Preliminary trial on the reproducibility of epizootic lymphangitis through experimental infection of two horses.

The research involves an experiment demonstrating that Epizootic Lymphangitis (EL), a veterinary disease, can be intentionally produced in horses using two different forms of the Histoplasma capsulatum var. farciminosum (HCF) organism. The findings provide an important foundation for further research to develop a vaccine against EL.

Objective and Methodology

• The aim of this study was to replicate Epizootic Lymphangitis (EL), a disease affecting horses, through controlled infection. The ultimate aim was to establish a foundation for future research on developing a virus against EL.
• Four horses from EL-free districts were used for the experiment. Two were injected with different forms of the HCF organism, while the other two served as controls.
• Horse 1 was injected with 0.2 mL of the yeast form of HCF, while Horse 2 received 0.2 mL of a suspension of the mycelial form of HCF.
• The injections were administered into both their pre-scapular and pre-femoral lymph nodes alongside skin scarification of their left hind limb, right-eye conjunctiva, and the nasal membrane of the right nostril.

Findings and Conclusion

• Nodular lesions of EL form of the infectious disease appeared after four weeks on Horse 1 that was injected with the yeast form at all sites.
• The horse that received the mycelial suspension showed lesions only after three months, and only in the lymph nodes and skin scratches.
• No clinical signs were observed in the two control horses, confirming the infections were a result of experimental procedures and not occurring naturally.
• HCF organism was recovered from the lesions of the two infected horses, both in yeast and mycelial forms, confirming that the infection was the cause of the lesions.
• The study confirmed the experimental reproduction of clinical EL and laid an essential groundwork for evaluating a vaccine’s potency against EL using a vaccination and challenge experiment.