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Interpretive Handbook

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Test 83900 :
California Virus (La Crosse) Encephalitis Antibody Panel, IgG and IgM, Spinal Fluid

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

California (La Crosse) virus is a member of bunyaviridae and it is 1 of the arthropod-borne encephalitides. It is transmitted by various Aedes and Culex mosquitoes and is found in such intermediate hosts as the rabbit, squirrel, chipmunk, and field mouse.

 

California meningoencephalitis is usually mild and occurs in late summer. Ninety percent of infections are seen in children <15 years of age, usually from rural areas. The incubation period is estimated to be 7 days and acute illness lasts < or =10 days in most instances. Typically, the first symptoms are nonspecific, last 1 to 3 days, and are followed by the appearance of central nervous system signs and symptoms such as stiff neck, lethargy, and seizures, which usually abate within 1 week. Symptomatic infection is almost never recognized in those >18 years old. The most important sequelae of California virus encephalitis is epilepsy, which occurs in about 10% of children; almost always in patients who have had seizures during the acute illness. A few patients (estimated 2%) have persistent paresis. Learning disabilities or other objective cognitive deficits have been reported in a small proportion (<2%) of patients. Learning performance and behavior of most recovered patients are not distinguishable from comparison groups in these same areas.

 

Infections with arboviruses can occur at any age. The age distribution depends on the degree of exposure to the particular transmitting arthropod relating to age, sex, and occupational, vocational, and recreational habits of the individuals. Once humans have been infected, the severity of the host response may be influenced by age. Serious

California (La Crosse) virus infections primarily involve children, especially boys. Adult males exposed to California viruses have high prevalence rates of antibody but usually show no serious illness. Infection among males is primarily due to working conditions and sports activities taking place where the vector is present.

Useful For Suggests clinical disorders or settings where the test may be helpful

Aiding the diagnosis of California (La Crosse) encephalitis

Interpretation Provides information to assist in interpretation of the test results

A positive result indicates intrathecal synthesis of antibody and is indicative of neurological infection.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

All results must be correlated with clinical history and other data available to the attending physician.

 

False-positive results may be caused by breakdown of the blood-brain barrier, or by the introduction of blood into the cerebrospinal fluid at collection.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

IgG: <1:10

IgM: <1:10

Reference values apply to all ages.

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Gonzalez-Scarano F, Nathanson N: Bunyaviruses. In Fields Virology. Vol. 1. Second edition. Edited by BM Fields, DM Knipe. New York, Raven Press, 1990, pp 1195-1228

2. Donat JF, Rhodes KH, Groover RV, Smith TF: Etiology and outcome in 42 children with acute nonbacterial meningoencephalitis. Mayo Clin Proc 1980:55:156-160

3. Tsai TF: Arboviruses. In Manual of Clinical Microbiology. Seventh edition. Edited by PR Murray, EF Baron, MA Pfaller, et al. Washington, DC, ASM Press, 1999, pp 1107-1124

4. Calisher CH: Medically important arboviruses of the United States and Canada. Clin Microbiol Rev 1994;7:89-116


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