North American Veterinary Licensing Examination (NAVLE) Practice Test

What is the condition in horses characterized by muscle tremors and decreased activity linked to Vitamin E deficiency?

1. Purpura hemorrhagica

2. Acquired equine motor neuron disease

3. Cantharidin toxicity

4. Idiopathic thrombocytopenia

The correct answer is: Acquired equine motor neuron disease

The condition characterized by muscle tremors and decreased activity linked to Vitamin E deficiency in horses is acquired equine motor neuron disease. This disease is primarily associated with oxidative damage to motor neurons in the spinal cord, which occurs due to insufficient levels of vitamin E. Vitamin E plays a critical role as an antioxidant, protecting cells from oxidative stress. When there is a deficiency, particularly in diets low in fresh forage, it can lead to progressive muscle weakness, stiffness, and tremors. Horses with acquired equine motor neuron disease exhibit signs such as muscle wasting (especially in the hindquarters), tremors, and generalized weakness, impacting their overall activity level. This condition can often be linked to poor nutritional practices that do not meet the horses' vitamin E requirements. Other options presented do not relate to vitamin E deficiency. For instance, purpura hemorrhagica is an immune-mediated disease associated with Streptococcus equi infections, while cantharidin toxicity arises from the ingestion of blister beetles and affects the gastrointestinal tract and kidneys. Idiopathic thrombocytopenia refers to a blood disorder affecting platelet count but is not directly associated with vitamin deficiencies. Thus, the correct answer aligns with the specific effects Vitamin E deficiency has on muscle function in horses