Cerebrospinal fluid changes in two horses with central nervous system nematodiasis (Micronema deletrix).

The study investigated changes in the cerebrospinal fluid (CSF) in two horses affected with a disease of the central nervous system caused by Micronema deletrix, a type of roundworm. The researchers found changes consistent with those seen in equine protozoal myeloencephalitis and verminous encephalitis, along with lesions and inflammation in the horses’ brains. Final diagnosis required a histopathologic examination for confirmation.

Study Subjects and Initial Findings

• The research involved two horses suffering from cerebrospinal nematodiasis, specifically caused by the nematode Micronema deletrix. The observed symptoms in these horses were similar to neurological diseases seen in horses resulting from the migration of various parasites through the central nervous system.
• The first horse, a 13-year-old Paso Fino stallion, showed slightly xanthochromic cerebrospinal fluid and a cell count revealing a pleocytosis condition. The protein level in the CSF was normal.
• The second horse, a 19-year-old Tennessee Walking Horse stallion, had a slightly darker CSF and a higher cell count indicating pleocytosis. Additionally, the protein concentration in this horse’s CSF was moderately elevated.

Key Observations

• Both horses showed changes in cerebrospinal fluid that were consistent with the changes usually seen in cases of equine protozoal myeloencephalitis and verminous encephalitis.
• Microscopic examination revealed the presence of lesions in different areas of the brains of both horses. These lesions contained multiple areas of softening tissue (malacia) and granulomatous inflammation, indicating chronic inflammation.
• The vessels in the meninges (layers that cover the brain) were extensively thickened and inflamed and contained parasites both in and around them.

Conclusions

• The observed changes in the cerebrospinal fluid were not inherently specific enough to diagnose the disease only based on these parameters.
• A histopathologic examination, including a microscopic investigation of the affected tissues, was crucial to confirm the diagnosis of central nervous system nematodiasis in the studied horses.