Encephalitis: An overview

Mohd Riyaz Beg | M. Pharm, ICT, Mumbai | B. Pharm, SPER, Jamia Hamdard, New Delhi | Race With Dreams! ©

 

What is Encephalitis?

Encephalitis referred as injury directly to Brain tissue by a bacterial or viral infection.

Symptoms

involved are fever and headache, altered consciousness, focal neurologic signs, or seizures. [a]

Encephalitis may be the result of bacterial, viral, fungal and protozoal infections.

Bacterial Encephalitis:

Bacterial infection of the brain substance is usually secondary to involvement of the meninges rather than a primary bacterial parenchymal infection. This results in bacterial cerebritis that progresses to form brain abscess. However, tuberculosis and neurosyphilis are the two primary bacterial involvements of the brain parenchyma. [b]

Fungal and Protozoal Encephalitis:

Systemic mycoses in the body usually disseminate to CNS by blood stream. They are particularly more common in immunosuppressed individuals such as in AIDS, patients of lymphomas and other cancers.
Examples of some fungi which disseminate to the CNS are Candida albicans, Mucor, Aspergillus fumigatus, Cryptococcus neoformans, Histoplasma capsulatum and Blastomyces
dermatitidis. These fungal infections may produce either of the three possible diseases: fungal chronic meningitis, vasculitis and encephalitis.
Besides fungal infections, CNS may be involved in protozoal diseases such as in malaria, toxoplasmosis, amoebiasis, trypanosomiasis and cysticercosis [b]

VIRAL ENCEPHALITIS:

Viral encephalitis is the inflammation of brain parenchyma. In many patients meningitis is associated with encephalitis (meningoencephalitis) and, in some cases, involvement of the spinal cord or nerve roots (encephalomyelitis, encephalomyeloradiculitis). [a]

Viruses causing acute encephalitis:

S. No.	Common Viruses
1	HSV
2	CMV
3	Varicella-zoster virus
4	Epstein-Barr virus
5	La Crosse Virus
6	West Nile Virus
7	St. Louis encephalitis virus
8	Rabies virus

Japanese encephalitis:

Causative agent: Japanese encephalitis virus (JEV) Flaviviruses (mosquito-borne)

Principal Reservoir Host(s): Ardeid wading birds (in particular herons), horses, pigs

Vector(s): Mosquitoes (Culex spp., in particular C. tritaeniorhynchus)

It is an infection transmitted by mosquitoes in rural Asian and Southeast Asian countries, can be as high as ~1 case per 5000 travellers per month of stay in an endemic area. Most infections are asymptomatic, with a very small proportion of infected persons becoming ill. However, among those who do become ill, severe neurologic sequelae are common. The vaccine efficacy rate is >90%. The vaccine is recommended for persons staying >1 month in rural endemic areas or for shorter periods if their activities (e.g., camping, bicycling, hiking) in these areas will increase exposure risk. [1]

Note: https://www.downtoearth.org.in/interviews/health/-it-s-absurd-to-blame-litchi-for-aes-malnourishment-the-real-cause--65130

References:

a.      Meningitis, Encephalitis, Brain Abscess, and Empyema, Harrison Principles of Internal Medicine 19th Edition

b.      The Nervous System, Harsh Mohan textbook of Pathology, 7^th Edition

1.      Health Recommendations for International Travel, Harrison Principles of Internal Medicine 19th Edition