Meningitis and meningoencephalomyelitis in horses: 28 cases (1985-2010).

The research article is a retrospective study analyzing clinical data from 28 horses diagnosed with meningitis and meningoencephalomyelitis over a 25-year period. It reports the causes, symptoms, diagnostic findings, treatment outcomes, and mortality rates of these rare but serious conditions in horses.

Methodology of the Research

• The study is a retrospective examination of 28 horses diagnosed with meningitis and meningoencephalomyelitis over a quarter of a century.
• The horses’ medical records were reviewed, including details such as breed, history, clinical symptoms, reasons for admission, results from clinicopathologic testing and diagnostic procedures, their treatment, the outcome, and findings from necropsies (post-mortem exams)
• To be included in the study, the horses had to have a definitive diagnosis of meningitis or meningoencephalomyelitis.

Results and Findings

• Of the total horses, 22 had confirmed infectious diseases (19 bacterial, 2 parasitic, and 1 fungal). Four had suspected infectious diseases based on cytologic examination of cerebrospinal fluid (CSF), and two had noninfectious meningitis or meningoencephalomyelitis.
• In most cases, the infection was introduced into the body through trauma to the head or vertebral column that disrupted the blood-brain barrier, or by ascending or hematogenous (blood-borne) spread of the infection.
• The most common neurological symptoms included abnormal mental status, cranial nerve deficits, dysfunction of the vestibular system (which controls balance), ataxia (loss of full control of bodily movements), tetraparesis (weakness of all four limbs), and apparent neck pain.
• Common hematologic abnormalities included leukocytosis (increase in white blood cells), neutrophilia (increase in neutrophils), lymphopenia (low lymphocyte count), and hyperfibrinogenemia (high fibrinogen-a protein that helps in clotting- in the blood).
• Examination of CSF samples revealed moderate to severe inflammatory responses.
• The mortality rate was high, at 96.4%. In 15 of the 23 horses, microbial culture of the CSF yielded bacterial growth.

Conclusions from the Study

• The study concludes that meningitis and meningoencephalomyelitis are rare disorders in horses.
• Infectious diseases are more common causes of these conditions than noninfectious ones.
• The most common causes of meningitis and meningoencephalomyelitis are local trauma, ascending infection, or hematogenous spread of infection.
• Horses affected by these conditions commonly present with neurological deficits, an increase in neutrophils, a decrease in lymphocytes, an increase in fibrinogen, and cerebrospinal fluid showing an increase in neutrophils.