Nigropallidal encephalomalacia in horses in New South Wales.

This research article discusses a condition of brain damage, specifically nigropallidal encephalomalacia, observed in horses in New South Wales. The condition, which exhibited symptoms such as difficulty in eating and drinking, was suspected to be botulism and was associated with horses feeding on pastures containing possibly toxic plants.

Overview

• The abnormalities were first observed in June 1971 in five spring-drop foals in the Molong area. These foals showed signs of tongue weakness and were unable to eat or drink but could be sustained when fed through a stomach tube. However, all died when returned to the pasture.
• In July 1972, a 9-month old foal from the same area also exhibited similar symptoms and had to be euthanized. A post-mortem examination of the brain revealed a clearly demarcated, pale-yellow ovoid mass in the corpus striatum along with a smaller mass in the substantia nigra. These masses, referred to as malacia, indicate softening or degeneration of the brain tissues. The researchers also noted the almost total loss of neurons within the lesion area.

Historical Context and Similarities

• The researchers also referenced a 1954 study by Cordy in which similar symptoms were observed in 16 horses aged between 4 months and 10 years in northern California. These horses suffered a variable impairment of eating and drinking, most eventually dying of starvation, dehydration, or related diseases.
• Post-mortem examinations revealed focal necrosis (localized tissue death) in sections of the globus pallidus and substantia nigra, both brain structures usually being symmetrically affected.
• Interestingly, Cordy had noted that these horses had been feeding on pastures rife with the plant Centaurea solstitialis, commonly known as yellow star thistle. Furthermore, Young et al. (1970) demonstrated that the ingestion of Russian knapweed could result in similar symptoms of brain damage and impaired motor functionality.

Conclusion

• This clinical report alerts the veterinary community about the health hazards associated with possible toxic pastures and highlights the need for comprehensive investigations to establish the exact causes of such incidents.