La Crosse encephalitis is a rare infection caused by La Crosse virus that is endemic to certain parts of the United States. The infection is transmitted from animal hosts by a mosquito bite. Most patients are asymptomatic, but a small number progresses to severe and life-threatening encephalitis characterized by a range of neurological symptoms and fever. Microbiological studies, either serology or molecular methods, are necessary to confirm the diagnosis.
La Crosse encephalitis, caused by the La Crosse virus (LACV), is a rare central nervous system (CNS) infection that is predominantly seen in the basins of the Mississippi and Ohio rivers, and the name was given after the first case was confirmed in La Crosse, Wisconsin  . Humans are infected by this virus after being bitten by Aedes triseriatus, the local forest-dwelling mosquito, and a stable animal reservoir of the virus was identified to be among chipmunks and squirrels in these areas  . For this reason, the infection is considered to be of zoonotic nature, and the summer months are when most cases are reported   . The majority of individuals who get infected by the LACV develop an asymptomatic form of illness and rough estimates suggest that approximately 1 in 1000 patients suffers from a more severe form of illness  . La Crosse encephalitis is predominantly diagnosed in children under 15 years of age, and the incubation period symptoms appear about 3-7 days after being bitten by an infected mosquito  . Seizures, altered mental state, cognitive impairment, and coma are main clinical features, whereas fever headaches, vomiting, and other neurological deficits (hemiparesis, dysarthria, chorea, and aphasia) are common manifestations as well    . Rapid clinical deterioration, stemming from increased intracranial pressure, cerebral herniation, respiratory insufficiency requiring intubation, and status epilepticus, is encountered in a minority of cases    . It must be noted that the majority of deaths by LACV occur due to La Crosse encephalitis, indicating that early recognition is vital for preventing complications   . In addition, long-term neurological sequelae are readily observed among survivors .
Entire Body System
- Intravenous Administration
Oral ribavirin for La Crosse encephalitis is not deemed to be a viable option due to even lower CSF levels compared to intravenous administration. The work of Cassidy and Patterson to date remains the strongest indicator of potential ribavirin benefit [ncbi.nlm.nih.gov]
The signs and symptoms of La Crosse encephalitis point to a nonspecific infection of the CNS and the differential diagnosis is often turned toward more common causes of viral encephalitis, such as herpes simplex virus (HSV) and enteroviruses  . However, the specific geographical location is of crucial importance for including LACV as a possible cause. Thus, a detailed patient history must cover recent traveling to endemic areas of the United States (or if patients are living in these areas) and note whether mosquito bites occurred. The physical examination, if conducted properly, can immediately point to a CNS infection, in which case both laboratory and microbiological studies should be employed. A lumbar puncture will show mild lymphocytic (or sometimes neutrophilic) pleocytosis, and increased protein levels are observed in up to 30% of patients, while leukocytosis in a complete blood count (CBC) is also seen   . A definite diagnosis of La Crosse encephalitis is made after conducting one of the two microbiological procedures - serology or polymerase chain reaction (PCR)   . Identification of immunoglobulin (Ig) M or high titer IgG antibodies is a reliable and effective method, whereas detection of viral deoxyribonucleic acid (DNA) in the cerebrospinal fluid (CSF) through molecular methods, such as PCR and reverse transcriptase-PCR has increased the overall efficacy in identifying LACV in human tissue     .
"Safety and pharmacokinetics of ribavirin for the treatment of la crosse encephalitis". The Pediatric Infectious Disease Journal. 30 (10): 860–5. doi:10.1097/INF.0b013e31821c922c. PMID 21544005. [en.wikipedia.org]
Outline the treatment and management options available for La Crosse encephalitis. [ncbi.nlm.nih.gov]
Treatment Patients with suspected LAC encephalitis should be hospitalized, appropriate serologic and other diagnostic tests ordered, and supportive treatment (including seizure control) provided. [bu.edu]
There is no specific treatment for LaCrosse encephalitis. Antibiotics are not effective against viruses, and no effective anti-viral drugs have been discovered. Care of patients centers on treatment of symptoms and complications. [web.archive.org]
The material is in no way intended to replace professional medical care by a qualified specialist and should not be used as a basis for diagnosis or treatment. [orpha.net]
(Outcomes/Resolutions) The prognosis of La Crosse Encephalitis is dependent upon the severity of the signs and symptoms and associated complications, if any Individuals with mild conditions have better prognosis than those with severe symptoms and complications [dovemed.com]
Less than 1% of cases result in mortality.  Complications Common complications of La Crosse encephalitis virus include: Recurring seizures Coma Loss of basic motor skills Loss of coordination Prognosis Prognosis for La Crosse encephalitis virus is [wikidoc.org]
Louis encephalitis, West Nile virus, Western equine encephalitis, chikungunya. Prognosis The prognosis for La Crosse encephalitis is relatively favorable with a low risk of mortality. [ncbi.nlm.nih.gov]
Prognosis • The mortality rate varies with etiology, and epidemics due to the same virus vary in severity in different years. • Bad: Eastern equine encephalitis virus infection, nearly 80% of survivors have severe neurological sequelae. • Not so Bad: [slideshare.net]
In addition, even experienced physicians often are uncertain about the cause, appropriate therapy, and prognosis. [pedsinreview.aappublications.org]
Studies comparing LAC cases with non-LAC (no etiologic diagnosis) central nervous system infections have yielded no statistical significance in signs and symptoms or laboratory values. [ncbi.nlm.nih.gov]
It has long been suspected that LAC has a broader distribution and a higher incidence in the Eastern United States than is reported, but is under-reported because the etiologic agent is often not specifically identified. [nemosquito.org]
PMID 11248155. ^ "Epidemiology & Geographic Distribution | la Crosse encephalitis | CDC". 2018-09-14. ^ Center for Disease Control and Prevention (CDC) (January 2009). [en.wikipedia.org]
Objectives: Identify the etiology and epidemiology of La Crosse encephalitis. Describe the appropriate history, physical, and diagnostic workup in the evaluation of La Crosse encephalitis. [ncbi.nlm.nih.gov]
Epidemiology of California encephalitis in Minnesota. [genome.jp]
Epidemiology Epidemiology & Geographic Distribution In the United States, approximately 80-100 La Crosse encephalitis virus (LACV) neuroinvasive disease cases are reported each year. [usaebn.org]
Please visit the Centers for Disease Control and Prevention (CDC) page for details on: Symptoms Diagnosis Treatment Statistics and epidemiology Guidance for health practitioners [mcevbd.wisc.edu]
Useful For Suggests clinical disorders or settings where the test may be helpful Aiding the diagnosis of California (La Crosse) encephalitis Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a [mayocliniclabs.com]
Pathophysiology La Crosse virus is transmitted subcutaneously through penetration of the skin by a feeding mosquito. Two surface glycoproteins subtypes are involved in the transmission of the virus. [ncbi.nlm.nih.gov]
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test California (La Crosse) virus is a member of the Bunyaviridae family and it is one of the arthropod-borne encephalitides. [mayomedicallaboratories.com]
The La Crosse virus is the principal member of the California encephalitis serogroup, which contains genetically similar viruses such as California encephalitis virus.  Pathophysiology La Crosse encephalitis virus is usually transmitted via mosquitos [wikidoc.org]
 Prevention People reduce the chance of getting infected with LACV by preventing mosquito bites. There is no vaccine or preventive drug. Prevention measures against LACV include reducing exposure to mosquito bites. [en.wikipedia.org]
Avoidance of mosquitoes using protective clothing and repellent sprays can help prevent infections. [medicinenet.com]
Tips on preventing mosquito bites. Questions about illnesses spread by mosquitoes? Contact us! Phone: 608-267-9003 | Fax: 608-261-4976 Last Revised: June 15, 2022 [dhs.wisconsin.gov]
While it's not 100 percent preventable, as someone who has experienced the disease herself, she said, "do what you can to try" to prevent your child from going through the same thing. [newsweek.com]
How would the transmission of this agent be prevented? No vaccination or preventative medication discovered for La Crosse virus infection. [slideplayer.com]
- McJunkin JE, de los Reyes EC, Irazuzta JE, et al. La Crosse encephalitis in children. N Engl J Med. 2001;344(11):801-807.
- Davis LE, Beckham JD, Tyler KL. North American encephalitic arboviruses. Neurol Clin. 2008;26(3):727-ix.
- Lambert AJ, Fryxell RT, Freyman K, et al. Comparative Sequence Analyses of La Crosse Virus Strain Isolated from Patient with Fatal Encephalitis, Tennessee, USA . Emerg Infect Dis. 2015;21(5):833-836.
- Haddow AD, Odoi A. The Incidence Risk, Clustering, and Clinical Presentation of La Crosse Virus Infections in the Eastern United States, 2003–2007. Rénia L, ed. PLoS One. 2009;4(7):e6145.
- Mandell GL, Bennett JE, Dolin R. Mandel, Douglas and Bennett's Principles and Practice of Infectious Diseases. 8th ed. Philadelphia, Pennsylvania: Churchill Livingstone; 2015.
- Jones TF, Erwin PC, Craig AS, et al. Serological survey and active surveillance for La Crosse virus infections among children in Tennessee. Clin Infect Dis. 2000;31:1284-1287.
- Lambert AJ, Nasci RS, Cropp BC, et al. Nucleic Acid Amplification Assays for Detection of La Crosse Virus RNA. J Clin Microbiol. 2005;43(4):1885-1889.
- Murray PR, Rosenthal KS, Pfaller MA. Medical Microbiology. Seventh edition. Philadelphia: Elsevier/Saunders; 2013.