Attempts to control swollen-head syndrome in a broiler farm

An illness characterized by swollen heads of four-week-old chicks broke out in a broiler farm in northern Okayama prefecture in October 2004. Avian pneumovirus virus (APV) vaccination had been initiated in this farm, but the same symptom was subsequently observed in three-week-old chicks. Histologically, the heads of the chicks exhibited subcutaneous edema and purulent inflammation, and Escherichia coli were isolated from subcutaneous tissues. No histopathological changes were observed in the weekly sampling tests of these flocks, and no significant bacteria were isolated from the head skin of the chicks at one week old. However, purulent inflammation was observed in facial subcutaneous tissues, and E. coli and Staphylococcus were isolated from the facial skin of chicks aged two weeks or older. The antibody responses to the vaccines of the chicks were the same as that of the control group, and no significant problems were observed in the chicken house environment. APV vaccination and disinfection were continued, and work clothing and boots were changed before entering each chicken house. As a result, the symptom has not been seen since January 2006.