Isolation of Leptospira interrogans Hardjoprajitno from vaginal fluid of a clinically healthy ewe suggests potential for venereal transmission

Molecular and serological prevalence of Leptospira spp. among slaughtered cattle and associated risk factors in the Bahr El Ghazal region of South Sudan

INTRODUCTION

Leptospirosis is a neglected emerging and zoonotic disease reported worldwide. This study sought to determine the molecular and serological prevalence of Leptospira spp. and the associated risk factors in slaughtered cattle from the Bahr El Ghazal region of South Sudan.

MATERIALS AND METHODS

Between January 16th and February 25th, 2023, blood and urine samples were collected from 402 cattle at the Lokoloko Municipal Slaughterhouse in Western Bahr El-Ghazal State. Serum samples were tested using the microscopic agglutination test (MAT), with a panel of 12 serovars (sv) from 12 serogroups (sg) and 4 species (spp) of Leptospira spp. These serovars had been previously identified in Sudan and the East African region. Simultaneously, 400 corresponding urine samples were screened using qualitative real-time polymerase chain reaction (PCR) to detect the shedding of Leptospira spp. in urine. To identify the associated risk factors, the age, sex, breed and body condition score of each sampled cattle was noted at the time of sampling and subsequently analysed using logistic regression models.

RESULTS

Among the 402 serum samples screened, a substantial 81.8% (329/402, 95% CI 77.9-85.3) displayed seropositivity for Leptospira spp. with a MAT titre ≥ 100. The prevalence of urine shedding determined by PCR was 6% (23/400, 95% CI 3.8-8.4), while probable recent leptospirosis with a MAT ≥ 1:800 was observed in 33.1% (133/402, 95% CI 28.6-37.8) of the cattle. Multiple reactions were detected in 34.8% (140/402, 95% CI 30.6-39.5) serum samples. The seropositivity was against L. borgpetersenii sg. Tarassovi (78.6%; 316/402, 95% CI 74.4-82.3), followed by L. borgpetersenii sg. Ballum at 20.4% (82/402, 95% CI, 16.7-24.4%), L. kirschneri sg. Autumnalis At 8.7% (35/402, 95% CI 5.7-11.7), L. interrogans sg. of Pomona at 7.0% (28/402, 95% CI 4.5-9.5), and L. interrogans sg. Hebdomadis was 5.0% (20/402, 95% CI 2.8-7.2). Several risk factors are associated with seropositivity. Older animals (≥ 2 years) had 2.0 times greater odds (95% CI 1.14-3.5) of being seropositive than younger animals (< 2 years), P-value = 0.016. Female animals demonstrated 2.1 times greater odds (95% CI 1.2-3.6) of seropositivity than males did (P-value = 0.008). Additionally, Felata/Mbororo cattle exhibited 2.4 times greater odds (95% CI 1.3-4.5) of being seropositive than did local Nilotic cattle (P-value = 0.005). The agreement between the MAT and PCR results was poor, as indicated by a kappa statistic value of 0.001 and a P-value of 0.913. But there was a moderate agreement between MAT high titres ≥ 800 and PCR positivity with a kappa statistic value = 0.501 and a P-value < 0.001.

CONCLUSION

In addition to the high seroprevalence, Leptospira spp. were found in the urine of slaughtered cattle, suggesting that leptospirosis is endemic to the study area. This finding underscores the significance of cattle as potential sources of infection for slaughterhouse workers, the general public, and other animal species. To address this issue effectively in the Bahr El Ghazal Region and South Sudan, a comprehensive strategy involving a multidisciplinary approach is essential to minimize disease among animals, hence reducing potential zoonotic risks to humans.

New insights on Leptospira sp. infection in ewes maintained in field semiarid conditions

Leptospirosis is poorly studied in small ruminants raised in field semiarid conditions. In this study we compared serological, bacteriological and molecular diagnostic methods in ewes maintained in field Brazilian semiarid conditions. Blood, vaginal fluid and urine samples were collected from 60 Morada Nova ewes raised in a semi-intensive system in the Brazilian semiarid. Diagnostic tests performed were microscopic agglutination test (MAT), polymerase chain reaction (PCR) and bacterial isolation. Anti-Leptospira sp. antibodies were found in eight (13.33%) animals analyzed by MAT at reciprocal titer 25 (cut-off 25), while Leptospira sp. DNA was detected in urine or vaginal fluid of 56 animals (93.33%). There was growth of leptospires in 10 urine cultures and in 11 vaginal fluid cultures, however, two of urine (2/60-3.33%) and eight cultures of vaginal fluid (8/60-13.33%) were confirmed by PCR. Two samples of vaginal fluid (one of each animal) were submitted to sequencing demonstrating 99% similarity with L. santarosai and L. interrogans. The highest MAT sensitivities were obtained with reciprocal titer 25 (cut-off 25) compared to 50 and 100. The performance of different diagnostic techniques for leptospirosis in ewes raised in field semiarid conditions allowed a better evaluation of the herd, as well as made it possible to identify carrier animals. Genital route may be important for efficient transmission and without dependence on environmental factors in ewes from semiarid, as well as it's highlighted that titer 1:25 in serology was more efficient, indicating its use in ewes in field semiarid conditions.

Transient Presence of Live Leptospira interrogans in Murine Testes

Analysis of Leptospira dissemination and colonization of sex organs in rodents is of significant value as it queries the possibility of mammal-to-mammal venereal transmission. The aim of our study was to evaluate the presence and viability of Leptospira interrogans in testes of mice using models of infection that we previously developed. Using sublethal and lethal doses of bioluminescent strains of L. interrogans serovars Manilae and Copenhageni, we visualized the presence of leptospires in testes of C57BL/6 mice as early as 30 min and up to days 3-4 postinfection. This was confirmed by qPCR for the Copenhageni serovar after lethal infection of C3H/HeJ mice. In this model, no histopathological changes were noticed in testis. We further studied persistence of serovar Copenhageni in C3H/HeJ testes after lethal and sublethal infection, with different doses of leptospires. No viable leptospires were recovered from testes of lethally infected mice. However, we found live culturable Leptospira in testes of 19/19 (100%) sublethally infected mice at the acute phase but not at 15 days postinfection, which corresponds to the chronic phase of renal colonization. The data suggest that colonization of testes with live and potentially infectious leptospires is transient and limited to the spirochetemic phase of infection. Further studies are necessary to evaluate if presence of Leptospira in testes of mice leads to excretion in semen and to venereal transmission to female mice. IMPORTANCE Analysis of venereal transmission of Leptospira is important to determine if direct animal to animal transmission occurs, which could impact measures to prevent and treat leptospirosis. The goal of this study was to determine if live Leptospira colonize mouse testes. We found that colonization of mouse testes with live Leptospira was transient and limited to the acute spirochetemic phase of infection and that transient colonization of the testes was insufficient to cause histopathological changes.

Isolation of Leptospira interrogans Serovar Canicola in a Vaccinated Dog without Clinical Symptoms

More than one million cases of leptospirosis occur across the globe annually, resulting in about 59,000 deaths. Dogs are one of the most important reservoirs of Leptospira species and play an important role in transmitting the pathogen to humans. Many of these infections are controlled by routine vaccination that has reduced the possible reintroduction of leptospiral serovars into the human population. However, it is still not clear how a vaccinated dog can become infected with one or more Leptospira serovars contained in the vaccine formulation and thus against which it should be immunized. Here, we present the case of an asymptomatic dog who developed leptospiral infection despite being vaccinated. This unusual case emphasizes the substantial impact of immunization on mitigating the acute signs of the disease, even while providing limited protection against infection. Further studies will be required to better understand the role of dogs in the environmental circulation of leptospiral serovars in Sardinia. Asymptomatic leptospiral infection in vaccinated dogs should be considered to allow for better diagnosis and management of the infection. This will be essential for preventing Leptospira outbreaks in the future.

An overview on the molecular diagnosis of animal leptospirosis

The most common presentation of animal leptospirosis is the subclinical and silent chronic form, that can lead to important reproductive disorders. The diagnosis of this chronic form remains a challenge. The aim of the present study is to gather and critically analyse the current information about molecular tools applied to animal leptospirosis diagnosis, particularly the silent chronic presentation of the infection. Regarding clinical specimens, samples from urinary tract were the most used (69/102, 67·7%), while few studies (12/102, 11·8%) investigated samples from reproductive tract. Concerning the molecular methods applied, the most used is still the conventional polymerase chain reaction (PCR) (46/102, 45%), followed by real-time PCR (38/102, 37·2%). The lipL32 gene is currently the most common target used for Leptospira detection, with 48% of studies applying this genetic marker. From all the studies, only few (21/102, 20·5%) performed gene sequencing. According to the majority of authors, current evidence suggests that lipL32-PCR is useful for an initial screening for Leptospira DNA detection in animal clinical samples. Posteriorly, if DNA sequencing could be performed on positive lipL32-PCR samples, we encourage the use of secY gene as a genetic marker. The molecular methods appear as the most important tools for the diagnosis of the chronic silent leptospirosis on domestic animals, reinforcing its evident impact not only on animal reproduction but also on a One Health context.

Histopathology of the kidney and seroprevalence of leptospirosis in wild rats in Baghdad Province, Iraq

Background and Aim: Leptospirosis, caused by pathogenic leptospires, is a globally emerging infectious disease affecting both humans and animals, which act as reservoirs, with large outbreaks worldwide. The role of rats in dispersing leptospirosis was never investigated in Iraq. Because of the seriousness of the disease and the scarce data regarding this disease in Iraq, this study determines the incidence of leptospirosis in rats and its renal histopathological profile. Materials and Methods: Of 211 captured rats, 82 apparently healthy rats were included in this study. After euthanatizing, 3-5-ml blood was collected by cardiac puncture. Approximately 0.5 cm3 of the kidney was collected for routine histopathology and stained using hematoxylin and eosin (H&E) and Warthin–Starry (WS) stains. Blood smears were prepared and stained with the WS stain. Results: All rats (100%) with different age groups were immunoglobulin G (IgG)-positive, and 90.24% of them had the IgG against leptospiral antigens in kidney tissues. The juvenile age group had higher IgG levels than other age groups. Considering sex, no significant differences in the overall results were observed. Serum concentrations of blood urea nitrogen and creatinine showed significant increments in the sub-adult and adult IgG- positive groups compared with the IgG-negative groups. No significant alterations were observed in the juvenile group. Using WS stains, 13 and 1 blood smears and 0 and 8 kidney tissues were positive for leptospires in the sub-adult and adult groups, respectively. Microscopical findings of the renal cortex and medulla in the sub-adult IgG-positive group showed hemorrhage, glomerular deterioration, tubular cell degeneration and necrosis with cast formation, periarterial edema, and focal hemorrhage with congestion of peritubular arteries. The adult IgG-positive group revealed deterioration similar to that in the sub-adult group and tended to be chronic. No leptospires were observed using H&E staining. Conclusion: IgG-positive carrier rats refer to previously exposed or infected rats. Understanding the risk of transmitting the disease to human and animals through a carrier rat's urine is highly predicted and possible mitigation of zoonotic transmission.

Serological, molecular and bacteriological approaches for detecting Leptospira sp. carrier rams maintained in semiarid conditions

Even in the adverse environmental conditions of the semiarid region, leptospires can survive and spread by alternative routes of transmission, such as sexual in ewes, however, there is no data on rams. Thus, the present study aimed to evaluate the use of serological, molecular and microbial tools applied to diagnosis of Leptospira sp. Infection in rams maintained in semiarid conditions. Biological samples of urinary (urine, kidney and bladder) and genital (vas deferens, epididymis tail and vesicular gland) tracts were collected from 40 slaughtered rams for polymerase chain reaction (PCR) and bacterial isolation, as well as blood samples for antibody detection through microscopic serum agglutination test (MAT). Anti-Leptospira antibodies were found in five (12.5%) animals with antibody titer of 50 and 2 (5%) for the titer 100 for serogroups Pyrogenes, Ballum, Icterohaemorrhagiae and Australis. Leptospira sp. DNA was found in PCR of organs and urine of 30 (75%) animals. Overall, 240 fragments of organs from the urinary and genital tracts and urine were evaluated, with 93 (38.7%) positive samples, being 48/120 (40%) for the urinary tract and 45/120 (37.5%) for the genital. There was no statistically significant difference between the tracts. A bladder sample was sent for sequencing and showed 99% similarity with L. interrogans. Of the 240 cultures evaluated, 59 (24.5%) had leptospire growth, being that 23 (39%) were confirmed in PCR. Considering the PCR of organs and urine and bacterial growth as gold standards, the cut-off 50 in MAT showed greater sensitivity when compared to cut-off 100, regardless of the material used. The great proportion of leptospiral DNA in organs, urine and culture and bacterial growth from the genital tracts reinforce its importance as an extra-renal site and highlights the possible role of rams in venereal transmission, as well as the sensitivity of the cut-off 50 suggested its adoption in the serology of rams maintained in semiarid conditions.

Use of serological and molecular techniques for detection of Leptospira sp. carrier sheep under semiarid conditions and the importance of genital transmission route

It is possible that there are peculiarities in the epidemiology of leptospirosis in regions with a semiarid climate, where the environment is often adverse, allowing the occurrence of alternative transmission routes. The objective of the work was to generate contributions to the diagnosis and epidemiology of Leptospira sp. infection in sheep reared in semiarid conditions, using serological, molecular and microbiological techniques for diagnosis in dry and rainy seasons. Samples of blood, vaginal fluid, urine, bladder, kidney, uterus, uterine tube, ovary and placenta were collected from 104 sheep (52 animals per season - dry and rainy) slaughtered in the Brazilian semiarid. Diagnostic tests performed were microscopic agglutination test (MAT), polymerase chain reaction (PCR) and bacterial isolation. Anti-Leptospira sp. antibodies were found in 26 (25%) of the animals analyzed by MAT at 1:50 dilution (cut-off 50), while 69 (66.3%) animals had at least one organ/fluid with the presence of Leptospira sp. DNA. Overall, PCR was performed on 758 fragments of organs/fluids from the genital and urinary tracts, and 519 (68.5%) samples tested positive. PCR-positivity was statistically different in dry (46.2%) and rainy (11.5%) seasons for vaginal fluid. It was possible to perform the DNA sequencing in nine samples with 99% similarity to L. interrogans and recovery of viable strains in three samples of vaginal fluid. Regardless of the biological material used in PCR to detect carrier animals and the season, the highest MAT sensitivity values were obtained with cut-off 50 compared to 100. The results obtained indicate that, even in the adverse environmental conditions of the semiarid region, leptospires may survive and propagate by alternative routes of transmission, such as sexual, and the presence of PCR-positive genital tracts in ewes suggests that sexual transmission may play an important role in the epidemiology of the disease in sheep in Brazilian semiarid. In addition, it is suggested the use of titer 50 as cut-off point at serology in semiarid conditions.

Leptospira sp. vertical transmission in ewes maintained in semiarid conditions

Leptospirosis is a globally distributed disease associated with reproductive failures in livestock; however, its pathogenesis has not been fully elucidated. Results from the present study indicate there is a presence of Leptospira sp. in organs and fluids of fetuses from ewes slaughtered in the semiarid region of Brazil. Twenty-nine fetuses from 23 ewes determined to be Leptospira sp.-positive using PCR were sampled (14 and 15 in dry and rainy seasons, respectively). Fetal samples of blood, central nervous system (CNS), lung, liver, spleen, stomach contents, peritoneal fluid, kidney, bladder, urine and reproductive system were collected. Diagnostic methods included the microscopic agglutination test (MAT), polymerase chain reaction (PCR) and bacterial isolation. Of the 29 fetuses, 24 (82.8 %) had at least one Leptospira sp.-positive organ or fluid, as determined using PCR, and of a total of 209 samples, 62 (29.7 %) contained leptospiral DNA. Of the 99 samples collected during the dry season, 42 (42.4 %) were positive, and of 110 samples collected during the rainy season, 20 (18.2 %) were positive (P = 0.0001). There was deoxyribonucleic acid (DNA) sequencing of three samples of kidney, CNS and liver, and in all of these, there was 99.3 % similarity with Leptospira interrogans. Leptospires were present in cultures of pooled samples from fetuses with deformities. Results indicate there is vertical (maternal-to-fetus) transmission which would represent an alternative transmission route for the spread of Leptospira sp. in ewes, suggesting molecular detection is essential in the investigation of leptospirosis in fetuses to identify animals that have been infected with this bacterium.

Leptospira transport medium (LTM): A practical tool for leptospires isolation

The isolation of Leptospira is challenging, since the bacteria of this genus are susceptible to adverse environmental conditions and may not remain viable for extend periods in urine samples. This study attempted to develop and evaluate a simple and practical method to isolate leptospires from bovine urine samples. A culture medium for sample transport, named Leptospira Transport Medium (LTM), was described and validated using reference serovars of Leptospira spp. in addition to autochthonous strains isolated in Brazil. We evaluated LTM in the field, by collecting 215 urine samples from slaughtered cattle and immediately seeding them in LTM and Fletcher's medium, used as control. The cultures were sent to a laboratory within 10 days for further processing. Moreover, 16S PCR was also performed on the urine samples directly to detect Leptospira DNA. Using LTM enabled 52 isolates (24.2%) to be obtained in pure culture, and contamination was only observed in 15/215 samples (7.0%). Regarding the samples in Fletcher's medium, 10 (4.6%) isolates were obtained. With 16S PCR performed in the urine samples, 31 samples (14.4%) were determined to be positive. LTM was developed and used in a simple and practical way and can significantly improve the isolation of leptospires from urine samples, as well as being highly useful in remote areas, not only in Brazil but also in other countries where few easily accessible laboratories are available. Furthermore, LTM can be prepared by laboratories and provided to veterinarians and technicians for urine collection in the field.

Identification of Pathogenic Leptospira Species in the Urogenital Tract of Water Buffaloes (Bubalus bubalis) From the Amazon River Delta Region, Brazil

In the current context of deforestation and fire in the Amazon, buffaloes could be a cost-effective and sustainable alternative for cattle production in the region, as they can convert low-quality foods and be raised in floodplain areas. However, little is known about the reproductive diseases that affect these animals; thus, the purpose of this study was to perform the molecular characterization of Leptospira spp. in the urogenital tract of water buffaloes (Bubalus bubalis) raised in the Amazon River Delta region in Brazil. Samples were collected from 114 kidneys, 204 ovaries, and 160 uterine swabs of slaughtered buffaloes in the Macapá microregion of Amapá State (Brazil) and were subjected to PCR to detect bacterial DNA. Positive amplicons were sequenced to identify Leptospira species. Among the total samples, 11/473 were PCR positive (2.3%), including 10 kidney samples and one uterine swab sample. DNA sequencing identified two pathogenic species from the kidney samples: L. interrogans, accounting for 60.0% (6/10) of these samples, and L. borgpetersenii, accounting for 20.0% (2/10), while 20.0% (2/10) were identified only at the genus level. The bacterium in the uterine swab sample was identified as L. interrogans with genetic proximity to strains belonging to the serovar Hardjo. This is the first report of leptospires species identified in buffaloes from the Amazon River Delta region and revealed that these animals may be carriers of different pathogenic Leptospira species, similar to bovines, including showing genital colonization.

Cultural, histochemical, and immunohistochemical detection of pathogenic Leptospira species in the kidneys of cattle slaughtered in two abattoirs in Southwest Nigeria

The impact of leptospirosis on food animals and humans has not been fully elucidated. This study was designed to determine the prevalence of pathogenic Leptospira organism in renal tissues of slaughtered cattle from two major abattoirs in southwestern Nigeria. One hundred and seventy (170) kidney samples of different breeds, ages, and sexes were collected and examined using cultural isolation, microscopic agglutination test (MAT), Warthin silver (WSs) impregnation and immunohistochemistry (IH). Chi-square test was used with a confidence level set at 0.05 to ascertain associations between positive cases and sex, age, and breed. One hundred and thirty (76.5%) of the kidney samples were culturally positive while 83.3% (25/31), 41.6% (37/89), and 35% (7/20) were MAT, WSss, and immunohistochemically positive, respectively. Interstitial nephritis (87%, 94/108) and tubular nephrosis (77.8%, 84/108) were the most prominent and consistent microscopic lesions observed.Serovars Hardjoprajitno (29%) and Bratislava (22.6%) were the most prevalent serovars. To the best of our knowledge, studies on determination of pathogenic Leptospira serovars using cultural isolation, MAT, WSSs, and IH from kidneys of naturally infected cattle in Nigeria are rare. This study is the most comprehensive work in the detection of pathogenic Leptospira species from cattle in Nigeria.

Short communication: Uterine leptospiral infection is strongly associated to strains of serogroup Sejroe on experimentally infected hamsters

Leptospira infection is influenced by the host species and the bacterial strain involved. Important differences on their tissue distribution are referred, also depending on the host and the studied strain. Considering tissue distribution of leptospires the majority of the studies focus on a single strain, or strains from the same serogroup with different inoculation doses. Nevertheless, none had associated different serogroups with their tissue distribution. Thus, the present study aims to investigate the hypothesis that tissue distribution of Leptospira spp. on experimentally infected hamsters may vary according to the strain serogroup. Females of Golden Syrian hamsters were used for the experimental infection with Leptospira isolates (n = 13) belonging to serogroups Icterohaemorrhagiae (n = 8) and Sejroe (n = 5). PCRs were conducted in renal, hepatic and uterine tissue. Seven out of the thirteen studied hamsters presented acute clinical signs and were euthanized before the 21° day p.i. (strains VF237, VF52, U81, UFF-SG001, UFF-G19, UFF-B15, L1-130), while the others presented a subclinical infection. Regarding to the PCR results it was possible to observe that, all but one strain (UFF-SG001), which was detected on all the studied tissues, presented some differences on their tissue distribution. All strains could be detected on at least one tissue and a significant association was observed for the occurrence of the strains of serogroup Sejroe in uterus (p = 0.044). The results of the present study indicate that strains of serogroup Sejroe are strongly associated to uterine infection on experimentally infected hamsters.

Serological and molecular characterization of Leptospira kirschneri serogroup Grippotyphosa isolated from bovine in Brazil

Leptospirosis is a zoonotic disease caused by a bacterium of the genus Leptospira that affects domestic animals, including cattle. Despite of this importance in livestock, little is known about the epidemiology of leptospirosis in cattle in Brazil and other tropical countries. In this context, the objective of this study was to perform the culture of urine and kidney (n = 372 animals) of slaughtered bovines of Minas Gerais state (Brazil), in order to obtain pure cultures of Leptospira strains and carry out its characterization by serological (microscopic agglutination test) and molecular techniques (rrs, secY sequencing and variable-number tandem-repeat genotyping). One strain, named UFU 02, was obtained from a male bovine without apparent alterations in ante-mortem examination. The strain was characterized belonging to species Leptospira kirschneri and serogroup Grippotyphosa. The serogroup Grippotyphosa is most often described in wild species, suggesting a link between domestic and wild cycles/environments. Considering the importance of the country in livestock breeding, the knowledge about leptospiral strains could help to control the disease in the herds.

Genital bovine leptospirosis: A new look for an old disease

Bovine leptospirosis is often associated with host-adapted leptospires infections, such as strains belonging to the Sejroe serogroup. Although bovine leptospirosis by adapted strains may result in abortions, fetal death, premature births and the birth of weak and/or low-weight calves, this infection is more closely associated with subtler syndromes, such as subfertility and early embryonic death. In this way, this silent disease can go unnoticed and undiagnosed, compromising reproductive efficiency with a consequent decrease in the productivity of herds over long periods. For many years, genital tract infection has been considered a secondary effect of renal infection with the assumption being that leptospires are found in the genital tract due to bacteremia caused by renal colonization. In contrast to this hypothesis, there is some evidence in the literature that suggests that genital leptospirosis should be considered a specific syndrome dissociated from renal/systemic disease. Therefore, this paper aims to gather and critically analyze information about genital leptospirosis in cattle, considering the disease a distinct syndrome, herein denominated bovine genital leptospirosis (BGL), that requires a unique approach to diagnosis and treatment.

Infectivity and virulence of leptospiral strains of serogroup Sejroe other than Hardjo on experimentally infected hamsters

To assess the virulence of leptospires from the serogroup Sejroe (from ruminants), hamsters were tested against 12 strains. Three Guaricura strains induced severe lethal disease, in contrast to the Hardjo strains. Although with the preliminary outcomes, this finding may be useful for the control of bovine leptospirosis in the Americas, where Guaricura is prevalent.

Investigation of chronic infection by Leptospira spp. in asymptomatic sheep slaughtered in slaughterhouse

The study aimed to evaluate the histopathological characteristics of renal lesions in chronically infected sheep and with low titers of anti-Leptospira antibodies from a slaughterhouse. In the serological analysis, 24.74% (48/194) presented seroreactivity with a titer equal to or greater than 100. Among these seroreactive sheep, titers of 100 were predominant (58.33%, 28/48), with the highest titer being 1,600 (2.08%, 1/48). Serogroup Sejroe (sv. Hardjo) was the most frequent at 35.42% (17/48). Leptospiral DNA was verified in 4.12% (8/194) of the kidney samples tested, and no urine sample was positive. All the samples corresponded to the pathogenic species L. interrogans. The eight amplicons with 202-nucleotides were identical with two mismatches (presented 100% of identity) using the PCR targeting to secY gene. Histological sections of PCR-positive kidneys were submitted to direct detection by the anti-LipL32 immunohistochemistry (IHC) technique. The Leptospira spp. antigen was evident in 62.5% (5/8) of the kidneys. Positive staining was observed in the cytoplasm of tubular cells and in the form of brownish aggregates that adhered to tubular epithelial cells and projected into the lumen. Inflammatory lymphoplasmacytic infiltrate, ranging from mild to moderate, with multifocal distribution, was the predominant finding in seroreactive animals (33.33%, 16/48). The demonstration of the leptospiral antigen lining the renal tubules through IHC of naturally infected sheep confirmed by PCR characterizes renal colonization in a species with the presence of histological changes compatible with leptospirosis.

Isolation of pathogenic Leptospira strains from naturally infected cattle in Uruguay reveals high serovar diversity, and uncovers a relevant risk for human leptospirosis

Leptospirosis is a neglected zoonosis with worldwide distribution. The causative agents are spirochete bacteria of the Leptospira genus, displaying huge diversity of serovars, the identity of which is critical for effective diagnosis and vaccination purposes. Among many other mammalian species, Leptospira infects cattle, eliciting acute signs in calves, and chronic disease in adult animals often leading to abortions. In South America, and including in Uruguay, beef and dairy export are leading sources of national income. Despite the importance of bovine health, food safety, and bovine-related dissemination of leptospirosis to humans, extremely limited information is available as to the identity of Leptospira species and serovars infecting cattle in Uruguay and the South American subcontinent. Here we report a multicentric 3-year study resulting in the isolation and detailed characterization of 40 strains of Leptospira spp. obtained from infected cattle. Combined serologic and molecular typing identified these isolates as L. interrogans serogroup Pomona serovar Kennewicki (20 strains), L. interrogans serogroup Canicola serovar Canicola (1 strain), L. borgpetersenii serogroup Sejroe serovar Hardjo (10 strains) and L. noguchii (9 strains). The latter showed remarkable phenotypic and genetic variability, belonging to 6 distinct serogroups, including 3 that did not react with a large panel of reference serogrouping antisera. Approximately 20% of cattle sampled in the field were found to be shedding pathogenic Leptospira in their urine, uncovering a threat for public health that is being largely neglected. The two L. interrogans serovars that we isolated from cattle displayed identical genetic signatures to those of human isolates that had previously been obtained from leptospirosis patients. This report of local Leptospira strains shall improve diagnostic tools and the understanding of leptospirosis epidemiology in South America. These strains could also be used as new components within bacterin vaccines to protect against the pathogenic Leptospira strains that are actually circulating, a direct measure to reduce the risk of human leptospirosis.

Several species of the genus Leptospira cause leptospirosis, a disease that is transmitted from animals to humans (zoonosis). Leptospirosis is the most extended zoonosis worldwide, with over a million human cases each year. Leptospira spp. infect a broad range of wildlife and domestic animals, including cattle. In several South American countries beef and dairy exports rank among the most important national income sources, explaining why in Uruguay cattle outnumber human population by a factor of 4. Yet, we did not know which Leptospira species and serovariants (serovars) circulate among Uruguayan cattle. Current serologic diagnostic methods and whole killed-cell vaccination approaches, critically depend on using the proper serovars, which are hugely variable in Leptospira spp. from different regions of the world. Through a multidisciplinary consortium effort, we now report the isolation and typing of 40 strains of pathogenic Leptospira spp. An unexpectedly large variation in terms of species and serovars was found. These data are extremely important: 1- to improve diagnostics by updating the available reference antigen panels; 2- to evaluate the efficacy of novel vaccines; and, 3- to implement efficacious bovine vaccination as a means of reducing the incidence of bovine and human leptospirosis.

Detection of bovine carriers of Leptospira by serological, bacteriological, and molecular tools

Bovine leptospirosis is an important infectious disease that causes reproductive problems and economic risks, particularly in the tropics. The present study aimed to determine the extent of Leptospira infection among bovines on a slaughterhouse from Rio de Janeiro, Brazil via serological, bacteriological, and molecular tests. Two hundred eight bovines were examined in total, and we obtained 208 blood samples for serology, 198 urine samples collected via direct bladder puncture for polymerase chain reaction (PCR) and culture, 208 kidney samples (one from each animal) for PCR and culture, and 92 vaginal fluid samples from sterile swabs for PCR and culture. Serology demonstrated that 77/208 (37%) of the animals presented anti-Leptospira antibodies. Serogroup Sejroe was by far the most common. One hundrd thirty-three animals (63.9%) were PCR positive in at least one of the tested samples and were considered as Leptospira carriers. Furthermore, ten isolates were obtained by pure culture, all of them from urine samples. Bovine leptospirosis is widely prevalent, and the occurrence of renal carriers was unexpectedly much higher than generally reported.

Occurrence of uterine carriers for Leptospira interrogans on slaughtered cows

Reproductive tract is an important site of infection for chronic leptospirosis and cooperate in pathogenesis of reproductive failure, leading to economic losses. Since serology techniques cannot detect chronic carriers, the molecular analysis of clinical samples is an alternative to detect these animals on livestock. The aim of the present study was to perform a retrospective study in order to detect leptospiral uterine carriers in slaughtered cows. Tissue samples were collected from 50 post-pubertal, nonpregnant cows. These samples were fixed in 10% buffered formalin, paraffin-embedded and stored. PCR targeting lipL32 gene and molecular characterization by secY sequence was performed. Leptospiral DNA was identified in 18% (9/50) examined blocks. Two sequences were characterized as L. interrogans. These findings suggest that the presence of infectious leptospires in uterus is associated with the physiopathogenesis of the reproductive failure.

Culture Strategies for Isolation of Fastidious Leptospira Serovar Hardjo and Molecular Differentiation of Genotypes Hardjobovis and Hardjoprajitno

The Leptospira serovar Hedjo belongs to the serogroup sejroe and this serovar is the most prevalent in bovine herds worldwide. The sejroe serogroup is the most frequently detected by serology in Brazilian cattle herds suggesting that it is due serovar Hardjo. In the molecular classification, this serovar has two genotypes: Hardjobovis and Hardjoprajitno. This serovar is as considered as fastidious pathogens, and their isolation is one of the bottlenecks in leptospirosis laboratories. In addition, its molecular characterization using genomic approaches is oftentimes not simple and time-consuming. This study describes a method for isolating the two genotypes of serovar Hardjo using culture medium formulations and suggests a get-at-able molecular characterization. Ten cows naturally infected which were seropositive were selected from small dairy farms, and their urine was collected for bacterial isolation. We evaluated three modifications of liquid Leptospira medium culture supplemented with sodium pyruvate, superoxide dismutase enzyme and fetal bovine serum, and the isolates were characterized by molecular techniques. After isolation and adaptation in standard culture medium, the strains were subcultured for 1 week in the three modified culture media for morphologic evaluation using electronic microscopy. Strains were molecularly identified by multilocus variable-number tandem-repeat analysis (MLVA), partial sequencing and phylogenic analyses of gene sec Y. Combining the liquid culture medium formulations allowed growth of the Leptospira serovar Hardjo in three tubes. Two isolates were identified as genotype Hardjobovis, and the other as genotype Hardjoprajitno. Morphologically, compared with control media, cells in the medium supplemented with the superoxide dismutase enzyme were more elongated and showed many cells in division. The cells in the medium supplemented with fetal bovine serum were fewer and lost their spirochete morphology. This indicated that the additional supplementation with fetal bovine serum assisted in the initial growth and maintenance of the viable leptospires and the superoxide dismutase enzyme allowed them to adapt to the medium. These culture strategies allowed for the isolation and convenient molecular characterization of two genotypes of serovar Hardjo, creating new insight into the seroepidemiology of leptospirosis and its specific genotypes. It also provides new information for the immunoprophylaxis of bovine leptospirosis.

Plurality of Leptospira strains on slaughtered animals suggest a broader concept of adaptability of leptospires to cattle

Leptospirosis in bovines is in majority determined by the host-adapted serovars, mainly Hardjo (types Hardjoprajitno and Hardjobovis), that belong to the serogroup Sejroe. Members of other serogroups as Pomona and Tarassovi have been eventually reported, mainly when outbreaks occurs. Nevertheless, the real role of other strains (non-Hardjo) on determining disease or being transmitted by cattle free of apparent clinical signs of acute infection remains to be elucidated. In that context, the aim of the present study was to investigate the hypothesis that strains of serovars/serogroups other than Hardjo may also be maintained and shed by cattle free of clinical signs. Samples of urine and/or vaginal fluid were collected from 697 bovines from a slaughterhouse located close to Rio de Janeiro, Brazil. Culturing yielded 19 isolates what represents the largest number ever obtained in Brazil on similar studies. These strains were serogrouped and genetically characterized. Fifteen of those were described in other papers and four are first described on the present study. Isolates belong to three different species (Leptospira santarosai, L. alstonii and L. interrogans) and five serogroups (Sarmin, Tarassovi, Shermani, Grippotyphosa and Sejroe). The majority (84.2%) of the isolates belongs to the species L. santarosai, the most prevalent species on cattle in the studied region. Non-Hardjo (non-Sejroe) strains represent 57.9% of the isolates, what indicates an unexpected high diversity of serogroups obtained from these cattle. This suggest that non-Hardjo (non-Sejroe) strains may also be maintained and shed by cattle and that finding must be considered in the epidemiology and control of the disease.

High frequency of leptospiral vaginal carriers among slaughtered cows

Bovine leptospirosis is one of the most important reproductive diseases that compromise the productivity of cattle farming. However, the presence of the agent on vaginal environment is still poorly understood in cattle. Considering this context, the present study aimed to detect the presence of pathogenic Leptospira sp. in vaginal fluid (VF) of cows. VF and urine were collected from 254 cows from a slaughterhouse for bacteriological culture and PCR (lipL32 gene). Overall, eleven pure culture (4.3%) of leptospiral isolates were obtained. Leptospiral DNA was detected in 128 (50.4%) of VF samples and 81 (31.0%) of urine samples, while on 75 (29.5%) it was exclusively in VF and 28 (11.3%) only in the urine. Detection of leptospiral DNA and the recovery of viable leptospires from VF of a high number of cows without apparent symptoms highlight the role of vaginal carriers and indicate that venereal transmission (female-to-male) could occur in that species. Moreover, VF should be encouraged as a valuable sample for diagnosis of bovine genital leptospirosis.

Usage of Leptospira spp. local strains as antigens increases the sensitivity of the serodiagnosis of bovine leptospirosis

Leptospirosis is a zoonotic disease that occurs worldwide, particularly in tropical countries. In livestock the agent is responsible for reproductive problems such as infertility and abortion. Serogroup Sejroe, particularly serovar Hardjo, prevails in cattle in several regions. The microscopic agglutination test (MAT) is the current method for diagnosing leptospirosis. It has been proposed that the inclusion of local strains could detect a larger set of seroreactive animals. In that context, the aim of the present study was to evaluate if the usage of local strains as antigens increases the sensitivity of the serodiagnosis of bovine leptospirosis. Blood and urine samples were collected from 314 bovines from several herds randomly selected in a slaughterhouse in Rio de Janeiro, Brazil. Serological diagnosis was made with MAT using a 21 reference-strains panel (MAT21). Additionally, 12 local strains (MAT33) were included as antigens. PCR was performed with the urine samples and it was positive on 71 out of 222 samples (31.9%). MAT21 identified as seroreactive 173 (55.1%) out of the 314 animals studied, with Sejroe the most common (38.1%). In MAT33, 204 (65.0%) animals were seroreactive with a significant increase on seroreactivity (9.9%). In conclusion, MAT presented with a significant increase of sensitivity when local strains were used as antigens. Among the local strains, 2013_U152 (KP263062) (serogroup Shermani) and 2013_U280 (KP263069) (serogroup Grippotyphosa) showed to be more antigenic.

Genotyping of Leptospira directly in urine samples of cattle demonstrates a diversity of species and strains in Brazil

The aim of this study was to identify Leptospira in urine samples of cattle by direct sequencing of the secY gene. The validity of this approach was assessed using ten Leptospira strains obtained from cattle in Brazil and 77 DNA samples previously extracted from cattle urine, that were positive by PCR for the genus-specific lipL32 gene of Leptospira. Direct sequencing identified 24 (31·1%) interpretable secY sequences and these were identical to those obtained from direct DNA sequencing of the urine samples from which they were recovered. Phylogenetic analyses identified four species: L. interrogans, L. borgpetersenii, L. noguchii, and L. santarosai with the most prevalent genotypes being associated with L. borgpetersenii. While direct sequencing cannot, as yet, replace culturing of leptospires, it is a valid additional tool for epidemiological studies. An unexpected finding from this study was the genetic diversity of Leptospira infecting Brazilian cattle.