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Veterinary research communications2026; 50(2); 91; doi: 10.1007/s11259-025-11031-0

Post-surgical seroreversion in a case of equine cutaneous leishmaniosis by Leishmania infantum.

Abstract: Equine leishmaniosis, caused by Leishmania infantum and transmitted by infected sand flies, has been increasingly reported in Europe, although clinical and immunological data remain scarce. We describe a 10-year-old mare from southern Spain presenting with periocular nodular lesions. Histopathology and immunohistochemistry confirmed granulomatous dermatitis with intrahistiocytic Leishmania amastigotes. Additionally, Leishmania infantum DNA was detected in paraffin embedded skin biopsy. Following surgical removal of the lesions, sequential serological monitoring using enzyme-linked immunosorbent assay, and immunofluorescent antibody tests were performed over 90 days. Enzyme-linked immunosorbent assay and Western Blot results varied depending on conjugate type (Protein A versus Protein A/G). Western Blot revealed immunoreactivity against multiple Leishmania infantum antigen fractions, including early infection markers 14-16 kDa by conjugated Protein A/G and the absence of band by conjugated Protein A. Immunofluorescent antibody test using an anti-horse IgG fluorescein-labeled conjugate, where titers declined from 1:160 at 45 days to seronegativity by day 90, indicating antibody seroreversion within three months post-surgery. Similar results were detected by enzyme-linked immunosorbent assay with the absence of detection by Protein A but seropositivity was detected by Protein A/G. Finally, no parasitemia was detected by molecular test during the follow-up. This case represents the first documented seroreversion kinetics in equine leishmaniosis and highlights the low and transient humoral response in horses compared to dogs. Our findings underscore the importance of combining histopathology and immunohistochemistry, for the accurate equine leishmaniosis diagnosis, and emphasize the need for further studies to clarify the epidemiological role of horses in Leishmania infantum transmission.
Publication Date: 2026-01-08 PubMed ID: 41504811PubMed Central: PMC12783306DOI: 10.1007/s11259-025-11031-0Google Scholar: Lookup
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Summary

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Overview

  • This study reports the case of a 10-year-old mare in southern Spain infected with Leishmania infantum, causing equine cutaneous leishmaniosis.
  • It details the diagnosis, surgical treatment, and sequential monitoring of the horse’s immune response, documenting for the first time the kinetics of antibody seroreversion after lesion removal.

Background

  • Equine leishmaniosis is an emerging disease in Europe caused by the parasite Leishmania infantum, which is transmitted by sand fly bites.
  • The disease in horses is less studied compared to dogs, and there is limited knowledge about the clinical signs, immune responses, and disease progression in horses.
  • Infection typically causes dermatological lesions characterized by granulomatous inflammation where the parasite resides inside histiocytes (a type of immune cell).

Case Description

  • The subject was a 10-year-old mare presenting with nodular lesions around the eyes (periocular region).
  • Diagnosis was confirmed with:
    • Histopathology showing granulomatous dermatitis.
    • Immunohistochemistry identifying Leishmania amastigote forms inside histiocytes.
    • Molecular detection of Leishmania infantum DNA in a skin biopsy sample processed in paraffin.
  • The lesions were surgically removed as part of the treatment.

Serological Monitoring and Immune Response

  • Following surgery, the horse was monitored for antibody levels for 90 days, using:
    • Enzyme-linked immunosorbent assay (ELISA).
    • Western Blot (WB).
    • Immunofluorescent antibody test (IFAT).
  • Different types of conjugates (Protein A and Protein A/G) were used, resulting in:
    • Variable ELISA and WB results depending on the conjugate.
    • WB with Protein A/G detected immune responses against multiple L. infantum antigen fractions, including early infection markers at 14-16 kDa.
    • WB with Protein A did not detect these specific bands, showing differing sensitivity.
  • Immunofluorescence showed antibody titers declining from 1:160 at 45 days post-surgery to seronegative by 90 days, demonstrating antibody seroreversion (loss of detectable antibodies) within three months.
  • ELISA results parallel the IFAT findings:
    • No antibody detection with Protein A conjugate.
    • Positivity detected with Protein A/G.

Parasitological Monitoring

  • During follow-up, molecular testing showed no evidence of parasitemia (circulating parasites in the blood).
  • This suggests effective surgical removal and absence of systemic infection during the monitored period.

Significance and Conclusions

  • This is the first case documenting antibody seroreversion kinetics in equine leishmaniosis, highlighting that:
    • Horses exhibit a lower and more transient antibody response to L. infantum infection compared to dogs, which usually show stronger and long-lasting antibodies.
  • The study emphasizes the importance of:
    • Using combined diagnostic approaches — histopathology, immunohistochemistry, molecular detection, and different serological tests — for accurate diagnosis in horses.
    • Recognizing that serological tests may vary in sensitivity depending on the method and reagents used.
  • These findings suggest that horses may have a distinct immunological profile in leishmaniosis, potentially impacting their role as reservoirs or in transmission dynamics.
  • Further research is needed to better understand the epidemiological role of horses in the spread of Leishmania infantum.

Cite This Article

APA
Murillo A, Lebrero ME, Valdés M, Ramos J, Villanueva-Saz S, Davies JE, Gómez Á, Pérez E, Riera C, Marteles-Aragüés D. (2026). Post-surgical seroreversion in a case of equine cutaneous leishmaniosis by Leishmania infantum. Vet Res Commun, 50(2), 91. https://doi.org/10.1007/s11259-025-11031-0

Publication

ISSN: 1573-7446
NlmUniqueID: 8100520
Country: Switzerland
Language: English
Volume: 50
Issue: 2
Pages: 91
PII: 91

Researcher Affiliations

Murillo, Antonio
  • Hospital de Referencia La Equina, Camino de Martagina Km 1, Manilva, 29692, Málaga, Spain.
Lebrero, María Eugenia
  • Clinical Immunology Laboratory, Veterinary Faculty, University of Zaragoza, Calle Miguel Servet, 177, 50013, Zaragoza, Spain.
  • Department of Animal Pathology, Veterinary Faculty, University of Zaragoza, Calle Miguel Servet, 177, 50013, Zaragoza, Spain.
Valdés, Miguel
  • Hospital de Referencia La Equina, Camino de Martagina Km 1, Manilva, 29692, Málaga, Spain.
Ramos, Joana
  • Equine Care Group Spain, Calle Santa Engracia, 14-16, 28010, Pozuelo de Alarcón, Spain.
Villanueva-Saz, Sergio
  • Clinical Immunology Laboratory, Veterinary Faculty, University of Zaragoza, Calle Miguel Servet, 177, 50013, Zaragoza, Spain. svs@unizar.es.
  • Department of Animal Pathology, Veterinary Faculty, University of Zaragoza, Calle Miguel Servet, 177, 50013, Zaragoza, Spain. svs@unizar.es.
  • Instituto Agroalimentario de Aragón-IA2 (Universidad de Zaragoza-CITA), Calle Miguel Servet, 177, 50013, Zaragoza, Spain. svs@unizar.es.
Davies, Janine E
  • Clinical Immunology Laboratory, Veterinary Faculty, University of Zaragoza, Calle Miguel Servet, 177, 50013, Zaragoza, Spain.
  • Department of Animal Pathology, Veterinary Faculty, University of Zaragoza, Calle Miguel Servet, 177, 50013, Zaragoza, Spain.
Gómez, Álex
  • Department of Animal Pathology, Veterinary Faculty, University of Zaragoza, Calle Miguel Servet, 177, 50013, Zaragoza, Spain.
  • Instituto Agroalimentario de Aragón-IA2 (Universidad de Zaragoza-CITA), Calle Miguel Servet, 177, 50013, Zaragoza, Spain.
Pérez, Estela
  • Department of Animal Pathology, Veterinary Faculty, University of Zaragoza, Calle Miguel Servet, 177, 50013, Zaragoza, Spain.
  • Instituto Agroalimentario de Aragón-IA2 (Universidad de Zaragoza-CITA), Calle Miguel Servet, 177, 50013, Zaragoza, Spain.
Riera, Cristina
  • Departament de Biologia, Salut I Medi Ambient, Facultat de Farmacia, Universitat de Barcelona, Av. De Joan XXIII, 08028, Barcelona, Spain.
Marteles-Aragüés, Diana
  • Clinical Immunology Laboratory, Veterinary Faculty, University of Zaragoza, Calle Miguel Servet, 177, 50013, Zaragoza, Spain. dmartelesaragues@unizar.es.
  • Department of Animal Pathology, Veterinary Faculty, University of Zaragoza, Calle Miguel Servet, 177, 50013, Zaragoza, Spain. dmartelesaragues@unizar.es.

MeSH Terms

  • Animals
  • Leishmania infantum / isolation & purification
  • Horses
  • Horse Diseases / surgery
  • Horse Diseases / parasitology
  • Horse Diseases / immunology
  • Female
  • Leishmaniasis, Visceral / veterinary
  • Leishmaniasis, Visceral / surgery
  • Leishmaniasis, Visceral / parasitology
  • Leishmaniasis, Cutaneous / veterinary
  • Leishmaniasis, Cutaneous / surgery
  • Leishmaniasis, Cutaneous / parasitology
  • Leishmaniasis, Cutaneous / immunology
  • Enzyme-Linked Immunosorbent Assay / veterinary

Conflict of Interest Statement

Declarations. Ethical approval: The animal was sampled with the owner´s consent and due to spontaneous clinical disease. No additional ethical approval was required. Consent to participate: Not applicable. Consent to publish: Not applicable. Competing interest: All authors have read and approved the final manuscript. Its contents are solely the responsibility of the authors. All authors declare that they have no competing interests. Sergio Villanueva-Saz is an Associate Editor for the journal and has not taken part in the manuscript's peer review process.

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Citations

This article has been cited 1 times.
  1. Villanueva-Saz S, González A, Pérez MD, Lacasta D, Fernández A, Quilez P, Ortín A, Guallar D, Gómez Á, Marteles-Aragüés D. Evaluation of a commercial multispecies rapid test for anti-Leishmania infantum antibodies in unconventional animal species. Vet Res Commun 2026 Feb 28;50(3).
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