Diseases and Health Problems of Horses
Equine Gastric Ulcer Syndrome
Equine Gastric Ulcer Syndrome (EGUS) is increasingly recognized as a major problem
affecting the well being and performance of horses. In fact, stomach ulcers are
quite common in horses.
- Up to 93% of racehorses get stomach ulcers, regardless of age
- Almost 60% of other performance horses have ulcers
- Up to 57% of foals have stomach ulcers, particularly during the first several months
Equine ulcers can be difficult to diagnose
- 50% of horses with ulcers show no outward signs of gastrointestinal disease
Views inside a healthy horse stomach (left) and a horse in training with ulcers
(right). Photos courtesy of MJ Murray.
Signs of equine Gastric Ulcer Syndrome (EGUS) range from mild to severe –
cases of perforated equine gastric ulcers can even be fatal.
Parasites of Horses
All horses should be included in a regular parasite control program. Foals should
be treated initially at 6 to 8 weeks of age, and routine treatment repeated as appropriate.
Click below for information about equine parasites (PDF format):
Viral Diseases of Horses
Eastern and western encephalitis (encephalomyelitis)
These variations of equine encephalomyelitis are clinically similar syndromes characterized
by signs of CNS dysfunction and moderate to high mortality. The causal arboviruses
are transmitted by mosquitoes or ticks and infect a variety of vertebrate hosts,
including man, in which they occasionally cause serious infections. Horses may be
infected by alphaviruses including eastern (EEE), western (WEE), and Venezuelan
(VEE) equine encephalomyelitis viruses. Clinical signs of an encephalomyelitis occur
approximately 5 days after infection, and most deaths occur 2-3 days later. Signs
can include fever, impaired vision, irregular gait, wandering, reduced reflexes,
circling, incoordination, yawning, grinding of teeth, drowsiness, pendulous lower
lip, inability to swallow, photophobia, head-pressing, inability to rise, paralysis,
occasional convulsions, and death. Mildly affected animals may recover slowly in
a few weeks but may have residual brain damage. Mortality in horses is 20-50% from
WEE, 50-90% from EEE, and 50-70% from VEE.
Equine influenza is an acute, highly contagious, febrile respiratory disease. The
clinical outcome following viral exposure largely depends on immunological conditioning;
in susceptible animals this may vary from a mild, inapparent infection to a severe
disease that is rarely fatal except in young, old, or debilitated horses. Transmission
occurs via the respiratory route through contact with infective respiratory secretions.
Epidemics arise when one or more acutely infected horses are introduced into a susceptible
group for show, sale, training, or racing.
Horses are the most sensitive species to this disease, with the possible exception
of humans. Tetanus is a toxemia caused by a specific neurotoxin produced by Clostridium
tetani in necrotic tissue. The incubation period varies from one to several
weeks, but usually averages 10-14 days. Localized stiffness, often involving the
masseter muscles and muscles of the neck, the hindlimbs, and the region of the infected
wound is seen first; general stiffness becomes pronounced approximately 1 day later,
and tonic spasms and hyperesthesia become evident. Mortality averages 80%.
Rabies is an acute, viral encephalomyelitis that affects all warm-blooded animals.
The mortality rate approaches 100%. The incubation period is prolonged and variable.
Rabid animals of all species exhibit typical signs of CNS disturbance. Horses may
show extreme agitation evidenced by rolling, as with colic. They may bite or strike
viciously and, because of size and strength, become unmanageable in a few hours.
Such animals frequently suffer self-inflicted wounds.