Detection of antibodies against Sarcocystis neurona in cerebrospinal fluid from clinically normal neonatal foals.

This study explores the presence of antibodies for the parasite Sarcocystis neurona in the cerebrospinal fluid (CSF) of healthy neonatal foals, with the results revealing that testing of neonatal CSF is not a reliable method of diagnosing equine protozoal myeloencephalitis in foals born to mares that are seropositive.

Methods

• The researchers conducted a prospective study, examining 15 neurologically and clinically healthy newborn Thoroughbred foals, ranging from 2 to 7 days old in age.
• CSF and blood samples were collected from the studied foals, in addition to blood samples from their respective mothers, and tested for the presence of S. neurona antibodies by applying western blotting techniques.
• Additionally, subsequent rounds of blood and CSF sampling were done on five foals between 13 to 41 days and 62 to 90 days post-birth.

Results

• The test results showed that antibodies against S. neurona were found in both the blood of 13 mares and their corresponding foals. Out of these 13 foals, S. neurona antibodies were detected in the CSF of 12.
• The level of immunoreactivity, apparent in both the blood and CSF samples, was observed to decrease gradually over time. S. neurona antibodies could not be detected in the CSF of two foals 83 and 84 days after birth. However, the remaining three foals, sampled between 62 and 90 days after birth, maintained detectable levels of CSF antibodies.

Conclusions

• The research revealed the ability to detect S. neurona antibodies in CSF from perfectly healthy newborn foals born to seropositive mares. This demonstrates the transfer of antibodies from the dam to the offspring, likely through the placenta and colostrum.
• This finding raises concerns on the utilization of CSF testing to diagnose equine protozoal myeloencephalitis, a common neurological disorder among horses caused by S. neurona, in foals under the age of three months that have been born to seropositive mares. The fact that healthy foals test positive suggests there may be false-positive results when using this diagnostic technique in such cases.