Eight hundred skin samples from broiler carcasses condemned or downgraded for skin lesions were collected at five processing plants. Histologicall y, 45.25% were cellulitis, 19.00% were atypical fowlpox, 3.25% were dermal squamous cell carcinoma (DSCC), 17.00% were non-specific dermatitis, 0.5% were focal haemorrhages and 0.25% were haemangiomas. Of the samples, 14.75% were histologically normal. Macroscopically, increased thickening of the skin was a frequent finding occurring in all the skin diseases, as well as skin discoloration, dark nodules in feather follicles and crusts. Skin scratches were associated with all of the diseases, except DSCC. Crater-like ulcers occurred in DSCC and fowlpox. Cellulitis was more frequent on the abdomen, fowlpox on the dorsum, DSCC in thighs, and non-specific dermatitis on the dorsum, thighs, legs and breast. It was concluded that macroscopic changes are not specific and examinations at slaughterhouses do not allow classification of broiler skin diseases. Histological examination appears to be an important tool to provide more accurate data.

Dermal squamous cell carcinoma (DSCC; avian keratoacanthoma) is a neoplastic skin lesion of broiler chickens of unknown aetiology. In previous studies, the possibility of the involvement of pox viruses in the cause of DSCC was considered. In this work, a sensitive and specific nested polymerase chain reaction (PCR) protocol was developed that could amplify a 419 base pair DNA fragment of fowlpox virus with a detection limit of less than one infectious unit. Fowlpox virus DNA was always detected in skin samples with fowlpox lesions while it was not detected in samples of unrelated diseases such as cowpox, Marek's disease or infectious laryngotracheitis. Some macroscopically normal skin samples from vaccinated and non-vaccinated birds also produced PCR-positive results, corroborating previous studies on the possibility that a latent or chronic form of fowlpox occurs. Fowlpox virus DNA was consistently detected from DSCC skin lesions, and this finding is discussed.

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