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Meningo-Encephalitis, Meningitis

Synonyms: Brain Infection

The meninges are the lining layers surrounding the brain and spinal cord- the central nervous system. Meningitis refers to inflammation (usually caused by bacterial or viral infection) of this lining. Meningitis is a very rare condition in the adult horse.

In order for infection of the meninges to take place, bacteria or virus must gain access to the central nervous system. Some viruses readily gain access.

Bacterial penetration is more difficult and this is why bacterial meningitis is so rare. Because of the protection of skull and spinal column, penetrating wounds into the central nervous system are rare. The central nervous system is also protected by something called the blood-brain barrier, which is a buffer between these two compartments that generally isolates the brain from blood infections.

Meningo-encephalitis is more common in foals because of their reduced ability to clear bacteria from the bloodstream (septicemia). In foals, unlike adults, bacteria are usually introduced to the brain via the bloodstream. In septicemic neonatal foals, there may also be further breakdown of the blood brain barrier, and bacteria present in the bloodstream are able to gain access to the central nervous system, enabling infection.

In normal healthy adult horses, the blood-brain barrier prevents access of bacteria to the brain itself and to the cerebrospinal fluid. But disease processes close to the brain and spinal cord can lead to meningitis. Examples of this are severe inner ear infections, skull fractures open to the sinus. and advanced bacterial eye infections that can actually infect the brain through the optic nerve.

DIAGNOSIS requires vet physical and neurologic exam, and requires analysis and culture of cerebrospinal fluid for confirmation.

TREATMENT is usually aggressive antibiotics, hopefully (but not always) guided by culture and sensitivity.

I Might ObserveRelated Observations

Foal or Newborn, Seizure or Convulsion
Newborn Foal, Not Nursing or Depressed
Noticeably Wobbly or Weak
Rigid, Stiff Limbs or Legs
Circling Compulsively in One Direction
Hypersensitive to Touch on Back or Topline
Seizures or Convulsions (in Adult)
Staring Into Space, Seems Unresponsive
Change in Personality, Strange Behavior
Unconscious, Lying Down & Not Responsive
Drooping Lip, Face or Muzzle
Eye is Making Abnormal Rapid & Jerky Movements
Fever, Rectal Temperature Greater than 101.5 (in Adult)
Foal or Newborn, Fever, Rectal Temperature Greater than 102.5 Degrees
Seems Dazed or Confused
Drowsy, Seems to Fall Asleep on Feet, Could Even Collapse
Ear Drooping or Cocked
Pupil, One Larger than Other
Vision Seems Poor, Running into Things or Objects
Extending or Stretching Out Neck
Hesitant to Walk on Hard Surfaces
Vision Seems Poor, Running into Things or Objects
Sudden Collapse or Apparent Loss of Consciousness
Cannot Chew, Chewing Abnormally
Eye is Making Abnormal Rapid & Jerky Movements
Leaning Against Stall Wall or Fence
Eyeballs Seem to be Pointing Different Directions
Lying Down & Paddling
Eyelid is Drooping or Eye is Closed
Local Muscle Twitching
Knuckling Over or Rolling Over on a Fetlock
Hind-End Leans or Falls to One Side, One Hind Limb Seems Weak
Eye is Bulging or Sticking Out from Socket
Shivering, Muscle Trembling All Over
Itching, Rubbing or Scratching, Generally
Eye is Draining, Discharge
Back Spasm, Muscles Feel Swollen, Tense or Hard After Exercise
Spasm or Tensing of Neck Muscle
Down with Limbs Tipped Up, Cast
Striking with Front Feet
Eyeball Seems Enlarged


  • How did my horse acquire this infection?

    Treat septicemia in foals early and aggressively. For adult horses, treat sinusitis and other infections of the head aggressively early on.
    Author: Doug Thal DVM Dipl. ABVP


    Hepburn, RJ. Improving Survival in Bacterial Meningitis Equine Vet Education, October 2014, 513.


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