Isolation of eastern equine encephalitis virus in A549 and MRC-5 cell cultures.

Eastern equine encephalitis (EEE) has been diagnosed either serologically or by virus isolation. Until now, the recovery of EEE virus has been delegated to reference laboratories with the expertise and resources needed to amplify the virus in a susceptible vertebrate host and/or to isolate and identify the virus in cell culture. We report a case in which EEE virus was recovered directly from a patient's cerebrospinal fluid in A549 and MRC-5 cell cultures. Many clinical virology laboratories routinely use these cells to recover adenovirus, herpes simplex virus, and enterovirus. To the best of our knowledge, this is the first report of isolation of EEE virus in A549 cell culture. This report demonstrates the possibility of recovery of EEE virus in cell culture without the necessity of bioamplification or maintaining unusual cell lines.

Agents of equine viral encephalomyelitis: correlation of serum and cerebrospinal fluid antibodies.

A survey was conducted by testing 115 paired equine serum and cerebrospinal fluid samples by hemagglutination-inhibition for antibodies to Powassan and snowshoe hare viruses, and by virus neutralization for antibodies to equine herpesvirus type 1. Twenty-five samples were from horses with spontaneous neurological disease and the remainder from horses euthanized because of various nonneurological disorders. All sera and cerebrospinal fluids were negative for antibodies to Powassan virus. Fifty-one sera (44.3%) and 15 cerebrospinal fluids (13.0%) had antibodies to snowshoe hare virus. Ninety-eight sera (85.2%) and four cerebrospinal fluids (3.5%) were positive for antibodies to equine herpesvirus type 1. Powassan virus was inoculated intracerebrally into one, and intravenously into four ponies. Neurological signs associated with a nonsuppurative encephalomyelitis occurred in three ponies. Antibodies to Powassan virus were detected in sera of all animals but in cerebrospinal fluids of only two. Powassan virus was isolated from brain and spinal cord of only the intracerebrally inoculated animal.

Cytology of equine cerebrospinal fluid.

The cytology of cerebrospinal fluid samples from horses is described. The samples were obtained from 24 normal horses, 35 horses with axonal degeneration and/or spinal cord compression, 29 horses with encephalomyelitis, 14 horses with other lesions of the nervous system, and eight horses with signs of neurologic dysfunction of undetermined origin. (Three of the latter were suspected botulinum intoxications.) Fluid was aspirated from the atlanto-occipital space following general anesthesia or immediately after a lethal dose of barbiturate. In two horses, fluid also was aspirated from the lumbosacral space. Small mononuclear cells were predominant in normal horses, and in most horses with axonal degeneration and encephalomyelitis. Several horses with encephalomyelitis also had neutrophils, eosinophils, and some mitotic figures. Although the cytologic findings were abnormal in many of the horses with disease of the central nervous system, in most horses the cytologic findings were normal.