First case report of Sarcocystis neurona-induced equine protozoal myeloencephalitis in Japan.

This study looks at the first case of Equine protozoal myeloencephalitis (EPM) in a horse, specifically a Thoroughbred racehorse, in Japan caused by the Sarcocystis neurona (S. neurona) parasite.

Background

• The paper focuses on a health condition in horses known as Equine protozoal myeloencephalitis (EPM), a neurologic disease that arises due to an infection by the parasite Sarcocystis neurona (S. neurona).
• This study is significant as it reports on the first identified case of EPM caused by the S. neurona in Japan.

Case Report

• The documented case details a three-year-old Thoroughbred male racehorse that was imported from the United States and developed EPM after its arrival to Japan.
• The horse exhibited astasia (an inability to stand independently) five days following the onset of ataxia (lack of muscle control or coordination).

Histopathological Observations

• The researchers observed nonpurulent myelitis, which is inflammation of the spinal cord not associated with pus, accompanied by hemorrhage (bleeding) and perivascular infiltration (white blood cells moving into tissues surrounding blood vessels). This was specifically in the fourth and fifth cervical spinal cord of the horse.
• Immunohistochemistry – a technique used to visualize specific antigens (proteins) in tissues – was also conducted, and shizonts (a structure formed by the asexual reproduction of S. neurona) were occasionally observed.
• These shizonts tested positive for anti-Sarcocystis neurona (S. neurona) antiserum, indicating an immune response in the horse towards the parasite.

Detection

• The researchers detected S. neurona-specific antibodies in the horse’s serum and cerebrospinal fluid using the Western blot technique. This is a widely used analytical technique used to detect specific proteins in a sample of tissue homogenate or extract.
• The presence of these antibodies also confirmed an immune response against the parasite, corroborating the histopathological findings and confirming the diagnosis of EPM in the horse.