Reproductive Disorders and Leptospirosis: A Case Study in a Mixed-Species Farm (Cattle and Swine)

A systematic review on leptospirosis in cattle: A European perspective

Leptospirosis is a zoonotic disease which is globally distributed and represents a classic One Health issue that demands a comprehensive understanding of the hosts, transmission paths, and risk factors of transmission. Bovine leptospirosis often results in economic losses through its severe impact on reproduction performance while it threatens human health at human-cattle-environment interfaces. However, a clear analysis of the disease characteristics in European cattle is currently lacking. The objective of this review was to summarise the current knowledge on the epidemiology of bovine leptospirosis in Europe. We conducted a systematic literature review, screening four electronic databases, and filtered articles published between 2001 and 2021, in English, German, and French. Sixty-two articles were ultimately included in the review. The seroprevalence of leptospirosis in cattle was remarkably variable among studies, probably reflecting local variations but also heterogeneity in the study designs, laboratory methods, and sample sizes. Risk factors positively associated with the disease were diverse, related to local, environmental, and climatic parameters as well as farming practices. The most reported circulating Leptospira serogroups in European cattle were Sejroe (58.5%), Australis (41.5%), Grippotyphosa (41.5%), Icterohaemorrhagiae (37.7%), and Pomona (26.4%), which have also been associated with human infections worldwide. Abortion (58.6%) and fertility disorders (24.1%) were the most frequently reported signs of leptospirosis in European cattle and were generally associated with chronic infections. This work highlights several research gaps, including a lack of harmonisation in diagnostic methods, a lack of large-scale studies, and a lack of molecular investigations. Given that predictions regarding the climatic suitability for leptospirosis in Europe suggest an increase of leptospirosis risk it is important to raise awareness among stakeholders and motivate an integrated One Health approach to the prevention and control of this zoonotic disease in cattle and humans.

Leptospirosis and the Environment: A Review and Future Directions

Leptospirosis is a zoonotic disease of global importance with significant morbidity and mortality. However, the disease is frequently overlooked and underdiagnosed, leading to uncertainty of the true scale and severity of the disease. A neglected tropical disease, leptospirosis disproportionately impacts disadvantaged socioeconomic communities most vulnerable to outbreaks of zoonotic disease, due to contact with infectious animals and contaminated soils and waters. With growing evidence that Leptospira survives, persists, and reproduces in the environment, this paper reviews the current understanding of the pathogen in the environment and highlights the unknowns that are most important for future study. Through a systematic Boolean review of the literature, our study finds that detailed field-based study of Leptospira prevalence, survival, and transmission in natural waters and soils is lacking from the current literature. This review identified a strong need for assessment of physical characteristics and biogeochemical processes that support long-term viability of Leptospira in the environment followed by epidemiological assessment of the transmission and movement of the same strains of Leptospira in the present wildlife and livestock as the first steps in improving our understanding of the environmental stage of the leptospirosis transmission cycle.

Unconventional Sites for Diagnosis of Leptospirosis in Bovine Anicteric Fetuses

BACKGROUND

Bovine leptospirosis is an important reproductive disease and abortion is a major sign, leading to economic impacts. Due to its multifactorial etiology, the proper diagnosis of the cause of the abortion is crucial. Necropsy of the fetuses followed by molecular analysis is recommended for diagnosis, and the investigation mainly occurs in the kidneys and liver. This study aimed to analyze unconventional sites for the presence of leptospiral DNA in bovine anicteric aborted fetuses.

METHODS

Five fetuses of the same herd were received for necropsy and diagnosis. Conventional lipL32-PCR was performed in the fetuses' kidneys, livers, lungs, hearts, spleens, subcapsular kidney content, abomasal fluid, and in the cavity's hemorrhagic contents. To complete the investigation, the sera of 30 cows of the herd were collected to perform the serologic screening by Microscopic Agglutination Test. In addition, six subfertile non-pregnant cows from the same herd were selected due to their low reproductive performance, and genital samples (uterine fragment and cervicovaginal mucus) and urine were collected for lipL32-PCR. PCR-positive samples were submitted to a nested PCR of the secY gene and intended for sequencing.

RESULTS

The herd presented seroreactive animals (11/30, 36.6%), all against the Sejroe serogroup, with titers between 200 and 1600. In necropsy, four fetuses showed hemorrhagic and anicteric lesions, while one fetus had no macroscopic lesions. Regarding molecular analysis, all the fetuses were positive in lipL32-PCR and the positive sites were the heart, lungs, subcapsular kidney content, thymus, kidneys, liver, and abomasal fluid. Only one fetus presented positive results in the kidney and liver, while three fetuses were positive in the abomasal fluid. Five of six cows were positive for lipL32-PCR, all being positive only in genital samples. Of the fetuses and the cows, seven sequences were obtained and all were identified as Leptospira interrogans serogroup Sejroe serovar Hardjoprajitno.

CONCLUSIONS

In order to improve the diagnosis of leptospirosis in cows, it is recommended to perform a comprehensive analysis of the samples, beyond the kidneys and liver. Thus, we highly encourage testing multiple organs by PCR to investigate abortions suspected of bovine leptospirosis, particularly in anicteric fetuses.

Global Seropositivity of Swine Leptospirosis: Systematic Review and Meta-Analysis

Leptospirosis is a major threat to public health worldwide; however, there is no study focused on global seropositivity in pigs. In this study, we grouped publications and performed a systematic review with meta-analysis to gather data related to swine leptospirosis seropositivity published globally. The search method initially used returned a total of 1183 results, of which 20 met all predefined criteria and were therefore included in this review. Meta-analysis with general data was performed and a combined seropositivity of 21.95% was found. Seropositivity was 36.40% in South America, 34.05% in North America, 22.18% in Africa, 17.40% in Oceania, 13.30% in Europe and 13.36% in Asia. The results suggest that there is high seropositivity for leptospirosis in pigs worldwide. Information compiled from this research is relevant to understanding the spread of leptospirosis globally. It is expected that these indicators will contribute to a better understanding of the epidemiology of the disease with a focus on its control and, consequently, on the reduction of cases in the human and animal population.

Bovine leptospirosis: effects on reproduction and an approach to research in Colombia

Leptospirosis is the most widespread zoonosis worldwide, causing severe effects on beef and dairy cattle farming and other livestock. Colombia geographical location in the tropical zone, high biodiversity, and climatic conditions promote Leptospira growth and prevalence. This review article presents state-of-the-art knowledge about the effects of leptospirosis on bovine reproduction and a critical analysis of the research carried out in Colombia. The analysis of the information allows us to infer a sustained increase in prevalence over the last decade in the densest livestock production areas and a high serovar diversity of circulating pathogenic Leptospira. Given the zoonotic nature of leptospirosis, an inter-institutional effort is required to implement prevention, control, and monitoring programs under one-health concept.

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.

An historical view of the experimental leptospiral infection in ruminants

The first experimental infections with Leptospira in ruminants were conducted in the 1950s, primarily assessed the pathogenesis caused by serovar Pomona in cows. Throughout the decades, experimental infections have also demonstrated the clinical aspects of the infection by other strains, mainly Hardjo. Despite the important outcomes observed in experimental infections in ruminants, there is still a large discrepancy regarding the ideal dose, route, strain, model species or animal age that should be used to reproduce the acute and chronic leptospirosis in ruminants. In this context, the present study aimed to review the historical processes involved on the experimental leptospiral infection in ruminants. The inclusion criteria were papers that clearly described inoculation route, strain, dose, clinical signs and animal age. Overall, 37 experiments were noted. The most frequently reported clinical signs were fever, prostration, hematuria and death, with the majority of them occurring in young animals infected by incidental strains. Regarding reproductive problems, they occurred in the majority of the experiments and were also more related to incidental strains. In this context, abortions, retained placenta and weak fetuses were the most frequent symptoms. Noteworthy that although the mechanisms of the clinical acute disease either systemic or reproductive, is reasonably well understood, the physiopathology involved on reproductive problems due to the silent chronic infection is less discussed and remains to be elucidated. In this context, it is evident the need for studies focused on the genital infection and reproductive aspects of leptospiral infection in ruminants.

SEROLOGIC SURVEY OF LEPTOSPIRA SPP. IN CAPTIVE ANIMALS FROM VERACRUZ, MEXICO

Leptospirosis is the most common zoonotic disease worldwide and is considered endemic in countries with tropical climates. It is caused by 10 species of the Leptospira genus and by more than 275 serovars which can affect a wide range of vertebrates. In the Americas, 122 species of four classes of vertebrates have been reported to be infected or exposed to many Leptospira species. Many of these reports are from zoos and rehabilitation centers. Mexico has one single study that reported antibody titers against Leptospira in zoo animals. The purpose of this research was to identify the degree of exposure of some captive mammals and reptiles in Veracruz, a Mexican state with endemic leptospirosis, through microagglutination using 14 live strains of five Leptospira species. Sera samples were collected from 55 animals of 11 species from two classes (Mammalia and Reptilia), four orders (Primates, Artiodactyla, Carnivora, Crocodilia), and nine genera. The more prevalent serovars were Icterohaemorrhagiae and Tarassovi and the highest titers were reactive to the serovar Icterohaemorrhagiae with a value of 1: 51,200.

High frequency of seropositive and carriers of Leptospira spp. in pigs in the semiarid region of northeastern Brazil

Carrier animals are considered key in the transmission cycle of leptospirosis. Although investigations have been carried out on several species, the role of pigs in the epidemiology of the disease is still poorly studied in the semi-arid region. Thus, the objective of this study was to determine the presence of Leptospira spp. in the genitourinary tract of pigs intended for slaughter. Fifty pigs were used: adults and unvaccinated. Samples of the kidney, urine, and vaginal fluid were collected for the molecular detection of Leptospira spp. and blood samples for the serological test. The molecular test was performed using the polymerase chain reaction (PCR), and the serological test was performed with the microscopic agglutination test (MAT). Samples with DNA amplification were submitted to genetic sequencing. Twenty (40%) animals were found with anti-Leptospira spp. antibodies, and the majority of the reactions (50%) occurred for the serogroup Tarassovi. Leptospiral DNA was found in the tissue of 11 (22%) pigs. The gene from a urine sample was sequenced and showed similarity to L. borgpetersenii. The results evidenced a high rate of porcine carriers; therefore, they appear to be important sources of agent infection, being potential transmitters of the disease to other animal species and man.

Poly(diaminosulfide) Microparticle-Based Vaccine for Delivery of Leptospiral Antigens

Leptospirosis is a debilitating infectious disease that detrimentally affects both animals and humans; therefore, disease prevention has become a high priority to avoid high incidence rates of disease in the herd and break the transmission cycle to humans. Thus, there remains an important unmet need for a prophylactic vaccine that can provide long-term immunity against leptospirosis in cattle. Herein, a novel vaccine formulation was developed where poly(diaminosulfide) polymer was employed to fabricate microparticles encapsulating the antigen of Leptospira borgpetersenii serovar Hardjo strain HB15B203 (L203-PNSN). A prime-boost vaccination with a L203-PNSN microparticle formulation increased the population of L203-specific CD3⁺ T cells and CD21⁺ B cells to levels that were significantly higher than those of cattle vaccinated with L203-AlOH or the vehicle control (empty PNSN microparticles and blank AlOH). In addition, L203-PNSN was demonstrated to stimulate durable humoral immune responses as evidenced by the increases in the antibody serum titers following the vaccination. It was also found that cattle vaccinated with L203-PNSN produced higher macroscopic agglutinating titers than cattle in other groups. Thus, it can be concluded that L203-PNSN is a novel first-in-class microparticle-based Leptospira vaccine that represents a powerful platform with the potential to serve as a prophylactic vaccine against leptospiral infection in cattle.

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.

Reduced susceptibility in leptospiral strains of bovine origin might impair antibiotic therapy

Leptospirosis is a worldwide zoonotic disease determined by pathogenic spirochetes of the genus Leptospira. The control of bovine leptospirosis involves several measures including antibiotic treatment of carriers. Despite its importance, few studies regarding antimicrobial susceptibility of strains from bovine origin have been conducted. The aim of this study was to determine the in vitro susceptibility of Leptospira strains obtained from cattle in Rio de Janeiro, Brazil, against the main antibiotics used in bovine veterinary practice. A total of 23 Leptospira spp. strains were investigated for minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) using broth macrodilution. At the species level, there were not differences in MIC susceptibility except for tetracycline (P < 0.05). Nevertheless, at the serogroup level, differences in MIC were observed among Sejroe strains, mainly for ceftiofur, doxycycline and in MBC for streptomycin (P < 0.05). One strain presented MBC values above maximum plasmatic concentration described for streptomycin and was classified as presenting reduced susceptibility. Efficacy of antimicrobial therapy on bovine leptospirosis could be compromised due to occurrence of infection by Leptospira strains presenting reduced susceptibility.