Abstract: Equine leptospirosis can result in abortion, stillbirth, neonatal death, placentitis, and uveitis. Horses can also act as subclinical reservoir hosts of infection, which are characterized as asymptomatic carriers that persistently excrete leptospires and transmit disease. In this study, PCR and culture were used to assess urinary shedding of pathogenic Leptospira from 37 asymptomatic mares. Three asymptomatic mares, designated as H2, H8, and H9, were PCR-positive for lipL32, a gene specific for pathogenic species of Leptospira. One asymptomatic mare, H9, was culture-positive, and the recovered isolate was classified as L. kirschneri serogroup Australis serovar Rushan. DNA capture and enrichment of Leptospira genomic DNA from PCR-positive, culture-negative samples determined that asymptomatic mare H8 was also shedding L. kirschneri serogroup Australis, whereas asymptomatic mare H2 was shedding L. interrogans serogroup Icterohaemorrhagiae. Sera from all asymptomatic mares were tested by the microscopic agglutination test (MAT) and 35 of 37 (94.6%) were seropositive with titers ranging from 1:100 to 1:3200. In contrast to asymptomatic mares, mare H44 presented with acute spontaneous abortion and a serum MAT titer of 1:102,400 to L. interrogans serogroup Pomona serovar Pomona. Comparison of L. kirschneri serogroup Australis strain H9 with that of L. interrogans serogroup Pomona strain H44 in the hamster model of leptospirosis corroborated differences in virulence of strains. Since lipopolysaccharide (LPS) is a protective antigen in bacterin vaccines, the LPS of strain H9 (associated with subclinical carriage) was compared with strain H44 (associated with spontaneous abortion). This revealed different LPS profiles and immunoreactivity with reference antisera. It is essential to know what species and serovars of Leptospira are circulating in equine populations to design efficacious vaccines and diagnostic tests. Our results demonstrate that horses in the US can act as reservoir hosts of leptospirosis and shed diverse pathogenic Leptospira species via urine. This report also details the detection of L. kirschneri serogroup Australis serovar Rushan, a species and serotype of Leptospira, not previously reported in the US.
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The research article focuses on an investigation regarding equine horses, focusing on how they can act as reservoir hosts for leptospirosis-causing bacteria. The study utilized testing and culture methods to identify pathogenic species of Leptospira in healthy horses, and discovered divergent strains of the bacteria that differed in terms of their virulence.
Assessing Urinary Shedding in Mares
The research involved the collection of data from 37 asymptomatic mares.
Testing was conducted using a polymerase chain reaction (PCR) and culture techniques to check for urinary shedding of pathogenic Leptospira.
Three of the horses yielded a positive result for Leptospira, echoing the role of horses as subclinical reservoir hosts or passive carriers of the disease that can cause a variety of health complications from spontaneous abortions to uveitis.
Identification of Diverse Pathogenic Leptospira
Different asymptomatic mares were observed to be shedding distinct strains of Leptospira, including serogroups Australis and Icterohaemorrhagiae.
The researchers examined the serum from each of these horses using the microscopic agglutination test (MAT) and found a majority (94.6%) to be seropositive for Leptospira, with a range of MAT titers from 1:100 to 1:3200.
Distinction in Strains and Virulence Factors
The virulence of different Leptospira strains was compared in hamster models, showing distinct levels of virulence based on the specific strain.
Furthermore, the research highlighted the importance of lipopolysaccharide (LPS) as a protective antigen in vaccines, because differing LPS profiles were found in Leptospira strains associated with subclinical carriage and spontaneous abortion.
Importance of the Study and Future Directions
This research contributes valuable data, showing that horses in the US can propagate leptospirosis by shedding various pathogenic Leptospira species in their urine.
The study highlights the need for further research to design effective vaccines and diagnostic tests, tailoring them to the species and serovars of Leptospira prevalent among equine populations.
The detection of the Leptospira serogroup Australis serovar Rushan, previously unreported in the US, emphasizes the importance of regular testing and continuous research to understand the evolving nature of diseases in animal populations.
Cite This Article
APA
Hamond C, Adam EN, Stone NE, LeCount K, Anderson T, Putz EJ, Camp P, Hicks J, Stuber T, van der Linden H, Bayles DO, Sahl JW, Schlater LK, Wagner DM, Nally JE.
(2024).
Identification of equine mares as reservoir hosts for pathogenic species of Leptospira.
Front Vet Sci, 11, 1346713.
https://doi.org/10.3389/fvets.2024.1346713
National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Ames, IA, United States.
National Centers for Animal Health Leptospira Working Group, U.S. Department of Agriculture, Ames, IA, United States.
Adam, Emma N
Department of Veterinary Science, University of Kentucky, Maxwell H. Gluck Equine Research Center, Lexington, KY, United States.
Stone, Nathan E
The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, AZ, United States.
LeCount, Karen
National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Ames, IA, United States.
National Centers for Animal Health Leptospira Working Group, U.S. Department of Agriculture, Ames, IA, United States.
Anderson, Tammy
National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Ames, IA, United States.
National Centers for Animal Health Leptospira Working Group, U.S. Department of Agriculture, Ames, IA, United States.
Putz, Ellie J
Infectious Bacterial Diseases Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Ames, IA, United States.
Camp, Patrick
National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Ames, IA, United States.
Hicks, Jessica
National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Ames, IA, United States.
Stuber, Tod
National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Ames, IA, United States.
van der Linden, Hans
Department of Medical Microbiology and Infection Prevention, World Organisation for Animal Health (WOAH) and National Collaborating Centre for Reference and Research on Leptospirosis, Amsterdam University Medical Center, University of Amsterdam, Amsterdam, Netherlands.
Bayles, Darrell O
Infectious Bacterial Diseases Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Ames, IA, United States.
Sahl, Jason W
The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, AZ, United States.
Schlater, Linda K
National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Ames, IA, United States.
National Centers for Animal Health Leptospira Working Group, U.S. Department of Agriculture, Ames, IA, United States.
Wagner, David M
The Pathogen and Microbiome Institute, Northern Arizona University, Flagstaff, AZ, United States.
Nally, Jarlath E
National Centers for Animal Health Leptospira Working Group, U.S. Department of Agriculture, Ames, IA, United States.
Infectious Bacterial Diseases Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Ames, IA, United States.
Conflict of Interest Statement
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.
References
This article includes 92 references
Ellis WA. Animal leptospirosis. Curr Top Microbiol Immunol (2015) 387:99–137.
Faine S, Adler B, Bolin C, Perolat P. Leptospira and Leptospirosis. 2nd ed. Melbourne, Australia: MediSci; (1999).
Vincent AT, Schiettekatte O, Goarant C, Neela VK, Bernet E, Thibeaux R. Revisiting the taxonomy and evolution of pathogenicity of the genus leptospira through the prism of genomics. PLoS Negl Trop Dis (2019) 13:e0007270.
Fernandes LGV, Stone NE, Roe CC, Goris MGA, van der Linden H, Sahl JW. Leptospira sanjuanensis sp. nov., a pathogenic species of the genus leptospira isolated from soil in Puerto Rico. Int J Syst Evol Microbiol (2022) 72:5560.
Casanovas-Massana A, Vincent AT, Bourhy P, Neela VK, Veyrier FJ, Picardeau M. Leptospira dzianensis and Leptospira putramalaysiae are later heterotypic synonyms of Leptospira yasudae and Leptospira stimsonii. Int J Syst Evol Microbiol (2021) 71:4713.
Korba AA, Lounici H, Kainiu M, Vincent AT, Mariet JF, Veyrier FJ. Leptospira abararensis sp. nov. and Leptospira chreensis sp. nov., four new species isolated from water sources in Algeria. Int J Syst Evol Microbiol (2021) 71:5148.
Costa F, Hagan JE, Calcagno J, Kane M, Torgerson P, Martinez-Silveira MS. Global morbidity and mortality of leptospirosis: a systematic review. PLoS Negl Trop Dis (2015) 9:e0003898.
Polle F, Storey E, Eades S, Alt D, Hornsby R, Zuerner R. Role of intraocular Leptospira infections in the pathogenesis of equine recurrent uveitis in the southern United States. J Equine Vet (2014) 34:1300–6.
Brem S, Gerhards H, Wollanke B, Meyer P, Kopp H. Demonstration of intraocular leptospira in 4 horses suffering from equine recurrent uveitis (ERU). Berliner und Munchener Tierarztliche Wochenschrift (1998) 111:415–7.
Nally JE, Hornsby RL, Alt DP, Bayles D, Wilson-Welder JH, Palmquist DE. Isolation and characterization of pathogenic leptospires associated with cattle. Vet Microbiol (2018) 218:25–30.
Nally JE, Ahmed AA, Putz EJ, Palmquist DE, Goris MG. Comparison of real-time PCR, bacteriologic culture and fluorescent antibody test for the detection of Leptospira borgpetersenii in urine of naturally infected cattle. Vet Sci (2020) 7:66.
Bankevich A, Nurk S, Antipov D, Gurevich AA, Dvorkin M, Kulikov AS. SPAdes: a new genome assembly algorithm and its applications to single-cell sequencing. J Comput Biol (2012) 19:455–77.
Hartskeerl R, Smits H, Korver H, Goris M, Terpstra W. Manual international course on laboratory methods for the diagnosis of leptospirosis. Amsterdam, The Netherlands: KIT; (2006).
Stone NE, McDonough RF, Hamond C, LeCount K, Busch JD, Dirsmith KL. DNA capture and enrichment: a culture-independent approach for characterizing the genomic diversity of pathogenic Leptospira species. Microorganisms (2023) 11:51282.
McKenna A, Hanna M, Banks E, Sivachenko A, Cibulskis K, Kernytsky A. The genome analysis toolkit: a MapReduce framework for analyzing next-generation DNA sequencing data. Genome Res (2010) 20:1297–303.
Sahl JW, Lemmer D, Travis J, Schupp JM, Gillece JD, Aziz M. NASP: an accurate, rapid method for the identification of SNPs in WGS datasets that supports flexible input and output formats. Microb Genom (2016) 2:e000074.
Nguyen LT, Schmidt HA, von Haeseler A, Minh BQ. IQ-TREE: a fast and effective stochastic algorithm for estimating maximum-likelihood phylogenies. Mol Biol Evol (2015) 32:268–74.
Kalyaanamoorthy S, Minh BQ, Wong TKF, von Haeseler A, Jermiin LS. ModelFinder: fast model selection for accurate phylogenetic estimates. Nat Methods (2017) 14:587–9.
Putz EJ, Andreasen CB, Stasko JA, Fernandes LG, Palmer MV, Rauh MJ. Circulating foamy macrophages in the Golden Syrian Hamster (Mesocricetus auratus) model of leptospirosis. J Comp Pathol (2021) 189:98–109.
R. Core Team. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. Available at: https://www.R-project.org/. (2021).
Hamond C, Browne AS, de Wilde LH, Hornsby RL, LeCount K, Anderson T. Assessing rodents as carriers of pathogenic Leptospira species in the U.S. Virgin Islands and their risk to animal and public health. Sci Rep (2022) 12:4846.
Nascimento AL, Ko AI, Martins EA, Monteiro-Vitorello CB, Ho PL, Haake DA. Comparative genomics of two Leptospira interrogans serovars reveals novel insights into physiology and pathogenesis. J Bacteriol (2004) 186:2164–72.
Nascimento AL, Verjovski-Almeida S, Van Sluys MA, Monteiro-Vitorello CB, Camargo LE, Digiampietri LA. Genome features of Leptospira interrogans serovar Copenhageni. Braz J Med Biol Res (2004) 37:459–77.
Nally JE, Wilson-Welder JH, Hornsby RL, Palmer MV, Alt DP. Inbred rats as a model to study persistent renal leptospirosis and associated cellular immune responsiveness. Front Cell Infect Microbiol (2018) 8:66.
Stallman ND. International committee on systematic bacteriology subcommittee on the taxonomy of Leptospira: minutes of the meeting, 5 and 6 September 1986, Manchester, England. Int J Syst Evol Microbiol (1987) 37:472–3.
Brenner DJ, Kaufmann AF, Sulzer KR, Steigerwalt AG, Rogers FC, Weyant RS. Further determination of DNA relatedness between serogroups and serovars in the family Leptospiraceae with a proposal for Leptospira alexanderi sp. nov. and four new Leptospira genomospecies. Int J Syst Evol Microbiol (1999) 49:839–58.
Que-Gewirth NL, Ribeiro AA, Kalb SR, Cotter RJ, Bulach DM, Adler B. A methylated phosphate group and four amide-linked acyl chains in Leptospira interrogans lipid a. the membrane anchor of an unusual lipopolysaccharide that activates TLR2. J Biol Chem (2004) 279:25420–9.
Nally JE, Monahan AM, Miller IS, Bonilla-Santiago R, Souda P, Whitelegge JP. Comparative proteomic analysis of differentially expressed proteins in the urine of reservoir hosts of leptospirosis. PLoS One (2011) 6:e26046.
Ristow P, Bourhy P, da Cruz McBride FW, Figueira CP, Huerre M, Ave P. The OmpA-like protein Loa22 is essential for leptospiral virulence. PLoS Pathog (2007) 3:e97.
Fernandes LGV, Teixeira AF, Nascimento A. Evaluation of Leptospira interrogans knockdown mutants for LipL32, LipL41, LipL21, and OmpL1 proteins. Front Microbiol (2023) 14:1199660.
Guitian J, Thurmond MC, Hietala SK. Infertility and abortion among first-lactation dairy cows seropositive or seronegative for Leptospira interrogans serovar Hardjo. J Am Vet Med Assoc (1999) 215:515–8.
Putz EJ, Nally JE. Investigating the immunological and biological equilibrium of reservoir hosts and pathogenic Leptospira: balancing the solution to an acute problem?. Front Microbiol (2020) 11:2005.
Steven EW, Rogers GM, Ramachandran S, Engelken TJ, Epperson WB, Larson RL. Herd prevalence and risk factors of Leptospira infection in beef cow/calf operations in the United States. The. Bovine Practitioner (2007) 41:15–23.
Ellis WA, O’Brien JJ, Cassells J. Role of cattle in the maintenance of Leptospira interrogans serotype Hardjo infection in Northern Ireland. Vet Rec (1981) 108:555–7.
Ellis W, Montgomery J, Cassells J. Dihydrostreptomycin treatment of bovine carriers of Leptospira interrogans serovar Hardjo. Res Vet Sci (1985) 39:292–5.
Nally JE, Grassmann AA, Planchon S, Sergeant K, Renaut J, Seshu J. Pathogenic Leptospires modulate protein expression and post-translational modifications in response to mammalian host signals. Front Cell Infect Microbiol (2017) 7:362.
Putz EJ, Fernandes LG, Sivasankaran SK, Bayles DO, Alt DP, Lippolis JD. Some like it hot, some like it cold; proteome comparison of Leptospira borgpetersenii serovar Hardjo strains propagated at different temperatures. J Proteome (2022) 262:104602.
Sykes JE, Haake DA, Gamage CD, Mills WZ, Nally JE. A global one health perspective on leptospirosis in humans and animals. J Am Vet Med Assoc (2022) 260:1589–96.
Hamond C, LeCount K, Anderson T, Putz EJ, Stuber T, Hicks J. Isolation and characterization of saprophytic and pathogenic strains of Leptospira from water sources in the Midwestern United States. Frontiers in Water (2024) 6:8088.
Nally JE, Arent Z, Bayles DO, Hornsby RL, Gilmore C, Regan S. Emerging infectious disease implications of invasive mammalian species: the greater white-toothed shrew (Crocidura russula) is associated with a novel Serovar of pathogenic Leptospira in Ireland. PLoS Negl Trop Dis (2016) 10:e0005174.
Hamond C, Tibbs-Cortes B, Fernandes LGV, LeCount K, Putz EJ, Anderson T, Camp P, Stuber T, Hicks J, van der Linden H, Dos Santos Ribeiro P, Bayles DO, Schlater LK, Nally JE. Leptospira gorisiae sp. nov, L. cinconiae sp. nov, L. mgodei sp. nov, L. milleri sp. nov and L. iowaensis sp. nov: five new species isolated from water sources in the Midwestern United States. Int J Syst Evol Microbiol 2025 Jan;75(1).
Ackermann MR, Bannantine JP. Progress and persistence of diseases of high consequence to livestock in the United States. One Health 2024 Dec;19:100865.