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 lesion. One hundred percent of the birds injected with the isolate on the dorsal and ventral surfaces developed characteristic fibrino-caseous plaques. A slightly lower percentage (90%) of the birds injected subcutaneously in the inguinal area developed the same lesions. Only 30% of the birds that had been inoculated by scratching the skin and swabbing the bacterial inoculum onto the wound developed the lesion. No birds inoculated by swabbing the inoculum onto a feather follicle, from which 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-to-orange-tinged fluid appeared as early as 6 hr PI. The lesions progressed, changing to a more thin, yellow, purulent fluid by 12 hr PI followed by plaque 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 injected subcutaneously on the dorsal surface sometimes extended into other regions of the body, including the abdominal region, and thereby resembled the type of lesions that have previously been described as type I or hatchery-borne cellulitis.