Central neuropathology of equine grass sickness.

This research focused on investigating the neurological impacts of Equine Grass Sickness (EGS), a disease affecting horses that results in nervous system dysfunction. The researchers found that EGS affects multiple neurological centers in various ways, establish that it should be considered a multisystem disease.

Background

• Equine Grass Sickness (EGS) is a disease that affects horses, particularly those kept on grass. The exact cause of this disease is unknown.
• EGS is characterized by a disruption in both sympathetic and parasympathetic neurons, which constitutes a group of conditions known as dysautonomias.

Research Method

• The researchers systematically examined the nuclei of cranial nerves in the brain stems of 59 cases of EGS.
• They particularly focused on identifying chromotolysis, a state where neurons show an indication of damage, in the lower motor neurons of the general visceral efferent nucleus of cranial nerves III and X and the general somatic efferent nuclei of cranial nerves III, V, VII, and XII.

Key Findings

• The most consistent finding was chromotolysis in the lower motor neurons of the mentioned cranial nerves.
• The frequency of chromatolysis varied significantly across the diagnostic categories and was found to be inversely related to the horse’s age— the younger the horse, the higher the frequency.
• The duration of the disease also had a small but significant negative effect on the proportion of nuclei presenting chromatolysis in chronic cases. This means that the longer the disease persists, the greater the damage to the neurons.

Conclusion and Implications

• The findings indicate that the distribution of chromatolytic neurons in EGS differs from any other known equine or human diseases. However, they are similar to findings in other animals suffering from primary dysautonomias.
• These insights suggest that EGS affects multiple nervous systems, implying that it should be considered a multisystem disease. This view could influence future research and treatment strategies for managing EGS.