Equine Neurological Diseases: Arboviral Encephalomyelitis and Differentials

This set of vocabulary flashcards covers equine arboviral encephalomyelitis viruses (WNV, EEE, WEE, VEE), their clinical signs, transmission cycles, and key differential diagnoses such as Rabies, EPM, and Neuroborreliosis.

Equine arboviral encephalomyelitis (Classic case)

A presentation characterized by

1- altered mentation

2- cranial nerve abnormalities

3- ataxia

4- paresis or paralysis.

West Nile virus (WNV)

An arbovirus found throughout the US and Canada causing

1- fever

2- fasciculations of the face and neck

3- hyperesthesia

4- colic.

Eastern equine encephalomyelitis (EEE)

A highly pathogenic virus found east of the Mississippi river and eastern Canada with a mortality rate of $50-90\%$.

EEE forebrain signs

Specific clinical manifestations including

1- head pressing

2- circling

3- seizures.

Western equine encephalomyelitis (WEE)

An arbovirus found west of the Mississippi river and western Canada characterized by a head droop; it is currently less active and less pathogenic than other arboviruses.

Venezuelan equine encephalomyelitis (VEE)

A highly pathogenic virus with $50-90\%$ mortality; unlike other arboviruses, horses are not dead end hosts because they are viremic.

Culex mosquito

The main transmitter of West Nile virus that prefers feeding on crows and robins, which serve as the primary reservoir hosts.

Dead end hosts

The status of horses in WNV, EEE, and WEE transmission cycles, meaning they do not develop sufficient viremia to infect mosquitoes.

Equine Arbovirus Diagnosis

Achieved through cerebrospinal fluid analysis and IgM capture ELISA specifically for WNV.

Rabies (equine clinical signs)

Serious zoonosis presenting as

1- behavioral changes

2- progressive flaccid paralysis

3- distress

4- rolling (mistaken for colic)

5- self-inflicted wounds.

Equine protozoal myeloencephalitis (EPM)

A disease caused by Sarcocystis neurona resulting in

1- ataxia

2- cranial nerve deficits

3- asymmetric muscle atrophy, particularly in the gluteal muscles.

Opossum

The definitive host for Sarcocystis neurona; horses are infected orally via feed contaminated with its feces.

Neuroborreliosis

A condition caused by Borrelia burgdorferi from an infected tick, common in the Northeast and upper Midwest, presenting with

1- neck stiffness

2- ataxia

3- vestibular deficits.

Neuroborreliosis Treatment

The standard pharmacological intervention using Tetracyclines.