FREE SHIPPING over $40
OVER 10000 FIVE-STAR REVIEWS
5% OFF ALL SUBSCRIPTIONS
100% HAPPINESS GUARANTEE
Analyze Diet
0
Veterinary research communications2026; 50(5); 497; doi: 10.1007/s11259-026-11438-3

Intrauterine ozone therapy reduces bacterial load in mares with mixed bacterial endometritis: a longitudinal study.

Abstract: Mixed bacterial endometritis poses a therapeutic challenge in mares due to the coexistence of multiple pathogens with divergent antimicrobial susceptibility profiles. This study evaluated the effects of intrauterine ozone insufflation on uterine bacterial load and endometrial inflammatory response in mares with naturally acquired mixed bacterial endometritis. Fifteen mares with mixed bacterial infection were allocated to two treatment groups: a pathological control group receiving pure medical oxygen insufflation (PC; n = 6) and an ozone-treated group receiving 42 µg/mL ozone for three consecutive days (O3; n = 9). Eight clinically healthy mares subjected to the same ozone protocol served as a safety control group. Bacterial load was quantified in colony-forming units per milliliter (CFU/mL) from low-volume uterine flushings obtained at baseline (C1D0), six days post-treatment (C1D6), and at the onset of the subsequent estrous cycle (C2D0). A linear mixed model revealed significant group-by-time interactions for both bacterial load and neutrophil counts (P < 0.001). At C1D6, the O3 group showed a median 100% reduction in bacterial load (from 65,000 to 0 CFU/mL; P < 0.001), a culture positivity rate of 22.2% not significantly different from healthy controls (P = 0.260) and an 88.9% reduction in neutrophil counts. At C2D0, although bacterial cultures became positive again in all mares in the O3 group, bacterial load remained 77.5% below baseline (P < 0.001), and neutrophil counts remained 42.4% below baseline, indicating a sustained biological response following treatment. The PC group showed no microbiological or inflammatory variation throughout follow-up. The healthy control group remained culture-negative at all time points. Intrauterine ozone insufflation substantially reduced bacterial load and endometrial neutrophil infiltration in mares with mixed bacterial endometritis, without inducing bacterial colonization in healthy animals.
© 2026. The Author(s).
Get Full Text
Publication Date: 2026-07-31 PubMed ID: 42536262PubMed Central: 12474077DOI: 10.1007/s11259-026-11438-3Google Scholar: Lookup
The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
LinkedInCopy
  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Research Overview

  • This study investigated whether intrauterine ozone therapy can effectively reduce bacterial infection and inflammation in mares suffering from mixed bacterial endometritis.
  • Results showed that ozone treatment significantly lowered bacterial load and inflammatory cell counts in affected mares, demonstrating its therapeutic potential without harming healthy mares.

Background

  • Mixed bacterial endometritis in mares involves infection by multiple bacterial species, complicating treatment due to varied antibiotic resistance profiles.
  • Treatment is challenging as the presence of diverse pathogens requires broad or combinational antimicrobial approaches which may not always be effective.
  • Ozone therapy is a novel approach being explored for its antimicrobial properties and potential to modulate inflammation.

Study Design

  • Fifteen mares with naturally acquired mixed bacterial endometritis were divided into two groups:
    • Pathological control (PC) group, n=6, receiving medical oxygen insufflation (no ozone).
    • Ozone treatment (O3) group, n=9, receiving intrauterine ozone at 42 µg/mL for three consecutive days.
  • Additionally, eight clinically healthy mares were treated with the same ozone protocol to evaluate safety effects.
  • Bacterial load and uterine inflammation were assessed at three time points:
    • Baseline before treatment (C1D0)
    • Six days after treatment completion (C1D6)
    • At the start of the subsequent estrous cycle (C2D0)

Measurements

  • Bacterial load was quantified in terms of colony-forming units per milliliter (CFU/mL) using uterine flush samples.
  • Neutrophil counts, indicating endometrial inflammation, were also recorded from uterine samples.

Key Findings

  • Statistical analysis using a linear mixed model revealed significant changes over time that differed between groups for both bacterial load and neutrophil counts.
  • In the ozone-treated group at C1D6:
    • Bacterial load dropped by 100%, from a median of 65,000 CFU/mL to zero, with statistically significant results (P < 0.001).
    • The culture positivity rate was 22.2%, similar to healthy controls, indicating effective clearing of infection.
    • Neutrophil counts decreased by nearly 89%, indicating marked reduction in uterine inflammation.
  • At the subsequent estrous cycle (C2D0), in the ozone group:
    • Bacterial cultures became positive again in all mares, but the bacterial load remained significantly 77.5% below baseline values (P < 0.001).
    • Neutrophil counts stayed 42.4% below baseline, showing a sustained decrease in inflammation.
  • The pathological control group, receiving oxygen only, showed no significant changes in bacterial load or inflammation throughout the study.
  • Healthy mares treated with ozone remained free of bacterial growth, supporting the safety of the ozone therapy.

Conclusions and Implications

  • Intrauterine ozone insufflation markedly reduces the bacterial load responsible for mixed bacterial endometritis and decreases uterine inflammation in clinically ill mares.
  • The treatment also demonstrated a sustained biological response, with bacterial loads and inflammation remaining lower than baseline even several weeks after treatment.
  • The absence of bacterial colonization in healthy mares indicates that ozone therapy is safe and does not disrupt normal uterine microbial balance in uninfected animals.
  • This suggests ozone therapy as a promising non-antibiotic treatment for mixed bacterial endometritis, potentially overcoming challenges with antimicrobial resistance.
  • Further research could expand on optimized dosing, long-term efficacy, and application in clinical practice.

Cite This Article

APA
Campos DG, Araujo RR, Feltrin SR, Botelho JHV, Cargnelutti JF, Portela VM, Dos Santos Amaral C, Antoniazzi AQ. (2026). Intrauterine ozone therapy reduces bacterial load in mares with mixed bacterial endometritis: a longitudinal study. Vet Res Commun, 50(5), 497. https://doi.org/10.1007/s11259-026-11438-3

Publication

Veterinary research communications
ISSN: 1573-7446
NlmUniqueID: 8100520
Country: Switzerland
Language: English
Volume: 50
Issue: 5
PII: 497

Researcher Affiliations

Campos, Diego Guedes
  • Laboratory of Biotechnology and Animal Reproduction (BioRep), Federal University of Santa Maria (UFSM), Santa Maria, 97105-900, RS, Brazil.
Araujo, Reno Roldi
  • GeneTech Animal Reproduction, Campinas, 13080-650, SP, Brazil.
Feltrin, Suzana Rossato
  • Laboratory of Biotechnology and Animal Reproduction (BioRep), Federal University of Santa Maria (UFSM), Santa Maria, 97105-900, RS, Brazil.
Botelho, Jorge Henrique Villela
  • Universidade Professor Edson Antonio Velano, Alfenas, Minas Gerais, Brazil.
Cargnelutti, Juliana Felipetto
  • Laboratory of Bacteriology (LABAC), Department of Microbiology and Parasitology, Federal University of Santa Maria (UFSM), Santa Maria, 97105-900, RS, Brazil.
Portela, Valério Marques
  • Laboratory of Biotechnology and Animal Reproduction (BioRep), Federal University of Santa Maria (UFSM), Santa Maria, 97105-900, RS, Brazil.
Dos Santos Amaral, Carolina
  • Laboratory of Biotechnology and Animal Reproduction (BioRep), Federal University of Santa Maria (UFSM), Santa Maria, 97105-900, RS, Brazil. carolina.amaral@ufsm.br.
Antoniazzi, Alfredo Quites
  • Laboratory of Biotechnology and Animal Reproduction (BioRep), Federal University of Santa Maria (UFSM), Santa Maria, 97105-900, RS, Brazil.

MeSH Terms

  • Animals
  • Female
  • Horses
  • Endometritis / veterinary
  • Endometritis / microbiology
  • Endometritis / drug therapy
  • Endometritis / therapy
  • Ozone / therapeutic use
  • Ozone / administration & dosage
  • Horse Diseases / microbiology
  • Horse Diseases / drug therapy
  • Horse Diseases / therapy
  • Bacterial Load / veterinary
  • Bacterial Load / drug effects
  • Longitudinal Studies
  • Bacterial Infections / veterinary
  • Bacterial Infections / microbiology
  • Bacterial Infections / drug therapy
  • Coinfection / veterinary
  • Coinfection / microbiology
  • Coinfection / drug therapy
  • Uterus / microbiology

Conflict of Interest Statement

Declarations. Ethics approval and animal welfare: All procedures involving animals were approved by the Animal Ethics Committee of the Universidade José do Rosário Vellano (CEUA/UNIFENAS; protocol no. 05 A/2022) and were conducted in accordance with institutional and national guidelines for animal care and use. Consent to participate: Not applicable. Consent to publish: Not applicable. Competing interests: The authors declare no competing interests.

References

This article includes 32 references
  1. Ávila ACA, Diniz NC, Serpa RT. Effectiveness of ozone therapy in the treatment of endometritis in mares. J Equine Vet Sci 112:103900.
    doi: 10.1016/j.jevs.2022.103900pubmed: 35183680google scholar: lookup
  2. Ball BA, Shin SJ, Patten VH. Use of a low-volume uterine flush for microbiologic and cytologic examination of the mare’s endometrium. Theriogenology 29(6):1269–1283.
    doi: 10.1016/0093-691X(88)90007-6google scholar: lookup
  3. Beckers KF, Liu CC, Gomes VCL. Effects of intra-uterine ceftiofur on the equine uterine microbiome. Vet Sci 12:837.
    doi: 10.3390/vetsci12090837pubmed: 41012762pmc: 12474077google scholar: lookup
  4. Bocci V, Borrelli E, Travagli V. The ozone paradox: ozone is a strong oxidant as well as a medical drug. Med Res Rev 29:646–682.
    doi: 10.1002/med.20150pubmed: 19260079google scholar: lookup
  5. Bocci V. Ozone: a new medical drug, 2nd edn. .
    doi: 10.1007/978-90-481-9234-2google scholar: lookup
  6. Botelho JHV, Pessoa GO, Caixeta ES. Does the uterine ozone therapy alter the transcript profile of anti- and proinflammatory genes in mares with endometritis?. Reprod Domest Anim 59:e14718.
    doi: 10.1111/rda.14718pubmed: 39253801google scholar: lookup
  7. Canisso IF, Segabinazzi LGTM, Fedorka CE. Persistent breeding-induced endometritis in mares: a multifaceted challenge from clinical aspects to immunopathogenesis and pathobiology. Int J Mol Sci 21:1432.
    doi: 10.3390/ijms21041432pubmed: 32093296pmc: 7073041google scholar: lookup
  8. Carroll CL, Huntington PJ. Body condition scoring and weight estimation of horses. Equine Vet J 20(1):41–45.
    doi: 10.1111/j.2042-3306.1988.tb01451.xpubmed: 3366105google scholar: lookup
  9. Christoffersen M, Troedsson MHT. Inflammation and fertility in the mare. Reprod Domest Anim 52(Suppl 3):14–20.
    doi: 10.1111/rda.13013pubmed: 28815848google scholar: lookup
  10. Clinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing. 25th informational supplement, Clinical and Laboratory Standards Institute, Wayne, M100-S25.
  11. Cocchia N, Paciello O, Auletta L. Comparison of the cytobrush, cottonswab, and low-volume uterine flush techniques to evaluate endometrial cytology for diagnosing endometritis in chronically infertile mares. Theriogenology 77(1):89–98.
    doi: 10.1016/j.theriogenology.2011.07.020pubmed: 21855980google scholar: lookup
  12. Davis HA, Stanton MB, Thungrat K. Uterine bacterial isolates from mares and their resistance to antimicrobials: 8,296 cases (2003–2008). J Am Vet Med Assoc 242:977–983.
    doi: 10.2460/javma.242.7.977pubmed: 23517211google scholar: lookup
  13. Díaz-Bertrana ML, Deleuze S, Pitti Rios L. Microbial prevalence and antimicrobial sensitivity in equine endometritis in field conditions. Animals 11:1476.
    doi: 10.3390/ani11051476pubmed: 34065566pmc: 8160901google scholar: lookup
  14. Donato GG, Appino S, Bertero A. Safety and effects of a commercial ozone foam preparation on endometrial environment and fertility of mares. J Equine Vet Sci 121:104222.
    doi: 10.1016/j.jevs.2023.104222pubmed: 36623580google scholar: lookup
  15. Donato GG, Nebbia P, Stella MC. In vitro effects of different ozone preparations on microorganisms responsible for endometritis in the mare. Theriogenology 15(219):132–137.
    doi: 10.1016/j.theriogenology.2024.02.011google scholar: lookup
  16. Elvis AM, Ekta JS. Ozone therapy: A clinical review.. J Nat Sci Biol Med 2011 2(1):66–70.
    doi: 10.4103/0976-9668.82319pubmed: 22470237pmc: 3312702google scholar: lookup
  17. Ferreira JC, Amaral RS, Cardoso LM. Endometrial angiogenesis induced by uterine insufflation with an oxygen–ozone gas mixture in mares.. Reprod Domest Anim 2021 56:1176–1183.
    doi: 10.1111/rda.13958google scholar: lookup
  18. Ferrer MS, Palomares R. Aerobic uterine isolates and antimicrobial susceptibility in mares with post-partum metritis.. Equine Vet J 2018 50:202–207.
    doi: 10.1111/evj.12738pubmed: 28796905google scholar: lookup
  19. Ferris RA. Biofilm and latent bacteria in equine uterus.. Clin Theriogenology 2022 14:229–232.
    doi: 10.58292/ct.v14.9680google scholar: lookup
  20. Heil BA, van Heule M, Thompson SK. Effect of sampling method on detection of the equine uterine microbiome during estrus.. Vet Sci 2023 10(11):644.
    doi: 10.3390/vetsci10110644pubmed: 37999467pmc: 10675083google scholar: lookup
  21. Katila T. Post-mating inflammatory responses of the uterus.. Reprod Domest Anim 2012 47(Suppl 5):31–41.
    doi: 10.1111/j.1439-0531.2012.02120.xpubmed: 22913558google scholar: lookup
  22. Köhne M, Hofbauer L, Böttcher D. Comparison of systemic trimethoprim-sulfadimethoxine treatment and intrauterine ozone application as possible therapies for bacterial endometritis in equine practice.. Front Vet Sci 2023 10:1102149.
    doi: 10.3389/fvets.2023.1102149pubmed: 36777673pmc: 9911668google scholar: lookup
  23. LeBlanc MM. Advances in the diagnosis and treatment of chronic infectious and post-mating-induced endometritis in the mare.. Reprod Domest Anim 2010 45(Suppl 2):21–27.
    doi: 10.1111/j.1439-0531.2010.01634.xpubmed: 20591061google scholar: lookup
  24. LeBlanc MM, Causey RC. Clinical and subclinical endometritis in the mare: both threats to fertility.. Reprod Domest Anim 2009 44(Suppl 3):10–22.
    doi: 10.1111/j.1439-0531.2009.01485.xpubmed: 19660076google scholar: lookup
  25. LeBlanc MM, Magsig J, Stromberg AJ. Use of a low-volume uterine flush for diagnosing endometritis in chronically infertile mares.. Theriogenology 2007 68:403–412.
    doi: 10.1016/j.theriogenology.2007.04.038pubmed: 17543379google scholar: lookup
  26. Linton JK, Sertich PL. The impact of low-volume uterine lavage on endometrial biopsy classification.. Theriogenology 2016 86:1004–1007.
    doi: 10.1016/j.theriogenology.2016.03.028pubmed: 27118385google scholar: lookup
  27. Moroni R, Fanelli D, Maltinti S. Effects of intrauterine ozone insufflation in eleven subfertile mares: a case series.. J Equine Vet Sci 2026 157:105778.
    doi: 10.1016/j.jevs.2026.105778pubmed: 41513112google scholar: lookup
  28. Nunes GT, Machado CS, Seeger MG. Corynebacterium uterequi in the uterus of a mare from Rio Grande do Sul, Brazil.. Cienc Rural 2026 56:e20250194.
    doi: 10.1590/0103-8478cr20250194google scholar: lookup
  29. Petersen MR, Skive B, Christoffersen M. Activation of persistent Streptococcus equi subspecies zooepidemicus in mares with subclinical endometritis.. Vet Microbiol 2015 179:119–125.
    doi: 10.1016/j.vetmic.2015.06.006pubmed: 26123371google scholar: lookup
  30. Rasmussen CD, Haugaard MM, Petersen MR. Streptococcus equi subsp. zooepidemicus isolates from equine infectious endometritis belong to a distinct genetic group.. Vet Res 2013 44:26.
    doi: 10.1186/1297-9716-44-26pubmed: 23597033pmc: 3640914google scholar: lookup
  31. Skive B, Rohde M, Molinari G. Streptococcus equi subsp. zooepidemicus invades and survives in epithelial cells.. Front Cell Infect Microbiol 7:465.
    doi: 10.3389/fcimb.2017.00465pubmed: 29164073pmc: 5681531google scholar: lookup
  32. Troedsson MHT, Woodward EM. Our current understanding of the pathophysiology of equine endometritis with an emphasis on breeding-induced endometritis.. Reprod Biol 16(1):8–12.
    doi: 10.1016/j.repbio.2016.01.003pubmed: 26952748google scholar: lookup

Citations

This article has been cited 0 times.
Subscribe to our newsletter
Join 106,764 horse owners like you who receive our email updates on horse health and nutrition.
OmegaPrime+ Extra-Strength Omega-3 Oil - Mad Barn
NEW PRODUCT
OmegaPrime+
Extra-Strength Omega-3 Oil
Shop Now
×