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Veterinary medicine and science2026; 12(1); e70764; doi: 10.1002/vms3.70764

Evaluating the Biochemical and Haematological Safety of the Histoplasma capsulatum var. farciminosum ‘8ZH’ Vaccine in Foals.

Abstract: Epizootic lymphangitis (EEL), caused by Histoplasma capsulatum var. farciminosum (HCF), is a neglected equine fungal disease lacking effective vaccines. The newly developed inactivated '8ZH' vaccine requires safety validation in the target species. Objective: To evaluate the biochemical, haematological and clinical safety of the inactivated HCF '8ZH' vaccine in foals. Methods: A controlled, single-blinded study was conducted on 30 clinically healthy foals (4-6 months), randomized into vaccinated (n = 15) and control (n = 15) groups. Vaccinated animals received a 5 mL intramuscular dose (10 mg antigen, MONTANIDE GEL 01 PR adjuvant) on Day 0 and a booster on Day 21. Clinical observations (temperature, appetite, behaviour, injection site) were recorded daily. Blood was collected at baseline and on Days 7, 14, 21, 35 and 42 for biochemical, haematological and acute-phase protein analysis. Data were analysed using repeated measures ANOVA. Results: No severe or adverse reactions were observed. Mild, transient injection-site swelling (< 4 cm) occurred in three vaccinated foals and resolved spontaneously. All animals maintained normal temperature and appetite. AST showed a transient increase on Day 14 (p = 0.04); WBC also rose (p = 0.03), indicating a typical immune response. Other parameters, including ALT, GGT, creatinine, total bilirubin and acute-phase proteins (SAA, fibrinogen, haptoglobin), remained within physiological limits. No statistically significant long-term deviations or toxic effects were noted. Conclusions: The inactivated HCF '8ZH' vaccine demonstrated a favourable safety profile in foals. These results support its continued development for use in EEL prevention programs.
© 2026 The Author(s). Veterinary Medicine and Science published by John Wiley & Sons Ltd.
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Publication Date: 2026-01-07 PubMed ID: 41499477PubMed Central: PMC12779009DOI: 10.1002/vms3.70764Google Scholar: Lookup
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  • Journal Article
  • Randomized Controlled Trial
  • Veterinary

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.

Overview

  • This study assessed the safety of a new inactivated vaccine (‘8ZH’) against Epizootic lymphangitis (EEL) in young horses (foals).
  • The vaccine was evaluated for its effects on various health indicators to ensure it does not cause harmful side effects.

Background

  • Epizootic lymphangitis (EEL) is a fungal disease affecting horses, caused by Histoplasma capsulatum var. farciminosum (HCF).
  • The disease is neglected, meaning it has limited effective prevention or treatment strategies currently available.
  • Developing an effective vaccine is important to prevent EEL and improve equine health.
  • The ‘8ZH’ vaccine is a newly developed inactivated vaccine intended to protect against this disease.
  • Before widespread use, the vaccine must be shown to be safe in the target species — here, young horses (foals).

Study Design

  • A controlled, single-blinded study was performed using 30 healthy foals aged between 4 to 6 months.
  • Foals were randomly divided into two groups:
    • 15 foals vaccinated with the ‘8ZH’ vaccine
    • 15 foals serving as unvaccinated controls
  • Vaccinated foals received a 5 mL dose of vaccine containing 10 mg of antigen with MONTANIDE GEL 01 PR adjuvant, administered intramuscularly on Day 0, followed by a booster on Day 21.
  • Control foals did not receive vaccine but were observed in parallel.
  • Researchers monitored clinical signs daily, including:
    • Body temperature
    • Appetite
    • Behavior
    • Injection site reactions
  • Blood samples were collected at baseline and on Days 7, 14, 21, 35, and 42 for:
    • Biochemical tests (e.g., liver enzymes AST, ALT, GGT; kidney function creatinine; bilirubin)
    • Haematology (e.g., white blood cell counts)
    • Acute-phase proteins indicative of inflammation (serum amyloid A (SAA), fibrinogen, haptoglobin)
  • Data were analyzed using repeated measures ANOVA to detect statistically significant changes over time between groups.

Results

  • No severe or serious adverse reactions were noted in vaccinated foals.
  • Three vaccinated foals showed mild and temporary swelling at the injection site (less than 4 cm in diameter), which resolved on its own without intervention.
  • All animals, whether vaccinated or control, maintained normal body temperature and appetite throughout the study.
  • The liver enzyme aspartate aminotransferase (AST) showed a slight, temporary elevation on Day 14 in vaccinated foals, consistent with mild immune system activation (p=0.04).
  • White blood cell (WBC) counts were also slightly increased in vaccinated foals (p=0.03), suggesting an expected immune response to vaccination.
  • Other measured biochemical markers (ALT, GGT, creatinine, total bilirubin) and acute-phase proteins (SAA, fibrinogen, haptoglobin) stayed within normal physiological ranges, indicating no organ damage or harmful inflammation.
  • No long-term abnormalities or toxic effects were found in vaccinated animals throughout the observation period.

Conclusions and Implications

  • The inactivated HCF ‘8ZH’ vaccine demonstrated a favorable safety profile when administered to foals.
  • Mild, transient injection site swelling and transient increases in certain blood markers were consistent with normal immune responses to vaccination rather than adverse effects.
  • The absence of severe adverse events or biochemical disruptions supports continued development of this vaccine as a preventive tool against EEL.
  • This study provides important safety data required before broader use of the vaccine in equine disease control programs.
  • By confirming safety in foals, researchers can now focus on evaluating the vaccine’s efficacy in preventing infection.

Cite This Article

APA
(2026). Evaluating the Biochemical and Haematological Safety of the Histoplasma capsulatum var. farciminosum ‘8ZH’ Vaccine in Foals. Vet Med Sci, 12(1), e70764. https://doi.org/10.1002/vms3.70764

Publication

Veterinary medicine and science
ISSN: 2053-1095
NlmUniqueID: 101678837
Country: England
Language: English
Volume: 12
Issue: 1
Pages: e70764
PII: e70764

Researcher Affiliations

MeSH Terms

  • Animals
  • Horses
  • Horse Diseases / prevention & control
  • Horse Diseases / microbiology
  • Histoplasma / immunology
  • Fungal Vaccines / adverse effects
  • Fungal Vaccines / immunology
  • Fungal Vaccines / administration & dosage
  • Histoplasmosis / veterinary
  • Histoplasmosis / prevention & control
  • Histoplasmosis / microbiology
  • Male
  • Vaccines, Inactivated / adverse effects
  • Vaccines, Inactivated / immunology
  • Female
  • Vaccination / veterinary
  • Single-Blind Method

Conflict of Interest Statement

The authors declare no conflicts of interest.

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