Encephalitis:

• It is defined as inflammation of the encephalon (brain).
• It includes those diseases in which inflammatory lesions occur in the brain, whether there is inflammation of the nervous tissue or primarily of the vessel walls.
• It is characterized by initial hyperexcitability followed by paralysis and unconsciousness.
• The meninges and spinal cord may be involved in an encephalitis, causing varying degrees of meningoencephalomyelitis.
• It may be a primary ailment or a secondary lesion or consequence to disease elsewhere in the system.

Etiology:

• Viral agents: Rabies, Pseudo-rabies, Japenese B-encephalitis
  • Cattle: Sporadic bovine encephalomyelitis, Bovine malignant catarrh, Infectious bovine rhinotracheitis
  • Horse: Infectious encephalomyelitis, Bona disease
  • Pig: Viral encephalitis, Hog cholera, African swine fever
  • Sheep and goat: Scrapie, Louping ill, Visna, Viral caprine leukoencephalomyelitis,
  • Dog: Canine distemper
• Bacterial infections: Listeria, Necrobacillus infection, Enterotoxemia, Salmonella, Erysipelas, Borrelia burgdorferi
• Parasitic agents: Migrating larvae, Multiceps multiceps, Toxoplasmosis, Nervous coccidiosis, Neospora caninum, Hypoderma bovis, Oestrus ovis migration, Sarcocystis neurona
• Toxic agents: Lead, arsenic, salt poisoning, ipomia plant
• Fungal agent: Cryptococcosis

Clinical Findings:

• In case of infection, fever, anorexia and depression develops
• Mania, aggressiveness, stupor
• Circling movement, head pressing
• Clonic convulsion, muscular tremor, pawing on ground
• Frothy salivation from commissure of mouth
• Champing of jaws and hyperesthesia
• Spastic paralysis in either sides
• Ataxia or incoordination of gait
• Nystagmus of eyeball
• Unilateral facial paralysis due to Listeriosis
• Blindness of eye reflex
• Prostration- unable to stand, head is drawn under body
• Unilateral or bilateral blindness in horse

Diagnosis:

• Complete neurological examination of animals
• Blood test to rule out infections, inflammatory conditions
• Serological test for confirmation of certain infectious disease
• Analysis of CSF for biochemical, cellular and microbiological aspects.

Differential diagnosis:

• Acute cerebral edema: Less excitement, no fever, history of salt poisoning
• Poisoning: Salivation, history of poisoning, no fever, blindess, acute onset
• Avitaminosis-A: Young animal suffer, no fever, ataxia, hyperaesthesia, respond to vitamin-A therapy
• Encephalomalacia: History of grain engorgement, thiamine deficiency, respond to Vitamin-B therapy
• Meningitis: Temperature reaction, hyperaesthesia, rigidity of muscles, examination of C.S.F will assist diagnosis.

Treatment:

• Antibiotics are indicated for bacterial infection. Selection of antibiotics are based on sensitivity test of bacterial culture. Ampicillin, chloramphenicol is used for 5-7 day.
• Supportive therapy through administration of intravenous fluid and electrolyte therapy
• Stomach tube feeding is done during acute phase.
• Sedation of animals during excitement prevent animal from injuring itself. Diazepam @ 1mg/kg, IV or PO or chlorpromazine @ 0.5-4.4 mg/kg, IV, 3.2mg/kg, PO, TID-QID in dogs
• Corticosteroid therapy to reduce inflammation. Dexamethasone @ 10-30 mg, IM/IV OD
• Specific antidote is used against case of poisoning
• Use of mannitol to reduce intracranial pressure.