Effects of blood contamination of cerebrospinal fluid on results of indirect fluorescent antibody tests for detection of antibodies against Sarcocystis neurona and Neospora hughesi.

The research examines how blood contamination in cerebrospinal fluid (CSF) affects the results of indirect fluorescent antibody tests (IFATs) for detecting antibodies against two pathogens, Sarcocystis neurona and Neospora hughesi, in horses. The findings suggest that moderate levels of blood contamination (up to 10,000 red blood cells per microliter of CSF) do not significantly impact the test results.

Research Objective and Methodology

• The objective of the study was to understand how blood contamination in cerebrospinal fluid (CSF) can affect the detection of antibodies for Sarcocystis neurona and Neospora hughesi in horses. This was conducted through indirect fluorescent antibody tests (IFATs).
• The research was done in vitro, meaning it was performed in a controlled environment similar to a laboratory.
• The researchers collected CSF from horses that did not have neurological conditions immediately after euthanasia. This CSF was devoid of any antibodies. Blood samples were collected from 40 healthy horses with a range of antibody titers, i.e., the concentration of antibodies in their blood.
• The blood was then diluted in the seronegative (antibody-negative) CSF at different concentrations ranging from 10 to 100,000 red blood cells (RBC) for every microliter of CSF, thereby creating blood-contaminated CSF samples.

Research Findings

• The results showed that blood contamination of CSF had no detectable impact on IFAT results for either S. neurona or N. hughesi at any concentration of antibodies when the RBC concentration was less than 10,000 RBCs/microliter.
• However, when the RBC concentration was between 10,000 and 100,000 RBCs/microliter of CSF, positive results for S. neurona and N. hughesi were detected only when the corresponding antibody titer in the serum was equal to or greater than 160 and 80, respectively.
• Therefore, it can be concluded that the IFAT performed on CSF is useful in testing horses for diseases caused by S. neurona or N. hughesi. The tests were reliable even if the RBC concentration in the CSF was as high as 10,000 RBCs/microliter due to blood contamination.