Eastern & Western Encephalomyelitis:

The early clinical signs of EEE and WEE may be so mild that they go unnoticed, and may include transient fever and depression, lasting up to five days. Many cases of WEE do not progress beyond this stage. However, EEE is more likely to progress to central nervous signs, which may progress from depression and sleepiness to aggression and agitation. Late in the disease affected horses may develop blindness, head pressing, circling, head tilt, quivering face and leg muscles, and paralysis of the throat and tongue. Terminal horses will usually be down for several days before dying. Death from EEE occurs in 75 - 80% of horses that develop neurologic signs, and in 15 - 30% of those with WEE. Survivors show gradual improvement over weeks to months, but complete recovery is rare. Horses that recover from sleeping sickness often continue to show depression, abnormal behavior, and difficulty in walking.

EquineInfluenza

The signs of equine influenza usually start suddenly, with an affected horse abruptly developing a high fever. A dry, harsh cough begins early in the infection and may last for weeks. The nasal discharge initially is watery and scant, but usually becomes yellow and heavy, due to secondary bacterial infection. A sick horse may have watery eyes, enlarged lymph nodes between the mandibles, edema and stiffness in the legs, and breathing difficulty. Depression, weakness, and loss of appetite are common. Horses with relatively mild cases of equine influenza usually recover in a week or so, but severely ill horses may require weeks to months to recover fully, especially if they are not allowed to rest completely. Most uncomplicated cases recover fully, but affected animals under stress, or ones not allowed to rest, may develop secondary pneumonia, a chronic cough, or inflammation of the heart muscle, sometimes resulting in death.

Equine Rhinopneumonitis

Typical signs of equine herpesvirus respiratory disease include fever, congestion, cough, loss of appetite, nasal and eye discharges, fatigue, and swollen lymph nodes. An animal’s first exposure to the disease generally produces more severe signs, whereas later exposures cause mild or inapparent infections. Secondary bacterial infections can occur and should be suspected when fever persists beyond a week, the nasal discharge becomes thick and yellow instead of watery, or the cough worsens.

Tetanus(equine)

Signs of tetanus become apparent within several days to several weeks, depending on how close the contaminated wound is to the central nervous system. The extensor muscles of the jaw are often affected, leading to the common name of this disease, lockjaw. Saliva may drip from the horse’s mouth, and attempts to eat or drink may cause regurgitation of food or water from the nostrils. Paralysis and rigidity then progress to the face, neck, trunk, and legs. The third eyelid may prolapse, the ears may be held erect and rigid, and the nostrils may be flared. Once the limbs become affected, the horse stands with all four legs stiff, in a characteristic "sawhorse stance." The affected animal reacts violently to external stimuli, such as loud noises or sudden light, and may go into convulsions. Other possible signs of tetanus include profuse sweating, colic, and difficulty in walking and breathing. Laminitis and pneumonia may develop as secondary complications. After treament has begun, clinical signs may persist for up to six weeks, and muscle spasms may occur for weeks to months before full recovery. If death occurs, it is usually due to respiratory failure. Generally, about 80% of affected horses die.

Strangles

Infected horses become depressed, lose their appetite, develop a 104-106’ F fever and a cough. A thick, yellow nasal discharge is present, and lymph nodes of the head and neck swell. Sometimes the lymph nodes swell enough to restrict breathing, which is how the disease got its name. After a week or two the abscessed lymph nodes of the head and throat may rupture and drain. Read More

West Nile Virus

West Nile Virus (WNV) is a neurologic disease that first appeared in the Western Hemisphere in the fall of 1999, causing illness and death in horses, birds and humans.  The virus is spread by the bite of an infected mosquito and is harbored by birds, which have assisted in the disease’s spread from its original epicenter in New York to other areas over the past three years.  WNV has been recognized in 27 states.

Symptoms usually appear mainly in the late summer and fall, however some believe it could become a year-round cycle in warmer climates.  The last count of confirmed equine cases in the United States was 738.  Initially it was estimated that WNV would spread across the U.S. within four years, but many scientists think that it might move faster.

Clinical Signs of WNV:

Flu-like signs, where the horse seems mildly anorexic and depressed.
Muscle twitching or weakness.
Hyperesthesia or Hypersensitivity.  Affected horses startle easily, or seem “jumpy”.  Some seem unwilling to be touched or handled and may respond with aggression.
Changes in mentality.
Occasional drowsiness.  Horses can go from being over-responsive to showing no response to stimulation in a matter of minutes.
Propulsive walking or wandering (driving forward, often without control).
“Spinal” symptoms, including asymmetrical weakness.  They may also show incoordination on one or both sides.
Other neurological signs include facial paralysis, head tilt difficulty swallowing, and the inability to stand up.

Testing/Treatment/Outcome

West Nile Virus has a 30% mortality rate.  The majority of horses will get better with extensive supportive care which is very costly.  Advanced stages with paralysis have the higher probability of not surviving.  Horses in about 70% of the Florida cases (where WNV has hit hardest due to year around warm temperatures) appeared to make a full recovery, although some had prolonged weakness, taking several months to return to normal.

Mosquito prevention is an important factor in reducing the risk of West Nile Virus.  Here are some steps to follow:

House horses indoors during peak mosquito times (dawn and dusk).
Avoid turning lights on in the stable during evening and overnight.
Place incandescent bulbs around the perimeter of the stable to attract mosquitoes away from the horses.
Eliminate areas of standing water, such as discarded tires, birdbaths, etc.  Any stagnant water that has been standing for 4 days or more is an ideal breeding ground for mosquitoes.
Use repellants that are approved for horses.
Use fans on horses in the stable, air movement deters mosquitoes.
Fog the stable area in the evening.

The most effective prevention, however, is vaccination and as with any new vaccine it should be given twice, 3-6 weeks apart and boostered yearly, preferably late spring to early summer. Please call us at 619.659.1180 if you would like to schedule an appointment to have your horse vaccinated. Don’t hesitate to call our office if you have any further questions or concerns.