EXPERIMENTAL-INFECTION OF YOUNG BROILER-CHICKENS WITH EASTERN EQUINE ENCEPHALITIS-VIRUS AND HIGHLANDS J-VIRUS

Two-week-old broiler chickens were experimentally infected with either eastern equine encephalitis (EEE) virus or Highland J (HJ) virus. Mor tality rates were 24/30 (80%) in EEE-virus-inoculated chickens and 2/3 0 (7%) in HJ-virus-inoculated chickens. Chickens inoculated with EEE v irus exhibited severe depression and somnolence on days 1-6 postexposu re (PE), with 17/30 birds dying during this period. After 6 PE, EEE-vi rus-inoculated chickens exhibited abdominal distention, depression, an d growth retardation, and an additional seven chickens died. Pathologi c changes in EEE-virus-inoculated chickens dying on days 1-6 PE consis ted of multifocal necrosis in the heart and liver, as well as lymphoid depletion and necrosis in the thymus, spleen, and bursa of Fabricius. Ascites, pericardial effusion, and right ventricular dilatation of th e heart were the predominant lesions in chickens dying after day 6 PE. No clinical signs were observed in sham-inoculated controls or in mos t HJ-virus-inoculated chickens. Ascites, pericardial effusion, and mul tifocal myocardial necrosis were observed in 2/30 HJ-virus-inoculated chickens that died or were euthanatized after development of clinical signs. These findings indicate that both EEE virus and HJ virus are pa thogenic for young chickens.