Grass Sickness - Clinical Signs

Clinical Signs

Grass sickness is a polyneuropathy affecting the central, peripheral and enteric nervous systems. The majority of visible clinical signs are related to paralysis within the digestive tract although nerve damage occurs throughout the body. There are three forms of grass sickness:

• acute grass sickness (AGS) - horses display signs of colic and require euthanasia or die within 48 hours
• subacute grass sickness (SAGS) - horses display clinical signs similar to AGS but with less severity and may survive up to 7 days
• chronic grass sickness (CGS) - horses present with severe and rapid weight loss and a selected portion of these cases may survive.

Clinical signs common to all subsets include: depression, anorexia, colic (moderate with AGS/SAGS and mild with CGS), excess salivation, constipation, nasogastric fluid secretion, patchy sweating, muscle tremors and eyelid drooping.