A REPRODUCIBLE MODEL FOR THE INDUCTION OF AVIAN CELLULITIS IN BROILER-CHICKENS

Avian cellulitis was reproduced in 39-day-old broilers by subcutaneous injection of Escherichia coli originally isolated from a cellulitis l esion. One hundred percent of the birds injected with the isolate on t he dorsal and ventral surfaces developed characteristic fibrino-caseou s plaques. A slightly lower percentage (90%) of the birds injected sub cutaneously in the inguinal area developed the same lesions. Only 30% of the birds that had been inoculated by scratching the skin and swabb ing the bacterial inoculum onto the wound developed the lesion. No bir ds inoculated by swabbing the inoculum onto a feather follicle, from w hich the feather had been pulled, developed cellulitis. Characteristic cellulitis plaques could be produced as early as 18 hr postinfection (PI). Lesions, consisting of a serosanguinous, yellow-pink-co-orange-t inged fluid appeared as early as 6 hr PI. The lesions progressed, chan ging to a more thin, yellow, purulent fluid by 12 hr PI followed by pl aque formation. Although there was a trend for lesion size to diminish with time, the majority of the challenged birds, examined as late as 3 wk PI, still had prominent cellulitis plaques. Lesions in birds inje cted subcutaneously on the dorsal surface sometimes extended into othe r regions of the body, including the abdominal region, and thereby res embled the type of lesions that have previously been described as type I or hatchery-borne cellulitis.