Encephalitis

Definition

Inflammation of the brain parenchyma, typically triggered by infection, autoimmune response, or toxic insult. In medical and veterinary entomology, the term most commonly denotes arboviral encephalitides—neuroinvasive diseases transmitted by hematophagous arthropods. Vector-borne forms include mosquito-transmitted Japanese encephalitis, St. Louis encephalitis, Western equine encephalitis, and Venezuelan equine encephalitis, plus tick-borne encephalitis. Clinical severity ranges from subclinical to fatal, with pathology involving perivascular cuffing, neuronal necrosis, and cerebral edema. Diagnosis relies on cerebrospinal fluid analysis, serology, or nucleic acid detection; prevention emphasizes vector control and vaccination where available.

Etymology

From Greek enkephalos (brain) + -itis (inflammation)

Example

Tick-borne encephalitis virus, transmitted chiefly by Ixodes ricinus and I. persulcatus ticks across Eurasia, causes biphasic illness with a secondary neurological phase that may progress to meningoencephalitis; vaccination and tick avoidance are primary preventive measures in endemic forest habitats.

Synonyms

• cerebritis

Related Terms

• Arbovirus
• meningitis
• neuroinvasive disease
• vector-borne disease
• Japanese encephalitis
• Tick-borne encephalitis
• West Nile virus
• flavivirus
• alphavirus
• bunyavirus

Usage Notes

Distinguished from meningitis (inflammation of meninges) though both may coexist as meningoencephalitis. The plural 'encephalitides' is used for multiple disease types, not multiple instances. In entomological contexts, 'encephalitis' without modifier usually implies arboviral etiology and prompts investigation of local mosquito or tick vectors. Non-infectious forms (autoimmune, paraneoplastic) fall outside typical entomology scope.