What Is St. Louis Encephalitis?
Through the bite of an infected mosquito, the St. Louis encephalitis (SLE) virus is transferred to humans. The majority of SLE virus carriers do not exhibit any symptoms. Those who do contract the illness could experience fever, headache, nausea, vomiting, and fatigue. Some individuals may develop neuroinvasive illnesses like encephalitis, brain inflammation, or meningitis as well (inflammation of the membranes that surround the spinal cord and brain). Long-term impairment or death may occur in exceptional circumstances.
SLE cannot be prevented or treated with immunizations or medications. By applying insect repellent, donning long sleeves and long pants, and taking precautions to keep mosquitoes under control both indoors and outdoors, people can lower their chance of contracting the SLE virus.
Studies on the evolution of the SLE virus show that in the late 19th century, the virus was brought into North America from tropical America. Because of its more effective transmission and cross-protective resistance in wild birds, the West Nile (WN) virus, which was brought into the country in 1999, has supplanted SLE, according to some data. As the West Nile virus has expanded across North America, the annual prevalence of SLE and the occurrence of epidemics have significantly decreased, despite minor outbreaks occurring in Southern California and Arizona between 2015 and 2017. In contrast, tropical America sees an increase in reports of SLE infections.
How Does the Transmission Of St. Louis Encephalitis Occur?
Common carriers of the St. Louis encephalitis virus include Culex species mosquitoes and birds like crows, ravens, and jays. A mosquito picks up the virus after feeding on an infected bird. The infection can then be spread to other birds during feeding time after roughly a week. The St. Louis encephalitis virus can also be spread by mosquitoes to humans and other species, including horses. Because they are unable to transmit the virus to other mosquitoes, humans and horses are regarded as "dead end" hosts. The West Nile virus has a similar transmission cycle. This disease can be spread from mosquitoes to birds, humans, horses, and other mammals, much like the West Nile virus.
What Are the Symptoms Of St. Louis Encephalitis?
The majority of those who carry the St. Louis encephalitis (SLE) virus do not exhibit any symptoms. The interval between being sick after being bitten by an infected mosquito and showing symptoms is four to 14 days.
The typical onset of symptoms is sudden and includes fever, headache, nausea, dizziness, and widespread weakness. Usually, they deteriorate over the course of a few days to a week. Some patients improve beyond this time. Some people experience symptoms of infections of the central nervous system, such as stiff necks, disorientation, confusion, dizziness, tremors, and unsteadiness. In serious circumstances, a coma may occur.
In comparison to older persons, the condition is typically milder in children and young adults. Five to 20 percent of those with St. Louis encephalitis eventually die. Age raises one's mortality risk.
How to Diagnose St. Louis Encephalitis?
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Lumbar puncture, along with neuroimaging, is used as the initial evaluation method for patients who exhibit symptoms of encephalitis.
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CT (computed tomography) or MRI (magnetic resonance imaging) scans are often clear. Elevated opening pressure, normal or slightly lowered glucose, and cerebrospinal fluid (CSF) lymphocytic pleocytosis are all indications that a lumbar puncture should be performed. Rarely do cerebral spinal fluid (CSF) cell counts reach 500 cells/mm3, and 50 percent to 70 percent of the time, CSF protein levels are increased.
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Leukocytosis may be found in blood tests; however, it is frequently unimpressive. These results are typical of numerous encephalitis or viral meningitis types.
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About 30 percent of patients who have neurologic illnesses also suffer hyponatremia and fluid overload as a result of improper antidiuretic hormone secretion.
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On an electroencephalogram (EEG), there may be isolated spikes and diffused slowness. It has not been demonstrated that EEG abnormalities and clinical symptoms correlate well.
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The enzyme-linked immunosorbent assay (ELISA) test is typically used to identify St. Louis encephalitis by looking for IgM antibodies to the virus in serum. CSF can also be used for the ELISA test.
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In order to cast out an infection with enterovirus or herpes virus because of the comparable symptoms, a polymerase chain reaction (PCR) examination of CSF is frequently done. Virus cultures from sick people typically do not work.
How to Treat and Prevent Saint Louis Encephalitis?
There is no antiviral treatment that can effectively treat St. Louis encephalitis. Only supportive treatment using intravenous (IV) fluids and antipyretics is allowed. If SIADH or Syndrome of inappropriate antidiuretic hormone secretion is present, it is often moderate, and the majority of people will improve with just fluid restriction.
There are now no approved vaccines to protect against infection, nor are there any efficient antiviral medications. Because there is no effective medication or vaccination, prevention is essential.
The greatest form of prevention is to completely avoid mosquito bites.
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Long sleeves, long pants, socks, and closed-toe shoes should be worn as protection from bites, which can occur even after relatively brief outside exposure. To protect exposed ankles from being bit, pants legs can be tucked into socks.
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Since mosquitoes can bite through very thin clothes during the warmer months, spraying garments with permethrin, oil of lemon eucalyptus, or other insect repellents will lessen the risk of transmission. Although permethrin should not be applied directly to the skin, it can be used to treat clothing, which offers protection even after washing.
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Outdoor activity should be avoided between dawn and dark when mosquitoes are feeding when the transmission is most common.
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To avoid mosquito bites while sleeping, travelers should stay in air-conditioned areas or use mosquito nets or screens.
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Buckets, flower pots, and other containers should be drained since standing water attracts mosquitoes and serves as their breeding ground, and holes should be punched into tire swings' bottoms to allow any stored water to drain.
Conclusion:
An interprofessional team composed of a neurologist, internist, infectious disease specialist, emergency department physician, nurse, and intensivist works well to diagnose and treat St Louis encephalitis. There is no antiviral treatment that can effectively treat St. Louis encephalitis. Only supportive treatment using intravenous (IV) fluids and antipyretics is allowed. The majority of St. Louis encephalitis patients have a fair prognosis for survival. However, persistent neurological side effects have been documented.
