Question

A 1.5-year old Quarter Horse gelding is presented to you for symmetric ataxia, weakness, and spasticity of all limbs, but worse in the hind limbs. When walking, the horse frequently drags his toes and the hind limbs frequently interfere with one another. Based on the signalment, history and physical examination findings, which of the following is the most likely cause of these clinical signs?

Equine Degenerative Myeloencephalopathy (EDM)
Equine Motor Neuron Disease (EMND)
Equine Protozoal Myeloencephalitis (EPM)
Cauda Equina Syndrome
Botulism

Answer 1

The most likely cause of the clinical signs in the Quarter Horse gelding is Equine Protozoal Myeloencephalitis (EPM), caused by infection with the protozoan parasite Sarcocystis neurona.

Step-by-step explanation:

The most likely cause of the presented clinical signs in the 1.5-year old Quarter Horse gelding is Equine Protozoal Myeloencephalitis (EPM). EPM is caused by infection with the protozoan parasite Sarcocystis neurona, which can result in neurological symptoms including ataxia, weakness, and spasticity of the limbs. In this case, the hind limbs are particularly affected, with toe-dragging and frequent interference between them. To confirm the diagnosis, further diagnostic tests such as cerebrospinal fluid analysis and antibody titers can be performed. Treatment of EPM typically involves medications to target and eliminate the parasite.