Injection Site Injury in Poultry
Injection of antimicrobials and vaccines in any location can result in focal inflammatory myositis (see injection site injury image). Cellulitis and myositis in the neck region, causing postural and/or neurological signs, can develop in poultry after improper administration of vaccines.
Courtesy of Dr. A. J. Van Wettere.
Injection site injury is most common in broiler chicks. Affected birds might show ataxia, twisting of the neck, leg paralysis, and recumbency.
Swelling of the subcutis and muscle in the neck region at the injection site is evident grossly. Microscopically, lymphocytic and/or granulomatous inflammation is present within the muscle and subcutis.
Inflammatory infiltrate can extend to the epidural space. With oil-emulsion vaccines, empty spaces representing lipid droplets surrounded by a granulomatous inflammatory reaction are evident (see vaccination injection site injury image).
Courtesy of Dr. D. Frame.
Minimal Myopathy in Poultry
Minimal myopathy can occur in otherwise normal meat-type poultry. Affected birds show no clinical signs, and their muscles are grossly normal; microscopically, however, mild myofiber degeneration and fat accumulation between myofibers are observed (see minimal myopathy images). Focal or multifocal scattered myofibers are hyalinized and mineralized.
Images courtesy of Dr. H. J. Barnes.
More severe examples of minimal myopathy lesions contain individual myofiber necrosis, increased fat, and fibroplasia between fibers. No specific cause has been determined for these minimal changes, which have been observed by avian pathologists but are not well described in the literature.
"Minimal myopathy" is not an established name for this condition.
For More Information
Crespo R. Developmental, metabolic, and other noninfectious disorders. In: Swayne DE, ed. Boulianne M, Logue CM, McDougald LR, Nair V, Suarez DL, associate eds. Diseases of Poultry. 14th ed. Wiley Blackwell; 2020:1286-1329.
