Western encephalomyelitis virus infection in "indicator" chickens in southern Alberta.

Sera from indicator chicken flocks situated in southern Alberta near Lethbridge were tested by the hemagglutination-inhibition (HI) technique for antibodies to Western, Eastern and St. Louis Encephalitis viruses during the summer and early fall of the four years 1964 to 1967.One chicken in 1964, 90 in 1965 and five each in 1966 and 1967 were positive to Western encephalomyelitis (WE) virus by hemagglutination-inhibition tests. All of the positive sera were confirmed by neutralization test (NT) in infant mice. No antibodies to the Eastern and St. Louis viruses were detected. Infection with WE virus was detected in each of the four years, indicating that WE virus is endemic to southern Alberta with a marked seasonal incidence occurring between the second week in August and the third week in September. An improved technique for filtering sera is described.