The role of Leptospira santarosai serovar Guaricura as agent of Bovine Genital Leptospirosis

Molecular epidemiology of Leptospira spp. serogroup Sejroe associated with chronic bovine leptospirosis

Pathogenic bacteria Leptospira spp. are commonly associated with bovine leptospirosis, characterized chiefly by chronic and subclinical reproductive disorders. Strains from the Sejroe serogroup play a significant role in these chronic genital infections known as Bovine Genital Leptospirosis (BGL), which notably impact cattle health. This study aims to deepen our understanding of BGL by investigating the genetic diversity, geographical distribution, and specific anatomical sites of infection of the causative agents. Initially, uterine fragments and cervicovaginal mucus were collected from 47 cows and subjected to PCR targeting the lipL32 gene. Positive samples in lipL32-PCR (9 samples) underwent genotyping based on the secY gene. Subsequently, sequences were aligned with GenBank entries (108 sequences) and analyzed in silico. All nine sequences from this study were identified as L. interrogans with an identity >99 % to serogroup Sejroe reference strains (Norma and L53). In the broader analysis, the most prevalent species observed was L. borgpetersenii, followed by L. interrogans and L. santarosai. The haplotype network of L. interrogans revealed that haplogroups B and C exclusively included L. interrogans strains of genital origin, while haplogroup A encompassed strains from renal sources as well. These findings underscore the significance of the L. borgpetersenii genotype Hardjobovis and L. interrogans genotype Hardjoprajitno as the predominant circulating strains and highlight the existence of distinct haplogroups of pathogenic leptospires originating from genital sources. We advocate for the use of secY as an effective genetic marker for Leptospira spp. and stress the necessity for additional research prioritizing the genital tract. The outcomes of this study contribute to the development of improved control measures for chronic cattle diseases and provide valuable guidance for future investigations.

Molecular Characterization of Leptospira Species among Patients with Acute Undifferentiated Febrile Illness from the Municipality of Villeta, Colombia

Leptospira is a bacterial genus that includes several pathogenic species related to leptospirosis. In Colombia, leptospirosis is a mandatorily reported disease, widely distributed across the country. In the Villeta municipality, leptospirosis has been identified as an important cause of febrile illness; however, to date, no studies have been performed to identify the circulating species. A genus-specific qualitative qPCR was performed on DNA extracted from febrile patients' acute-phase whole-blood samples targeting a fragment of the rrs gene. Positive qPCR samples were further amplified for the adk, icdA, LipL32, LipL41, rrs, and secY genes through conventional PCR for sequencing. All high-quality obtained sequences were further assessed through concatenated phylogenetic analysis. A total of 25% (14/56) of febrile patients' acute blood samples were positive for Leptospira spp. High-quality sequences were obtained for only five genes, and analysis through concatenated phylogeny identified that all sequences clustered within the P1/pathogenic clade; some of them formed a robustly supported clade with Leptospira santarosai, and others were closely related with other Leptospira species but exhibited considerable genetic divergence. We describe the presence of pathogenic Leptospira species among febrile patients from the Villeta municipality and identify L. santarosai and other Leptospira species as causative agents of leptospirosis in the region.

Draft-genome sequences of Leptospira santarosai strains isolated from urogenital tract of cows

Leptospira santarosai serovar Guaricura is adapted to bovines and is associated with a chronic disease that causes reproductive disorders, leading to important economic losses. Here, we present the draft genomes of three L. santarosai strains isolated from vaginal fluid and one from the urine of cows with reproductive disorders from Brazil.

Field application of a combined serological-molecular testing protocol for diagnosing genital leptospirosis in naturally infected cows with gestational losses

BACKGROUND

Bovine genital leptospirosis (BGL) causes chronic reproductive disease in cattle. This study aimed to apply a combined serological-molecular testing protocol under field conditions for diagnosing BGL in cows with gestational losses.

METHODS

Three beef herds with reproductive failures were studied, and 60 cows with gestational losses (20 from each herd) were randomly selected for laboratory diagnosis of BGL. In addition, 40 cows with normal pregnancy were included as a control. Blood samples were collected from all 100 cows for microscopic agglutination testing, and cervicovaginal mucus (CVM) samples were collected from 28 cows with gestational losses and 20 control cows for lipL32-PCR.

RESULTS

All herds had high Leptospira seroreactivity (>65%), mainly against serogroup Sejroe. Ten of the 28 CVM samples from cows with gestational losses were PCR-positive, while all samples from the control group were negative (p < 0.05).

LIMITATIONS

Unfortunately, the positive samples did not amplify in secY-PCR for nucleotide sequencing, which would allow the identification of leptospiral strains.

CONCLUSION

Serology was sufficient to indicate leptospirosis at the herd level, but the definitive diagnosis of BGL was only possible using CVM PCR. Although seroreactivity against serogroup Sejroe has been associated with gestational losses, this is the first study to conduct CVM PCR as a confirmatory test for BGL diagnosis in extensive beef herds under field conditions.

Successful treatment with streptomycin of genital leptospirosis in naturally infected cows under field conditions

The single-dose protocol of streptomycin treatment has been recommended to treat renal leptospirosis in bovines. However, treating genital infection remains a challenge. Recently, a protocol using three doses of streptomycin demonstrated effectiveness in the genital clearance of experimentally infected ewes. Therefore, the present study aimed to apply this three-dose protocol for genital infection treatment in naturally infected cows under field conditions. Thirty beef cows were diagnosed as positive by lipL32-PCR in their genital samples. Nucleotide sequences (n = 10) characterized them as Leptospira interrogans sg Sejroe, genetically related to Hardjoprajitno strains. After molecular diagnosis, 13 cows received a single dose of 25 mg/kg streptomycin. The other 17 cows were submitted to the three-dose protocol. The successful treatment rate of genital infection on the single streptomycin dose was 7/13 (53.8%), while the cows that received the three doses 16/17 were negative (94.1% of efficacy). Based on those results, we conclude that the standard treatment preconized for renal infection is not adequate for genital infection, and the three-dose protocol was successful in eliminating the carrier status of genital leptospirosis.

Leptospira borgpetersenii serovar Hardjo and Leptospira santarosai serogroup Pyrogenes isolated from bovine dairy herds in Puerto Rico

Leptospirosis is one of the most common zoonotic diseases in the world and endemic in the Caribbean Islands. Bovine leptospirosis is an important reproductive disease. Globally, cattle are recognized as a reservoir host for L. borgpetersenii serovar Hardjo, which is transmitted via urine, semen, and uterine discharges, and can result in abortion and poor reproductive performance. The dairy industry in Puerto Rico comprises up to 25% of agriculture-related income and is historically the most financially important agricultural commodity on the island. In this study, we report the isolation of two different pathogenic Leptospira species, from two different serogroups, from urine samples collected from dairy cows in Puerto Rico: L. borgpetersenii serogroup Sejroe serovar Hardjo and L. santarosai serogroup Pyrogenes. Recovered isolates were classified using whole-genome sequencing, serotyping with reference antisera and monoclonal antibodies, and immunoblotting. These results demonstrate that dairy herds in Puerto Rico can be concurrently infected with more than one species and serovar of Leptospira, and that bacterin vaccines and serologic diagnostics should account for this when applying intervention and diagnostic strategies.

The Efficacy of Vaccination in the Prevention of Renal and Genital Leptospirosis in Experimentally Infected Sheep

(1) Background: Leptospirosis, mainly determined by strains belonging to serogroup Sejroe, has a direct impact on the reproductive efficiency of ruminants, such as sheep. In Brazil, Leptospira santarosai serovar Guaricura, known to be able to chronically colonize the uterine environment, is of special note. Although vaccination minimizes the effects of acute disease, whether or not it can protect from renal colonization remains controversial, and its effects on the genital tract are unknown. In this context, the present study aims to investigate the efficacy of vaccination in the prevention of experimental genital leptospirosis. (2) Methods: Eighteen sheep were divided into three groups: one vaccinated with a polyvalent commercial bacterin, one vaccinated with an autologous bacterin, and one unvaccinated. After 14 days, the sheep were experimentally challenged with 10⁸ leptospires (L. santarosai, serogroup Sejroe, serovar Guaricura, strain FV52) intraperitoneally. Serology and colonization of the urinary and genital tracts were carried out monthly by PCR for 210 days in all animals. (3) Results: Vaccination significantly elicited antibody titers with a predominance of agglutinins against serogroup Sejroe. Both urinary and genital infections were confirmed by PCR. Positivity in urine PCR was absent after D120, while genital infection persisted until the end of the study. Serological results and the finding that vaccination did not avoid renal colonization align with previous studies. Despite vaccination, Leptospira established chronic and asymptomatic colonization of the genital tract until D210, an outstanding finding that remains to be fully understood in its mechanisms. (4) Conclusions: This is the first study conducted to analyze the effects of vaccination in the prevention of genital leptospirosis.