Preliminary trial on the reproducibility of epizootic lymphangitis through experimental infection of two horses.
Authors: Ameni Gobena
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Experimental Reproduction of Epizootic Lymphangitis Epizootic lymphangitis (EL), caused by *Histoplasma capsulatum* var. *farciminosum*, remains a significant disease in equine populations, yet reliable experimental models for testing interventions have been lacking. Gobena's 2006 trial established a reproducible infection protocol by inoculating the yeast or mycelial forms of the organism directly into lymph nodes (pre-scapular and pre-femoral) of naïve horses, with concurrent scarification of skin and mucous membranes, whilst maintaining uninfected controls. The yeast form produced characteristic nodular lesions within four weeks across all inoculation sites, whereas the mycelial suspension took three months to manifest clinically and appeared only at the lymph nodes and skin lesions—both forms were subsequently recovered from affected tissue. These findings validate experimental infection as a reproducible model for EL pathogenesis, establishing a framework for vaccine efficacy studies and providing practitioners with evidence that the infective stage and inoculation route significantly influence disease onset and clinical presentation. For those managing EL-endemic populations, this work underscores the importance of understanding transmission routes and suggests that control strategies should account for variable incubation periods depending on the organism's morphological form.
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Practical Takeaways
- •Epizootic lymphangitis can be reliably reproduced experimentally, which will enable development and testing of protective vaccines for field use
- •The yeast form of HCF is more virulent and causes faster disease progression than the mycelial form, suggesting different transmission routes may have different clinical presentations
- •This preliminary work establishes a framework for vaccination-challenge trials to evaluate EL vaccine candidates before field deployment
Key Findings
- •Yeast form of HCF induced nodular lesions at all inoculation sites within 4 weeks, while mycelial suspension caused lesions only in lymph nodes and skin after 3 months
- •Both yeast and mycelial forms were successfully recovered from infected horse lesions, confirming reproducibility of experimental EL infection
- •Control horses showed no clinical signs, establishing the infectious nature of the inoculated material
- •Experimental infection protocol successfully reproduced clinical epizootic lymphangitis and provided methodology for future vaccine efficacy studies