North American Veterinary Licensing Examination (NAVLE) Practice Test

What clinical signs indicate that a horse may have EPM or a related neurological condition?

1. Head shaking and coughing

2. Unilateral facial paralysis and ataxia

3. Excessive sweating and tremors

4. Weight loss and lethargy

The correct answer is: Unilateral facial paralysis and ataxia

The presence of unilateral facial paralysis and ataxia is indicative of Equine Protozoal Myeloencephalitis (EPM) or a similar neurological condition in horses. EPM is caused by the protozoan parasite Sarcocystis neurona, which affects the central nervous system. Unilateral facial paralysis results from damage to the cranial nerves, particularly affecting the muscles of facial expression on one side of the horse’s face. Ataxia, or an uncoordinated gait, arises from the impact on the cerebellum or spinal cord due to inflammation and lesions caused by the parasite. These clinical signs can manifest as difficulty with balance and control during movement, making the diagnosis of EPM relevant. Identifying these neurological signs is crucial for prompt diagnosis and treatment to prevent further neurological deterioration. Other signs, while they may signal different conditions, do not point specifically to EPM. For instance, head shaking and coughing might suggest respiratory issues or allergies but lack the neurological components seen in EPM. Excessive sweating and tremors could accompany various metabolic or infectious conditions but are not specific enough to indicate EPM. Weight loss and lethargy are nonspecific signs that can be seen in many diseases, reflecting a general decline in