Evidence for Sarcocystis as the etiologic agent of equine protozoal myeloencephalitis.

The research article focuses on a study where Equine protozoal myeloencephalitis (EPM), a disease in horses, was diagnosed and it was found that the potential causative agent of the disease might be the Sarcocystis species of parasite.

Study Overview

• The research investigated about Equine protozoal myeloencephalitis (EPM), a disease which impacts the central nervous system of horses, potentially causing severe neurological disabilities.
• Postmortem examination was conducted on 10 horses that were diagnosed with EPM.

Microscopic Findings

• Various developmental stages of the parasite, suspected to be a Sarcocystis species, were observed under an electron microscope.
• The schizonts, a form of the parasite, were either located inside the host cells of the spinal cord of the horses or they were found free-floating in the extracellular spaces. The presence of schizonts usually indicates a parasitic infection.
• Notably, the final stage of schizont reproduction was characterized by endopolygeny, a process where several daughter cells are produced inside the mother cell.

Infected Tissues

• Free merozoites, another form of the parasite, were found within the cells of the spinal cord or in the extracellular spaces. These merozoites were most commonly located in pericytes of capillaries.
• Interestingly, merozoites were also discovered inside the cytoplasm of neurons, macrophages, tissue neutrophils, and axons of myelinated nerve fibers. Neutrophils are a type of white blood cell that typically responds to infection.

Possible Hematogenous Phase

• The presence of merozoites in the cytoplasm of both tissue neutrophils and circulating neutrophils suggested a potential hematogenous phase of infection. Hematogenous spread is a term for the process when infectious agents, like parasites, are dispersed throughout the body via the bloodstream.

Conclusion

• Overall, the study provides evidence supporting the possibility that the protozoan parasite, Sarcocystis, could be the causative agent of EPM in horses. Further research is needed to confirm this hypothesis and to understand the disease process in order to develop effective treatment strategies.