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St. Louis Encephalitis
 What Is St. Louis Encephalitis?
What is being done in Memphis to prevent SLE?
Signs and Symptoms
Causes
Risk Factors
When to Seek Medical Advice
Screening and Diagnosis
Complications
Treatment
Prevention
What Is St. Louis Encephalitis?
St. Louis Encephalitis (SLE) is an inflammation of the brain. This viral infection is transmitted only by the bite of infective mosquitoes. SLE is transmitted by mosquitoes from the Culex Genus whose feeding activity is most intense during cooler temperatures at dusk, night and at dawn. Mosquitoes become infected by feeding on birds infected with the St. Louis encephalitis virus.
When the virus enters the blood stream, it may localize in the brain causing inflammation of the brain cells and surrounding membranes. The brain tissue swells and can cause destruction of nerve cells, bleeding within the brain, and brain damage.
To contract SLE, you have to be bitten by an infected mosquito. Although the percentage of people who are bitten by an infected mosquito actually get SLE is low, proper precautions should still taken in areas where Culex genus mosquitoes live. Increased awareness and prevention methods are key to helping keep the number of SLE cases to a minimum.
What is being done in Memphis to prevent SLE?
SLE appears in epidemic form at intervals of approximately ten years. The last outbreak in Memphis occurred in 1975 with 62 reported cases and 12 fatalities. To date no cases have been reported in Memphis and Shelby County in over 20 years.
Since 1968, the Memphis and Shelby County Health Department's Mosquito Control Program has been actively involved in SLE surveillance by measuring antibodies to the virus in the blood of wild birds and chickens. These animals serve as a reservoir for the St. Louis Encephalitis virus. Positive antibody testing serves as an early warning signal.
Although mosquito control is an important means of decreasing transmission of SLE to humans, personal protective measures are also important.
Individuals can help by flushing any standing water in birdbaths, small wading pools, pets? water bowls, etc. and by adding fresh water daily. This will decrease the potential for mosquito breeding sites.
Although the majority of the cases reported during the outbreak were older adults, young children should not be considered low risk, since they are a target population by begin frequently outdoors.
Signs and Symptoms
The incubation period of SLE is 4-21 days with most cases being asymptomatic. The signs and symptoms of St. Louis Encephalitis may become more severe as the disease progresses
Common symptoms include:
- sudden fever
- drowsiness
- headache
- vomiting
- sensitive to light
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stiff neck
Emergency symptoms:
Causes
A virus carried by a mosquito from the Culex genus family, which is infected, causes St. Louis Encephalitis. To contract SLE, you have to be bitten by an infected mosquito.
Risk Factors
Where you live or vacation can increase your chances of getting St. Louis Encephalitis. So can the type of outdoor activities you enjoy. The most common risk factors include:
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Spending time in areas where there is alot of standing water ? particularly during spring and summer months.
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Leaving skin exposed while in wet, wooded or grassy areas that may be a breeding ground for mosquitoes.
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Outdoor activities during the evening, nighttime hours and at dawn without protective clothing.
When to Seek Medical Advice
Only a rare few mosquito bites lead to SLE. But if you know you've been bitten and experience symptoms of sudden fever, neurological changes, and other symptoms of encephalitis are present--GO to the emergency room immediately.
Screening and Diagnosis
A lumbar puncture test and cerebrospinal fluid (CSF) examination. Blood may be present in the CSF.
- Viral cultures of CSF or blood that reveal any type of virus will confirm the diagnosis. Serology tests are often the choice of a health care provider to provide evidence of viral infection.
- EEG test results are abnormal.
- A cranial MRI or a CT scan of the head may be used to determine the presence or absence of internal bleeding or edema.
Complications
If left untreated, permanent neurological impairments, which may include: loss of memory, speech difficulty or loss, diminished vision, hearing, and muscle control, can occur in people who survive severe cases of encephalitis.
Treatment
The goals of treatment are to provide supportive care and relieve symptoms.
Antibiotics and/or antiviral medications are the standard treatment along with other medications needed to relieve symptoms. Treatment with antibiotics for several weeks usually cures the infection and prevents complications. It's important to take the full course of medications; for treatment to be most successful, do not discontinue taking these medication prematurely.
If the disease has progressed to a later stage, hospitalization may be necessary in some cases.
Rest, nutrition, and plenty of fluids allows the body to fight the infection. Emotional support may also be helpful.
If brain function is severely affected, physical therapy and speech therapy may be necessary after the acute illness is controlled.
Prevention
You can decrease your chances of contracting St. Louis Encephalitis by following some simple precautions:
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Mosquito proof your yard by flushing any standing water in birdbaths where mosquitoes breed, twice weekly.
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Empty water from small wading pools and store indoors.
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If you have an ornamental pool, you can stock the pool with mosquito fish or treat the water with a larval control product.
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Provide fresh clean water in pet's bowls daily.
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Remove old tires, cans, non-working appliances or container that will hold water. |
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Repair leaky plumbing.
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Clean out rain gutters.
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Ensure proper screening around door and windows of your home.
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When outside, especially during cooler temperatures at dusk, night and at dawn, wear light-colored clothing, long-sleeved shirts, and long pants. Try to avoid walking through low bushes and tall grass where there may standing water.
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Insect repellents during the peak feeding times. Use EPA approved products containing DEET with approximately 30% active ingredient. Be sure to follow label instructions carefully. Do not apply directly on the skin of children under the age of five. |
For information on mosquitoes, contact the Memphis and Shelby County Health Department's Vector Control Section at 324-5547. For St. Louis Encephalitis information, contact the Epidemiology Section at 576-7717.
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