The following points will highlight the viruses associated with encephalitis. The viruses associated with encephalitis are:- 1. Western Equine Encephalitis 2. Eastern Equine Encephalitis 3. Venezuelan Equine Encephalitis 4. Japanese Encephalitis 5. St. Louis Encephalitis 6. Murray Valley Encephalitis 7. California Encephalitis 8. Tick Borne Encephalitis 9. Louping III and 10. Powassan.
1. Western Equine Encephalitis (WEE):
WEE occurs in Western states of USA. Most human infections are mild, only some show clinical symptoms. Mild cases are characterised by fever with headache and vomiting, sometimes stiffness of neck and back. More severe cases progress to stupor and coma; convulsions may occur particularly in children. Mortality rate is 3 per cent. Recovery is usually complete without sequelae.
2. Eastern Equine Encephalitis (EEE):
Occurs in eastern USA and Canada; mild infection is rare; mortality is high as 75 percent. Symptoms are similar to that of WEE but more severe headache to death. Mental deficiency and paralysis are common sequelae.
3. Venezuelan Equine Encephalitis (VEE):
Resembles WEE and is usually mild infection. In occurs in America.
4. Japanese Encephalitis (JE):
JE virus occurs over a wide area of Asia, Malaysia and Japan. Most infections are mild; some develop encephalitis which is of a severe type similar to that caused by EEE virus with a high mortality of 90% and mental impairment, personality change and paralysis as sequelae. The virus is transmitted among vertebrate host, birds by mosquitoes, Aedes and Culex. Pigs are also infected and the infection is mild.
Man is also in close contact with the pigs than he is with wild birds, so pigs act as “link host” for the infection of man. Only in man, the “dead-end” host, does clinical disease occur. CT scan appears to be of little use in making the specific diagnosis of Japanese encephalitis in India.
5. St. Louis Encephalitis (SLE):
SLE virus occurs in America. Most infections are mild and transmitted by Culex.
6. Murray Valley Encephalitis (MVE):
MVE virus occurs in Eastern Australia in New Guinea and is closely related to JE virus and induces a severe disease with a high mortality like JE virus. Ilheus virus is the cause of mild encephalitic disease in Central or South America and in Trinidad.
7. California Encephalitis (CE):
CE virus was first recognised as a cause of encephalitis in man in the valley of California. It is shown to be the cause of Central Nervous System (CNS) disease in the USA. The clinical disease varies from a mild undifferentiated febrile illness to acute CNS disease, even fatal.
Tabyna:
Tabyna virus is the cause of mild illness mainly of respiratory type in Czech republic. Wild vertebrate host and mosquito are involved in the transmission of virus to man.
8. Tick Borne Encephalitis (TBE):
TBE virus occurs widely in USA and in central America. It is cause of encephalitis and transmitted by hard tick, Ixodes. The incubation period is 8-14 days. Onset is sudden, pyrexia with signs of cerebral involvement, photophobia, coma and paralysis. The bulbar centres and cervical cord may be involved. Mild infections may occur. Mortality is highest (30%); paralysis may be permanent.
9. Louping III:
Louping (= Leaping) ill is an encephalomyelitis of sheep occurring in England, Scotland border.
The disease shows typically two phases:
(а) First, viraemia accompanied by high pyrexia, and
(b) Second, neurological incoordination, paralysis, even death.
The second may be absent and the infection may be in apparent. Human cases may derive from contact with infected sheep or from laboratory. Hard tick, Ixodes, may-transmit virus to sheep.
10. Powassan:
Virus first isolated from a child with encephalitis in USA, Canada and also isolated from ticks. Dermacenterand Ixodes.
Application to Nursing:
While dealing with arbor viral infections, nurse should strictly adopt all measures to destroy the arthropods and to protect patients from arthropod bite. She should promptly intimate the doctor as soon as she is detecting symptoms like pyrexia and encephalitis.