- Author: Nancy F Crum-Cianflone, MD, MPH; Chief Editor: Mark R Wallace, MD, FACP, FIDSA more...
Complete blood count
This test useful and may show thrombocytopenia, lymphopenia, and/or anemia. These findings may be transient.
In patients presenting with neurologic infection, collect cerebrospinal fluid (CSF) for cell count and differential, protein, glucose, bacterial culture, Gram stain, and viral culture.
In patients with the clinical signs of encephalitis or meningitis, obtain CSF to help establish a diagnosis, to rule out bacterial causes that may be life threatening if untreated, and to detect other viral causes.
In orbiviral infections, the protein and white blood cell count may be slightly elevated; however, little information on CSF findings is currently available in the literature. The CSF may be examined for evidence of an orbiviral infection with serology and/or viral isolation.
Testing specifically for orbiviral infection may be done via serological studies or viral isolation from the serum or CSF. The presence of viral-specific immunoglobin M (IgM) in the CSF suggests acute infection. Serologic studies may include complement fixation, enzyme immunoassay, and neutralizing antibodies. These tests are available at only a limited number of reference laboratories. Cases may be referred to the US Centers for Disease Control and Prevention at Fort Collins, Colorado or the US Army Medical Research Institute of Infectious Diseases in Fort Detrick, Md.
The serum may be used for viral isolation and for serology. Use the appropriate reference laboratory for these specimens.
The serologic diagnosis requires a 4-fold rise in acute and convalescent antibody titers. Viral isolation may be accomplished by the inoculation of suckling mice or by cell cultures (ie, Vero or BHK-21 cells). Only a limited number of reference laboratories test specifically for orbiviral infections.
In order to rule out other causes of encephalitis, one also must test for other etiologies, depending on the location of exposure.
In the western United States, test for Rocky Mountain spotted fever, Powassan virus, Colorado tick fever, western equine encephalitis virus, West Nile virus, and St. Louis encephalitis virus.
Seek other viral etiologies, including herpes viruses and enteroviruses.
No specific imaging studies are recommended to assist in the diagnosis of orbiviral infections.
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