Nigropallidal encephalomalacia in horses grazing Rhaponticum repens (creeping knapweed).

The research article describes a case of brain disorder, specifically nigropallidal encephalomalacia, diagnosed in two horses in northern Victoria, Australia, that had been grazing extensively on a plant known as Rhaponticum repens or creeping knapweed.

Background

• The study begins by introducing the case of two horses diagnosed with nigropallidal encephalomalacia. This is a type of brain disorder characterized by the softening of certain areas of the brain, specifically the substantia nigra and globus pallidus.

Nature of Disease and Symptoms

• The horses started showing symptoms like sudden subcutaneous edema (swelling under the skin) of the head, impaired mastication (chewing) and prehension (grasping of food), lethargy, dullness and repeated chewing-like jaw movements. These symptoms reflected a neurological disorder.

Role of Rhaponticum Repens

• The afflicted horses in this study case had a history of grazing on a dense growth of Rhaponticum repens, commonly known as creeping knapweed. The research suggests that this plant might have played a role in inducing the neurological disorder in horses.
• The infestation of Rhaponticum repens was linked to abnormal rainfall in the region where the horses resided. There was well above average rainfall for several months preceding the poisoning.

Diagnosis and Importance of the Case

• The brain disorder was confirmed through necropsy, which showed characteristic malacic (softening) lesions in the substantia nigra and globus pallidus of the brain.
• This is the first documented case of nigropallidal encephalomalacia in Australian horses associated with R. repens. The research article emphasizes the importance of this case as it adds new knowledge to the field and helps veterinarians diagnose and understand the effects of this poisonous plant on horses.