Natural Outbreak of Eastern and Western Encephalitis in Pen-Raised Chukars in Florida

Abstract

Eastern encephalitis (EE) and Western encephalitis (WE) have not been previously recognized as disease problems in pen-raised chukar partridges in Florida. Stamm (7) reported that 52 species of birds are known to be susceptible to EE virus and 51 species are known to be susceptible to WE virus by demonstrating a viremia resulting from natural or laboratory infections. Moulthrop and Gordy (6) isolated EE virus from 1 pen of chukars in Maryland in 1960 without gross lesions, and described clinical signs as those shown in crazy chick disease. Kissling (5) described clinical signs of EE in ring-necked pheasants as a central nervous system involvement with leg paralysis, torticollis, and tremors. Gross heart lesions from which EE was isolated have been reported in pheasants by Gainer (3). Dougherty and Price (2) reported that White Pekin ducks over 18 days are not susceptible to natural infection with EE. Vaccination of pheasants in New Jersey with a bivalent (EE, WE) vaccine indicates that mortality from natural infections with EE is significantly curbed (8). This paper describes the occurrence of encephalitis in 5 rather widely separated flocks of pen-raised chukars in Florida in the summer of 1963; the EE virus was isolated and specifically identified in 4 flocks; the WE virus was isolated and specifically identified in the 5th flock. In all flocks, clinical signs and gross lesions were consistent. Brief experimental infections were induced in chukars; follow-up hemagglution