Arthropod vectors transmits many vectors that causes encephalitis.Theprimary vector is mosquito.In case of West Nile virus,humans are the secondary host,birds are the primary host.Arbovirus infection occurs in specific geographic areas during summer.West Nile and St Louis are the most common type of arbovirus.
1. Viral infection occurs at the site of mosquito bite
2. The host immune response attempts to control the viral replication
3. If the immune response is not adequate viremia occurs
4. The virus gains access to the central nervous system via cerebral capillaries(It spreads from neuron to neuron typically affecting the cortical gray matter,brain stem and the thalamus.
5. Meningeal exudates will be formed irritating the meninges resulting in increased ICP
- St Louis and West Nile are the most commonly affecting Encephalitis.Climate and environment contributes to occurrence of St Louis and West Nile encephalitis
- Arboviral encephalitis begins with flu like symptoms,neurological symptoms depends on the virus involved
- St Louis encephalitis presents with SIADH
- West Nile encephalitis presents with maculopapular or morbiliform rash on the neck,trunk,arms and legs and flassid paralysis
- Both encephalitis can result in Parkinsonian like movements reflecting inflammation of the basal ganglia.
- Seizures is a poor prognostic indicator and is seen most commonly in St Louis type.
ASSESSMENT AND DIAGNOSTIC FINDINGS
- History collection and physical examination
- Neuroimaging,MRI scan demonstrates inflammation of the basal ganglia.
- CSF evaluation.
- Immunoglobulin M antibodies are observed in serum and CSF in West Nile encephalitis.
- No specific treatment exists for arboviral encephalitis
- Medical management is aimed at controlling increased ICP and seizures.
- Interferon is used for treating St Louis encephalitis.
- Ribavirin and Interferon alpha 2b is given for West Nile virus encephalitis.
- If the patient is very ill hospitalization may be required.
- The nurse should carefully observe the patient and note for improvement or deterioration.
- Injury prevention due to falls and seizures.
- Family should be taught regarding the disease condition a nd the outcome
- Public should be educated regarding the prevention of arboviral encephalitis.
- Clothing should be used to reduce the bites
- Blood donation centres should screen all the blood foe West Nile virus.
REFER ENCEPHALITIS FOR MANAGEMENT