Scratches as a component in the pathogenesis of avian cellulitis in broiler chickens exposed to cellulitis origin Escherichia coli isolates collected from different regions of the US.

Cellulitis was induced in broiler chickens in two experiments. Birds were placed on used pine-shaving litter at day of hatch and raised to 28 days of age, at which time one-half the birds in each pen were scratched and the litter was treated with either one of seven cellulitis origin Escherichia coli (collected from various locations in the US) or sterile saline. Although minor differences could be detected in the association of specific regional isolates with differing rates of cellulitis, all isolates were capable of inducing cellulitis in a preponderance of the scratched birds. These same isolates were not capable of producing cellulitis in birds that were not scratched by design, confirming the importance of scratches in the pathogenesis of cellulitis. Those birds in the unscratched groups placed on litter inoculated with either a cellulitis E. coli isolate (EC-AR1) or sterile saline that did develop cellulitis lesions showed the remnants of healed scratches which had occurred naturally during the course of the growout, again providing evidence as to the importance of scratches in the development of cellulitis.