What is California Encephalitis: Causes, Symptoms, Treatment, Prognosis, Pathophysiology, Prevention

California Encephalitis is a type of encephalitis (brain inflammation) which is caused by an arbovirus belonging to the Bunyaviridae family. This virus enters the human body through the bite of the mosquito named Aedes triseriatus. California Encephalitis was first discovered in Kern County, California, hence the name. This condition almost exclusively affects the children. California Encephalitis is more prevalent in the Midwestern areas of America. The initial symptoms of California Encephalitis consist of headache, fever, vomiting and pain in the abdomen. As the virus reaches the brain, patient experiences symptoms like neck stiffness and decreased consciousness. Patient can also have seizures and fall into a coma. There is no specific anti-viral medicine for California encephalitis and treatment primarily consists of supportive treatment to manage the symptoms.

The cause of California Encephalitis is arbovirus, which are a group of arthropod-borne viruses that can also cause general infection and hemorrhagic fever in human beings. The virus gets transmitted to human beings through the bite of a mosquito, which is scientifically known as Aedes triseriatus and commonly known as the eastern treehole mosquito.

Age: California encephalitis is mainly a childhood disease and commonly affects children that are aged between 6 months to 16 years. As the child grows and the age increases, the chances of contracting this disease get reduced. Children aged between 4 to 10 years are more affected from this disease.

Gender: Males are at a higher risk for developing California encephalitis than females, as males will spend more time outdoors than females.

Season: Majority of the cases of California encephalitis are seen in the late summer to early fall.

Geographical Location: California encephalitis is commonly seen in the Midwestern states in America.

When the Aedes triseriatus mosquito bites a human being, the virus enter the body where it replicates at the location of the bite and slowly spreads to different areas in the body, especially the spleen, liver and the lymph nodes. At this stage, patient starts experiencing nonspecific symptoms of California encephalitis, such as fever and headache. As the virus keeps multiplying, it leads to increase in the viral load. The virus then starts spreading to other areas of the body as well and finally enters the central nervous system via choroid plexus or cerebral capillary endothelial cells where it further multiplies producing symptoms such as lethargy, stiff neck and seizures along with other neurological signs, which finally results in encephalitis where there is acute inflammation of the brain due to the viral infection along with damage to the nerve cells that affects the signals transmitted by the brain to the body.

Some of the common symptoms of California encephalitis include fever, lethargy, focal motor abnormalities, focal neurologic findings and paralysis. California encephalitis has incubation period of around 3–7 days. There is a stage where the patient experiences early symptoms about 1–4 days before the onset of encephalitis. California encephalitis patient experiences symptoms, such as chills, fever, nausea, headache, vomiting and abdominal pain. Afterwards when the virus reaches the central nervous system, patient has symptoms, such as neck stiffness, drowsiness, disorientation and other neurological signs and symptoms.

About half of the patients with California encephalitis have symptoms of seizures. Other focal neurologic signs, such as abnormal and irregular reflexes occur in around 20% of the children. About 10% of the patients slip into coma. The duration of California encephalitis lasts for about 10–14 days and rarely exceeds this length of time. About 20% of patients also experience recurrent unprovoked seizures, especially those patients who have had seizures during the acute phase of California encephalitis. California encephalitis usually does not affect the adults. Most of the adults will be asymptomatic, which indicates that the patient is a carrier of the infection, but has no symptoms or only has mild fever.

There are different types of investigations, which help in diagnosing California Encephalitis

Testing of the Cerebrospinal Fluid (CSF): In most of the patients, the causative agent can be isolated from the cerebrospinal fluid. Other changes in the cerebrospinal fluid can also help in detecting California Encephalitis. Some of the changes seen in CSF in this disease include: Slight increase in the protein content, increase in white cell count with primary increase in the monocytes or lymphocytes. The intracranial pressure is also slightly increased in patients with California Encephalitis.

Blood Tests: There are no significant changes seen upon blood analysis. There is slight increase in the white blood cell count and the other parameters are often normal.

Antibody Titers: There are various antibody titers, which help with the diagnosis of California encephalitis. Enzyme Linked Immunosorbent Assay (ELISA) can help in detecting IgM antibodies against the viral antigens.

Histologic Investigations: Histologic tests can be carried out where perivascular infiltration with plasma cells and lymphocytes can be seen on the biopsy specimen under light microscope. Areas of necrosis and degeneration of the nerve cells can also be seen.

Imaging Tests such as Computed Tomography (CT) scan and Magnetic Resonance Imaging (MRI) scan commonly do not help in the way of diagnosis of california encephalitis and significant changes are not observed upon imaging studies, except in extremely severe cases where nonspecific enhancement can be visualized on CT scan.

As of now, there is no specific treatment for California Encephalitis and treatment is done for managing the symptoms and primarily comprises of supportive treatment. Bed rest is important for the patient to boost the recovery process of California encephalitis. Mannitol can be given to the patient to reduce the increased intracranial pressure. Paracetamol helps in alleviating fever and headache associated with California Encephalitis. Steroids help in reducing the inflammation and swelling in the brain. Anti-convulsant drugs, which comprise of diazepam and phenytoin, are given to patients who are suffering from seizures. Sedatives are prescribed if the California Encephalitis patient is irritable and restless.

If the patient is very sick, then supportive treatment which includes mechanical ventilation is also given. If the brain function of the patient is severely affected, then interventions, such as speech therapy and physical therapy are required after California Encephalitis has abated.

In order to prevent California Encephalitis, mosquito control should be done by using mosquito mats, insecticide sprays and mosquito coils. Use of mosquito repellant sprays also helps with preventing mosquito bites and California Encephalitis.

The prognosis of California encephalitis is often good. The mortality rate in patients with California encephalitis is very low, about 1%. However, the prognosis is not that good in younger children. There is complete recovery seen in majority of the patients suffering from California Encephalitis. Some patients may be left with epileptic seizures or speech disorders.