subjected to sperm viability analysis and PCR based on the 16S rRNA gene. PCR-positive results of semen samples were confirmed by sequencing. A modified seminal plasma agglutination (MSPA) test, replacing the blood serum of all bulls in the MAT with seminal plasma was performed as well. Eight (8/203 = 3.9%) semen samples from bulls were considered nonviable (necrospermia and azoospermia) without relation to the PCR diagnosis. No agglutinin titers were identified in MSPA test. A high frequency (132/203 = 65%) of leptospiral agglutinin titers was identified in the MAT, particularly for the Sejroe serogroup (Hardjo CTG, 100/203 = 49.3%; Wolffi 74/203 = 36.4%; Guaricura 72/203 = 35.5%; and Hardjoprajitno 56/203 = 27.6%). Three (3/203 = 1.5%) semen samples of bulls were positive in the PCR, but these results were not confirmed by sequencing. The high frequency of serovars from the Sejroe serogroup typically adapted to bovines indicates the need for measures for the prophylaxis/control of the pathogen on the sampled farms. Discrepancies among the MAT, sperm viability, and molecular detection of leptospires in semen highlight the need for a combination of methods to diagnose leptospirosis in bovine bulls. To our knowledge, modified seminal plasma agglutination is described for the first time here to investigate anti-Leptospira antibodies produced locally in the genital tract in the diagnosis of bovine leptospirosis among bulls that reproduce by natural means.

Pathology and One Health implications of fatal Leptospira interrogans infection in an urbanized, free-ranging, black-tufted marmoset (Callithrix penicillata) in Brazil

Leptospirosis is a zoonotic neglected disease of worldwide public health concern. Leptospira species can infect a wide range of wild and domestic mammals and lead to a spectrum of disease, including severe and fatal forms. Herein, we report for the first time a fatal Leptospira interrogans infection in a free-ranging nonhuman primate (NHP), a black-tufted marmoset. Icterus, pulmonary haemorrhage, interstitial nephritis, and hepatocellular dissociation were the main findings raising the suspicion of leptospirosis. Diagnostic confirmation was based on specific immunohistochemical and PCR assays for Leptospira species. Immunolocalization of leptospiral antigens and identification of pathogenic species (L. interrogans species) were important for better understanding the pathogenesis of the disease. One Health-related implications of free-ranging NHPs in anthropized areas and transmission dynamics of human and animal leptospirosis are discussed.

Spatio-temporal distribution and agroecological factors associated with canine leptospirosis in Great Britain

Leptospirosis is an important global zoonotic disease that affects a wide range of mammalian species. Canine leptospirosis outbreaks have been reported after metereological events such as flooding (eg. in Brazil and the United States of America) suggesting an environmental association, but there has been no such study in Great Britain (GB). The distribution of cases across GB is also unreported. Objectives of this study were to: (1) assess the spatio-temporal variation of leptospirosis test submissions (2) explore associations between agroecological risk factors and distribution of different canine leptospirosis serogroups in GB, and (3) generate probability of presence maps for the different serogroups. Data analysed comprised laboratory submissions (n = 3986) to IDEXX laboratories between 1st January 2009 and 31st December 2018 for PCR or MAT leptospirosis testing. Spatial and seasonal scan statistics were used to investigate spatial and temporal clustering of positive tests, logistic regression was used to identify significant agroecological risk factors for positive tests, and the Maxent algorithm was used to model the environmental niche of four serogroups. There was an increased risk of a positive test result in the West Midlands of England (relative risk = 2.16) and between October and January (relative risk = 1.54). Logistic regression identified season and region to be significantly associated with a positive diagnosis,with higher odds of a positive test in Autumn (OR = 1.86 95 %CI 1.29-2.69) and Winter (OR = 1.51, 95 %CI 1.02-2.23) and in the East (OR = 2.20, 95 %CI = 1.31-3.71) and West Midlands (OR = 2.32, 95 %CI 1.45-3.71). The increased test-positive proportion in Autumn together with the increased odds of a positive diagnosis in Autumn suggests there may be a seasonal pattern to the canine leptospirosis in GB. The most important variable associated with higher leptospirosis presence in all ecological niche models was higher average annual temperature. The importance and retention of other variables differed between serogroups. Overall, a higher probability of leptospirosis presence was predicted in southern England and a low probability in Scotland and northern England. Although leptospirosis vaccine usage provides protection against the majority of serogroups identified here, one is not represented in the currently licensed vaccine formulations and therefore leptospirosis should remain a differential diagnosis in vaccinated dogs demonstrating consistent clinical signs of the disease.

Survey of Zoonotic Bacterial Pathogens in Native Foxes in Central Chile: First Record of Brucella canis Exposure

Simple Summary

Wild canids play a crucial role in the environment, being an ecological agent of flora dispersal, top predators, and environmental sentinels for zoonotic emerging pathogens, such as Brucella spp. and pathogenic Leptospira. In Chile, three species of non-domestic native canids are present, and due to the growing concern about their interaction with humans and domestic animals, it is of utmost relevance to determine the role of these animals in the epidemiology of brucellosis and leptospirosis. This study aimed to detect the exposure to B. abortus, B. canis, and pathogenic Leptospira by serologic, bacteriologic, and molecular techniques in native foxes from rehabilitation and exhibition centers in Central Chile. Forty-six blood samples were obtained from culpeo and grey foxes, detecting exposure to B. canis and L. Javanica in 10.9% and 7.7%, respectively. Exposure was not registered by culture and qPCR in any of the sampled animals. Our results show for the first time in Chile exposure to B. canis in native foxes, highlighting the need to establish integrated surveillance programs to better evaluate the role of wild animals in the epidemiology of emerging zoonotic pathogens that may affect One Health.

Abstract

Brucella abortus, B. canis, and pathogenic Leptospira are zoonotic pathogens that infect humans, as well as domestic and wild animals. In wild canids, they may affect their fertility and reproduction, threatening their conservation. Wild canids play a crucial role in the environment as meso- and top-predators and environmental sentinels for zoonotic pathogens. In Chile, three species of wild canids are present, and due to changes in land use and environmental dynamics, it is of utmost relevance to determine the role of these species in the epidemiology of brucellosis and leptospirosis. This study aimed to detect the exposure to B. abortus, B. canis, and pathogenic Leptospira by serologic, bacteriologic, and molecular techniques in native foxes from rehabilitation and exhibition centers in Central Chile. Forty-six blood samples were obtained from Lycalopex culpaeus and L. griseus, detecting 10.9% of seropositivity to B. canis and 7.7% to L. Javanica. No seropositivity was seen for B. abortus. Exposure was not registered by culture and qPCR in any of the sampled animals. Our findings are the first register of exposure to any Brucella species in wild canids in Chile and highlight the need to establish surveillance programs of these emerging pathogens.

Use of the Leptospira sp. ligB C-terminus coding region as a diagnostic tool of animal leptospirosis

Leptospirosis is the most widespread zoonosis worldwide, and it can cause reproductive failures in livestock, while in humans may vary from a mild fever to multi-organ failure and death. Due to this, in this study, we evaluated the usefulness of the segment encoding LigB C-terminus region, only present in pathogenic as target for a diagnostic PCR. This new PCR yielded a 100 % positivity for pathogenic Leptospira species and no cross-reactivity was found with intermediate or non-pathogenic species, or with other microorganisms, demostrating its high analytical specificity. The estimated analytical sensitivity was higher in serum samples than in blood or urine samples (6-9 × 10² lept/mL and 6-9 × 10⁵ and 6-9 × 10⁶ lept/mL, respectively). Multiple sequence alignment of the target region from different pathogenic Leptospira species confirmed that this gene region is highly conserved among these species, with few single nucleotide polymorphisms. The ligb-ct PCR here developed appears as a useful tool for the molecular diagnosis of leptospirosis.

Climate influence the human leptospirosis cases in Brazil, 2007-2019: a time series analysis

BACKGROUND

Human leptospirosis is responsible for great losses and deaths, especially in developing countries, which can be mitigated by knowing the correct health indicators and climate influence on the disease.

METHODS

Leptospirosis cases and deaths, population and precipitation were recovered from different databases (2007-2019). Annual incidence, mortality and case fatality rates (CFRs) of human leptospirosis and average precipitation were calculated for Brazil and its regions. Time series analysis using an moving average with external variable (ARMAX) model was used to analyse the monthly contribution and precipitation influence over leptospirosis cases for each Brazilian region and for the whole country. A forecast model to predict cases for 2020 was created for Brazil.

RESULTS

Human leptospirosis exhibited heterogeneous distribution among Brazilian regions, with most cases occurring during the rainy season and precipitation influenced the disease occurrence in all regions but the South. The forecast model predicted 3276.99 cases for 2020 (mean absolute percentage error 14.680 and root mean square error 53.013). Considering the annual average for the period, the leptospirosis incidence was 1913 cases per 100 000 inhabitants, mortality was 0.168 deaths per 100 000 inhabitants and the CFR was 8.83%.

CONCLUSIONS

The models built can be useful for planning leptospirosis surveillance and control actions for the whole country and its regions and, together with the health indicators, revealed no uniform epidemiological situation of leptospirosis in Brazil.

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.

Leptospira spp. Antibody in Wild Boars (Sus scrofa), Hunting Dogs (Canis lupus familiaris), and Hunters of Brazil

Hunting activities are a potential risk factor for human infection with Leptospira spp. and, although wild boar seroprevalence has been studied, there are no concurrent serosurveys of wild boars (Sus scrofa), hunting dogs (Canis lupus familiaris), and hunters. The aim of our study was to assess the seroprevalence of Leptospira spp. antibodies in free-ranging wild boars, hunting dogs, and hunters, and risk factors associated with exposure in southern and central-western Brazil. Leptospira spp. antibodies were serologically detected using the microscopic agglutination test, with a total 30 serovars. Overall, 12.2% (9/74) of wild boars and 10.6% (16/170) of hunting dogs were seropositive for at least one serovar and all hunters 0.0% (0/49) were seronegative for Leptospira spp. Seropositivity was statistically higher in 42.1% (8/19) wild boars from natural areas when compared to 2.4% (1/41) from anthropized areas (P<0.001), with prevalence ratio of 17.14 (95% confidence interval: 2.29-128.36). Despite the limited sample size, our findings showed that hunters may be less exposed to Leptospira spp. than are wild boars, particularly in natural areas where Leptospira spp. may be maintained by wild reservoirs. In addition to acting as sentinels, hunting dogs may play a role in disease transmission of sylvatic leptospiral serovars.

Molecular and serological characterization of pathogenic Leptospira spp. isolated from symptomatic dogs in a highly endemic area, Brazil

Abstract

Background

Leptospirosis is an endemic zoonosis in Brazil, with a great impact on human and animal health. Although dogs are frequently infected by pathogenic Leptospira, the current epidemiological understanding of canine leptospirosis is mainly based on serological tests that predict the infecting serogroup/serovar. Thus, the present study aimed at identifying the causative agent for severe cases of canine leptospirosis in a highly endemic area through the isolation and characterization of the isolated strains.

Results

Urine, serum and blood samples were collected from 31 dogs with suspected acute leptospirosis treated at the Veterinary Hospital Service of Santo Amaro University between 2018 and 2019. Acute infection was confirmed in 17 dogs (54.8%) by the associated use of Polymerase Chain Reaction (PCR), Microscopic Agglutination (MAT) and bacteriological culture. Eleven dogs (35.5%) had titers ≥800, with the most frequent serogroups being Autumnalis and Icterohaemorrhagiae (n = 4 each) and Canicola (n = 2). Leptospires were recovered from four dogs, and Multilocus Sequence Analysis (MLSA) revealed infection caused by L. interrogans, which were further characterized as serogroups Canicola (n = 1) and Icterohaemorrhagiae (n = 3).

Conclusion

The identity of the isolates and serological pattern of MAT suggest that dogs are highly exposed to the serogroup Icterohaemorrhagiae and Canicola, also indicating possible circulation of serogroups not yet isolated in Brazil, notably serogroup Autumnalis. Our findings also reinforce the usefulness of using multiple diagnostic approaches to confirm acute canine leptospirosis.