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Diagnosis of eastern equine encephalomyelitis by immunofluorescent staining of brain tissue
Abstract:
Brain tissues were obtained from 5 horses with clinical encephalomyelitis during an epizootic in southwestern Michigan in August-September 1980. These tissues were tested for virus by intracerebral inoculation of suckling mice and by examination of frozen sections and impression smears by the indirect fluorescent antibody (FA) technique. Eastern equine encephalomyelitis virus was isolated and detected by FA technique in brains of 3 horses which died or were euthanatized within approximately 24 hours of onset of the disease but not from 2 horses at 2 and 3 days after onset. The latter 2 animals had serum-neutralizing antibodies at the time of death. Seven areas of the brain of 1 horse were tested. The proportion of fluorescing cells in frozen sections correlated with infectivity titers. Impression smears were negative. Viral titers ranged from 10(5.7) to 10(10.0) suckling mouse intracerebral median lethal doses/g; highest titers and most intense fluorescence were present in the thalamus and pons, emphasizing the need to obtain selective samples of central brain structures for diagnostic examination. The FA technique appears useful for the rapid diagnosis of fatal eastern equine encephalomyelitis and may be applicable in laboratories not equipped for isolation of viruses.
Insights
Rapid diagnosis of Eastern equine encephalomyelitis (EEE) in horses is possible using the indirect fluorescent antibody (FA) technique on brain tissues. This method proved effective within 24 hours of disease onset, aiding in quick identification of EEE virus.
Area of Science:
- Veterinary Pathology
- Virology
- Immunofluorescence
Background:
- Equine encephalomyelitis poses a significant threat during epizootics.
- Accurate and rapid diagnosis is crucial for disease management and control.
Purpose of the Study:
- To evaluate the efficacy of the indirect fluorescent antibody (FA) technique for diagnosing Eastern equine encephalomyelitis (EEE) in horses.
- To correlate FA staining with viral infectivity titers in brain tissues.
Main Methods:
- Brain tissues from horses with clinical encephalomyelitis were examined.
- Virus detection was performed using intracerebral inoculation of suckling mice and the indirect FA technique on frozen sections and impression smears.
- Serum neutralization tests were conducted.
Main Results:
- Eastern equine encephalomyelitis virus was isolated and detected by FA in 3 of 5 horses that died within 24 hours of disease onset.
- FA detection was negative in horses examined 2-3 days post-onset, who had developed antibodies.
- A correlation was observed between the proportion of fluorescing cells in frozen sections and viral infectivity titers, with highest titers in the thalamus and pons.
- Impression smears yielded negative results.
Conclusions:
- The indirect FA technique is a valuable tool for the rapid diagnosis of fatal Eastern equine encephalomyelitis in equine cases.
- The FA technique can be utilized in laboratories lacking specialized virus isolation equipment.
- Selective sampling of central brain structures, such as the thalamus and pons, is recommended for optimal diagnostic yield.