California encephalitis is an arbovirus-induced, arthropod-borne encephalitis. California encephalitis virus belongs to the Bunyaviridae family of viruses and was first discovered and isolated from mosquitoes collected in California in 1943.
Only 26% of the arbovirus infections have been found to be symptomatic. Infections with arbovirus are more likely to be symptomatic in the female gender and the highly viremic cases. Nevertheless, when present, the signs and symptoms in patients suffering from California encephalitis are similar to those present in other arbovirus-induced encephalitidis.
Initially, before encephalitis occurs, there is a prodromal phase of 1 to 4 days. In this phase, headache, fever, chills, malaise and other non-specific symptoms start appearing. Vomiting, abdominal pain and other symptoms of gastrointestinal upset are also often present.
Later on, as the virus reaches the central nervous symptoms, stiffness of the neck and neurological signs and symptoms start becoming apparent. There is a progressive clouding of consciousness. In up to 10 to 15% of the cases, coma and convulsions can also occur.
A number of investigations are helpful in diagnosing this disease.
Cerebrospinal fluid (CSF) examination: In most cases of viral encephalitis, it is possible to isolate the causal agent from the cerebrospinal fluid.
The La Crosse virus however, cannot be isolated from the cerebrospinal fluid. Still, a number of other changes in the cerebrospinal fluid can be evaluated in order to detect this disease. These include a mild elevation in the protein content with a normal glucose level. The white cell count is also raised with a predominance of lymphocytes or monocytes. In addition, the intracranial pressure will be only slightly raised .
Blood tests do not show significant changes. There may only be a mild increase in the number of white blood cells. Other parameters are usually normal .
Antibody titers: A number of specific antibody titers are of importance in the diagnosis of California encephalitis. IgM antibodies against viral antigens can also be detected by Enzyme Linked Immunosorbent Assay (ELISA) .
Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) are usually not of any diagnostic importance. No significant changes are observed except in the most severe cases where some nonspecific enhancement is seen on CT.
Upon examination under light microscope, biopsy specimen show perivascular infiltration with lymphocytes and plasma cells. Degeneration of nerve cells and areas of necrosis are also seen.
Currently, no specific antiviral therapy is available against La Crosse virus. California encephalitis is therefore treated with supportive aims.
The La Crosse virus is transmitted to the human host by the bite of a mosquito that is scientifically known as Aedes triseriatus . It is commonly known as the eastern treehole mosquito and is commonly found in the eastern and Midwestern states of the United States .
California encephalitis is a very common cause of arbovirus-induced encephalitis in the United States. As many as 75 cases are reported each year .
It is influenced by a number of epidemiological factors that are listed below:
The La Crosse virus enters the human body by the bite of Aedes triseriatus mosquito. It then replicates at the site of the bite and then gradually spreads to various sites in the body, in particular the liver, spleen and the lymph nodes.
At this stage, nonspecific symptoms of California encephalitis start appearing. Meanwhile, the virus keeps multiplying and the viral loads keeps on increasing.
The virus spreads to other sites of the body as well. When it finally enters the central nervous system through the cerebral capillary endothelial cells or the choroid plexus, the signs and symptoms of encephalitis as well as various other neurological signs are seen.
In endemic areas, control of the vector (by insecticide sprays, mosquito mats and coils); and application of measures against mosquito bites (e.g. the use of mosquito repellant sprays, mosquito nets etc.) is very useful in preventing California encephalitis .
California encephalitis is a caused by an arbovirus belonging to the Bunyaviridae family. It is transmitted by the bite of the mosquito Aedes triseriatus.
Discovered first in Kern County, California, this disease almost exclusively affects children.
California encephalitis is caused by a virus that is transmitted by the bite of a specific mosquito. It is more common in the Midwestern areas of the United States.
Initially, there is fever, headache, vomiting and abdominal pain. Later, when the virus reaches the brain, there is stiffness of the neck and diminishing of consciousness. Seizures and coma also occur.
The treatment for California encephalitis is mainly supportive.