Encephalomyelitis:

• Inflammation of both brain and spinal cord is known as encephalomyelitis.
• It is typically an acute viral infection affecting equine species. Other animals such as pig, Llamas, bat, reptiles, amphibian and rodents can also be infected.
• On basis of causative agent, encephalomyelitis is of two types:
  • Bacterial encephalomyelitis
  • Viral encephalomyelitis

Bacterial Encephalomyelitis:

Etiology:

• coli
• Neisseria
• Streptococcus
• Chlamydia sps

Clinical Findings:

• Depression
• Appetite may be unaffected for several days
• Nasal discharge and salivation with drooling are frequently observed.
• Fever; 105-107°F
• Dyspnoea, coughing
• Mild catarrhal nasal discharge
• Difficulty in walking, lack of desire to stand
• Opisthotonus may occur but there is no excitement or head pressing

Diagnosis:

• Isolation and identification of organism especially from brain samples
• On basis of history and clinical signs
• Serological test: CFT, ELISA
• Histological examination of CNS

Treatment:

• No specific treatment available.
• Tetracycline/OTC short-acting @25-50 mg/kg for 5-7 days
• Tylosin tartrate @5-10 mg/kg, b.wt. IM for 5 days

Viral Encephalomyelitis:

Etiology:

• Horse: Eastern equine encephalomyelitis by toga virus, WEE, VEE, Western Nile Encephalomyelitis
• Cattle: sporadic bovine encephalomyelitis, Rabies
• Sheep and goat: Louping-Ill, Viral caprine leukoencephalitis
• Pig: Teschen diz
• Dog: Rabies, Canine distemper

Clinical Signs:

• Equine encephalitic alphavirus infection in horse may be sub-clinical with only a transient fever or may present with protracted fever, anorexia, tachycardia, depression
• Progressive systemic disease occurs when virus gains access to CNS. After incubation period of 4-6 days, affected horse develops:
  • Fever
  • Signs of drowsiness
  • Incoordination
  • Severe depression
  • Abnormally wide stance
  • Hanging head, drooping ear, flaccid lips
  • Irregular gait
  • Wandering
  • Signs of encephalitis including impaired vision, photophobia, inability to swallow, circling, yawning and grinding of teeth.
  • Constant head pressing against corner of stall or fence is typical presentation
  • In terminal stages of disease, there is inability to rise, paralysis, and occasionally convulsion.

Diagnosis:

• CSF examination: pleocytosis, high protein, low glucose level
• Identification of virus through immunofluorescence analysis
• PCR
• Serological test: Hemagglutination inhibition test, virus neutralization test, ELISA

Treatment:

• No specific treatment
• Supportive treatment: Fluid therapy to maintain hydration, maintenance of nutritional status.
• In case of louping ill, antiserum can be used and affords protection, if given within 48 hrs of exposure.