Marek's disease virus-induced transient paralysis: clinical and electrophysiologic findings in susceptible and resistant lines of chickens.

Results of neurologic examination, EEG, and motor nerve conduction velocity quantitation were analyzed in a line of chickens susceptible to Marek's disease virus-induced transient paralysis and compared with findings in a resistant line. Both lines were evaluated on the day before virus inoculation (day 1; base line) and on days 12 and 19. The susceptible birds frequently became depressed and paretic on day 11 or 12 and then recovered, and the resistant line rarely was affected clinically. The EEG of clinically affected birds from the susceptible line correlated well with the clinical course of the disease. Electroencephalographic abnormalities were absent in these birds at base line, evident at 12 days, and had remitted when they were reevaluated on day 19. The pattern in these clinically affected birds was predominantly low voltage-fast activity with frequent spikes. In contrast, the EEG recorded in resistant birds remained essentially the same throughout the study. Mean motor nerve conduction velocity values for the 2 lines of birds did not differ significantly when compared either between or within groups. These findings indicate that Marek's disease virus-induced transient paralysis may be an inflammatory encephalopathy.