Levels of serum Phosphorylated Neurofilament Heavy subunit in clinically healthy Standardbred horses

Neurofilaments heavy chain proteins (pNF-H) have been identified as useful serum biomarkers for humans and animals with neurologic conditions, some of which can lead to poor performance and athletic injuries. However, there are no published reports that describe a reference range for serum pNF-H levels in healthy racehorses. This cross-sectional study was carried out to determine the serum concentration of pNF-H in 1349 samples collected from 1291 clinically healthy standardbred (SB) racehorses. Data on age, time of sampling (pre-race or post-race), and finishing position during a race were collected. The concentration of pNF-H in serum samples was determined using an enzyme-linked immunosorbent assay (ELISA). The appropriate statistical techniques were used to determine the median serum concentration of pNF-H in these horses, if the serum concentration of pNF-H changed with age, if there were changes in the serum concentration of pNF-H during a race, and if there was an association between serum concentration of pNF-H and the finishing position for the horse. The median serum concentration of pNF-H in this group of clinically healthy SB horses was 0.0 ng/ml. The concentration of pNF-H in serum was not associated with the age of the horses in this study as was determined by regression analysis. There was no significant change in the serum concentration of pNF-H before and after a race in paired samples. There was no association of serum concentration of pNF-H and the finishing position of the horses after the race. The data from this study supports use of < 0.412 ng/ml as a reference interval for measurement of serum levels of pNF-H in SB racehorses as 95% of the collected samples fell into the range 0.0 - 0.412 ng/ml.

Serum and cerebrospinal fluid phosphorylated neurofilament heavy protein concentrations in equine neurodegenerative diseases

BACKGROUND

Currently, there is little information regarding the concentrations of phosphorylated neurofilament heavy protein (pNfH) in the serum and cerebrospinal fluid (CSF) of horses with neurodegenerative diseases. Specifically, pNfH concentrations have not yet been evaluated in horses with equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM).

OBJECTIVES

To determine pNfH concentrations using a commercial enzyme-linked immunosorbent assay (ELISA) in serum and CSF from control horses and horses with eNAD/EDM, cervical vertebral compressive myelopathy (CVCM) and Shivers.

STUDY DESIGN

Case-control study using biobanked samples from diseased horses and prospective or biobanked samples from control horses.

METHODS

The pNfH ELISA was performed on samples from horses diagnosed with eNAD/EDM (n = 64), CVCM (n = 26) and Shivers (n = 9) and 51 neurologically normal control horses.

RESULTS

Median and 95% confidence interval (CI) serum pNfH concentrations in control, CVCM, and eNAD/EDM horses were 0.08 ng/mL (0.07-0.15), 0.07 ng/mL (0.07-0.15) and 0.07 ng/mL (0.07-1.13), respectively. Serum pNfH concentrations were below the limit of detection (<0.07 ng/mL) for all Shivers horses. CSF pNfH concentrations in control, CVCM-, eNAD/EDM- and Shivers-affected horses were 1.26 ng/mL (1.06-1.5), 3.07 ng/mL (1.15-29.9), 1.78 ng/mL (1.5-2.28) and 1.39 ng/mL (0.74-3.89), respectively. CSF pNfH concentrations were significantly higher in CVCM (P = .001) and eNAD/EDM (P  = .01) affected horses compared to control horses. Serum pNfH concentrations >1 ng/mL were significantly associated with eNAD/EDM (P = .01) with only 12% sensitivity but 99% specificity. CSF pNfH concentrations >3 ng/mL were significantly associated with CVCM (P = .0002), with 50% sensitivity and 86% specificity.

MAIN LIMITATIONS

A limited number of control horses tested were <1 year of age.

CONCLUSIONS

Serum pNfH concentrations are specifically increased (>1 ng/mL) in some horses with eNAD/EDM. Increased CSF pNfH concentrations (>3 ng/mL) can be observed with eNAD/EDM or CVCM.

Biofluid Markers of Equine Neurological Disorders Reviewed From Human Perspectives

Neurological disorders (NDs) are often fatal to horses. Thus, symptoms of equine NDs commonly indicate euthanasia. Current diagnostic approaches for equine NDs is based on clinical signs, differential diagnoses, analysis of cerebrospinal fluid (CSF), assessment of histopathological lesions, and imaging. However, advances in biofluid biomarkers in the diagnosis of human neurological diseases can potentially be applied to equine NDs. In this review, we described the established human blood and CSF neurobiomarkers that could potentially be used to diagnose equine NDs.

Equine grass sickness

Equine grass sickness (EGS; equine dysautonomia) is a polyneuronopathy affecting both the central and the peripheral nervous systems of horses. As the name implies, EGS almost exclusively affects grazing horses, resulting in the development of a characteristic array of clinical signs, most of which can be attributed to neuronal degeneration in the autonomic and enteric nervous systems. Varying disease severities occur, largely determined by the extent of neuronal degeneration in the myenteric and submucous plexuses of the enteric nervous system. Extensive neuronal degeneration, as seen in acute and subacute forms of EGS, results in intestinal dysmotility, the severity of which is incompatible with survival. In comparison, a proportion of chronic forms of EGS, characterised by less severe neuronal degeneration, will survive. Despite extensive research efforts since EGS was first reported over 100 years ago, the precise aetiology remains elusive. This article reviews much of the scientific literature on EGS, covering epidemiology, pathology, diagnosis, treatment and aetiological hypotheses.